Tab Metadati: editor dei tag audio (MP3, M4A, FLAC)

Nuova sezione 'Metadati' nella sidebar con editor completo dei tag:
titolo, artista, album, album artist, anno, traccia, genere, BPM,
key, commento, copertina.

- core/metadata.py: read/write metadati via mutagen, supporto ID3
  (MP3), MP4 atoms (M4A/AAC) e Vorbis comments (FLAC)
- api/bridge.py: pick_audio_file, pick_image_file, read_metadata,
  save_metadata. Cover passata come base64 al frontend per preview
- webui: hero ambra, form a griglia 2 colonne, anteprima cover 180x180,
  bottoni cambia/rimuovi copertina, ricarica file
- requirements.txt: aggiunto mutagen>=1.47.0
- build_macos.py / build_windows.py: --collect-all mutagen

Modifiche correlate (in attesa di decisione utente sulla
distribuzione degli aggiornamenti):
- VERSION bumpato a v1.2.2 in core/config.py
- check_update ora interroga l'API GitHub Releases invece di
  djluza.com/version.json (funzionera quando il repo sara pubblico)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

core/metadata.py

@@ -0,0 +1,301 @@
+"""Lettura e scrittura metadati audio (ID3 per MP3, MP4 per M4A, Vorbis per FLAC)."""
+
+from __future__ import annotations
+
+import base64
+from pathlib import Path
+from typing import Optional
+
+from mutagen import File as MutagenFile
+from mutagen.id3 import (
+    ID3, ID3NoHeaderError,
+    APIC, TIT2, TPE1, TPE2, TALB, TDRC, TRCK, TCON, COMM, TBPM, TKEY,
+)
+from mutagen.mp4 import MP4, MP4Cover
+from mutagen.flac import FLAC, Picture
+
+
+SUPPORTED_EXTS = (".mp3", ".m4a", ".mp4", ".aac", ".flac")
+
+
+def _text(value) -> str:
+    """Estrai testo da un frame mutagen."""
+    if value is None:
+        return ""
+    if hasattr(value, "text"):
+        t = value.text
+        if isinstance(t, list) and t:
+            return str(t[0])
+        return str(t)
+    if isinstance(value, list) and value:
+        return str(value[0])
+    return str(value)
+
+
+def _read_mp3(path: str, result: dict) -> dict:
+    result["format"] = "MP3"
+    try:
+        tags = ID3(path)
+    except ID3NoHeaderError:
+        return result
+
+    result["title"] = _text(tags.get("TIT2"))
+    result["artist"] = _text(tags.get("TPE1"))
+    result["album_artist"] = _text(tags.get("TPE2"))
+    result["album"] = _text(tags.get("TALB"))
+    result["year"] = _text(tags.get("TDRC"))
+    result["track"] = _text(tags.get("TRCK"))
+    result["genre"] = _text(tags.get("TCON"))
+    result["bpm"] = _text(tags.get("TBPM"))
+    result["key"] = _text(tags.get("TKEY"))
+
+    for k in tags.keys():
+        if k.startswith("COMM"):
+            result["comment"] = _text(tags[k])
+            break
+
+    for k in tags.keys():
+        if k.startswith("APIC"):
+            apic = tags[k]
+            result["cover_base64"] = base64.b64encode(apic.data).decode("ascii")
+            result["cover_mime"] = apic.mime or "image/jpeg"
+            break
+
+    return result
+
+
+def _read_mp4(path: str, result: dict) -> dict:
+    result["format"] = "M4A/MP4"
+    m = MP4(path)
+    tags = m.tags or {}
+    result["title"] = _text(tags.get("\xa9nam"))
+    result["artist"] = _text(tags.get("\xa9ART"))
+    result["album_artist"] = _text(tags.get("aART"))
+    result["album"] = _text(tags.get("\xa9alb"))
+    result["year"] = _text(tags.get("\xa9day"))
+    track_pair = tags.get("trkn")
+    if track_pair and isinstance(track_pair, list) and track_pair:
+        num, tot = track_pair[0] if isinstance(track_pair[0], tuple) else (track_pair[0], 0)
+        result["track"] = f"{num}/{tot}" if tot else str(num)
+    result["genre"] = _text(tags.get("\xa9gen"))
+    result["comment"] = _text(tags.get("\xa9cmt"))
+    result["bpm"] = _text(tags.get("tmpo"))
+
+    covers = tags.get("covr")
+    if covers:
+        c = covers[0]
+        result["cover_base64"] = base64.b64encode(bytes(c)).decode("ascii")
+        result["cover_mime"] = "image/jpeg" if c.imageformat == MP4Cover.FORMAT_JPEG else "image/png"
+    return result
+
+
+def _read_flac(path: str, result: dict) -> dict:
+    result["format"] = "FLAC"
+    f = FLAC(path)
+    g = lambda k: (f.get(k) or [""])[0] if f.get(k) else ""
+    result["title"] = g("title")
+    result["artist"] = g("artist")
+    result["album_artist"] = g("albumartist")
+    result["album"] = g("album")
+    result["year"] = g("date")
+    result["track"] = g("tracknumber")
+    result["genre"] = g("genre")
+    result["bpm"] = g("bpm")
+    result["key"] = g("initialkey")
+    result["comment"] = g("comment")
+    if f.pictures:
+        pic = f.pictures[0]
+        result["cover_base64"] = base64.b64encode(pic.data).decode("ascii")
+        result["cover_mime"] = pic.mime or "image/jpeg"
+    return result
+
+
+def read_metadata(path: str) -> dict:
+    """Ritorna un dict con tutti i metadati leggibili dal file."""
+    p = Path(path)
+    if not p.exists():
+        raise FileNotFoundError(path)
+
+    ext = p.suffix.lower()
+    if ext not in SUPPORTED_EXTS:
+        raise ValueError(f"Formato non supportato: {ext}")
+
+    result = {
+        "path": str(p),
+        "filename": p.name,
+        "format": "",
+        "title": "", "artist": "", "album_artist": "",
+        "album": "", "year": "", "track": "",
+        "genre": "", "comment": "",
+        "bpm": "", "key": "",
+        "duration": 0, "bitrate": 0,
+        "cover_base64": "", "cover_mime": "",
+    }
+
+    audio = MutagenFile(str(p))
+    if audio is None:
+        raise ValueError(f"Impossibile leggere: {ext}")
+
+    info = getattr(audio, "info", None)
+    if info:
+        result["duration"] = int(getattr(info, "length", 0) or 0)
+        result["bitrate"] = int((getattr(info, "bitrate", 0) or 0) // 1000)
+
+    if ext == ".mp3":
+        return _read_mp3(str(p), result)
+    if ext in (".m4a", ".mp4", ".aac"):
+        return _read_mp4(str(p), result)
+    if ext == ".flac":
+        return _read_flac(str(p), result)
+    return result
+
+
+def _write_mp3(path: str, data: dict, cover_path: Optional[str], remove_cover: bool) -> None:
+    try:
+        tags = ID3(path)
+    except ID3NoHeaderError:
+        tags = ID3()
+
+    def set_or_del(key, frame_cls, value):
+        if value:
+            tags[key] = frame_cls(encoding=3, text=value)
+        elif key in tags:
+            del tags[key]
+
+    set_or_del("TIT2", TIT2, data.get("title", ""))
+    set_or_del("TPE1", TPE1, data.get("artist", ""))
+    set_or_del("TPE2", TPE2, data.get("album_artist", ""))
+    set_or_del("TALB", TALB, data.get("album", ""))
+    set_or_del("TDRC", TDRC, data.get("year", ""))
+    set_or_del("TRCK", TRCK, data.get("track", ""))
+    set_or_del("TCON", TCON, data.get("genre", ""))
+    set_or_del("TBPM", TBPM, data.get("bpm", ""))
+    set_or_del("TKEY", TKEY, data.get("key", ""))
+
+    # Rimuovi tutti i COMM esistenti
+    for k in list(tags.keys()):
+        if k.startswith("COMM"):
+            del tags[k]
+    comment = data.get("comment", "")
+    if comment:
+        tags.add(COMM(encoding=3, lang="ita", desc="", text=comment))
+
+    # Cover
+    if remove_cover or cover_path:
+        for k in list(tags.keys()):
+            if k.startswith("APIC"):
+                del tags[k]
+    if cover_path:
+        cp = Path(cover_path)
+        if cp.exists():
+            ext = cp.suffix.lower()
+            mime = "image/png" if ext == ".png" else "image/jpeg"
+            with open(cp, "rb") as f:
+                cover_data = f.read()
+            tags.add(APIC(encoding=3, mime=mime, type=3, desc="Cover", data=cover_data))
+
+    tags.save(path, v2_version=3)
+
+
+def _write_mp4(path: str, data: dict, cover_path: Optional[str], remove_cover: bool) -> None:
+    m = MP4(path)
+
+    def set_or_del(key, value):
+        if value:
+            m[key] = value
+        elif key in m:
+            del m[key]
+
+    set_or_del("\xa9nam", data.get("title", ""))
+    set_or_del("\xa9ART", data.get("artist", ""))
+    set_or_del("aART", data.get("album_artist", ""))
+    set_or_del("\xa9alb", data.get("album", ""))
+    set_or_del("\xa9day", data.get("year", ""))
+    set_or_del("\xa9gen", data.get("genre", ""))
+    set_or_del("\xa9cmt", data.get("comment", ""))
+
+    track = data.get("track", "")
+    if track:
+        try:
+            parts = track.split("/")
+            num = int(parts[0])
+            tot = int(parts[1]) if len(parts) > 1 else 0
+            m["trkn"] = [(num, tot)]
+        except (ValueError, IndexError):
+            pass
+    elif "trkn" in m:
+        del m["trkn"]
+
+    bpm = data.get("bpm", "")
+    if bpm:
+        try:
+            m["tmpo"] = [int(bpm)]
+        except ValueError:
+            pass
+    elif "tmpo" in m:
+        del m["tmpo"]
+
+    if remove_cover or cover_path:
+        if "covr" in m:
+            del m["covr"]
+    if cover_path:
+        cp = Path(cover_path)
+        if cp.exists():
+            ext = cp.suffix.lower()
+            fmt = MP4Cover.FORMAT_PNG if ext == ".png" else MP4Cover.FORMAT_JPEG
+            with open(cp, "rb") as f:
+                cover_data = f.read()
+            m["covr"] = [MP4Cover(cover_data, imageformat=fmt)]
+
+    m.save()
+
+
+def _write_flac(path: str, data: dict, cover_path: Optional[str], remove_cover: bool) -> None:
+    f = FLAC(path)
+
+    def set_or_del(key, value):
+        if value:
+            f[key] = value
+        elif key in f:
+            del f[key]
+
+    set_or_del("title", data.get("title", ""))
+    set_or_del("artist", data.get("artist", ""))
+    set_or_del("albumartist", data.get("album_artist", ""))
+    set_or_del("album", data.get("album", ""))
+    set_or_del("date", data.get("year", ""))
+    set_or_del("tracknumber", data.get("track", ""))
+    set_or_del("genre", data.get("genre", ""))
+    set_or_del("bpm", data.get("bpm", ""))
+    set_or_del("initialkey", data.get("key", ""))
+    set_or_del("comment", data.get("comment", ""))
+
+    if remove_cover or cover_path:
+        f.clear_pictures()
+    if cover_path:
+        cp = Path(cover_path)
+        if cp.exists():
+            ext = cp.suffix.lower()
+            pic = Picture()
+            with open(cp, "rb") as fh:
+                pic.data = fh.read()
+            pic.type = 3
+            pic.mime = "image/png" if ext == ".png" else "image/jpeg"
+            f.add_picture(pic)
+
+    f.save()
+
+
+def write_metadata(path: str, data: dict, cover_path: Optional[str] = None,
+                    remove_cover: bool = False) -> None:
+    """Salva i metadati. Se remove_cover=True rimuove la copertina esistente
+    senza sostituirla. Se cover_path e fornito, la sostituisce."""
+    ext = Path(path).suffix.lower()
+    if ext == ".mp3":
+        _write_mp3(path, data, cover_path, remove_cover)
+    elif ext in (".m4a", ".mp4", ".aac"):
+        _write_mp4(path, data, cover_path, remove_cover)
+    elif ext == ".flac":
+        _write_flac(path, data, cover_path, remove_cover)
+    else:
+        raise ValueError(f"Formato non supportato: {ext}")