| 1 | /** |
| 2 | * download.ts - 下载工具函数 |
| 3 | * 提供带进度回调的文件下载功能 |
| 4 | */ |
| 5 | |
| 6 | /** |
| 7 | * 带进度回调的 fetch 下载 |
| 8 | * 通过 ReadableStream 读取响应体，实时计算下载百分比 |
| 9 | * 无 Content-Length 时降级为无进度下载（直接 blob） |
| 10 | */ |
| 11 | export async function fetchWithProgress( |
| 12 | url: string, |
| 13 | onProgress?: (progress: number) => void, |
| 14 | init?: RequestInit, |
| 15 | ): Promise<Blob> { |
| 16 | const response = await fetch(url, init ?? { mode: 'no-cors' }) |
| 17 | if (!response.ok) { |
| 18 | throw new Error(`Download failed: ${response.status}`) |
| 19 | } |
| 20 | |
| 21 | const contentLength = response.headers.get('Content-Length') |
| 22 | // 无 Content-Length 或无 body，降级为直接 blob |
| 23 | if (!contentLength || !response.body) { |
| 24 | const blob = await response.blob() |
| 25 | onProgress?.(100) |
| 26 | return blob |
| 27 | } |
| 28 | |
| 29 | const total = Number.parseInt(contentLength, 10) |
| 30 | let loaded = 0 |
| 31 | const reader = response.body.getReader() |
| 32 | const chunks: Uint8Array[] = [] |
| 33 | |
| 34 | while (true) { |
| 35 | const { done, value } = await reader.read() |
| 36 | if (done) |
| 37 | break |
| 38 | chunks.push(value) |
| 39 | loaded += value.length |
| 40 | onProgress?.(Math.round((loaded / total) * 100)) |
| 41 | } |
| 42 | |
| 43 | return new Blob(chunks as BlobPart[]) |
| 44 | } |
| 45 |