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:
@@ -209,6 +207,14 @@ def _derive_format_selectors(info: dict[str, Any]) -> list[FormatChoice]:
         container = _guess_merge_container(video_fmt, audio_fmt)
         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:
@@ -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