added image resizer

src/agent/cover_variants.rs

@@ -0,0 +1,102 @@
+use std::path::{Path, PathBuf};
+
+use image::codecs::jpeg::JpegEncoder;
+use image::imageops::FilterType;
+
+#[derive(Debug, Clone, Copy)]
+pub struct CoverVariant {
+    pub name: &'static str,
+    pub max_edge: u32,
+    pub quality: u8,
+}
+
+pub const COVER_VARIANTS: &[CoverVariant] = &[
+    CoverVariant {
+        name: "small",
+        max_edge: 96,
+        quality: 80,
+    },
+    CoverVariant {
+        name: "medium",
+        max_edge: 256,
+        quality: 82,
+    },
+    CoverVariant {
+        name: "large",
+        max_edge: 512,
+        quality: 85,
+    },
+];
+
+pub fn variant_by_name(name: &str) -> Option<CoverVariant> {
+    COVER_VARIANTS
+        .iter()
+        .copied()
+        .find(|variant| variant.name == name)
+}
+
+pub fn variant_path(original_path: &Path, variant: CoverVariant) -> PathBuf {
+    let stem = original_path
+        .file_stem()
+        .and_then(|value| value.to_str())
+        .filter(|value| !value.is_empty())
+        .unwrap_or("cover");
+    let filename = format!("{stem}.{}.jpg", variant.name);
+    original_path.with_file_name(filename)
+}
+
+pub fn missing_variants(original_path: &Path) -> Vec<CoverVariant> {
+    COVER_VARIANTS
+        .iter()
+        .copied()
+        .filter(|variant| !variant_path(original_path, *variant).exists())
+        .collect()
+}
+
+pub async fn ensure_cover_variants(original_path: &Path) -> anyhow::Result<usize> {
+    let missing = missing_variants(original_path);
+    if missing.is_empty() {
+        return Ok(0);
+    }
+
+    let original_path = original_path.to_path_buf();
+    tokio::task::spawn_blocking(move || generate_missing_variants_sync(&original_path, &missing))
+        .await
+        .map_err(|err| anyhow::anyhow!("cover variant task failed: {err}"))?
+}
+
+fn generate_missing_variants_sync(
+    original_path: &Path,
+    variants: &[CoverVariant],
+) -> anyhow::Result<usize> {
+    let data = std::fs::read(original_path)?;
+    let image = image::load_from_memory(&data)?;
+
+    let mut created = 0usize;
+    for variant in variants {
+        let path = variant_path(original_path, *variant);
+        if path.exists() {
+            continue;
+        }
+
+        if let Some(parent) = path.parent() {
+            std::fs::create_dir_all(parent)?;
+        }
+
+        let resized = image
+            .resize(variant.max_edge, variant.max_edge, FilterType::Lanczos3)
+            .to_rgb8();
+        let mut output = Vec::new();
+        let mut encoder = JpegEncoder::new_with_quality(&mut output, variant.quality);
+        encoder.encode(
+            &resized,
+            resized.width(),
+            resized.height(),
+            image::ExtendedColorType::Rgb8,
+        )?;
+        std::fs::write(path, output)?;
+        created += 1;
+    }
+
+    Ok(created)
+}