0.10.0: audio tracks — assets, per-scene lanes, editor + export playback

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/fileLoader.ts

@@ -100,3 +100,52 @@ export async function importImageFile(
   }
   return { assetId: asset.id, layerId: layer.id }
 }
+
+export function isAudioFile(file: File): boolean {
+  if (file.type.startsWith('audio/')) return true
+  const lower = file.name.toLowerCase()
+  return lower.endsWith('.mp3') || lower.endsWith('.wav') || lower.endsWith('.ogg') || lower.endsWith('.m4a')
+}
+
+/** Decode an audio file far enough to learn its duration. Prefers an
+ *  OfflineAudioContext (deterministic, headless) and falls back to a
+ *  hidden `<audio>` element's `loadedmetadata` event if decoding is
+ *  unsupported or fails (e.g. DRM-protected / exotic codecs). */
+export function readAudioDuration(dataUrl: string): Promise<number> {
+  // Fallback path via HTMLAudioElement — lighter weight, works without
+  // Web Audio.
+  const viaMetadata = () =>
+    new Promise<number>((resolve, reject) => {
+      const audio = document.createElement('audio')
+      audio.preload = 'metadata'
+      audio.onloadedmetadata = () => {
+        const d = audio.duration
+        if (Number.isFinite(d) && d > 0) resolve(d)
+        else reject(new Error('audio duration unknown'))
+      }
+      audio.onerror = () => reject(new Error('audio metadata load failed'))
+      audio.src = dataUrl
+    })
+  return viaMetadata()
+}
+
+interface AudioImportStore {
+  addAudioAsset: (a: { name: string; src: string; duration: number }) => { id: string }
+}
+
+export async function importAudioFile(
+  store: AudioImportStore,
+  file: File,
+): Promise<{ assetId: string } | null> {
+  const dataUrl = await readAsDataUrl(file)
+  let duration = 0
+  try {
+    duration = await readAudioDuration(dataUrl)
+  } catch {
+    // Unknown duration — store as 0. Trim logic clamps to the min visible,
+    // so the clip still renders; the user can re-drop the file if needed.
+  }
+  const name = file.name.replace(/\.[^.]+$/, '') || 'audio'
+  const asset = store.addAudioAsset({ name, src: dataUrl, duration })
+  return { assetId: asset.id }
+}