Initial commit

backend/services/converter.py

@@ -0,0 +1,130 @@
+import re
+import shutil
+import subprocess
+import sys
+import unicodedata
+from pathlib import Path
+
+
+class ConversionError(RuntimeError):
+    pass
+
+
+SUPPORTED_FORMATS = {"mp3", "wav", "flac", "m4a", "ogg"}
+MP3_QUALITIES = {"128", "192", "256", "320"}
+
+
+def normalize_format(format_name: str) -> str:
+    normalized = (format_name or "").strip().lower()
+    if normalized not in SUPPORTED_FORMATS:
+        raise ConversionError("Choose a supported output format.")
+    return normalized
+
+
+def normalize_quality(format_name: str, quality: str | None) -> str:
+    if format_name != "mp3":
+        return "192"
+
+    normalized = (quality or "192").strip()
+    if normalized not in MP3_QUALITIES:
+        raise ConversionError("Choose a supported MP3 quality.")
+    return normalized
+
+
+def sanitize_filename(name: str, fallback: str = "youtube-audio") -> str:
+    normalized = unicodedata.normalize("NFKD", name or "").encode("ascii", "ignore").decode("ascii")
+    normalized = re.sub(r"[^\w\s.-]", "", normalized)
+    normalized = re.sub(r"[\s_]+", "-", normalized).strip(".-")
+    return (normalized or fallback)[:120]
+
+
+def download_audio(url: str, workdir: Path) -> Path:
+    workdir.mkdir(parents=True, exist_ok=True)
+    output_template = str(workdir / "source.%(ext)s")
+    command = [
+        sys.executable,
+        "-m",
+        "yt_dlp",
+        "--no-playlist",
+        "--no-warnings",
+        "-f",
+        "bestaudio/best",
+        "-o",
+        output_template,
+        url,
+    ]
+
+    _run_process(command, "Could not download audio from YouTube.", timeout=1800)
+
+    source_files = sorted(
+        path for path in workdir.glob("source.*") if path.is_file() and not path.name.endswith(".part")
+    )
+    if not source_files:
+        raise ConversionError("The audio download finished, but no source file was created.")
+    return source_files[0]
+
+
+def convert_audio(source_path: Path, output_path: Path, format_name: str, quality: str) -> Path:
+    if not shutil.which("ffmpeg"):
+        raise ConversionError("ffmpeg is not installed or is not available on PATH.")
+
+    format_name = normalize_format(format_name)
+    quality = normalize_quality(format_name, quality)
+    output_path.parent.mkdir(parents=True, exist_ok=True)
+
+    command = ["ffmpeg", "-y", "-i", str(source_path), "-vn"]
+
+    if format_name == "mp3":
+        command.extend(["-codec:a", "libmp3lame", "-b:a", f"{quality}k"])
+    elif format_name == "wav":
+        command.extend(["-codec:a", "pcm_s16le"])
+    elif format_name == "flac":
+        command.extend(["-codec:a", "flac"])
+    elif format_name == "m4a":
+        command.extend(["-codec:a", "aac", "-b:a", "192k"])
+    elif format_name == "ogg":
+        command.extend(["-codec:a", "libvorbis", "-q:a", "5"])
+
+    command.append(str(output_path))
+    _run_process(command, "Could not convert the downloaded audio.", timeout=1800)
+
+    if not output_path.exists():
+        raise ConversionError("Conversion finished, but no output file was created.")
+    return output_path
+
+
+def clean_source_files(workdir: Path) -> None:
+    for path in workdir.glob("source.*"):
+        if path.is_file():
+            path.unlink(missing_ok=True)
+
+
+def _run_process(command: list[str], fallback: str, timeout: int) -> None:
+    try:
+        result = subprocess.run(
+            command,
+            check=False,
+            capture_output=True,
+            text=True,
+            timeout=timeout,
+        )
+    except subprocess.TimeoutExpired as exc:
+        raise ConversionError(f"{fallback} The process timed out.") from exc
+
+    if result.returncode != 0:
+        raise ConversionError(_friendly_process_error(result.stderr, fallback))
+
+
+def _friendly_process_error(stderr: str, fallback: str) -> str:
+    lines = [line.strip() for line in (stderr or "").splitlines() if line.strip()]
+    if not lines:
+        return fallback
+
+    useful = [line for line in lines if "error" in line.lower() or line.startswith(("ERROR:", "WARNING:"))]
+    message = useful[-1] if useful else lines[-1]
+
+    for prefix in ("ERROR:", "WARNING:"):
+        if message.startswith(prefix):
+            message = message.removeprefix(prefix).strip()
+
+    return message or fallback