feat: integrate analysis cache into video session processing

Co-authored-by: Cursor <cursoragent@cursor.com>

src/lib/stores/videoSession.svelte.ts

@@ -10,6 +10,12 @@ import {
 } from '$lib/bindings/mediaAnalysis';
 import { clearThumbnailCache } from '$lib/timeline/thumbnailRenderer';
 import { clearAll as clearAllClips } from '$lib/stores/clips.svelte';
+import {
+  loadCachedAnalysis,
+  saveAnalysisToCache,
+  getThumbnailCacheDir,
+  clearVideoCache,
+} from '$lib/bindings/cache';
 
 export type SessionStatus = 'idle' | 'resolving' | 'ready' | 'error';
 export type DownloadStatus = 'idle' | 'downloading' | 'complete' | 'failed';
@@ -159,7 +165,7 @@ export function dismissUpgradeToast() {
   session.showUpgradeToast = false;
 }
 
-async function loadCaptions(filePath: string) {
+async function loadCaptionsWithCache(filePath: string) {
   session.processingStep = 'captions';
 
   // Priority 1: Check for embedded subtitle streams in the file
@@ -187,10 +193,34 @@ async function loadCaptions(filePath: string) {
 async function triggerPostDownloadProcessing(filePath: string) {
   const duration = session.duration;
 
-  // Run processing SEQUENTIALLY to avoid overloading the CPU with
-  // concurrent ffmpeg subprocesses. Each one decodes the full file.
-  // Order: waveform first (most useful for editing), then keyframes, then thumbnails.
+  // Check cache first
+  try {
+    const cached = await loadCachedAnalysis(session.url);
+    if (cached) {
+      console.log('[triggerPostDownloadProcessing] cache hit for', session.url);
+      if (cached.waveformTiers) {
+        session.waveformTiers = cached.waveformTiers;
+      }
+      if (cached.keyframePositions.length > 0) {
+        session.keyframePositions = cached.keyframePositions;
+      }
+      if (cached.thumbnailSpritesheets.length > 0) {
+        session.thumbnailSpritesheets = cached.thumbnailSpritesheets;
+      }
+      if (cached.captionFilePath) {
+        session.captionFilePath = cached.captionFilePath;
+      }
+      session.processingStep = 'done';
+      if (session.exportStatus === 'complete' && session.exportFilePath) {
+        session.showUpgradeToast = true;
+      }
+      return;
+    }
+  } catch (err) {
+    console.error('Cache load failed, proceeding with extraction:', err);
+  }
 
+  // Cache miss — run extraction sequentially
   session.processingStep = 'waveform';
   session.processingProgress = 0;
   try {
@@ -214,18 +244,34 @@ async function triggerPostDownloadProcessing(filePath: string) {
   session.processingStep = 'thumbnails';
   session.processingProgress = 0;
   try {
-    const sheets = await extractThumbnails(filePath, duration);
+    const thumbDir = await getThumbnailCacheDir(session.url);
+    const sheets = await extractThumbnails(filePath, duration, thumbDir);
     session.thumbnailSpritesheets = sheets;
   } catch (err) {
     console.error('Thumbnail extraction failed:', err);
   }
 
-  // Captions can run after analysis since they use yt-dlp, not ffmpeg
-  await loadCaptions(filePath);
+  // Captions — use cache dir for output
+  await loadCaptionsWithCache(filePath);
 
   session.processingStep = 'done';
 
-  // If export download already completed while we were processing, show upgrade toast
+  // Save to cache
+  try {
+    await saveAnalysisToCache(
+      session.url,
+      session.title,
+      session.duration,
+      session.fps,
+      session.waveformTiers,
+      session.keyframePositions,
+      session.thumbnailSpritesheets,
+      session.captionFilePath
+    );
+  } catch (err) {
+    console.error('Failed to save analysis to cache:', err);
+  }
+
   if (session.exportStatus === 'complete' && session.exportFilePath) {
     session.showUpgradeToast = true;
   }
@@ -353,3 +399,26 @@ export async function beginDownload() {
     console.error('Export download failed:', e);
   });
 }
+
+/** Clear cache for the current video and re-extract all analysis data. */
+export async function reprocessCurrentVideo() {
+  if (!session.url || !session.activeVideoPath) return;
+  const filePath = session.activeVideoPath;
+
+  // Clear cache
+  try {
+    await clearVideoCache(session.url);
+  } catch (err) {
+    console.error('Failed to clear video cache:', err);
+  }
+
+  // Reset analysis state
+  clearThumbnailCache();
+  session.keyframePositions = [];
+  session.waveformTiers = null;
+  session.thumbnailSpritesheets = [];
+  session.captionFilePath = null;
+
+  // Re-run processing (will miss cache and extract fresh)
+  await triggerPostDownloadProcessing(filePath);
+}