Initial commit

backend/routers/export_routes.py

@@ -0,0 +1,132 @@
+"""
+/export/pdf  - MusicXML to PDF via music21 + LilyPond (or Audiveris)
+/export/mp3  - WAV buffer to MP3 via FFmpeg
+"""
+import base64
+import binascii
+import logging
+import os
+import subprocess
+import tempfile
+
+from fastapi import APIRouter, BackgroundTasks, HTTPException
+from fastapi.responses import FileResponse
+from pydantic import BaseModel
+
+logger = logging.getLogger(__name__)
+router = APIRouter()
+
+# C2 - size caps
+MAX_B64_BYTES = 300 * 1024 * 1024    # 300 MB base64 string  (≈ 200 MB decoded)
+MAX_WAV_BYTES = 200 * 1024 * 1024    # 200 MB decoded WAV
+
+
+MAX_MUSICXML_BYTES = 10 * 1024 * 1024   # 10 MB
+
+# M5 - WAV magic bytes: "RIFF....WAVE"
+_WAV_RIFF  = b"RIFF"
+_WAV_WAVE  = b"WAVE"
+
+
+class ExportPdfRequest(BaseModel):
+    musicxml: str
+
+
+class ExportMp3Request(BaseModel):
+    wav_base64: str  # base64-encoded WAV
+
+
+def _rm(path: str) -> None:
+    try:
+        os.unlink(path)
+    except OSError:
+        pass
+
+
+@router.post("/pdf")
+async def export_pdf(req: ExportPdfRequest, background_tasks: BackgroundTasks):
+    """Convert MusicXML to PDF sheet music."""
+    if len(req.musicxml.encode()) > MAX_MUSICXML_BYTES:
+        raise HTTPException(status_code=413, detail="MusicXML payload too large (max 10 MB)")
+    try:
+        from services.music21_svc import musicxml_to_pdf
+        pdf_path = await musicxml_to_pdf(req.musicxml)
+        background_tasks.add_task(_rm, pdf_path)   # H5
+
+        return FileResponse(
+            pdf_path,
+            media_type="application/pdf",
+            filename="sheet.pdf",
+            headers={
+                "Cache-Control": "no-store",
+                "Content-Disposition": 'attachment; filename="sheet.pdf"',
+            },
+        )
+    except HTTPException:
+        raise
+    except Exception:
+        logger.exception("export_pdf failed")
+        raise HTTPException(status_code=500, detail="PDF export failed. Please try again.")
+
+
+@router.post("/mp3")
+async def export_mp3(req: ExportMp3Request, background_tasks: BackgroundTasks):
+    """Convert base64 WAV to MP3 using FFmpeg."""
+    # L6 - size-check before decoding; catch malformed base64 explicitly
+    if len(req.wav_base64) > MAX_B64_BYTES:
+        raise HTTPException(status_code=413, detail="WAV payload too large (max 200 MB)")
+
+    try:
+        wav_bytes = base64.b64decode(req.wav_base64, validate=True)
+    except binascii.Error:
+        raise HTTPException(status_code=422, detail="Invalid base64 encoding")
+
+    # C2 - check decoded size too
+    if len(wav_bytes) > MAX_WAV_BYTES:
+        raise HTTPException(status_code=413, detail="WAV data too large (max 200 MB)")
+
+    # M5 - validate WAV magic bytes: "RIFF....WAVE"
+    if len(wav_bytes) < 12 or wav_bytes[:4] != _WAV_RIFF or wav_bytes[8:12] != _WAV_WAVE:
+        raise HTTPException(status_code=422, detail="Not a valid WAV file")
+
+    try:
+        wav_tmp = tempfile.NamedTemporaryFile(suffix=".wav", delete=False)
+        wav_tmp.write(wav_bytes)
+        wav_tmp.close()
+
+        mp3_tmp = tempfile.NamedTemporaryFile(suffix=".mp3", delete=False)
+        mp3_tmp.close()
+
+        # H5 - register cleanup regardless of success/failure
+        background_tasks.add_task(_rm, wav_tmp.name)
+        background_tasks.add_task(_rm, mp3_tmp.name)
+
+        result = subprocess.run(
+            [
+                "ffmpeg", "-y",
+                "-i", wav_tmp.name,
+                "-codec:a", "libmp3lame",
+                "-q:a", "2",
+                mp3_tmp.name,
+            ],
+            capture_output=True,
+            timeout=60,
+        )
+        if result.returncode != 0:
+            logger.error("ffmpeg failed: %s", result.stderr.decode(errors="replace")[:500])
+            raise RuntimeError("ffmpeg conversion failed")
+
+        return FileResponse(
+            mp3_tmp.name,
+            media_type="audio/mpeg",
+            filename="export.mp3",
+            headers={
+                "Cache-Control": "no-store",
+                "Content-Disposition": 'attachment; filename="export.mp3"',
+            },
+        )
+    except HTTPException:
+        raise
+    except Exception:
+        logger.exception("export_mp3 failed")
+        raise HTTPException(status_code=500, detail="MP3 export failed. Please try again.")