feat: Initialize k-convert application with core structure, UI components, and conversion logic.

src/workers/audio.worker.ts

@@ -0,0 +1,207 @@
+// =============================================================================
+// Audio Worker
+// Handles audio conversions using FFmpeg WASM
+// =============================================================================
+
+import * as Comlink from 'comlink';
+import { FFmpeg } from '@ffmpeg/ffmpeg';
+import { toBlobURL } from '@ffmpeg/util';
+
+type AudioFormat = 'mp3' | 'wav' | 'ogg' | 'm4a' | 'flac';
+
+let ffmpeg: FFmpeg | null = null;
+let ffmpegLoading: Promise<void> | null = null;
+
+async function ensureFFmpegLoaded(): Promise<FFmpeg> {
+  if (ffmpeg?.loaded) return ffmpeg;
+
+  if (ffmpegLoading) {
+    await ffmpegLoading;
+    return ffmpeg!;
+  }
+
+  ffmpegLoading = (async () => {
+    ffmpeg = new FFmpeg();
+
+    // Load FFmpeg core from CDN with proper CORS
+    const baseURL = 'https://unpkg.com/@ffmpeg/core@0.12.6/dist/esm';
+    
+    await ffmpeg.load({
+      coreURL: await toBlobURL(`${baseURL}/ffmpeg-core.js`, 'text/javascript'),
+      wasmURL: await toBlobURL(`${baseURL}/ffmpeg-core.wasm`, 'application/wasm'),
+    });
+  })();
+
+  await ffmpegLoading;
+  return ffmpeg!;
+}
+
+function getFFmpegArgs(
+  _inputFormat: AudioFormat,
+  outputFormat: AudioFormat,
+  bitrate?: number
+): string[] {
+  const args: string[] = [];
+
+  // Codec selection based on output format
+  switch (outputFormat) {
+    case 'mp3':
+      args.push('-c:a', 'libmp3lame');
+      args.push('-b:a', `${bitrate || 192}k`);
+      break;
+    case 'wav':
+      args.push('-c:a', 'pcm_s16le');
+      break;
+    case 'ogg':
+      args.push('-c:a', 'libvorbis');
+      args.push('-q:a', '4'); // Quality level 0-10
+      break;
+    case 'm4a':
+      args.push('-c:a', 'aac');
+      args.push('-b:a', `${bitrate || 192}k`);
+      break;
+    case 'flac':
+      args.push('-c:a', 'flac');
+      args.push('-compression_level', '5');
+      break;
+  }
+
+  return args;
+}
+
+function getExtension(format: AudioFormat): string {
+  return format;
+}
+
+function getMimeType(format: AudioFormat): string {
+  const mimeMap: Record<AudioFormat, string> = {
+    mp3: 'audio/mpeg',
+    wav: 'audio/wav',
+    ogg: 'audio/ogg',
+    m4a: 'audio/mp4',
+    flac: 'audio/flac',
+  };
+  return mimeMap[format];
+}
+
+const audioConverter = {
+  /**
+   * Convert audio file using FFmpeg
+   */
+  async convert(
+    arrayBuffer: ArrayBuffer,
+    inputFormat: AudioFormat,
+    outputFormat: AudioFormat,
+    bitrate?: number,
+    onProgress?: (progress: number) => void
+  ): Promise<Blob> {
+    const ff = await ensureFFmpegLoaded();
+
+    const inputExt = getExtension(inputFormat);
+    const outputExt = getExtension(outputFormat);
+    const inputFileName = `input.${inputExt}`;
+    const outputFileName = `output.${outputExt}`;
+
+    // Register progress callback if provided
+    if (onProgress) {
+      ff.on('progress', ({ progress }) => {
+        onProgress(Math.round(progress * 100));
+      });
+    }
+
+    try {
+      // Write input file to FFmpeg's virtual filesystem
+      await ff.writeFile(inputFileName, new Uint8Array(arrayBuffer));
+
+      // Build FFmpeg command
+      const codecArgs = getFFmpegArgs(inputFormat, outputFormat, bitrate);
+      
+      await ff.exec([
+        '-i', inputFileName,
+        ...codecArgs,
+        '-y', // Overwrite output
+        outputFileName,
+      ]);
+
+      // Read output file
+      const data = await ff.readFile(outputFileName);
+      
+      // Cleanup
+      await ff.deleteFile(inputFileName);
+      await ff.deleteFile(outputFileName);
+
+      // Convert to regular ArrayBuffer to avoid SharedArrayBuffer issues
+      const buffer = new ArrayBuffer((data as Uint8Array).length);
+      new Uint8Array(buffer).set(data as Uint8Array);
+      return new Blob([buffer], { type: getMimeType(outputFormat) });
+    } catch (error) {
+      // Attempt cleanup on error
+      try {
+        await ff.deleteFile(inputFileName);
+        await ff.deleteFile(outputFileName);
+      } catch {
+        // Ignore cleanup errors
+      }
+      throw error;
+    }
+  },
+
+  /**
+   * Extract audio from video file (useful for iPhone MOV files)
+   */
+  async extractAudio(
+    arrayBuffer: ArrayBuffer,
+    inputExtension: string,
+    outputFormat: AudioFormat,
+    bitrate?: number,
+    onProgress?: (progress: number) => void
+  ): Promise<Blob> {
+    const ff = await ensureFFmpegLoaded();
+
+    const inputFileName = `input.${inputExtension}`;
+    const outputExt = getExtension(outputFormat);
+    const outputFileName = `output.${outputExt}`;
+
+    if (onProgress) {
+      ff.on('progress', ({ progress }) => {
+        onProgress(Math.round(progress * 100));
+      });
+    }
+
+    try {
+      await ff.writeFile(inputFileName, new Uint8Array(arrayBuffer));
+
+      const codecArgs = getFFmpegArgs('m4a', outputFormat, bitrate);
+      
+      await ff.exec([
+        '-i', inputFileName,
+        '-vn', // No video
+        ...codecArgs,
+        '-y',
+        outputFileName,
+      ]);
+
+      const data = await ff.readFile(outputFileName);
+      
+      await ff.deleteFile(inputFileName);
+      await ff.deleteFile(outputFileName);
+
+      // Convert to regular ArrayBuffer
+      const buffer = new ArrayBuffer((data as Uint8Array).length);
+      new Uint8Array(buffer).set(data as Uint8Array);
+      return new Blob([buffer], { type: getMimeType(outputFormat) });
+    } catch (error) {
+      try {
+        await ff.deleteFile(inputFileName);
+        await ff.deleteFile(outputFileName);
+      } catch {
+        // Ignore cleanup errors
+      }
+      throw error;
+    }
+  },
+};
+
+Comlink.expose(audioConverter);
+
+export type AudioConverterWorker = typeof audioConverter;