furumi_tui/src/app/update.rs

use std::time::{Duration, Instant};

use super::action::Action;
use crate::library::models::TrackItem;

use super::state::{
    AppState, GlobalView, Loadable, OpenedPlaylist, SearchState, TILE_HEIGHT, TILE_WIDTH, Tab,
    TrackSelectionScope, ViewMode, artist_merged_releases, artist_release_display_order,
    artist_release_rows, fed_artist_visible_appearance_indices, fed_artist_visible_release_indices,
    fed_release_display_order, fed_release_rows, fed_release_visible_track_indices, settings_rows,
    track_content_id, track_key,
};

pub const QUIT_CONFIRM_WINDOW: Duration = Duration::from_millis(1500);
pub const QUIT_CONFIRM_HINT: &str = "press quit again to exit";

/// Side effects requested by `update()`; executed by the app loop, which
/// owns the Runtime (audio controller, API client). Keeps update() pure.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Effect {
    /// (Re)start playback of `queue[queue_pos]`.
    PlayCurrent,
    TogglePause,
    StopPlayback,
    /// Seek relative to the current position, in seconds.
    SeekBy(i64),
    SetVolume(u8),
    SetOptions,
    /// Fetch a release and append all its tracks to the queue.
    EnqueueRelease {
        id: i64,
        next: bool,
    },
    ToggleLikes {
        track_ids: Vec<i64>,
        fed_tracks: Vec<crate::federation::FedTrack>,
    },
    /// Remove tracks from a stored playlist in the library.
    RemoveFromPlaylist {
        playlist_id: i64,
        track_ids: Vec<i64>,
        content_ids: Vec<String>,
    },
    RemoveQueueIndices {
        indices: Vec<usize>,
        restart_paused: Option<bool>,
        stop: bool,
    },
    /// Queue/options changed without a direct audio engine action.
    PlaybackQueueChanged,
    /// Persist the federation settings and start/stop the node.
    FedApplySettings,
    /// Force an immediate library publish into the DHT.
    FedSyncNow,
    /// Fetch this peer's ticket and show it in a popup.
    FedShowTicket,
    /// Generate a personal-device invite and show it in a popup.
    DeviceShowInvite,
    /// Connect this client to a trusted device by opaque frid invite.
    DeviceConnectInvite(String),
    /// Force an immediate personal-device sync.
    DeviceSyncNow,
    /// Persist and publish this device's display name.
    DeviceSetName(String),
    /// Revoke a trusted device.
    DeviceRevoke(String),
    /// Leave the current personal-device group after publishing self-revoke.
    DeviceLeaveGroup,
    /// Assemble the federated artist card (fan-out to the owning peers).
    FedOpenArtist(String),
    /// Download federated tracks into the local library, one by one.
    FedDownload {
        tracks: Vec<crate::federation::FedTrack>,
    },
    /// Fetch richer metadata for federated tracks without downloading audio.
    FedFetchTrackInfo {
        tracks: Vec<(i64, crate::federation::FedTrack)>,
    },
    /// Temporarily leaves the TUI and opens a visualization script in $EDITOR.
    OpenVisualizerEditor {
        path: std::path::PathBuf,
    },
}

pub fn update(state: &mut AppState, action: Action) -> Option<Effect> {
    // Any action other than a second Quit press disarms the confirmation.
    let quit_armed = state
        .quit_armed_until
        .take()
        .is_some_and(|deadline| Instant::now() <= deadline);
    state.status_message = None;
    match action {
        // While the help window is open, quit/back just close it.
        Action::Quit | Action::Back if state.help_visible => {
            state.help_visible = false;
            None
        }
        Action::Quit => {
            if quit_armed {
                state.should_quit = true;
            } else {
                state.quit_armed_until = Some(Instant::now() + QUIT_CONFIRM_WINDOW);
                state.status_message = Some(QUIT_CONFIRM_HINT.to_string());
            }
            None
        }
        Action::ToggleHelp => {
            state.help_visible = !state.help_visible;
            None
        }
        Action::OpenConnectedDevices => {
            state.popup = Some(super::state::Popup::ConnectedDevices { cursor: 0 });
            None
        }
        Action::NextTab => {
            switch_tab(state, state.active_tab.next());
            None
        }
        Action::PrevTab => {
            switch_tab(state, state.active_tab.prev());
            None
        }
        Action::GoToTab(index) => {
            if let Some(tab) = Tab::from_index(index) {
                // Pressing the current tab's number again resets it to its
                // top level (closes drill-down views).
                if tab == state.active_tab {
                    reset_tab(state, tab);
                } else {
                    switch_tab(state, tab);
                }
            }
            None
        }
        Action::PlayPause => {
            if state.player.current.is_some() {
                state.player.paused = !state.player.paused;
                Some(Effect::TogglePause)
            } else if state.player.queue.is_empty() {
                state.status_message = Some("nothing queued — open a track and press enter".into());
                None
            } else {
                Some(Effect::PlayCurrent)
            }
        }
        Action::NextTrack => queue_step(state, 1),
        Action::PrevTrack => queue_step(state, -1),
        Action::SeekForward { seconds } => state
            .player
            .current
            .is_some()
            .then_some(Effect::SeekBy(seconds as i64)),
        Action::SeekBackward { seconds } => state
            .player
            .current
            .is_some()
            .then_some(Effect::SeekBy(-(seconds as i64))),
        Action::VolumeUp => {
            state.player.volume = (state.player.volume + 5).min(100);
            Some(Effect::SetVolume(state.player.volume))
        }
        Action::VolumeDown => {
            state.player.volume = state.player.volume.saturating_sub(5);
            Some(Effect::SetVolume(state.player.volume))
        }
        Action::ToggleShuffle => {
            state.player.shuffle = !state.player.shuffle;
            // Shuffle physically reorders the unplayed tail, so the Queue
            // tab always shows the real upcoming order; turning it off
            // restores the original ordering.
            if state.player.shuffle {
                shuffle_upcoming(&mut state.player);
            } else {
                restore_queue_order(&mut state.player);
            }
            Some(Effect::SetOptions)
        }
        Action::CycleRepeat => {
            state.player.repeat = state.player.repeat.next();
            Some(Effect::SetOptions)
        }
        Action::ToggleVisualizer => {
            if state.visualizer.active {
                state.visualizer.close();
            } else if state.player.current.is_some() {
                state.visualizer.open();
                state.help_visible = false;
                state.popup = None;
                state.cmdline.active = false;
                state.pending_keys = None;
            } else {
                state.status_message = Some("nothing playing — start a track first".into());
            }
            None
        }
        Action::MoveUp => {
            move_selection(state, 0, -1);
            None
        }
        Action::MoveDown => {
            move_selection(state, 0, 1);
            None
        }
        Action::MoveLeft => {
            move_selection(state, -1, 0);
            None
        }
        Action::MoveRight => {
            move_selection(state, 1, 0);
            None
        }
        Action::PageUp => {
            move_selection(state, 0, -page_step(state));
            None
        }
        Action::PageDown => {
            move_selection(state, 0, page_step(state));
            None
        }
        Action::SelectFirst => {
            jump_selection(state, true);
            None
        }
        Action::SelectLast => {
            jump_selection(state, false);
            None
        }
        Action::ToggleViewMode => {
            match state.active_tab {
                Tab::Global => state.global.view = state.global.view.toggle(),
                // On the Logs tab the same key cycles the severity filter.
                Tab::Logs => {
                    state.logs.level_index =
                        (state.logs.level_index + 1) % super::state::LOG_LEVELS.len();
                    state.logs.selected_seq = None;
                    state.logs.follow = true;
                }
                _ => {}
            }
            None
        }
        Action::OpenLibraryFilters => {
            if state.active_tab == Tab::Global {
                state.popup = Some(super::state::Popup::LibraryFilters { cursor: 0 });
            }
            None
        }
        Action::OpenCommandLine => {
            state.cmdline.active = true;
            state.cmdline.input.clear();
            None
        }
        Action::OpenSearch => {
            // The command line opens pre-filled with "/": typing continues
            // the live search, exactly as if `:` then `/` were pressed.
            state.cmdline.active = true;
            state.cmdline.input = crate::app::input::LineEdit::new("/");
            state.cmdline.live = true;
            state.search = SearchState::default();
            state.active_tab = Tab::Global;
            if !matches!(state.global.stack.last(), Some(GlobalView::Search { .. })) {
                state.global.stack.push(GlobalView::Search { cursor: 0 });
            }
            None
        }
        Action::Select => select_current(state),
        Action::Back if state.visualizer.active => {
            state.visualizer.close();
            None
        }
        Action::Back if state.track_selection.is_active() => {
            state.track_selection.clear();
            state.status_message = Some("selection cleared".into());
            None
        }
        Action::Back => {
            go_back(state);
            None
        }
        Action::ToggleLike => {
            let mut tracks = selected_tracks(state);
            if tracks.is_empty() {
                tracks = state
                    .player
                    .current
                    .as_ref()
                    .map(|track| vec![track.clone()])
                    .unwrap_or_default();
            }
            let mut local_tracks: Vec<TrackItem> = Vec::new();
            let mut fed_tracks: Vec<crate::federation::FedTrack> = Vec::new();
            let mut seen = std::collections::HashSet::new();
            for track in tracks {
                if !seen.insert(track_key(&track)) {
                    continue;
                }
                match &track.fed {
                    Some(fed) => fed_tracks.push(fed.clone()),
                    None if track.id >= 0 && track_content_id(&track).is_some() => {
                        local_tracks.push(track)
                    }
                    None => {}
                }
            }
            if local_tracks.is_empty() && fed_tracks.is_empty() {
                state.status_message = Some("no track selected".into());
                None
            } else {
                let should_like = local_tracks.iter().any(|track| !state.track_liked(track))
                    || fed_tracks.iter().any(|fed| !state.fed_track_liked(fed));
                let toggles: Vec<i64> = local_tracks
                    .into_iter()
                    .filter(|track| state.track_liked(track) != should_like)
                    .map(|track| track.id)
                    .collect();
                let fed_toggles: Vec<crate::federation::FedTrack> = fed_tracks
                    .into_iter()
                    .filter(|fed| state.fed_track_liked(fed) != should_like)
                    .collect();
                let total = toggles.len() + fed_toggles.len();
                state.status_message = Some(if should_like {
                    format!("liking {total} track(s)")
                } else {
                    format!("removing like from {total} track(s)")
                });
                Some(Effect::ToggleLikes {
                    track_ids: toggles,
                    fed_tracks: fed_toggles,
                })
            }
        }
        Action::ToggleTrackSelection => {
            toggle_track_selection(state);
            None
        }
        Action::OpenTrackInfo => {
            let tracks = selected_tracks(state);
            open_track_info(state, tracks, "no track selected")
        }
        Action::OpenCurrentTrackInfo => {
            let tracks = state.player.current.clone().into_iter().collect();
            open_track_info(state, tracks, "nothing playing")
        }
        Action::RemoveFromQueue => remove_selected_from_queue(state),
        Action::QueueAddNext => queue_add(state, true),
        Action::QueueAddLast => queue_add(state, false),
        Action::GoToRelease => {
            let track = selected_track(state).or_else(|| state.player.current.clone());
            match track {
                Some(track) => open_release_for_track(state, &track),
                None => state.status_message = Some("no track selected".into()),
            }
            None
        }
        Action::AddToPlaylist => {
            let target = selected_playlist_target(state, true);
            match target {
                Some(target) => {
                    state.popup = Some(super::state::Popup::AddToPlaylist { target, cursor: 0 });
                    state.track_selection.clear();
                }
                None => state.status_message = Some("no track selected".into()),
            }
            None
        }
        Action::DownloadSelected => {
            let tracks = selected_downloadable_fed_tracks(state);
            if tracks.is_empty() {
                state.status_message = Some("select federated tracks first".into());
                None
            } else {
                state.track_selection.clear();
                state.status_message = Some(format!(
                    "federation: downloading {} track(s) to the library…",
                    tracks.len()
                ));
                Some(Effect::FedDownload { tracks })
            }
        }
        Action::NewPlaylist => {
            let for_target = selected_playlist_target(state, false);
            state.popup = Some(super::state::Popup::NewPlaylist {
                for_target,
                input: crate::app::input::LineEdit::default(),
                busy: false,
            });
            state.track_selection.clear();
            None
        }
        Action::ClearQueue => {
            let had_tracks = !state.player.queue.is_empty();
            state.player.queue.clear();
            state.player.queue_pos = 0;
            state.player.current = None;
            state.player.playing = false;
            state.player.paused = false;
            state.player.prefetched_pos = None;
            state.player.original_order = None;
            state.queue_tab.cursor = 0;
            state.track_selection.clear();
            if had_tracks {
                state.status_message = Some("queue cleared".into());
                Some(Effect::StopPlayback)
            } else {
                None
            }
        }
        Action::EditSelected => {
            open_edit_popup(state);
            None
        }
        Action::DeleteSelected => delete_selected(state),
    }
}

fn track_info_needs_fed_metadata(track: &TrackItem) -> bool {
    track.fed.is_some()
        && (track.featured_artists.is_empty()
            || track.audio_format.is_none()
            || track.audio_bitrate.is_none()
            || track.audio_sample_rate.is_none()
            || track.audio_bit_depth.is_none()
            || track.file_size_bytes.is_none()
            || track.file_path.is_empty())
}

fn open_track_info(
    state: &mut AppState,
    tracks: Vec<TrackItem>,
    empty_message: &'static str,
) -> Option<Effect> {
    if tracks.is_empty() {
        state.status_message = Some(empty_message.into());
        return None;
    }

    let fed_tracks = tracks
        .iter()
        .filter(|track| track_info_needs_fed_metadata(track))
        .filter_map(|track| track.fed.as_ref().map(|fed| (track.id, fed.clone())))
        .collect::<Vec<_>>();
    state.popup = Some(super::state::Popup::TrackInfo {
        tracks,
        cursor: 0,
        scroll: 0,
    });
    if fed_tracks.is_empty() {
        None
    } else {
        state.status_message = Some("federation: fetching track metadata…".to_string());
        Some(Effect::FedFetchTrackInfo { tracks: fed_tracks })
    }
}

fn selected_playlist_target(
    state: &AppState,
    include_current: bool,
) -> Option<super::state::PlaylistAddTarget> {
    let fed = selected_fed_tracks(state);
    if !fed.is_empty() {
        return Some(super::state::PlaylistAddTarget::Fed(fed));
    }

    let local = selected_tracks(state);
    if !local.is_empty() {
        return Some(super::state::PlaylistAddTarget::Local(local));
    }

    include_current
        .then(|| state.player.current.clone())
        .flatten()
        .map(|track| super::state::PlaylistAddTarget::Local(vec![track]))
}

/// `e`: open the metadata edit form for whatever is under the cursor —
/// an artist tile, a release, a track or a playlist.
fn open_edit_popup(state: &mut AppState) {
    use super::state::{EditField, EditTarget, Popup};

    if state.active_tab == Tab::Playlists && state.playlists.opened.is_none() {
        let card = match &state.playlists.list {
            Some(Loadable::Ready(list)) => list.get(state.playlists.selected).cloned(),
            _ => None,
        };
        let Some(card) = card else {
            return;
        };
        if card.kind == "likes" {
            state.status_message = Some("the Likes playlist cannot be edited".into());
            return;
        }
        state.popup = Some(Popup::Edit {
            target: EditTarget::Playlist(card.id),
            title: format!("Edit playlist — {}", card.title),
            fields: vec![EditField::new("Title", card.title.clone())],
            focus: 0,
            error: None,
        });
        return;
    }
    if state.active_tab == Tab::Global && state.global.stack.is_empty() {
        let Some(artist) = state.global.artists.get(state.global.selected).cloned() else {
            return;
        };
        if artist.id < 0 {
            state.status_message = Some("remote artists cannot be edited here".into());
            return;
        }
        state.popup = Some(artist_edit_popup(
            artist.id,
            &artist.name,
            artist.image_path,
        ));
        return;
    }
    if let Some(artist) = selected_search_artist(state) {
        state.popup = Some(artist_edit_popup(
            artist.id,
            &artist.name,
            artist.image_path,
        ));
        return;
    }
    if let Some(release) = selected_release_card(state) {
        state.popup = Some(Popup::Edit {
            target: EditTarget::Release(release.id),
            title: format!("Edit release — {}", release.title),
            fields: vec![
                EditField::new("Title", release.title.clone()),
                EditField::new("Type", release.release_type.clone()),
                EditField::new(
                    "Year",
                    release.year.map(|y| y.to_string()).unwrap_or_default(),
                ),
            ],
            focus: 0,
            error: None,
        });
        return;
    }
    if let Some(track) = selected_track(state).or_else(|| state.player.current.clone()) {
        state.popup = Some(track_edit_popup(&track));
        return;
    }
    state.status_message = Some("nothing to edit here".into());
}

fn artist_edit_popup(id: i64, name: &str, image_path: Option<String>) -> super::state::Popup {
    use super::state::{EditField, EditTarget, Popup};
    Popup::Edit {
        target: EditTarget::Artist(id),
        title: format!("Edit artist — {name}"),
        fields: vec![
            EditField::new("Name", name),
            EditField::new("Image path", image_path.unwrap_or_default()),
        ],
        focus: 0,
        error: None,
    }
}

fn track_edit_popup(track: &TrackItem) -> super::state::Popup {
    use super::state::{EditField, EditTarget, Popup};
    let join = |artists: &[crate::library::models::ArtistRef]| {
        artists
            .iter()
            .map(|a| a.name.clone())
            .collect::<Vec<_>>()
            .join("; ")
    };
    Popup::Edit {
        target: EditTarget::Track(track.id),
        title: format!("Edit track — {}", track.title),
        fields: vec![
            EditField::new("Title", track.title.clone()),
            EditField::new("Artists", join(&track.artists)),
            EditField::new("Featured", join(&track.featured_artists)),
            EditField::new(
                "Track #",
                track
                    .track_number
                    .map(|n| n.to_string())
                    .unwrap_or_default(),
            ),
            EditField::new(
                "Disc #",
                track.disc_number.map(|n| n.to_string()).unwrap_or_default(),
            ),
            EditField::new("Cover path", track.cover_path.clone().unwrap_or_default()),
        ],
        focus: 0,
        error: None,
    }
}

/// shift-d: delete whatever is under the cursor. Library entities ask for
/// confirmation; playlist/queue rows are removed directly.
fn delete_selected(state: &mut AppState) -> Option<Effect> {
    use super::state::{DeleteTarget, Popup};

    if state.active_tab == Tab::Queue {
        return remove_selected_from_queue(state);
    }
    if state.active_tab == Tab::Playlists {
        match state.playlists.opened {
            None => {
                let card = match &state.playlists.list {
                    Some(Loadable::Ready(list)) => list.get(state.playlists.selected).cloned(),
                    _ => None,
                };
                let card = card?;
                if card.kind == "likes" {
                    state.status_message = Some("the Likes playlist cannot be deleted".into());
                    return None;
                }
                state.popup = Some(Popup::ConfirmDelete {
                    target: DeleteTarget::Playlist(card.id),
                    label: format!("playlist \"{}\"", card.title),
                });
                return None;
            }
            Some(opened) => {
                let tracks = selected_tracks(state);
                if tracks.is_empty() {
                    state.status_message = Some("no track selected".into());
                    return None;
                }
                let track_ids: Vec<i64> = tracks.iter().map(|track| track.id).collect();
                let content_ids: Vec<String> = tracks.iter().filter_map(track_content_id).collect();
                state.track_selection.clear();
                if opened.id == super::state::LIKES_PLAYLIST_ID {
                    let mut seen = std::collections::HashSet::new();
                    let mut liked = Vec::new();
                    let mut fed_tracks = Vec::new();
                    for track in tracks {
                        if !state.track_liked(&track) || !seen.insert(track_key(&track)) {
                            continue;
                        }
                        if let Some(fed) = track.fed {
                            fed_tracks.push(fed);
                        } else if track.id >= 0 && track_content_id(&track).is_some() {
                            liked.push(track.id);
                        }
                    }
                    let total = liked.len() + fed_tracks.len();
                    state.status_message = Some(format!("removing {} like(s)", total));
                    return Some(Effect::ToggleLikes {
                        track_ids: liked,
                        fed_tracks,
                    });
                }
                let content_ids: Vec<String> = content_ids
                    .into_iter()
                    .collect::<std::collections::BTreeSet<_>>()
                    .into_iter()
                    .collect();
                let track_ids: Vec<i64> = track_ids.into_iter().filter(|id| *id >= 0).collect();
                state.status_message = Some(format!(
                    "removing {} track(s) from playlist",
                    content_ids.len().max(track_ids.len())
                ));
                return Some(Effect::RemoveFromPlaylist {
                    playlist_id: opened.id,
                    track_ids,
                    content_ids,
                });
            }
        }
    }
    if state.active_tab != Tab::Global {
        return Some(Effect::PlaybackQueueChanged);
    }
    if state.global.stack.is_empty() {
        let artist = state.global.artists.get(state.global.selected).cloned()?;
        if artist.id < 0 {
            state.status_message = Some("remote artists cannot be deleted here".into());
            return None;
        }
        state.popup = Some(Popup::ConfirmDelete {
            target: DeleteTarget::Artist(artist.id),
            label: format!(
                "artist \"{}\" with all their releases and tracks",
                artist.name
            ),
        });
        return None;
    }
    if let Some(artist) = selected_search_artist(state) {
        state.popup = Some(Popup::ConfirmDelete {
            target: DeleteTarget::Artist(artist.id),
            label: format!(
                "artist \"{}\" with all their releases and tracks",
                artist.name
            ),
        });
        return None;
    }
    if let Some(release) = selected_release_card(state) {
        state.popup = Some(Popup::ConfirmDelete {
            target: DeleteTarget::Release(release.id),
            label: format!("release \"{}\" with all its tracks", release.title),
        });
        return None;
    }
    if let Some(track) = selected_track(state) {
        state.popup = Some(Popup::ConfirmDelete {
            target: DeleteTarget::Track(track.id),
            label: format!("track \"{}\" (the audio file stays on disk)", track.title),
        });
    } else {
        state.status_message = Some("nothing to delete here".into());
    }
    None
}

/// The artist under the cursor in the search view, if any.
fn selected_search_artist(state: &AppState) -> Option<crate::library::models::ArtistCard> {
    if state.active_tab != Tab::Global {
        return None;
    }
    let Some(GlobalView::Search { cursor }) = state.global.stack.last() else {
        return None;
    };
    state.search.results.as_ref()?.artists.get(*cursor).cloned()
}

/// The release card under the cursor (artist view tiles/rows or search).
fn selected_release_card(state: &AppState) -> Option<crate::library::models::ReleaseCard> {
    if state.active_tab != Tab::Global {
        return None;
    }
    match state.global.stack.last()? {
        GlobalView::Artist { id, cursor } => match state.artist_views.get(id)? {
            Loadable::Ready(detail) => {
                let position = cursor.checked_sub(detail.top_tracks.len())?;
                let merged = artist_merged_releases(state, *id, detail);
                let order = artist_release_display_order(&merged);
                order
                    .get(position)
                    .and_then(|&index| merged[index].local_index)
                    .map(|index| detail.releases[index].clone())
            }
            _ => None,
        },
        GlobalView::Search { cursor } => {
            let results = state.search.results.as_ref()?;
            let offset = cursor.checked_sub(results.artists.len())?;
            results.releases.get(offset).cloned()
        }
        GlobalView::Release { .. }
        | GlobalView::FedArtist { .. }
        | GlobalView::FedRelease { .. } => None,
    }
}

fn toggle_track_selection(state: &mut AppState) {
    let Some((scope, cursor, len)) = current_track_list_context(state) else {
        state.status_message = Some("track selection is unavailable here".into());
        return;
    };
    if len == 0 {
        state.status_message = Some("no tracks here".into());
        return;
    }
    if state.track_selection.is_active_for(&scope) {
        state.track_selection.clear();
        state.status_message = Some("selection cleared".into());
    } else {
        state.track_selection.start(scope, cursor);
        visual_selection_status(state);
    }
}

fn visual_selection_status(state: &mut AppState) {
    let Some((scope, _, len)) = current_track_list_context(state) else {
        return;
    };
    if let Some(indices) = state.track_selection.indices(&scope, len) {
        state.status_message = Some(format!("-- VISUAL LINE -- {} track(s)", indices.len()));
    }
}

fn refresh_track_selection_cursor(state: &mut AppState) {
    let Some((scope, cursor, _)) = current_track_list_context(state) else {
        state.track_selection.clear();
        return;
    };
    state.track_selection.set_cursor(scope, cursor);
    if state.track_selection.is_active() {
        visual_selection_status(state);
    }
}

fn set_track_scope_cursor(state: &mut AppState, scope: &TrackSelectionScope, value: usize) {
    match scope {
        TrackSelectionScope::ArtistTop(id) => {
            if matches!(
                state.global.stack.last(),
                Some(GlobalView::Artist { id: current, .. }) if current == id
            ) {
                set_view_cursor(state, value);
            }
        }
        TrackSelectionScope::ArtistFeatured(id) => {
            let Some(GlobalView::Artist { id: current, .. }) = state.global.stack.last() else {
                return;
            };
            if current != id {
                return;
            }
            let Some(Loadable::Ready(detail)) = state.artist_views.get(id) else {
                return;
            };
            let releases = artist_merged_releases(state, *id, detail).len();
            let flat = detail.top_tracks.len() + releases + value;
            set_view_cursor(state, flat);
        }
        TrackSelectionScope::Release(id) => {
            if matches!(
                state.global.stack.last(),
                Some(GlobalView::Release { id: current, .. }) if current == id
            ) {
                set_view_cursor(state, value);
            }
        }
        TrackSelectionScope::Playlist(id) => {
            if let Some(opened) = &mut state.playlists.opened
                && opened.id == *id
            {
                opened.cursor = value;
            }
        }
        TrackSelectionScope::Queue => {
            state.queue_tab.cursor = value;
        }
        TrackSelectionScope::FedSearch => {
            let base = state.search.results.as_ref().map_or(0, |r| r.len())
                + state.search.fed_artists.len();
            set_view_cursor(state, base + value);
        }
        TrackSelectionScope::FedRelease(_) => {
            set_view_cursor(state, value + 1);
        }
        TrackSelectionScope::FedAppearsOn => {
            let Some((_, Loadable::Ready(card))) = &state.fed_artist_view else {
                return;
            };
            let release_count = fed_artist_visible_release_indices(state, card).len();
            set_view_cursor(state, release_count + value);
        }
    }
}

fn current_track_list_context(state: &AppState) -> Option<(TrackSelectionScope, usize, usize)> {
    match state.active_tab {
        Tab::Global => match state.global.stack.last()? {
            GlobalView::Artist { id, cursor } => match state.artist_views.get(id)? {
                Loadable::Ready(detail) => {
                    let tracks = detail.top_tracks.len();
                    let releases = artist_merged_releases(state, *id, detail).len();
                    if *cursor < tracks {
                        Some((TrackSelectionScope::ArtistTop(*id), *cursor, tracks))
                    } else {
                        let featured = cursor.checked_sub(tracks + releases)?;
                        (featured < detail.featured_tracks.len()).then_some((
                            TrackSelectionScope::ArtistFeatured(*id),
                            featured,
                            detail.featured_tracks.len(),
                        ))
                    }
                }
                _ => None,
            },
            GlobalView::Release { id, cursor } => match state.release_views.get(id)? {
                Loadable::Ready(detail) => Some((
                    TrackSelectionScope::Release(*id),
                    *cursor,
                    detail.tracks.len(),
                )),
                _ => None,
            },
            GlobalView::Search { cursor } => {
                // Only the federated tracks section is selectable here.
                let base = state.search.results.as_ref().map_or(0, |r| r.len())
                    + state.search.fed_artists.len();
                let len = state.search.fed_tracks.len();
                let relative = cursor.checked_sub(base)?;
                (relative < len).then_some((TrackSelectionScope::FedSearch, relative, len))
            }
            GlobalView::FedRelease { index, cursor } => {
                let len = fed_release_tracks(state, *index).len();
                let relative = cursor.checked_sub(1)?;
                (relative < len).then_some((TrackSelectionScope::FedRelease(*index), relative, len))
            }
            GlobalView::FedArtist { cursor } => {
                let Some((_, Loadable::Ready(card))) = &state.fed_artist_view else {
                    return None;
                };
                let release_count = fed_artist_visible_release_indices(state, card).len();
                let appearance_count = fed_artist_visible_appearance_indices(state, card).len();
                let relative = cursor.checked_sub(release_count)?;
                (relative < appearance_count).then_some((
                    TrackSelectionScope::FedAppearsOn,
                    relative,
                    appearance_count,
                ))
            }
        },
        Tab::Playlists => {
            let opened = state.playlists.opened.as_ref()?;
            let len = playlist_tracks(state, opened.id)?.len();
            Some((TrackSelectionScope::Playlist(opened.id), opened.cursor, len))
        }
        Tab::Queue => Some((
            TrackSelectionScope::Queue,
            state.queue_tab.cursor,
            state.player.queue.len(),
        )),
        Tab::Federation | Tab::Logs => None,
    }
}

fn current_track_list(state: &AppState) -> Option<(TrackSelectionScope, usize, &[TrackItem])> {
    match state.active_tab {
        Tab::Global => match state.global.stack.last()? {
            GlobalView::Artist { id, cursor } => match state.artist_views.get(id)? {
                Loadable::Ready(detail) => {
                    let tracks = detail.top_tracks.len();
                    let releases = artist_merged_releases(state, *id, detail).len();
                    if *cursor < tracks {
                        Some((
                            TrackSelectionScope::ArtistTop(*id),
                            *cursor,
                            &detail.top_tracks,
                        ))
                    } else {
                        let featured = cursor.checked_sub(tracks + releases)?;
                        (featured < detail.featured_tracks.len()).then_some((
                            TrackSelectionScope::ArtistFeatured(*id),
                            featured,
                            &detail.featured_tracks,
                        ))
                    }
                }
                _ => None,
            },
            GlobalView::Release { id, cursor } => match state.release_views.get(id)? {
                Loadable::Ready(detail) => {
                    Some((TrackSelectionScope::Release(*id), *cursor, &detail.tracks))
                }
                _ => None,
            },
            _ => None,
        },
        Tab::Playlists => {
            let opened = state.playlists.opened.as_ref()?;
            Some((
                TrackSelectionScope::Playlist(opened.id),
                opened.cursor,
                playlist_tracks(state, opened.id)?,
            ))
        }
        Tab::Queue => Some((
            TrackSelectionScope::Queue,
            state.queue_tab.cursor,
            &state.player.queue,
        )),
        Tab::Federation | Tab::Logs => None,
    }
}

pub fn selected_tracks(state: &AppState) -> Vec<TrackItem> {
    // Federated contexts produce queueable placeholders that behave like
    // regular tracks (queue, info, playback-on-demand).
    {
        let fed = selected_fed_tracks(state);
        if !fed.is_empty() {
            return fed.iter().map(crate::federation::pending_track).collect();
        }
    }
    let Some((scope, cursor, tracks)) = current_track_list(state) else {
        return selected_track(state).into_iter().collect();
    };
    let indices = state
        .track_selection
        .indices(&scope, tracks.len())
        .unwrap_or_else(|| vec![cursor.min(tracks.len().saturating_sub(1))]);
    indices
        .into_iter()
        .filter_map(|index| tracks.get(index).cloned())
        .collect()
}

fn selected_queue_indices(state: &AppState) -> Vec<usize> {
    if state.active_tab != Tab::Queue || state.player.queue.is_empty() {
        return Vec::new();
    }
    state
        .track_selection
        .indices(&TrackSelectionScope::Queue, state.player.queue.len())
        .unwrap_or_else(|| vec![state.queue_tab.cursor.min(state.player.queue.len() - 1)])
}

fn remove_selected_from_queue(state: &mut AppState) -> Option<Effect> {
    let indices = selected_queue_indices(state);
    if indices.is_empty() {
        state.status_message = Some("queue is empty".into());
        return None;
    }
    let outcome = remove_queue_indices(state, &indices);
    state.status_message = Some(format!("removed {} track(s) from queue", indices.len()));
    Some(Effect::RemoveQueueIndices {
        indices,
        restart_paused: outcome.restart_paused,
        stop: outcome.stop,
    })
}

struct QueueRemovalOutcome {
    restart_paused: Option<bool>,
    stop: bool,
}

fn remove_queue_indices(state: &mut AppState, indices: &[usize]) -> QueueRemovalOutcome {
    let len = state.player.queue.len();
    let mut unique: Vec<usize> = indices
        .iter()
        .copied()
        .filter(|index| *index < len)
        .collect();
    unique.sort_unstable();
    unique.dedup();
    if unique.is_empty() {
        return QueueRemovalOutcome {
            restart_paused: None,
            stop: false,
        };
    }

    let old_queue_pos = state.player.queue_pos;
    let current_key = state.player.current.as_ref().map(track_key);
    let current_removed = current_key.as_ref().is_some_and(|key| {
        unique.iter().any(|index| {
            state
                .player
                .queue
                .get(*index)
                .is_some_and(|track| track_key(track) == *key)
        })
    });
    let removed_before_current = unique
        .iter()
        .filter(|index| **index < old_queue_pos)
        .count();
    let was_loaded = state.player.playing;
    let was_paused = state.player.paused;

    for index in unique.iter().rev() {
        state.player.queue.remove(*index);
    }
    state.player.prefetched_pos = None;
    state.track_selection.clear();

    if state.player.queue.is_empty() {
        state.player = super::state::PlayerBar::default();
        state.queue_tab.cursor = 0;
        return QueueRemovalOutcome {
            restart_paused: None,
            stop: true,
        };
    }

    if current_removed {
        let desired = old_queue_pos.saturating_sub(removed_before_current);
        state.player.queue_pos = desired.min(state.player.queue.len() - 1);
        state.player.current = state.player.queue.get(state.player.queue_pos).cloned();
        state.player.position_secs = 0.0;
        state.player.track_started_at = None;
        state.queue_tab.cursor = state.queue_tab.cursor.min(state.player.queue.len() - 1);
        return QueueRemovalOutcome {
            restart_paused: was_loaded.then_some(was_paused),
            stop: false,
        };
    }

    if let Some(key) = current_key.as_ref() {
        if let Some(position) = state
            .player
            .queue
            .iter()
            .position(|track| track_key(track) == *key)
        {
            state.player.queue_pos = position;
        }
    } else {
        state.player.queue_pos = state.player.queue_pos.min(state.player.queue.len() - 1);
    }
    state.player.current = current_key.and_then(|key| {
        state
            .player
            .queue
            .iter()
            .find(|track| track_key(track) == key)
            .cloned()
    });
    state.queue_tab.cursor = state.queue_tab.cursor.min(state.player.queue.len() - 1);
    QueueRemovalOutcome {
        restart_paused: None,
        stop: false,
    }
}

/// The track under the cursor in whatever view is showing tracks.
pub fn selected_track(state: &AppState) -> Option<TrackItem> {
    match state.active_tab {
        Tab::Global => match state.global.stack.last()? {
            GlobalView::Artist { id, cursor } => match state.artist_views.get(id)? {
                Loadable::Ready(detail) => {
                    let tracks = detail.top_tracks.len();
                    if *cursor < tracks {
                        detail.top_tracks.get(*cursor).cloned()
                    } else {
                        let releases = artist_merged_releases(state, *id, detail).len();
                        cursor
                            .checked_sub(tracks + releases)
                            .and_then(|i| detail.featured_tracks.get(i).cloned())
                    }
                }
                _ => None,
            },
            GlobalView::Release { id, cursor } => match state.release_views.get(id)? {
                Loadable::Ready(detail) => detail.tracks.get(*cursor).cloned(),
                _ => None,
            },
            GlobalView::Search { cursor } => {
                let results = state.search.results.as_ref()?;
                let offset = cursor.checked_sub(results.artists.len() + results.releases.len())?;
                match results.tracks.get(offset) {
                    Some(track) => Some(track.clone()),
                    // Below the local tracks: the federated section.
                    None => {
                        let fed_offset = offset
                            .checked_sub(results.tracks.len() + state.search.fed_artists.len())?;
                        state
                            .search
                            .fed_tracks
                            .get(fed_offset)
                            .map(crate::federation::pending_track)
                    }
                }
            }
            GlobalView::FedArtist { cursor } => {
                let Some((_, Loadable::Ready(card))) = &state.fed_artist_view else {
                    return None;
                };
                let release_count = fed_artist_visible_release_indices(state, card).len();
                let appearance_indices = fed_artist_visible_appearance_indices(state, card);
                let index = cursor.checked_sub(release_count)?;
                appearance_indices
                    .get(index)
                    .and_then(|&appearance_index| card.appears_on.get(appearance_index))
                    .and_then(|appearance| {
                        fed_track_from_appearance(appearance, card.own_owner.as_deref())
                    })
                    .as_ref()
                    .map(crate::federation::pending_track)
            }
            GlobalView::FedRelease { index, cursor } => fed_release_tracks(state, *index)
                .into_iter()
                .nth(cursor.checked_sub(1)?)
                .as_ref()
                .map(crate::federation::pending_track),
        },
        Tab::Playlists => {
            let opened = state.playlists.opened.as_ref()?;
            playlist_tracks(state, opened.id)?
                .get(opened.cursor)
                .cloned()
        }
        Tab::Queue => state.player.queue.get(state.queue_tab.cursor).cloned(),
        Tab::Federation | Tab::Logs => None,
    }
}

/// Tracks backing an opened playlist, if loaded.
pub fn playlist_tracks(state: &AppState, id: i64) -> Option<&Vec<TrackItem>> {
    match state.playlist_views.get(&id)? {
        Loadable::Ready(detail) => Some(&detail.tracks),
        _ => None,
    }
}

/// A *release* under the cursor (artist-view tile/row or a search release).
fn selected_release_id(state: &AppState) -> Option<i64> {
    if state.active_tab != Tab::Global {
        return None;
    }
    match state.global.stack.last()? {
        GlobalView::Artist { id, cursor } => match state.artist_views.get(id)? {
            Loadable::Ready(detail) => {
                let position = cursor.checked_sub(detail.top_tracks.len())?;
                let merged = artist_merged_releases(state, *id, detail);
                let order = artist_release_display_order(&merged);
                order
                    .get(position)
                    .and_then(|&i| merged[i].local_index)
                    .map(|i| detail.releases[i].id)
            }
            _ => None,
        },
        GlobalView::Search { cursor } => {
            let results = state.search.results.as_ref()?;
            let offset = cursor.checked_sub(results.artists.len())?;
            results.releases.get(offset).map(|r| r.id)
        }
        GlobalView::Release { .. }
        | GlobalView::FedArtist { .. }
        | GlobalView::FedRelease { .. } => None,
    }
}

/// a / shift-a: queue the selection — a single track directly, a release via
/// an async fetch effect.
fn queue_add(state: &mut AppState, next: bool) -> Option<Effect> {
    let tracks = selected_tracks(state);
    if !tracks.is_empty() {
        let count = tracks.len();
        let title = tracks[0].title.clone();
        enqueue_tracks(state, tracks, next);
        state.track_selection.clear();
        state.status_message = Some(if count == 1 && next {
            format!("queued next: {title}")
        } else if count == 1 {
            format!("queued: {title}")
        } else if next {
            format!("queued next: {count} tracks")
        } else {
            format!("queued: {count} tracks")
        });
        return Some(Effect::PlaybackQueueChanged);
    }
    if let Some(id) = selected_release_id(state) {
        return Some(Effect::EnqueueRelease { id, next });
    }
    state.status_message = Some("nothing to queue here".into());
    None
}

/// Shift-J: open the release the track belongs to, with the cursor on that
/// track. If the release view is still loading, the focus is applied when
/// it arrives (`pending_release_focus`).
fn open_release_for_track(state: &mut AppState, track: &TrackItem) {
    if track.release_id < 0 {
        state.status_message = Some("this federated track has no local release".into());
        return;
    }
    let release_id = track.release_id;
    let cursor = match state.release_views.get(&release_id) {
        Some(Loadable::Ready(detail)) => detail
            .tracks
            .iter()
            .position(|t| t.id == track.id)
            .unwrap_or(0),
        _ => {
            state.pending_release_focus = Some((release_id, track.id));
            0
        }
    };
    let origin = state.active_tab;
    state.active_tab = Tab::Global;
    match state.global.stack.last_mut() {
        Some(GlobalView::Release {
            id,
            cursor: current,
        }) if *id == release_id => {
            *current = cursor;
        }
        _ => state.global.stack.push(GlobalView::Release {
            id: release_id,
            cursor,
        }),
    }
    // Jumps from another tab return there on Esc; jumps within Global
    // unwind the navigation stack as usual.
    if origin != Tab::Global {
        state.jump_origin = Some((origin, state.global.stack.len() - 1));
    }
}

/// Jumps to an artist page from anywhere: the local view when the artist is
/// in the library, the federated card otherwise. Returns the effect that
/// starts the federated fetch, if one is needed.
pub(crate) fn open_artist_ref(
    state: &mut AppState,
    artist: &crate::library::models::ArtistRef,
) -> Option<Effect> {
    let origin = state.active_tab;
    state.active_tab = Tab::Global;
    let effect = if artist.id >= 0 {
        match state.global.stack.last() {
            Some(GlobalView::Artist { id, .. }) if *id == artist.id => {}
            _ => state.global.stack.push(GlobalView::Artist {
                id: artist.id,
                cursor: 0,
            }),
        }
        None
    } else {
        state.fed_artist_view = Some((artist.name.clone(), Loadable::Loading));
        state.global.stack.push(GlobalView::FedArtist { cursor: 0 });
        Some(Effect::FedOpenArtist(artist.name.clone()))
    };
    if origin != Tab::Global {
        state.jump_origin = Some((origin, state.global.stack.len() - 1));
    }
    effect
}

/// The artists of a track as shown in the info popup: main artists first,
/// then featured, without duplicates.
pub(crate) fn track_artist_refs(track: &TrackItem) -> Vec<crate::library::models::ArtistRef> {
    let mut seen = std::collections::HashSet::new();
    let mut refs: Vec<crate::library::models::ArtistRef> = Vec::new();
    for artist in track.artists.iter().chain(track.featured_artists.iter()) {
        let key = music_dht::normalize_name(&artist.name);
        if key.is_empty() || !seen.insert(key) {
            continue;
        }
        refs.push(artist.clone());
    }
    refs
}

/// Insert tracks after the playing one (`next`) or at the end. Keeps the
/// gapless prefetch index pointing at the same track if items shift.
pub fn enqueue_tracks(state: &mut AppState, tracks: Vec<TrackItem>, next: bool) {
    let player = &mut state.player;
    if tracks.is_empty() {
        return;
    }
    let insert_at = if next && !player.queue.is_empty() {
        (player.queue_pos + 1).min(player.queue.len())
    } else if next {
        0
    } else {
        player.queue.len()
    };
    let count = tracks.len();
    for (offset, track) in tracks.into_iter().enumerate() {
        player.queue.insert(insert_at + offset, track);
    }
    if let Some(prefetched) = &mut player.prefetched_pos
        && insert_at <= *prefetched
    {
        *prefetched += count;
    }
    if insert_at <= player.queue_pos && player.current.is_some() {
        player.queue_pos += count;
    }
}

/// Manual queue navigation (n / p); the tail is pre-shuffled when shuffle
/// is on, so stepping is always sequential.
fn queue_step(state: &mut AppState, direction: isize) -> Option<Effect> {
    let player = &mut state.player;
    if player.queue.is_empty() {
        state.status_message = Some("queue is empty".into());
        return None;
    }
    let len = player.queue.len();
    let next = player.queue_pos as isize + direction;
    if next < 0 {
        player.queue_pos = 0;
    } else if next >= len as isize {
        if player.repeat == super::state::RepeatMode::All {
            player.queue_pos = 0;
        } else {
            state.status_message = Some("end of queue".into());
            return None;
        }
    } else {
        player.queue_pos = next as usize;
    }
    Some(Effect::PlayCurrent)
}

/// What plays after the current track, without mutating anything — used to
/// pick the gapless prefetch target. Mirrors `advance_after_finish`.
/// Shuffle needs no special case: the queue tail is already shuffled.
pub fn peek_next_pos(player: &super::state::PlayerBar) -> Option<usize> {
    if player.queue.is_empty() {
        return None;
    }
    match player.repeat {
        super::state::RepeatMode::One => Some(player.queue_pos),
        repeat => {
            if player.queue_pos + 1 < player.queue.len() {
                Some(player.queue_pos + 1)
            } else if repeat == super::state::RepeatMode::All {
                Some(0)
            } else {
                None
            }
        }
    }
}

/// The current track finished: play the next queue position (the tail is
/// pre-shuffled when shuffle is on), or stop at the end.
pub fn advance_after_finish(state: &mut AppState) -> Option<Effect> {
    let player = &mut state.player;
    if player.queue.is_empty() {
        player.playing = false;
        player.current = None;
        return None;
    }
    match player.repeat {
        super::state::RepeatMode::One => Some(Effect::PlayCurrent),
        repeat => {
            if player.queue_pos + 1 < player.queue.len() {
                player.queue_pos += 1;
                Some(Effect::PlayCurrent)
            } else if repeat == super::state::RepeatMode::All {
                player.queue_pos = 0;
                Some(Effect::PlayCurrent)
            } else {
                player.playing = false;
                player.paused = false;
                Some(Effect::StopPlayback)
            }
        }
    }
}

/// First index of the not-yet-played queue tail: everything after the
/// current track, or from the current position when nothing is loaded.
fn upcoming_start(player: &super::state::PlayerBar) -> usize {
    if player.current.is_some() {
        (player.queue_pos + 1).min(player.queue.len())
    } else {
        player.queue_pos.min(player.queue.len())
    }
}

/// Remember the original order and Fisher-Yates the unplayed tail.
pub fn shuffle_upcoming(player: &mut super::state::PlayerBar) {
    if player.queue.is_empty() {
        return;
    }
    if player.original_order.is_none() {
        player.original_order = Some(player.queue.iter().map(track_key).collect());
    }
    shuffle_range(player, upcoming_start(player));
}

/// Put the unplayed tail back into pre-shuffle order. Tracks queued while
/// shuffled (absent from the snapshot) keep their relative order at the end.
pub fn restore_queue_order(player: &mut super::state::PlayerBar) {
    let Some(order) = player.original_order.take() else {
        return;
    };
    let start = upcoming_start(player);
    if start >= player.queue.len() {
        return;
    }
    let tail = player.queue.split_off(start);
    let mut used = vec![false; order.len()];
    let mut keyed: Vec<(usize, usize, crate::library::models::TrackItem)> = tail
        .into_iter()
        .enumerate()
        .map(|(position, track)| {
            let key = order
                .iter()
                .enumerate()
                .position(|(slot, key)| !used[slot] && *key == track_key(&track))
                .inspect(|&slot| used[slot] = true)
                .unwrap_or(usize::MAX);
            (key, position, track)
        })
        .collect();
    keyed.sort_by_key(|(key, position, _)| (*key, *position));
    player
        .queue
        .extend(keyed.into_iter().map(|(_, _, track)| track));
    player.prefetched_pos = None;
}

/// Columns of the Global tile grid. Derived from the terminal width the same
/// way ui::global does (full width minus the surrounding block's borders),
/// so selection math and rendering agree.
pub fn grid_columns() -> usize {
    let width = crossterm::terminal::size().map(|(w, _)| w).unwrap_or(80);
    usize::from((width.saturating_sub(2) / TILE_WIDTH).max(1))
}

/// Lines of content visible in the main area (terminal height minus the tab
/// bar, status bar and the view's borders).
fn viewport_lines() -> isize {
    let height = crossterm::terminal::size().map(|(_, h)| h).unwrap_or(24);
    height.saturating_sub(5).max(1) as isize
}

/// One PageUp/PageDown step in MoveUp/MoveDown units for the current view:
/// move_selection() multiplies vertical steps by the column count in tile
/// zones, so tile views page by visible tile rows, line views by visible
/// lines.
fn page_step(state: &AppState) -> isize {
    let lines = viewport_lines();
    if state.active_tab != Tab::Global {
        return lines;
    }
    let tile_rows = (lines / TILE_HEIGHT as isize).max(1);
    match state.global.stack.last() {
        None => match state.global.view {
            ViewMode::Tiles => tile_rows,
            ViewMode::Table => lines,
        },
        Some(GlobalView::Artist { id, cursor }) => {
            let in_release_tiles = match state.artist_views.get(id) {
                Some(Loadable::Ready(detail)) => {
                    let releases = artist_merged_releases(state, *id, detail).len();
                    *cursor >= detail.top_tracks.len()
                        && *cursor < detail.top_tracks.len() + releases
                }
                _ => false,
            };
            if in_release_tiles && state.global.view == ViewMode::Tiles {
                tile_rows
            } else {
                lines
            }
        }
        Some(GlobalView::Release { .. })
        | Some(GlobalView::Search { .. })
        | Some(GlobalView::FedRelease { .. }) => lines,
        Some(GlobalView::FedArtist { cursor }) => {
            let in_release_tiles = match &state.fed_artist_view {
                Some((_, Loadable::Ready(card))) => {
                    *cursor < fed_artist_visible_release_indices(state, card).len()
                }
                _ => false,
            };
            if in_release_tiles { tile_rows } else { lines }
        }
    }
}

fn move_selection(state: &mut AppState, dx: isize, dy: isize) {
    if state.active_tab == Tab::Federation {
        if dy != 0 {
            let last = settings_rows(state).len() as isize - 1;
            state.settings_cursor = (state.settings_cursor as isize + dy).clamp(0, last) as usize;
        }
        return;
    }
    if state.active_tab == Tab::Logs {
        // The cursor anchors to an entry's seq, so freshly appended log
        // lines (including ones caused by this very keypress) don't shift
        // the selection.
        if dy != 0 {
            let level = super::state::LOG_LEVELS[state.logs.level_index];
            if let Some(buffer) = crate::config::logging::buffer() {
                let current = if state.logs.follow {
                    None
                } else {
                    state.logs.selected_seq
                };
                if let Some((seq, is_newest)) = buffer.move_selection(level, current, dy) {
                    state.logs.selected_seq = Some(seq);
                    state.logs.follow = is_newest && dy > 0;
                }
            }
        }
        return;
    }
    if state.track_selection.is_active()
        && dx == 0
        && let Some((scope, cursor, len)) = current_track_list_context(state)
    {
        if len == 0 {
            return;
        }
        let next = (cursor as isize + dy).clamp(0, len as isize - 1) as usize;
        set_track_scope_cursor(state, &scope, next);
        refresh_track_selection_cursor(state);
        return;
    }
    if state.active_tab == Tab::Playlists {
        let len = playlists_view_len(state);
        if len == 0 {
            return;
        }
        let last = len as isize - 1;
        match &mut state.playlists.opened {
            Some(opened) => {
                opened.cursor = (opened.cursor as isize + dy).clamp(0, last) as usize;
                refresh_track_selection_cursor(state);
            }
            None => {
                state.playlists.selected =
                    (state.playlists.selected as isize + dy).clamp(0, last) as usize;
                state.track_selection.clear();
            }
        }
        return;
    }
    if state.active_tab == Tab::Queue {
        let len = state.player.queue.len();
        if len == 0 {
            return;
        }
        state.queue_tab.cursor =
            (state.queue_tab.cursor as isize + dy).clamp(0, len as isize - 1) as usize;
        refresh_track_selection_cursor(state);
        return;
    }
    if state.active_tab != Tab::Global {
        return not_yet(state, "Navigation in this view");
    }
    match state.global.stack.last().copied() {
        None => {
            let global = &mut state.global;
            if global.artists.is_empty() {
                return;
            }
            let step = match global.view {
                ViewMode::Tiles => dx + dy * grid_columns() as isize,
                ViewMode::Table => dy,
            };
            let last = global.artists.len() as isize - 1;
            global.selected = (global.selected as isize + step).clamp(0, last) as usize;
            state.track_selection.clear();
        }
        Some(GlobalView::Artist { id, cursor }) => {
            let Some(Loadable::Ready(detail)) = state.artist_views.get(&id) else {
                return;
            };
            let merged = artist_merged_releases(state, id, detail);
            let tracks = detail.top_tracks.len();
            let releases = merged.len();
            let featured = detail.featured_tracks.len();
            let total = tracks + releases + featured;
            if total == 0 {
                return;
            }
            let in_release_tiles = state.global.view == ViewMode::Tiles
                && cursor >= tracks
                && cursor < tracks + releases;
            let next = if !in_release_tiles {
                // List zones (top tracks, featured tracks; releases in
                // table mode): plain vertical steps cross zone boundaries
                // in flat order.
                (cursor as isize + dy).clamp(0, total as isize - 1) as usize
            } else {
                // Release tiles: move by visual rows (groups break rows),
                // keeping the column, so Up lands on the tile above.
                let rows = artist_release_rows(&merged, grid_columns());
                let position = cursor - tracks;
                let (row, column) = rows
                    .iter()
                    .enumerate()
                    .find_map(|(r, items)| {
                        items.iter().position(|p| *p == position).map(|c| (r, c))
                    })
                    .unwrap_or((0, 0));
                if dx != 0 {
                    let last = releases as isize - 1;
                    tracks + (position as isize + dx).clamp(0, last) as usize
                } else {
                    let target = row as isize + dy;
                    if target < 0 {
                        if tracks > 0 { tracks - 1 } else { cursor }
                    } else if target as usize >= rows.len() {
                        // Below the last release row: the featured section.
                        if featured > 0 {
                            tracks + releases
                        } else {
                            cursor
                        }
                    } else {
                        let items = &rows[target as usize];
                        tracks + items[column.min(items.len() - 1)]
                    }
                }
            };
            set_view_cursor(state, next);
            state.track_selection.clear();
        }
        Some(GlobalView::Release { id, cursor }) => {
            let Some(Loadable::Ready(detail)) = state.release_views.get(&id) else {
                return;
            };
            let total = detail.tracks.len() as isize;
            if total == 0 {
                return;
            }
            let next = (cursor as isize + dy).clamp(0, total - 1);
            set_view_cursor(state, next as usize);
            refresh_track_selection_cursor(state);
        }
        Some(GlobalView::Search { cursor }) => {
            // Local results plus the federated section below them.
            let total = (state.search.results.as_ref().map_or(0, |r| r.len())
                + state.search.fed_artists.len()
                + state.search.fed_tracks.len()) as isize;
            if total == 0 {
                return;
            }
            let next = (cursor as isize + dy).clamp(0, total - 1);
            set_view_cursor(state, next as usize);
            state.track_selection.clear();
        }
        Some(GlobalView::FedArtist { cursor }) => {
            let Some((_, Loadable::Ready(card))) = &state.fed_artist_view else {
                return;
            };
            let release_indices = fed_artist_visible_release_indices(state, card);
            let releases = release_indices.len();
            let appears_on = fed_artist_visible_appearance_indices(state, card).len();
            let total = (releases + appears_on) as isize;
            if total == 0 {
                return;
            }
            let in_release_tiles = cursor < releases;
            let next = if !in_release_tiles {
                (cursor as isize + dy).clamp(0, total - 1) as usize
            } else {
                let visible_releases: Vec<_> = release_indices
                    .iter()
                    .map(|&index| card.releases[index].clone())
                    .collect();
                let rows = fed_release_rows(&visible_releases, grid_columns());
                let (row, column) = rows
                    .iter()
                    .enumerate()
                    .find_map(|(r, items)| items.iter().position(|p| *p == cursor).map(|c| (r, c)))
                    .unwrap_or((0, 0));
                if dx != 0 {
                    (cursor as isize + dx).clamp(0, releases as isize - 1) as usize
                } else {
                    let target = row as isize + dy;
                    if target < 0 {
                        cursor
                    } else if target as usize >= rows.len() {
                        if appears_on > 0 { releases } else { cursor }
                    } else {
                        let items = &rows[target as usize];
                        items[column.min(items.len() - 1)]
                    }
                }
            };
            set_view_cursor(state, next as usize);
            state.track_selection.clear();
        }
        Some(GlobalView::FedRelease { index, cursor }) => {
            let tracks = fed_card_release(state, index)
                .map_or(0, |r| fed_release_visible_track_indices(state, r).len())
                as isize;
            // Row 0 is the download button, 1..=tracks are the tracks.
            let next = (cursor as isize + dy).clamp(0, tracks);
            set_view_cursor(state, next as usize);
            refresh_track_selection_cursor(state);
        }
    }
}

/// Selectable rows of the open federated artist card: releases, then appearances.
pub(crate) fn fed_card_len(state: &AppState) -> usize {
    match &state.fed_artist_view {
        Some((_, Loadable::Ready(card))) => {
            fed_artist_visible_release_indices(state, card).len()
                + fed_artist_visible_appearance_indices(state, card).len()
        }
        _ => 0,
    }
}

fn set_view_cursor(state: &mut AppState, value: usize) {
    if let Some(view) = state.global.stack.last_mut() {
        match view {
            GlobalView::Artist { cursor, .. }
            | GlobalView::Release { cursor, .. }
            | GlobalView::Search { cursor }
            | GlobalView::FedArtist { cursor }
            | GlobalView::FedRelease { cursor, .. } => *cursor = value,
        }
    }
}

/// Items in the playlists tab's current view (list or opened playlist).
fn playlists_view_len(state: &AppState) -> usize {
    match &state.playlists.opened {
        Some(opened) => playlist_tracks(state, opened.id).map_or(0, Vec::len),
        None => match &state.playlists.list {
            Some(Loadable::Ready(list)) => list.len(),
            _ => 0,
        },
    }
}

fn current_view_len(state: &AppState) -> usize {
    if state.active_tab == Tab::Playlists {
        return playlists_view_len(state);
    }
    if state.active_tab == Tab::Queue {
        return state.player.queue.len();
    }
    if state.active_tab == Tab::Federation {
        return settings_rows(state).len();
    }
    match state.global.stack.last() {
        None => state.global.artists.len(),
        Some(GlobalView::Artist { id, .. }) => match state.artist_views.get(id) {
            Some(Loadable::Ready(d)) => {
                let releases = artist_merged_releases(state, *id, d).len();
                d.top_tracks.len() + releases + d.featured_tracks.len()
            }
            _ => 0,
        },
        Some(GlobalView::Release { id, .. }) => match state.release_views.get(id) {
            Some(Loadable::Ready(d)) => d.tracks.len(),
            _ => 0,
        },
        Some(GlobalView::Search { .. }) => {
            state.search.results.as_ref().map_or(0, |r| r.len())
                + state.search.fed_artists.len()
                + state.search.fed_tracks.len()
        }
        Some(GlobalView::FedArtist { .. }) => fed_card_len(state),
        Some(GlobalView::FedRelease { index, .. }) => fed_card_release(state, *index)
            .map_or(0, |r| fed_release_visible_track_indices(state, r).len() + 1),
    }
}

pub(crate) fn apply_library_filter_change(state: &mut AppState) {
    state.track_selection.clear();
    let len = current_view_len(state);
    if state.active_tab == Tab::Global {
        if state.global.stack.is_empty() {
            state.global.selected = state.global.selected.min(len.saturating_sub(1));
        } else if let Some(view) = state.global.stack.last_mut() {
            let cursor = match view {
                GlobalView::Artist { cursor, .. }
                | GlobalView::Release { cursor, .. }
                | GlobalView::Search { cursor }
                | GlobalView::FedArtist { cursor }
                | GlobalView::FedRelease { cursor, .. } => cursor,
            };
            *cursor = (*cursor).min(len.saturating_sub(1));
        }
    }

    if state.global.filters.source_mode.includes_network() {
        return;
    }
    let message = match state.global.stack.last() {
        Some(GlobalView::Artist { id, .. }) => match state.artist_views.get(id) {
            Some(Loadable::Ready(detail))
                if detail.top_tracks.is_empty()
                    && artist_merged_releases(state, *id, detail).is_empty()
                    && detail.featured_tracks.is_empty() =>
            {
                Some(format!(
                    "local filter: \"{}\" is not available locally",
                    detail.name
                ))
            }
            _ => None,
        },
        Some(GlobalView::FedArtist { .. }) if fed_card_len(state) == 0 => {
            let name = state
                .fed_artist_view
                .as_ref()
                .map(|(name, _)| name.as_str())
                .unwrap_or("artist");
            Some(format!("local filter: \"{name}\" is not available locally"))
        }
        Some(GlobalView::FedRelease { index, .. })
            if fed_release_tracks(state, *index).is_empty() =>
        {
            Some("local filter: release is not available locally".to_string())
        }
        _ => None,
    };
    if let Some(message) = message {
        state.status_message = Some(message);
    }
}

fn jump_selection(state: &mut AppState, first: bool) {
    if state.track_selection.is_active()
        && let Some((scope, _, len)) = current_track_list_context(state)
    {
        if len > 0 {
            let target = if first { 0 } else { len - 1 };
            set_track_scope_cursor(state, &scope, target);
            refresh_track_selection_cursor(state);
        }
        return;
    }
    if state.active_tab == Tab::Queue {
        let len = state.player.queue.len();
        if len > 0 {
            state.queue_tab.cursor = if first { 0 } else { len - 1 };
            refresh_track_selection_cursor(state);
        }
        return;
    }
    if state.active_tab == Tab::Federation {
        let last = settings_rows(state).len().saturating_sub(1);
        state.settings_cursor = if first { 0 } else { last };
        return;
    }
    if state.active_tab == Tab::Logs {
        if first {
            let level = super::state::LOG_LEVELS[state.logs.level_index];
            if let Some(buffer) = crate::config::logging::buffer()
                && let Some((seq, _)) = buffer.move_selection(level, None, isize::MIN)
            {
                state.logs.selected_seq = Some(seq);
                state.logs.follow = false;
            }
        } else {
            state.logs.follow = true;
            state.logs.selected_seq = None;
        }
        return;
    }
    if state.active_tab != Tab::Global && state.active_tab != Tab::Playlists {
        return not_yet(state, "Navigation in this view");
    }
    let len = current_view_len(state);
    if len == 0 {
        return;
    }
    let target = if first { 0 } else { len - 1 };
    if state.active_tab == Tab::Playlists {
        match &mut state.playlists.opened {
            Some(opened) => opened.cursor = target,
            None => state.playlists.selected = target,
        }
        refresh_track_selection_cursor(state);
    } else if state.global.stack.is_empty() {
        state.global.selected = target;
        state.track_selection.clear();
    } else {
        set_view_cursor(state, target);
        refresh_track_selection_cursor(state);
    }
}

/// Enter on the Playlists tab: open a playlist from the list, or play the
/// selected track with the playlist as the queue.
fn select_playlist(state: &mut AppState) -> Option<Effect> {
    match state.playlists.opened {
        Some(opened) => {
            let tracks = playlist_tracks(state, opened.id)?.clone();
            if tracks.is_empty() {
                return None;
            }
            state.player.queue = tracks;
            state.player.queue_pos = opened.cursor.min(state.player.queue.len() - 1);
            on_new_queue(state);
            Some(Effect::PlayCurrent)
        }
        None => {
            let id = match &state.playlists.list {
                Some(Loadable::Ready(list)) => list.get(state.playlists.selected)?.id,
                _ => return None,
            };
            state.playlists.opened = Some(OpenedPlaylist { id, cursor: 0 });
            None
        }
    }
}

/// Enter: drill down (grid → artist → release) or play the selected track
/// with its surrounding list as the queue.
fn select_current(state: &mut AppState) -> Option<Effect> {
    if state.active_tab == Tab::Playlists {
        return select_playlist(state);
    }
    // Logs: open the full, wrapped entry under the cursor.
    if state.active_tab == Tab::Logs {
        let level = super::state::LOG_LEVELS[state.logs.level_index];
        if let Some(buffer) = crate::config::logging::buffer() {
            let selected = if state.logs.follow {
                None
            } else {
                state.logs.selected_seq
            };
            if let Some(entry) = buffer.entry_at(level, selected) {
                state.popup = Some(super::state::Popup::LogDetail(entry));
            }
        }
        return None;
    }
    if state.active_tab == Tab::Federation {
        return federation_select(state);
    }
    // Queue: jump playback to the track under the cursor. Earlier tracks
    // stay in the queue as "played"; picking one of them just moves the
    // playing position back.
    if state.active_tab == Tab::Queue {
        if state.player.queue.is_empty() {
            return None;
        }
        state.player.queue_pos = state.queue_tab.cursor.min(state.player.queue.len() - 1);
        return Some(Effect::PlayCurrent);
    }
    if state.active_tab != Tab::Global {
        not_yet(state, "Navigation in this view");
        return None;
    }
    let outcome = match state.global.stack.last().copied() {
        None => match state.global.artists.get(state.global.selected) {
            Some(artist) if artist.id >= 0 => Outcome::Push(GlobalView::Artist {
                id: artist.id,
                cursor: 0,
            }),
            Some(artist) => Outcome::OpenFedArtist(artist.name.clone()),
            None => Outcome::Nothing,
        },
        Some(GlobalView::Artist { id, cursor }) => match state.artist_views.get(&id) {
            Some(Loadable::Ready(detail)) => {
                let tracks = detail.top_tracks.len();
                let releases = artist_merged_releases(state, id, detail);
                let releases_len = releases.len();
                if cursor < tracks {
                    Outcome::Play {
                        tracks: detail.top_tracks.clone(),
                        start: cursor,
                    }
                } else if cursor < tracks + releases_len {
                    let order = artist_release_display_order(&releases);
                    match order.get(cursor - tracks) {
                        Some(&original) => {
                            let slot = &releases[original];
                            if slot.availability.is_remoteish()
                                && let Some(index) = slot.fed_index
                                && let Some(card) =
                                    crate::app::state::artist_fed_card(state, id).cloned()
                            {
                                Outcome::OpenFedRelease {
                                    name: detail.name.clone(),
                                    card,
                                    index,
                                }
                            } else if let Some(index) = slot.local_index {
                                Outcome::Push(GlobalView::Release {
                                    id: detail.releases[index].id,
                                    cursor: 0,
                                })
                            } else if let Some(index) = slot.fed_index
                                && let Some(card) =
                                    crate::app::state::artist_fed_card(state, id).cloned()
                            {
                                Outcome::OpenFedRelease {
                                    name: detail.name.clone(),
                                    card,
                                    index,
                                }
                            } else {
                                Outcome::Nothing
                            }
                        }
                        None => Outcome::Nothing,
                    }
                } else if detail
                    .featured_tracks
                    .get(cursor - tracks - releases_len)
                    .is_some()
                {
                    Outcome::Play {
                        tracks: detail.featured_tracks.clone(),
                        start: cursor - tracks - releases_len,
                    }
                } else {
                    Outcome::Nothing
                }
            }
            _ => Outcome::Nothing,
        },
        Some(GlobalView::Release { id, cursor }) => match state.release_views.get(&id) {
            Some(Loadable::Ready(detail)) if !detail.tracks.is_empty() => Outcome::Play {
                tracks: detail.tracks.clone(),
                start: cursor.min(detail.tracks.len() - 1),
            },
            _ => Outcome::Nothing,
        },
        Some(GlobalView::Search { cursor }) => match &state.search.results {
            Some(results) => {
                let artists = results.artists.len();
                let releases = results.releases.len();
                if cursor < artists {
                    Outcome::Push(GlobalView::Artist {
                        id: results.artists[cursor].id,
                        cursor: 0,
                    })
                } else if cursor < artists + releases {
                    Outcome::Push(GlobalView::Release {
                        id: results.releases[cursor - artists].id,
                        cursor: 0,
                    })
                } else if results.tracks.get(cursor - artists - releases).is_some() {
                    Outcome::Play {
                        tracks: results.tracks.clone(),
                        start: cursor - artists - releases,
                    }
                } else {
                    fed_outcome(state, cursor - artists - releases - results.tracks.len())
                }
            }
            None => fed_outcome(state, cursor),
        },
        Some(GlobalView::FedArtist { cursor }) => match &state.fed_artist_view {
            Some((_, Loadable::Ready(card))) => {
                let release_indices = fed_artist_visible_release_indices(state, card);
                if cursor < release_indices.len() {
                    let visible_releases: Vec<_> = release_indices
                        .iter()
                        .map(|&index| card.releases[index].clone())
                        .collect();
                    let order = fed_release_display_order(&visible_releases);
                    let Some(&visible_index) = order.get(cursor) else {
                        return None;
                    };
                    let Some(&release_index) = release_indices.get(visible_index) else {
                        return None;
                    };
                    // Focus starts on the first track; Up from it reaches the
                    // download-release button (row 0).
                    let start =
                        if fed_release_visible_track_indices(state, &card.releases[release_index])
                            .is_empty()
                        {
                            0
                        } else {
                            1
                        };
                    Outcome::Push(GlobalView::FedRelease {
                        index: release_index,
                        cursor: start,
                    })
                } else {
                    let appearance_indices = fed_artist_visible_appearance_indices(state, card);
                    let start = cursor - release_indices.len();
                    if appearance_indices.get(start).is_none() {
                        Outcome::Nothing
                    } else {
                        let tracks: Vec<_> = appearance_indices
                            .iter()
                            .filter_map(|&appearance_index| card.appears_on.get(appearance_index))
                            .filter_map(|appearance| {
                                fed_track_from_appearance(appearance, card.own_owner.as_deref())
                            })
                            .map(|fed| crate::federation::pending_track(&fed))
                            .collect();
                        if tracks.is_empty() {
                            Outcome::Nothing
                        } else {
                            Outcome::Play { tracks, start }
                        }
                    }
                }
            }
            _ => Outcome::Nothing,
        },
        Some(GlobalView::FedRelease { index, cursor }) => match fed_card_release(state, index) {
            Some(_) if cursor == 0 => {
                // The download-whole-release button.
                match fed_release_tracks(state, index) {
                    tracks if tracks.is_empty() => Outcome::Nothing,
                    tracks => Outcome::DownloadFed(tracks),
                }
            }
            Some(_) => {
                // Play the whole release starting at the selected track,
                // exactly like a local release view.
                let tracks: Vec<_> = fed_release_tracks(state, index)
                    .iter()
                    .map(crate::federation::pending_track)
                    .collect();
                if tracks.is_empty() || cursor > tracks.len() {
                    Outcome::Nothing
                } else {
                    Outcome::Play {
                        tracks,
                        start: cursor - 1,
                    }
                }
            }
            None => Outcome::Nothing,
        },
    };
    match outcome {
        Outcome::Push(view) => {
            state.global.stack.push(view);
            None
        }
        Outcome::Play { tracks, start } => {
            state.player.queue = tracks;
            state.player.queue_pos = start;
            on_new_queue(state);
            Some(Effect::PlayCurrent)
        }
        Outcome::OpenFedArtist(name) => {
            state.fed_artist_view = Some((name.clone(), Loadable::Loading));
            state.global.stack.push(GlobalView::FedArtist { cursor: 0 });
            state.active_tab = Tab::Global;
            Some(Effect::FedOpenArtist(name))
        }
        Outcome::OpenFedRelease { name, card, index } => {
            let start =
                if card.releases.get(index).is_some_and(|release| {
                    fed_release_visible_track_indices(state, release).is_empty()
                }) {
                    0
                } else {
                    1
                };
            state.fed_artist_view = Some((name, Loadable::Ready(card)));
            state.global.stack.push(GlobalView::FedRelease {
                index,
                cursor: start,
            });
            state.active_tab = Tab::Global;
            None
        }
        Outcome::DownloadFed(tracks) => {
            state.status_message = Some(format!(
                "federation: downloading {} track(s) to the library…",
                tracks.len()
            ));
            Some(Effect::FedDownload { tracks })
        }
        Outcome::Nothing => None,
    }
}

/// The open card's release by index.
pub(crate) fn fed_card_release(
    state: &AppState,
    index: usize,
) -> Option<&crate::federation::FedRelease> {
    match &state.fed_artist_view {
        Some((_, Loadable::Ready(card))) => card.releases.get(index),
        _ => None,
    }
}

/// Every visible track of one card release as playable FedTracks.
pub(crate) fn fed_release_tracks(
    state: &AppState,
    index: usize,
) -> Vec<crate::federation::FedTrack> {
    let Some((name, Loadable::Ready(card))) = &state.fed_artist_view else {
        return Vec::new();
    };
    let Some(release) = card.releases.get(index) else {
        return Vec::new();
    };
    release
        .tracks
        .iter()
        .filter(|track| crate::app::state::fed_card_track_visible(state, track))
        .filter_map(|track| fed_track_from_card(name, release, track, card.own_owner.as_deref()))
        .collect()
}

pub(crate) fn fed_appears_on_tracks(state: &AppState) -> Vec<crate::federation::FedTrack> {
    let Some((_, Loadable::Ready(card))) = &state.fed_artist_view else {
        return Vec::new();
    };
    card.appears_on
        .iter()
        .filter(|appearance| crate::app::state::fed_appearance_visible(state, appearance))
        .filter_map(|appearance| fed_track_from_appearance(appearance, card.own_owner.as_deref()))
        .collect()
}

/// Federated tracks covered by the active visual selection, or the single
/// one under the cursor in a federated context.
pub(crate) fn selected_fed_tracks(state: &AppState) -> Vec<crate::federation::FedTrack> {
    // Federated cursors and selections live in Global-tab views only; on any
    // other tab a stale Global cursor must not shadow that tab's own
    // selection (e.g. `i` on a queue or playlist track).
    if state.active_tab != Tab::Global {
        return Vec::new();
    }
    // An active Shift-V range in a federated scope.
    if let Some(scope) = state.track_selection.scope.clone() {
        match scope {
            TrackSelectionScope::FedSearch => {
                let len = state.search.fed_tracks.len();
                if let Some(indices) = state.track_selection.indices(&scope, len) {
                    return indices
                        .into_iter()
                        .filter_map(|i| state.search.fed_tracks.get(i).cloned())
                        .collect();
                }
            }
            TrackSelectionScope::FedRelease(index) => {
                let all = fed_release_tracks(state, index);
                if let Some(indices) = state.track_selection.indices(&scope, all.len()) {
                    return indices
                        .into_iter()
                        .filter_map(|i| all.get(i).cloned())
                        .collect();
                }
            }
            TrackSelectionScope::FedAppearsOn => {
                let all = fed_appears_on_tracks(state);
                if let Some(indices) = state.track_selection.indices(&scope, all.len()) {
                    return indices
                        .into_iter()
                        .filter_map(|i| all.get(i).cloned())
                        .collect();
                }
            }
            _ => {}
        }
    }
    // No selection: the federated track under the cursor.
    match state.global.stack.last() {
        Some(GlobalView::Search { cursor }) => {
            let base = state.search.results.as_ref().map_or(0, |r| r.len())
                + state.search.fed_artists.len();
            cursor
                .checked_sub(base)
                .and_then(|i| state.search.fed_tracks.get(i).cloned())
                .into_iter()
                .collect()
        }
        Some(GlobalView::FedRelease { index, cursor }) => cursor
            .checked_sub(1)
            .and_then(|i| fed_release_tracks(state, *index).into_iter().nth(i))
            .into_iter()
            .collect(),
        Some(GlobalView::FedArtist { cursor }) => {
            let Some((_, Loadable::Ready(card))) = &state.fed_artist_view else {
                return Vec::new();
            };
            let release_count = fed_artist_visible_release_indices(state, card).len();
            cursor
                .checked_sub(release_count)
                .and_then(|i| fed_appears_on_tracks(state).into_iter().nth(i))
                .into_iter()
                .collect()
        }
        _ => Vec::new(),
    }
}

fn selected_downloadable_fed_tracks(state: &AppState) -> Vec<crate::federation::FedTrack> {
    let mut tracks = Vec::new();
    for track in selected_tracks(state) {
        if let Some(fed) = fed_track_for_download(&track)
            && !tracks
                .iter()
                .any(|existing| same_fed_download(existing, &fed))
        {
            tracks.push(fed);
        }
    }
    for fed in selected_fed_tracks(state) {
        if !tracks
            .iter()
            .any(|existing| same_fed_download(existing, &fed))
        {
            tracks.push(fed);
        }
    }
    tracks
}

fn fed_track_for_download(track: &TrackItem) -> Option<crate::federation::FedTrack> {
    if let Some(fed) = &track.fed {
        return Some(fed.clone());
    }
    let content_id = track
        .content_id
        .as_deref()
        .and_then(music_dht::normalize_content_id)?;
    Some(crate::federation::FedTrack {
        item_id: String::new(),
        owner: String::new(),
        own: false,
        title: track.title.clone(),
        artist_names: track
            .artists
            .iter()
            .map(|artist| artist.name.clone())
            .collect(),
        featured_artist_names: track
            .featured_artists
            .iter()
            .map(|artist| artist.name.clone())
            .collect(),
        year: track.release_year,
        duration_seconds: (track.duration_seconds > 0.0)
            .then(|| track.duration_seconds.round().max(0.0) as i64),
        content_id: Some(content_id),
        release_title: (!track.release_title.trim().is_empty())
            .then(|| track.release_title.clone()),
        track_number: track.track_number,
        disc_number: track.disc_number,
    })
}

fn same_fed_download(
    left: &crate::federation::FedTrack,
    right: &crate::federation::FedTrack,
) -> bool {
    let left_content = left
        .content_id
        .as_deref()
        .and_then(music_dht::normalize_content_id);
    let right_content = right
        .content_id
        .as_deref()
        .and_then(music_dht::normalize_content_id);
    if left_content.is_some() && left_content == right_content {
        return true;
    }
    !left.owner.is_empty()
        && !left.item_id.is_empty()
        && left.owner == right.owner
        && left.item_id == right.item_id
}

/// What Enter resolved to in the current view.
enum Outcome {
    Push(GlobalView),
    Play {
        tracks: Vec<crate::library::models::TrackItem>,
        start: usize,
    },
    OpenFedArtist(String),
    OpenFedRelease {
        name: String,
        card: crate::federation::FedArtistCard,
        index: usize,
    },
    DownloadFed(Vec<crate::federation::FedTrack>),
    Nothing,
}

/// Enter inside the federated section of the search results: artists open
/// their card, tracks queue up like a local track list.
fn fed_outcome(state: &AppState, fed_index: usize) -> Outcome {
    let artists = &state.search.fed_artists;
    if fed_index < artists.len() {
        return Outcome::OpenFedArtist(artists[fed_index].name.clone());
    }
    let start = fed_index - artists.len();
    if start >= state.search.fed_tracks.len() {
        return Outcome::Nothing;
    }
    Outcome::Play {
        tracks: state
            .search
            .fed_tracks
            .iter()
            .map(crate::federation::pending_track)
            .collect(),
        start,
    }
}

/// A playable FedTrack out of a card row (first source; the rest are
/// fallbacks for a later improvement).
fn fed_track_from_card(
    artist: &str,
    release: &crate::federation::FedRelease,
    track: &crate::federation::FedCardTrack,
    own_owner: Option<&str>,
) -> Option<crate::federation::FedTrack> {
    let (owner, item_id) = track.sources.first()?.clone();
    let own = own_owner == Some(owner.as_str());
    Some(crate::federation::FedTrack {
        item_id,
        owner,
        own,
        title: track.title.clone(),
        artist_names: fed_card_main_artist_names(track, Some(artist)),
        featured_artist_names: fed_card_featured_artist_names(track),
        year: release.year,
        duration_seconds: track.duration_seconds.map(|d| d.round() as i64),
        content_id: track.content_id.clone(),
        release_title: Some(release.title.clone()),
        track_number: track.track_number,
        disc_number: track.disc_number,
    })
}

fn fed_track_from_appearance(
    appearance: &crate::federation::FedAppearsOn,
    own_owner: Option<&str>,
) -> Option<crate::federation::FedTrack> {
    let (owner, item_id) = appearance.track.sources.first()?.clone();
    let own = own_owner == Some(owner.as_str());
    Some(crate::federation::FedTrack {
        item_id,
        owner,
        own,
        title: appearance.track.title.clone(),
        artist_names: fed_card_main_artist_names(&appearance.track, None),
        featured_artist_names: fed_card_featured_artist_names(&appearance.track),
        year: appearance.year,
        duration_seconds: appearance.track.duration_seconds.map(|d| d.round() as i64),
        content_id: appearance.track.content_id.clone(),
        release_title: (!appearance.release_title.is_empty())
            .then(|| appearance.release_title.clone()),
        track_number: appearance.track.track_number,
        disc_number: appearance.track.disc_number,
    })
}

fn fed_card_main_artist_names(
    track: &crate::federation::FedCardTrack,
    fallback: Option<&str>,
) -> Vec<String> {
    if track.artists.is_empty() {
        fallback.into_iter().map(str::to_string).collect()
    } else {
        track.artists.clone()
    }
}

fn fed_card_featured_artist_names(track: &crate::federation::FedCardTrack) -> Vec<String> {
    let mut names: Vec<String> = Vec::new();
    for artist in &track.featured_artists {
        if !names
            .iter()
            .any(|name| music_dht::normalize_name(name) == music_dht::normalize_name(artist))
        {
            names.push(artist.clone());
        }
    }
    names
}

/// Enter on Settings: toggle switches, open text inputs, run
/// one-shot operations. The heavy lifting happens in perform_effect().
fn federation_select(state: &mut AppState) -> Option<Effect> {
    use super::state::{FedInputField, FedRow, Popup, SettingsRow};
    match settings_rows(state).get(state.settings_cursor).copied()? {
        SettingsRow::Federation(FedRow::Toggle) => {
            let settings = &mut state.federation.settings;
            if !settings.enabled && settings.network_id.trim().is_empty() {
                state.popup = Some(Popup::FedInput {
                    field: FedInputField::NetworkId,
                    input: crate::app::input::LineEdit::default(),
                });
                return None;
            }
            settings.enabled = !settings.enabled;
            Some(Effect::FedApplySettings)
        }
        SettingsRow::Federation(FedRow::NetworkId) => {
            state.popup = Some(Popup::FedInput {
                field: FedInputField::NetworkId,
                input: crate::app::input::LineEdit::new(
                    state.federation.settings.network_id.clone(),
                ),
            });
            None
        }
        SettingsRow::Federation(FedRow::SaveOnListen) => {
            state.federation.settings.save_on_listen = !state.federation.settings.save_on_listen;
            Some(Effect::FedApplySettings)
        }
        SettingsRow::Federation(FedRow::SyncNow) => Some(Effect::FedSyncNow),
        SettingsRow::Federation(FedRow::ShowTicket) => Some(Effect::FedShowTicket),
        SettingsRow::Federation(FedRow::Connect) => {
            state.popup = Some(Popup::FedInput {
                field: FedInputField::ConnectTicket,
                input: crate::app::input::LineEdit::default(),
            });
            None
        }
        SettingsRow::StatusDetails => {
            state.popup = Some(Popup::FederationStatusDetails {
                focus: super::state::StatusDetailFocus::Status,
                status_cursor: 0,
                devices_scroll: 0,
                logs_scroll: 0,
            });
            None
        }
        SettingsRow::DeviceName => {
            if !require_connected_devices_enabled(state) {
                return None;
            }
            let name = state
                .federation
                .devices
                .as_ref()
                .map(|status| status.this_device_name.clone())
                .unwrap_or_default();
            state.popup = Some(Popup::FedInput {
                field: FedInputField::DeviceName,
                input: crate::app::input::LineEdit::new(name),
            });
            None
        }
        SettingsRow::DeviceInvite => {
            if !require_connected_devices_enabled(state) {
                return None;
            }
            Some(Effect::DeviceShowInvite)
        }
        SettingsRow::DeviceConnect => {
            if !require_connected_devices_enabled(state) {
                return None;
            }
            state.popup = Some(Popup::FedInput {
                field: FedInputField::ConnectInvite,
                input: crate::app::input::LineEdit::default(),
            });
            None
        }
        SettingsRow::DeviceSyncNow => {
            if !require_connected_devices_enabled(state) {
                return None;
            }
            Some(Effect::DeviceSyncNow)
        }
        SettingsRow::DeviceLeaveGroup => {
            if !require_connected_devices_enabled(state) {
                return None;
            }
            state.popup = Some(Popup::ConfirmDeviceLeave);
            None
        }
        SettingsRow::Device(index) => {
            if !require_connected_devices_enabled(state) {
                return None;
            }
            let Some(device) = state
                .federation
                .devices
                .as_ref()
                .and_then(|status| status.devices.get(index))
                .cloned()
            else {
                return None;
            };
            if device.is_self || device.revoked {
                state.status_message = Some("this device cannot be revoked here".to_string());
                return None;
            }
            state.popup = Some(Popup::ConfirmDeviceRevoke {
                device_id: device.device_id,
                name: device.name,
            });
            None
        }
        SettingsRow::VisualizationClock => {
            match state.visualizer.toggle_clock() {
                Ok(()) => {
                    state.status_message = Some(format!(
                        "visualization clock {}",
                        if state.visualizer.config.show_clock {
                            "on"
                        } else {
                            "off"
                        }
                    ));
                }
                Err(err) => state.status_message = Some(format!("visualization settings: {err:#}")),
            }
            None
        }
        SettingsRow::VisualizationScript(index) => {
            match state.visualizer.select_script(index) {
                Ok(()) => {
                    let name = state
                        .visualizer
                        .scripts
                        .get(index)
                        .map(|script| script.name.clone())
                        .unwrap_or_else(|| "visualization".to_string());
                    state.status_message = Some(format!("visualization: {name}"));
                }
                Err(err) => state.status_message = Some(format!("visualization settings: {err:#}")),
            }
            None
        }
        SettingsRow::VisualizationNew => match state.visualizer.create_script() {
            Ok(path) => Some(Effect::OpenVisualizerEditor { path }),
            Err(err) => {
                state.status_message = Some(format!("visualization script: {err:#}"));
                None
            }
        },
        SettingsRow::VisualizationEdit => match state.visualizer.selected_script_path() {
            Some(path) => Some(Effect::OpenVisualizerEditor { path }),
            None => {
                state.status_message = Some("no visualization script selected".into());
                None
            }
        },
    }
}

fn require_connected_devices_enabled(state: &mut AppState) -> bool {
    if state.connected_devices_enabled() {
        true
    } else {
        state.status_message = Some("enable federation before using connected devices".to_string());
        false
    }
}

/// A freshly created play context: drop the stale pre-shuffle snapshot and,
/// if shuffle is on, shuffle everything after the chosen track right away.
pub(super) fn on_new_queue(state: &mut AppState) {
    let player = &mut state.player;
    player.original_order = None;
    if player.shuffle && !player.queue.is_empty() {
        player.original_order = Some(player.queue.iter().map(track_key).collect());
        shuffle_range(player, (player.queue_pos + 1).min(player.queue.len()));
    }
}

fn shuffle_range(player: &mut super::state::PlayerBar, start: usize) {
    let tail = &mut player.queue[start..];
    let mut seed = std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .map(|d| d.as_nanos() as u64)
        .unwrap_or(1)
        | 1;
    let mut next = move || {
        seed ^= seed << 13;
        seed ^= seed >> 7;
        seed ^= seed << 17;
        seed
    };
    for i in (1..tail.len()).rev() {
        tail.swap(i, next() as usize % (i + 1));
    }
    player.prefetched_pos = None;
}

/// Esc/Backspace: pop the navigation stack; leaving a search view resets the
/// search so the next `:/` starts clean.
fn go_back(state: &mut AppState) {
    state.track_selection.clear();
    match state.active_tab {
        Tab::Playlists => {
            state.playlists.opened = None;
        }
        Tab::Global => {
            // Esc on a view opened by Shift-J from another tab goes back to
            // that tab, not down the Global stack.
            if let Some((origin, depth)) = state.jump_origin
                && state.global.stack.len() == depth + 1
            {
                state.global.stack.pop();
                state.jump_origin = None;
                state.active_tab = origin;
                return;
            }
            if let Some(popped) = state.global.stack.pop() {
                if matches!(popped, GlobalView::Search { .. }) {
                    state.search = SearchState::default();
                }
                if matches!(popped, GlobalView::FedArtist { .. }) {
                    state.fed_artist_view = None;
                }
            }
        }
        _ => {}
    }
}

fn switch_tab(state: &mut AppState, tab: Tab) {
    state.active_tab = tab;
    state.help_visible = false;
    state.track_selection.clear();
    // Manually leaving a view cancels any pending Shift-J return path.
    state.jump_origin = None;
}

fn reset_tab(state: &mut AppState, tab: Tab) {
    state.track_selection.clear();
    match tab {
        Tab::Global => {
            if state
                .global
                .stack
                .iter()
                .any(|v| matches!(v, GlobalView::Search { .. }))
            {
                state.search = SearchState::default();
            }
            state.global.stack.clear();
            state.fed_artist_view = None;
        }
        Tab::Playlists => state.playlists.opened = None,
        Tab::Federation => state.settings_cursor = 0,
        Tab::Logs => {
            state.logs.follow = true;
            state.logs.selected_seq = None;
        }
        Tab::Queue => {}
    }
}

fn not_yet(state: &mut AppState, what: &str) {
    state.status_message = Some(format!("{what}: coming in a later milestone"));
}

#[cfg(test)]
#[path = "update_tests.rs"]
mod tests;