修改一些bug

download-backend/app/main.py

@@ -5,6 +5,7 @@ videos via yt-dlp.
 
 from __future__ import annotations
 
+import mimetypes
 import shutil
 import tempfile
 from dataclasses import dataclass
@@ -15,6 +16,7 @@ from uuid import uuid4
 from fastapi import BackgroundTasks, FastAPI, HTTPException, Query, Request
 from fastapi.concurrency import run_in_threadpool
 from fastapi.middleware.cors import CORSMiddleware
+from fastapi.responses import FileResponse
 from fastapi.staticfiles import StaticFiles
 from pydantic import BaseModel, HttpUrl
 from yt_dlp import YoutubeDL
@@ -26,6 +28,9 @@ app = FastAPI(title="Video Download API", version="0.1.0")
 BASE_DIR = Path(__file__).resolve().parent.parent
 DOWNLOADS_DIR = BASE_DIR / "tmp_downloads"
 DOWNLOADS_DIR.mkdir(parents=True, exist_ok=True)
+WORKING_DIR = BASE_DIR / "tmp_work"
+WORKING_DIR.mkdir(parents=True, exist_ok=True)
+DOWNLOADS_ROOT = DOWNLOADS_DIR.resolve()
 
 DEFAULT_FORMAT = "bestvideo[ext=mp4]+bestaudio[ext=m4a]/best[ext=mp4]"
 ADDITIONAL_FALLBACKS: list[str] = [
@@ -127,7 +132,7 @@ async def download_video(
         raise HTTPException(status_code=500, detail="Failed to download video") from exc
 
     background_tasks.add_task(_cleanup_temp_dir, temp_dir)
-    download_url = str(request.url_for("downloads", path=file_path.name))
+    download_url = str(request.url_for("download_file", file_name=file_path.name))
 
     return DownloadResponse(
         file_name=file_path.name,
@@ -188,13 +193,6 @@ def _derive_format_selectors(info: dict[str, Any]) -> list[FormatChoice]:
     """Build a prioritized list of format selectors based on available formats."""
     choices: list[FormatChoice] = []
 
-    progressive_mp4 = _pick_best_progressive(info, preferred_ext="mp4")
-    if progressive_mp4:
-        choices.append(FormatChoice(str(progressive_mp4["format_id"])))
-
-    progressive_any = _pick_best_progressive(info)
-    if progressive_any:
-        choices.append(FormatChoice(str(progressive_any["format_id"])))
 
     combo_mp4 = _pick_best_combo(info, video_ext="mp4", audio_ext="m4a")
     if combo_mp4:
@@ -210,6 +208,14 @@ def _derive_format_selectors(info: dict[str, Any]) -> list[FormatChoice]:
         selector = f"{video_fmt['format_id']}+{audio_fmt['format_id']}"
         choices.append(FormatChoice(selector, container))
         
+    progressive_mp4 = _pick_best_progressive(info, preferred_ext="mp4")
+    if progressive_mp4:
+        choices.append(FormatChoice(str(progressive_mp4["format_id"])))
+
+    progressive_any = _pick_best_progressive(info)
+    if progressive_any:
+        choices.append(FormatChoice(str(progressive_any["format_id"])))
+
     best_declared = info.get("format_id")
     if best_declared:
         choices.append(FormatChoice(str(best_declared)))
@@ -323,7 +329,7 @@ def _download_video(
     url: str, format_id: str | None, filename: str | None
 ) -> tuple[Path, Path]:
     """Download a video with yt-dlp, selecting the best available format with graceful fallbacks, and persist it to the downloads directory."""
-    temp_dir = Path(tempfile.mkdtemp(prefix="yt_dlp_"))
+    temp_dir = Path(tempfile.mkdtemp(prefix="yt_dlp_", dir=str(WORKING_DIR)))
     output_template = _build_output_template(temp_dir, filename)
 
     selectors: list[FormatChoice]
@@ -396,7 +402,13 @@ def _store_download(file_path: Path) -> Path:
     """Move a completed download into the project downloads directory."""
     target = DOWNLOADS_DIR / file_path.name
     if target.exists():
-        target = DOWNLOADS_DIR / f"{file_path.stem}_{uuid4().hex}{file_path.suffix}"
+        try:
+            if target.is_file():
+                target.unlink(missing_ok=True)
+            else:
+                shutil.rmtree(target, ignore_errors=True)
+        except OSError:
+            raise HTTPException(status_code=500, detail="Failed to replace existing file")
 
     shutil.move(str(file_path), target)
     return target
@@ -427,3 +439,34 @@ def _cleanup_temp_dir(temp_dir: Path) -> None:
     except OSError:
         # Ignore cleanup errors; the directory lives in the system temp folder.
         pass
+
+
+@app.get("/api/download/{file_name}", name="download_file")
+async def stream_download(file_name: str) -> FileResponse:
+    """Stream a stored download with HTTP range support for resumable transfers."""
+    file_path = _resolve_download_path(file_name)
+    media_type = mimetypes.guess_type(str(file_path))[0] or "application/octet-stream"
+    stat_result = file_path.stat()
+    return FileResponse(
+        path=file_path,
+        filename=file_path.name,
+        media_type=media_type,
+        stat_result=stat_result,
+        headers={"Accept-Ranges": "bytes"},
+    )
+
+
+def _resolve_download_path(file_name: str) -> Path:
+    """Ensure the requested file lives inside the downloads directory and exists."""
+    safe_name = Path(file_name).name
+    candidate = (DOWNLOADS_DIR / safe_name).resolve()
+
+    try:
+        candidate.relative_to(DOWNLOADS_ROOT)
+    except ValueError as exc:
+        raise HTTPException(status_code=404, detail="File not found") from exc
+
+    if not candidate.is_file():
+        raise HTTPException(status_code=404, detail="File not found")
+
+    return candidate

download-frontend/app/page.tsx

@@ -205,37 +205,6 @@ export default function Home() {
     }
   };
 
-  const triggerBrowserDownload = async (
-    downloadUrl: string,
-    filename?: string
-  ) => {
-    try {
-      const response = await fetch(downloadUrl, {
-        mode: "cors",
-        credentials: "omit",
-      });
-      if (!response.ok) {
-        throw new Error(`文件获取失败，状态码 ${response.status.toString()}`);
-      }
-      const blob = await response.blob();
-      const objectUrl = URL.createObjectURL(blob);
-      const anchor = document.createElement("a");
-      anchor.href = objectUrl;
-      anchor.download = filename ?? "download";
-      anchor.rel = "noopener";
-      anchor.style.display = "none";
-      document.body.appendChild(anchor);
-      anchor.click();
-      document.body.removeChild(anchor);
-      URL.revokeObjectURL(objectUrl);
-    } catch (error) {
-      const message =
-        error instanceof Error ? error.message : "无法保存文件，请重试。";
-      // 仅在控制台输出，避免覆盖成功状态。用户可重新触发下载。
-      console.error("[download]", message);
-    }
-  };
-
   return (
     <main className="min-h-screen bg-gradient-to-br from-zinc-50 via-white to-zinc-100 py-16 px-4 font-sans text-zinc-900 dark:from-black dark:via-zinc-950 dark:to-black dark:text-zinc-100">
       <div className="mx-auto flex w-full max-w-4xl flex-col gap-8">
@@ -245,7 +214,7 @@ export default function Home() {
               Video Fetcher
             </span>
             <h1 className="text-3xl font-semibold tracking-tight md:text-4xl">
-              高可用视频下载服务
+              YTB视频下载服务
             </h1>
             <p className="max-w-2xl text-base text-zinc-600 dark:text-zinc-400">
               输入任意公共视频链接。系统将列出可用清晰度与格式，支持一键最佳质量下载或按需选择单独下载。
@@ -329,18 +298,14 @@ export default function Home() {
                     </span>
                     <span>自动采用服务推荐的最佳格式，适合快速下载。</span>
                     {downloads[DEFAULT_DOWNLOAD_KEY]?.status === "success" ? (
-                      <button
-                        type="button"
-                        onClick={() => {
-                          void triggerBrowserDownload(
-                            downloads[DEFAULT_DOWNLOAD_KEY].url,
-                            downloads[DEFAULT_DOWNLOAD_KEY].file
-                          );
-                        }}
-                        className="w-fit text-left text-sm font-medium text-zinc-900 underline underline-offset-4 transition hover:text-zinc-700 dark:text-zinc-200 dark:hover:text-zinc-50"
+                      <a
+                        href={downloads[DEFAULT_DOWNLOAD_KEY].url}
+                        target="_blank"
+                        rel="noopener"
+                        className="w-fit truncate text-left text-sm font-medium text-zinc-900 underline underline-offset-4 transition hover:text-zinc-700 dark:text-zinc-200 dark:hover:text-zinc-50"
                       >
                         {downloads[DEFAULT_DOWNLOAD_KEY].file}
-                      </button>
+                      </a>
                     ) : null}
                     {downloads[DEFAULT_DOWNLOAD_KEY]?.status === "error" ? (
                       <span className="text-sm text-red-500">
@@ -450,18 +415,14 @@ export default function Home() {
                                   : "下载"}
                               </button>
                               {downloadState.status === "success" ? (
-                                <button
-                                  type="button"
-                                  onClick={() => {
-                                    void triggerBrowserDownload(
-                                      downloadState.url,
-                                      downloadState.file
-                                    );
-                                  }}
+                                <a
+                                  href={downloadState.url}
+                                  target="_blank"
+                                  rel="noopener"
                                   className="truncate text-left text-xs font-medium text-zinc-900 underline underline-offset-4 transition hover:text-zinc-700 dark:text-zinc-200 dark:hover:text-zinc-50"
                                 >
                                   {downloadState.file}
-                                </button>
+                                </a>
                               ) : null}
                               {downloadState.status === "error" ? (
                                 <span className="text-xs text-red-500">