File Chunking

interface ChunkUploadConfig {
  file: File;
  chunkSize: number;
  uploadUrl: string;
  onProgress?: (percent: number) => void;
}

async function uploadFileInChunks(config: ChunkUploadConfig): Promise<void> {
  const { file, chunkSize, uploadUrl, onProgress } = config;
  const totalChunks = Math.ceil(file.size / chunkSize);
  
  for (let index = 0; index < totalChunks; index++) {
    const start = index * chunkSize;
    const end = Math.min(start + chunkSize, file.size);
    const chunk = file.slice(start, end);
    
    await uploadChunkWithRetry(chunk, index, totalChunks, uploadUrl);
    
    onProgress?.(((index + 1) / totalChunks) * 100);
  }
}

async function uploadChunkWithRetry(
  chunk: Blob,
  index: number,
  total: number,
  url: string,
  attempt = 1
): Promise<void> {
  const maxRetries = 3;
  
  try {
    const formData = new FormData();
    formData.append('chunk', chunk);
    formData.append('index', index.toString());
    formData.append('total', total.toString());
    
    const response = await fetch(url, {
      method: 'POST',
      body: formData
    });
    
    if (!response.ok) throw new Error(`HTTP ${response.status}`);
  } catch (error) {
    if (attempt < maxRetries) {
      const delay = Math.pow(2, attempt) * 1000; // Exponential backoff
      await new Promise(resolve => setTimeout(resolve, delay));
      return uploadChunkWithRetry(chunk, index, total, url, attempt + 1);
    }
    throw new Error(`Chunk ${index} failed after ${maxRetries} attempts`);
  }
}

// Usage
await uploadFileInChunks({
  file: selectedFile,
  chunkSize: 5 * 1024 * 1024, // 5MB
  uploadUrl: '/api/upload/chunk',
  onProgress: (percent) => console.log(`${percent.toFixed(1)}%`)
});