First working POC

src/lib/services/imageCache.ts

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+// Image cache service - Handles lazy caching of thumbnails with LRU eviction
+
+import { invoke } from "@tauri-apps/api/core";
+import { convertFileSrc } from "@tauri-apps/api/core";
+
+/**
+ * Statistics about the thumbnail cache
+ */
+export interface ImageCacheStats {
+  totalSizeBytes: number;
+  itemCount: number;
+  limitBytes: number;
+}
+
+/**
+ * Get an image URL, checking cache first then falling back to server.
+ * Triggers background caching if not cached.
+ *
+ * @param serverUrl - The Jellyfin server base URL
+ * @param itemId - The Jellyfin item ID
+ * @param imageType - The image type (Primary, Backdrop, etc.)
+ * @param options - Image options (maxWidth, maxHeight, quality, tag)
+ * @returns The image URL (local asset URL if cached, server URL otherwise)
+ */
+export async function getCachedImageUrl(
+  serverUrl: string,
+  itemId: string,
+  imageType: string = "Primary",
+  options: {
+    maxWidth?: number;
+    maxHeight?: number;
+    quality?: number;
+    tag?: string;
+  } = {}
+): Promise<string> {
+  const tag = options.tag || "default";
+
+  // Try to get cached version
+  try {
+    const cachedPath = await invoke<string | null>("thumbnail_get_cached", {
+      itemId,
+      imageType,
+      tag,
+    });
+
+    if (cachedPath) {
+      // Convert file path to asset URL for Tauri
+      return convertFileSrc(cachedPath);
+    }
+  } catch (e) {
+    console.debug("Failed to check thumbnail cache:", e);
+  }
+
+  // Build server URL
+  const params = new URLSearchParams();
+  if (options.maxWidth) params.set("maxWidth", options.maxWidth.toString());
+  if (options.maxHeight) params.set("maxHeight", options.maxHeight.toString());
+  if (options.quality) params.set("quality", options.quality.toString());
+  if (options.tag) params.set("tag", options.tag);
+
+  const serverImageUrl = `${serverUrl}/Items/${itemId}/Images/${imageType}?${params.toString()}`;
+
+  // Trigger background caching (fire and forget)
+  invoke("thumbnail_save", {
+    itemId,
+    imageType,
+    tag,
+    url: serverImageUrl,
+  }).catch((e) => {
+    // Silently fail - caching is best-effort
+    console.debug("Background thumbnail cache failed:", e);
+  });
+
+  // Return server URL for immediate display
+  return serverImageUrl;
+}
+
+/**
+ * Synchronous version that returns server URL immediately
+ * and triggers background caching. Useful for initial render.
+ *
+ * @param serverUrl - The Jellyfin server base URL
+ * @param itemId - The Jellyfin item ID
+ * @param imageType - The image type (Primary, Backdrop, etc.)
+ * @param options - Image options
+ * @returns The server image URL
+ */
+export function getImageUrlSync(
+  serverUrl: string,
+  itemId: string,
+  imageType: string = "Primary",
+  options: {
+    maxWidth?: number;
+    maxHeight?: number;
+    quality?: number;
+    tag?: string;
+  } = {}
+): string {
+  const tag = options.tag || "default";
+
+  // Build server URL
+  const params = new URLSearchParams();
+  if (options.maxWidth) params.set("maxWidth", options.maxWidth.toString());
+  if (options.maxHeight) params.set("maxHeight", options.maxHeight.toString());
+  if (options.quality) params.set("quality", options.quality.toString());
+  if (options.tag) params.set("tag", options.tag);
+
+  const serverImageUrl = `${serverUrl}/Items/${itemId}/Images/${imageType}?${params.toString()}`;
+
+  // Trigger background caching (fire and forget)
+  invoke("thumbnail_save", {
+    itemId,
+    imageType,
+    tag,
+    url: serverImageUrl,
+  }).catch(() => {
+    // Silently fail
+  });
+
+  return serverImageUrl;
+}
+
+/**
+ * Get thumbnail cache statistics
+ */
+export async function getCacheStats(): Promise<ImageCacheStats> {
+  return invoke("thumbnail_get_stats");
+}
+
+/**
+ * Set cache storage limit in bytes
+ *
+ * @param limitBytes - The maximum cache size in bytes (0 = unlimited)
+ */
+export async function setCacheLimit(limitBytes: number): Promise<void> {
+  return invoke("thumbnail_set_limit", { limitBytes });
+}
+
+/**
+ * Clear all cached thumbnails
+ */
+export async function clearCache(): Promise<void> {
+  return invoke("thumbnail_clear_cache");
+}
+
+/**
+ * Delete cached thumbnails for a specific item
+ *
+ * @param itemId - The Jellyfin item ID
+ */
+export async function deleteItemCache(itemId: string): Promise<void> {
+  return invoke("thumbnail_delete_item", { itemId });
+}
+
+/**
+ * Format bytes to human-readable string
+ *
+ * @param bytes - Number of bytes
+ * @returns Human-readable string (e.g., "1.5 GB")
+ */
+export function formatBytes(bytes: number): string {
+  if (bytes < 1024) return `${bytes} B`;
+  if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)} KB`;
+  if (bytes < 1024 * 1024 * 1024)
+    return `${(bytes / (1024 * 1024)).toFixed(1)} MB`;
+  return `${(bytes / (1024 * 1024 * 1024)).toFixed(2)} GB`;
+}
+
+/**
+ * Convert gigabytes to bytes
+ */
+export function gbToBytes(gb: number): number {
+  return gb * 1024 * 1024 * 1024;
+}
+
+/**
+ * Convert bytes to gigabytes
+ */
+export function bytesToGb(bytes: number): number {
+  return bytes / (1024 * 1024 * 1024);
+}