Initial commit

backend/routers/omr.py

@@ -0,0 +1,140 @@
+"""
+/omr/pdf   - PDF sheet music to MusicXML via Audiveris
+/omr/image - Image (PNG/JPG) sheet music to MusicXML via Audiveris
+"""
+import logging
+from pathlib import Path
+
+from fastapi import APIRouter, HTTPException, UploadFile
+from fastapi.responses import JSONResponse
+
+logger = logging.getLogger(__name__)
+router = APIRouter()
+
+# C2 - file size cap
+MAX_UPLOAD_BYTES = 50 * 1024 * 1024   # 50 MB
+
+# H4 - extension allowlists
+_PDF_EXTS   = {".pdf"}
+_IMAGE_EXTS = {".png", ".jpg", ".jpeg", ".tiff", ".tif"}
+
+# M5 - magic bytes
+_PDF_MAGIC  = b"%PDF"
+_PNG_MAGIC  = b"\x89PNG"
+_JPEG_MAGIC = b"\xff\xd8\xff"
+_TIFF_MAGIC = (b"II*\x00", b"MM\x00*")
+
+
+async def _read_with_limit(file: UploadFile, max_bytes: int = MAX_UPLOAD_BYTES) -> bytes:
+    """Stream-read upload in 64 KB chunks; reject as soon as total exceeds limit.
+
+    Unlike ``await file.read()`` followed by a size check, this never buffers
+    an arbitrarily large payload into memory (H2: memory-DoS prevention).
+    """
+    chunks: list[bytes] = []
+    total = 0
+    while True:
+        chunk = await file.read(65_536)
+        if not chunk:
+            break
+        total += len(chunk)
+        if total > max_bytes:
+            raise HTTPException(status_code=413, detail="Upload too large (max 50 MB)")
+        chunks.append(chunk)
+    return b"".join(chunks)
+
+
+def _check_ext(filename: str, allowed: set[str]) -> None:
+    ext = Path(filename).suffix.lower()
+    if ext not in allowed:
+        raise HTTPException(
+            status_code=422,
+            detail=f"Unsupported file type. Allowed: {', '.join(sorted(allowed))}",
+        )
+
+
+def _check_pdf_magic(data: bytes) -> None:
+    if not data.startswith(_PDF_MAGIC):
+        raise HTTPException(status_code=422, detail="Not a valid PDF file")
+
+
+def _check_image_magic(data: bytes, ext: str) -> None:
+    if ext in {".png"} and not data.startswith(_PNG_MAGIC):
+        raise HTTPException(status_code=422, detail="Not a valid PNG file")
+    if ext in {".jpg", ".jpeg"} and not data.startswith(_JPEG_MAGIC):
+        raise HTTPException(status_code=422, detail="Not a valid JPEG file")
+    if ext in {".tiff", ".tif"} and not any(data.startswith(m) for m in _TIFF_MAGIC):
+        raise HTTPException(status_code=422, detail="Not a valid TIFF file")
+
+
+@router.post("/pdf")
+async def omr_pdf(file: UploadFile):
+    """Run OMR on a PDF sheet music file to MusicXML."""
+    try:
+        _check_ext(file.filename or "score.pdf", _PDF_EXTS)
+        data = await _read_with_limit(file)
+        _check_pdf_magic(data)
+
+        from services.audiveris import pdf_to_musicxml
+        musicxml = await pdf_to_musicxml(data, suffix=".pdf")
+        return JSONResponse({"musicxml": musicxml}, headers={"Cache-Control": "no-store"})
+    except HTTPException:
+        raise
+    except Exception:
+        logger.exception("omr_pdf failed")
+        raise HTTPException(status_code=500, detail="OMR processing failed. Please try again.")
+
+
+@router.post("/image")
+async def omr_image(file: UploadFile):
+    """Run OMR on an image (PNG/JPG) of sheet music to MusicXML."""
+    try:
+        filename = file.filename or "image.png"
+        _check_ext(filename, _IMAGE_EXTS)
+        data = await _read_with_limit(file)
+        ext = Path(filename).suffix.lower()
+        _check_image_magic(data, ext)
+
+        from services.audiveris import pdf_to_musicxml
+        musicxml = await pdf_to_musicxml(data, suffix=ext)
+        return JSONResponse({"musicxml": musicxml}, headers={"Cache-Control": "no-store"})
+    except HTTPException:
+        raise
+    except Exception:
+        logger.exception("omr_image failed")
+        raise HTTPException(status_code=500, detail="OMR processing failed. Please try again.")
+
+
+@router.post("/pdf2midi")
+async def omr_pdf_to_midi(file: UploadFile):
+    """PDF sheet music, OMR to MusicXML + MIDI in one round-trip.
+
+    Returns JSON: { musicxml: str, midi_b64: str, filename: str }
+    Both artifacts arrive together so the frontend can render sheet music
+    AND enable playback without a second network request.
+    """
+    import base64
+
+    try:
+        _check_ext(file.filename or "score.pdf", _PDF_EXTS)
+        data = await _read_with_limit(file)
+        _check_pdf_magic(data)
+
+        from services.audiveris import pdf_to_musicxml_and_midi
+        musicxml, midi_bytes = await pdf_to_musicxml_and_midi(data, suffix=".pdf")
+        midi_b64 = base64.b64encode(midi_bytes).decode("ascii")
+
+        return JSONResponse(
+            {"musicxml": musicxml, "midi_b64": midi_b64, "filename": "score.mid"},
+            headers={"Cache-Control": "no-store"},
+        )
+
+    except HTTPException:
+        raise
+    except RuntimeError as exc:
+        # User-safe messages from audiveris.py (no JAR, no output, etc.)
+        logger.warning("omr_pdf_to_midi: %s", exc)
+        raise HTTPException(status_code=422, detail=str(exc))
+    except Exception:
+        logger.exception("omr_pdf_to_midi failed unexpectedly")
+        raise HTTPException(status_code=500, detail="PDF processing failed. Please try again.")