"""Music library maintenance, refactored from the original ``music-covers.py`` CLI.

The interactive terminal UI is gone; what remains is pure, importable logic the
web app drives. Two entry points matter:

* :func:`scan_library` — read-only analysis. Walks ``MUSIC_ROOT`` and reports, per
  album, what each maintenance mode *would* do. Safe to call any time.
* :func:`process_library` — performs the work. Honours ``dry_run`` (the web UI
  default) so nothing is renamed, deleted, or downloaded unless the caller opts in.

Both are synchronous (filesystem + blocking HTTP); call them from FastAPI via
``asyncio.to_thread``. Progress is reported through an optional ``log`` callback.
"""

from __future__ import annotations

import os
import re
import time
from dataclasses import dataclass, field
from pathlib import Path
from typing import Callable

import requests

try:  # Optional: only needed for the "find missing year/cover" online lookups.
    import musicbrainzngs

    musicbrainzngs.set_useragent("HomelabToolkit", "1.0", "homelab-toolkit@example.com")
    _HAS_MUSICBRAINZ = True
except Exception:  # pragma: no cover - optional dependency
    _HAS_MUSICBRAINZ = False

from mutagen import File as MutagenFile, MutagenError

MUSIC_ROOT = Path(os.environ.get("MUSIC_ROOT", r"\\Matt-htpc\d\Music"))

COVER_NAME_PRIORITY = ("cover.jpg", "folder.jpg", "front.jpg")
COVER_NAMES = set(COVER_NAME_PRIORITY)
COVER_MISSING_MARKER = ".cover-not-found"
LYRICS_MISSING_MARKER = ".lyrics-not-found"
LYRICS_SIDECAR_EXTENSIONS = {".lrc", ".txt"}
AUDIO_EXTENSIONS = {".mp3", ".flac", ".m4a"}
YEAR_ALBUM_FOLDER_RE = re.compile(r"^\s*(\d{4})\s*-\s*(.+?)\s*$")

LogCallback = Callable[[dict], None]


@dataclass
class ProcessOptions:
    folder_cleanup: bool = False
    rename: bool = False
    file_cleanup: bool = False
    lyrics: bool = False
    covers: bool = True
    dry_run: bool = True

    @classmethod
    def from_dict(cls, data: dict) -> "ProcessOptions":
        return cls(
            folder_cleanup=bool(data.get("folder_cleanup", False)),
            rename=bool(data.get("rename", False)),
            file_cleanup=bool(data.get("file_cleanup", False)),
            lyrics=bool(data.get("lyrics", False)),
            covers=bool(data.get("covers", True)),
            dry_run=bool(data.get("dry_run", True)),
        )


@dataclass
class _Recorder:
    """Collects structured action records and forwards them to an optional sink."""

    sink: LogCallback | None = None
    actions: list[dict] = field(default_factory=list)
    counts: dict[str, int] = field(default_factory=dict)

    def emit(self, level: str, action: str, message: str, **extra) -> None:
        record = {"level": level, "action": action, "message": message, **extra}
        self.actions.append(record)
        self.counts[action] = self.counts.get(action, 0) + 1
        if self.sink:
            self.sink(record)


# ── pure string helpers ──────────────────────────────────────────────────────


def clean_name(text: str) -> str:
    text = re.sub(r"\[(.*?)\]|\((.*?)\)", "", text)
    text = text.replace("_", " ").replace("-", " ")
    return " ".join(text.split()).strip()


def clean_album_folder_name(text: str) -> str:
    match = YEAR_ALBUM_FOLDER_RE.match(text)
    if match:
        text = match.group(2)
    return clean_name(text)


def get_year_from_album_folder_name(text: str) -> str | None:
    match = YEAR_ALBUM_FOLDER_RE.match(text)
    return match.group(1) if match else None


def safe_filename(text: str) -> str:
    text = re.sub(r'[<>:"/\\|?*]', "", text)
    text = text.strip().rstrip(".")
    return " ".join(text.split())


def clean_track_number(value) -> str | None:
    if not value:
        return None
    text = str(value[0] if isinstance(value, list) else value).strip()
    text = text.split("/")[0].strip()
    return text.zfill(2) if text.isdigit() else None


def extract_year(value: str | None) -> str | None:
    if not value:
        return None
    match = re.search(r"\b(19\d{2}|20\d{2})\b", str(value))
    return match.group(1) if match else None


# ── metadata reading ─────────────────────────────────────────────────────────


def _load_audio(path: Path):
    try:
        return MutagenFile(path, easy=True)
    except (MutagenError, OSError):
        return None


def _first_tag(audio, names):
    for name in names:
        value = audio.get(name)
        if value:
            return str(value[0]).strip()
    return None


def get_album_metadata_from_files(album_folder: Path):
    for file in album_folder.iterdir():
        if not file.is_file() or file.suffix.lower() not in AUDIO_EXTENSIONS:
            continue
        audio = _load_audio(file)
        if audio is None:
            continue
        artist = _first_tag(audio, ["albumartist", "artist"])
        album = _first_tag(audio, ["album"])
        year = extract_year(_first_tag(audio, ["date", "originaldate", "year"]))
        if artist or album or year:
            return artist, album, year
    return None, None, None


def get_track_metadata(path: Path):
    audio = _load_audio(path)
    if audio is None:
        return None, None, None, None
    artist = _first_tag(audio, ["artist", "albumartist"])
    album = _first_tag(audio, ["album"])
    title = _first_tag(audio, ["title"])
    duration = None
    info = getattr(audio, "info", None)
    if info and getattr(info, "length", None):
        duration = round(info.length)
    return artist, album, title, duration


# ── album inspection ─────────────────────────────────────────────────────────


def _cover_to_keep(album_folder: Path) -> str | None:
    existing = {p.name.lower() for p in album_folder.iterdir() if p.is_file()}
    for name in COVER_NAME_PRIORITY:
        if name in existing:
            return name
    return None


def _has_cover(album_folder: Path) -> bool:
    existing = {p.name.lower() for p in album_folder.iterdir() if p.is_file()}
    return any(name in existing for name in COVER_NAMES)


def _should_keep_file(path: Path, cover_to_keep: str | None) -> bool:
    name = path.name.lower()
    suffix = path.suffix.lower()
    return (
        suffix in AUDIO_EXTENSIONS
        or suffix in LYRICS_SIDECAR_EXTENSIONS
        or name == cover_to_keep
    )


def _has_lyrics(audio_file: Path) -> bool:
    return any(
        audio_file.with_suffix(extension).exists()
        for extension in LYRICS_SIDECAR_EXTENSIONS
    )


def analyze_album(album_folder: Path) -> dict:
    """Read-only summary of an album folder and the pending maintenance work."""
    tag_artist, tag_album, tag_year = get_album_metadata_from_files(album_folder)
    artist = tag_artist or clean_name(album_folder.parent.name)
    album = tag_album or clean_album_folder_name(album_folder.name)
    year = tag_year or get_year_from_album_folder_name(album_folder.name)

    audio_files = [
        f for f in album_folder.iterdir()
        if f.is_file() and f.suffix.lower() in AUDIO_EXTENSIONS
    ]
    cover_to_keep = _cover_to_keep(album_folder)
    extra_files = [
        f.name for f in album_folder.iterdir()
        if f.is_file() and not _should_keep_file(f, cover_to_keep)
    ]

    suggested_folder = None
    if album and year:
        candidate = f"{year} - {safe_filename(album)}"
        if candidate != album_folder.name:
            suggested_folder = candidate

    missing_lyrics = sum(1 for f in audio_files if not _has_lyrics(f))

    return {
        "path": str(album_folder),
        "folder_name": album_folder.name,
        "artist": artist or "",
        "album": album or "",
        "year": year,
        "track_count": len(audio_files),
        "has_cover": _has_cover(album_folder),
        "suggested_folder": suggested_folder,
        "needs_folder_rename": suggested_folder is not None,
        "extra_files": extra_files,
        "extra_file_count": len(extra_files),
        "missing_lyrics_count": missing_lyrics,
    }


def _iter_album_folders(root: Path):
    for first_level in root.iterdir():
        if not first_level.is_dir():
            continue
        try:
            has_audio = any(
                p.is_file() and p.suffix.lower() in AUDIO_EXTENSIONS
                for p in first_level.iterdir()
            )
        except OSError:
            continue
        if has_audio:
            # Top-level folder holding audio directly is not an Artist/Album tree.
            continue
        for album_folder in first_level.iterdir():
            if album_folder.is_dir():
                yield album_folder


def scan_library(root: Path | None = None) -> dict:
    root = root or MUSIC_ROOT
    if not root.exists():
        return {"root": str(root), "exists": False, "albums": []}

    albums = []
    for album_folder in _iter_album_folders(root):
        try:
            albums.append(analyze_album(album_folder))
        except OSError:
            continue
    albums.sort(key=lambda a: (a["artist"].lower(), a["year"] or "", a["album"].lower()))

    return {
        "root": str(root),
        "exists": True,
        "album_count": len(albums),
        "missing_cover_count": sum(1 for a in albums if not a["has_cover"]),
        "needs_rename_count": sum(1 for a in albums if a["needs_folder_rename"]),
        "extra_file_count": sum(a["extra_file_count"] for a in albums),
        "albums": albums,
    }


# ── online lookups (year / cover / lyrics) ───────────────────────────────────


def find_album_year(artist: str, album: str) -> str | None:
    if not _HAS_MUSICBRAINZ:
        return None
    try:
        result = musicbrainzngs.search_releases(artist=artist, release=album, limit=5)
        for release in result.get("release-list", []):
            year = extract_year(release.get("date"))
            if year:
                return year
    except Exception:
        return None
    return None


def find_album_cover(artist: str, album: str) -> bytes | None:
    if not _HAS_MUSICBRAINZ:
        return None
    try:
        result = musicbrainzngs.search_releases(artist=artist, release=album, limit=3)
        releases = result.get("release-list", [])
        if not releases:
            return None
        mbid = releases[0]["id"]
        url = f"https://coverartarchive.org/release/{mbid}/front-500"
        response = requests.get(url, timeout=20, allow_redirects=True)
        if response.status_code == 200 and response.headers.get("content-type", "").startswith("image"):
            return response.content
    except Exception:
        return None
    return None


def find_track_lyrics(artist: str, album: str, title: str, duration: int | None):
    if not duration:
        return None
    try:
        response = requests.get(
            "https://lrclib.net/api/get",
            params={
                "artist_name": artist,
                "track_name": title,
                "album_name": album,
                "duration": duration,
            },
            headers={"User-Agent": "HomelabToolkit/1.0 (local music library tool)"},
            timeout=20,
        )
        if response.status_code != 200:
            return None
        data = response.json()
        if data.get("syncedLyrics"):
            return ".lrc", data["syncedLyrics"].strip() + "\n"
        if data.get("plainLyrics"):
            return ".txt", data["plainLyrics"].strip() + "\n"
    except Exception:
        return None
    return None


# ── mutating operations (respect dry_run) ────────────────────────────────────


def _is_top_level(folder: Path, root: Path) -> bool:
    try:
        return folder.resolve().parent == root.resolve()
    except OSError:
        return folder.parent == root


def _rename_album_folder(album_folder, artist, album, year, root, opts, rec) -> Path:
    if not album or not year or _is_top_level(album_folder, root):
        return album_folder
    new_name = f"{year} - {safe_filename(album)}"
    if album_folder.name == new_name:
        return album_folder
    new_folder = album_folder.with_name(new_name)
    if new_folder.exists():
        rec.emit("skip", "folder", f"Rename target already exists: {new_name}")
        return album_folder
    rec.emit(
        "dry" if opts.dry_run else "ok",
        "folder",
        f"{album_folder.name}  →  {new_name}",
        path=str(album_folder),
    )
    if opts.dry_run:
        return album_folder
    album_folder.rename(new_folder)
    return new_folder


def _rename_track(path: Path, opts, rec) -> Path:
    audio = _load_audio(path)
    if audio is None:
        return path
    artist = _first_tag(audio, ["artist", "albumartist"])
    album = _first_tag(audio, ["album"])
    title = _first_tag(audio, ["title"])
    track = clean_track_number(audio.get("tracknumber"))
    if not (artist and album and title and track):
        return path
    new_name = f"{track} - {safe_filename(title)}{path.suffix.lower()}"
    if path.name == new_name:
        return path
    new_path = path.with_name(new_name)
    if new_path.exists():
        rec.emit("skip", "rename", f"Target exists: {new_name}")
        return path
    rec.emit("dry" if opts.dry_run else "ok", "rename", f"{path.name}  →  {new_name}")
    if opts.dry_run:
        return path
    path.rename(new_path)
    return new_path


def _clean_files(album_folder: Path, opts, rec) -> None:
    cover_to_keep = _cover_to_keep(album_folder)
    for file in album_folder.iterdir():
        if not file.is_file() or _should_keep_file(file, cover_to_keep):
            continue
        rec.emit("dry" if opts.dry_run else "ok", "remove", f"Remove {file.name}", path=str(file))
        if opts.dry_run:
            continue
        try:
            file.unlink()
        except OSError as exc:
            rec.emit("warn", "remove", f"Could not remove {file.name}: {exc}")


def _fetch_cover(album_folder, artist, album, opts, rec) -> None:
    if _has_cover(album_folder):
        return
    if not (artist and album):
        return
    rec.emit("info", "cover", f"Looking up cover: {artist} - {album}")
    image = find_album_cover(artist, album)
    if not image:
        rec.emit("skip", "cover", f"No cover found: {artist} - {album}")
        return
    output = album_folder / "cover.jpg"
    rec.emit("dry" if opts.dry_run else "ok", "cover", f"Save cover.jpg for {album}")
    if not opts.dry_run:
        output.write_bytes(image)
        time.sleep(1)


def _fetch_lyrics(audio_file, album_artist, album_name, opts, rec) -> None:
    if _has_lyrics(audio_file):
        return
    t_artist, t_album, title, duration = get_track_metadata(audio_file)
    artist = t_artist or album_artist
    album = t_album or album_name
    if not (artist and album and title):
        return
    lyrics = find_track_lyrics(artist, album, title, duration)
    if not lyrics:
        rec.emit("skip", "lyrics", f"No lyrics: {artist} - {title}")
        return
    extension, text = lyrics
    output = audio_file.with_suffix(extension)
    rec.emit("dry" if opts.dry_run else "ok", "lyrics", f"Save lyrics for {title}")
    if not opts.dry_run:
        output.write_text(text, encoding="utf-8")
        time.sleep(1)


def _process_album(album_folder: Path, root: Path, opts: ProcessOptions, rec: _Recorder) -> None:
    tag_artist, tag_album, tag_year = get_album_metadata_from_files(album_folder)
    artist = tag_artist or clean_name(album_folder.parent.name)
    album = tag_album or clean_album_folder_name(album_folder.name)
    year = tag_year or get_year_from_album_folder_name(album_folder.name)

    if opts.folder_cleanup and not year and artist and album:
        year = find_album_year(artist, album)
    if opts.folder_cleanup:
        album_folder = _rename_album_folder(album_folder, artist, album, year, root, opts, rec)

    audio_files = [
        f for f in album_folder.iterdir()
        if f.is_file() and f.suffix.lower() in AUDIO_EXTENSIONS
    ]
    if opts.rename:
        audio_files = [_rename_track(f, opts, rec) for f in audio_files]

    if opts.lyrics:
        for file in audio_files:
            _fetch_lyrics(file, artist, album, opts, rec)

    if opts.covers:
        _fetch_cover(album_folder, artist, album, opts, rec)

    if opts.file_cleanup:
        _clean_files(album_folder, opts, rec)


def process_library(
    options: ProcessOptions,
    *,
    root: Path | None = None,
    log: LogCallback | None = None,
    album_paths: list[str] | None = None,
) -> dict:
    """Run the selected maintenance modes. Honours ``options.dry_run``.

    ``album_paths`` optionally limits the run to specific album folders.
    """
    root = root or MUSIC_ROOT
    rec = _Recorder(sink=log)

    if not root.exists():
        rec.emit("warn", "root", f"Music root does not exist: {root}")
        return {"root": str(root), "dry_run": options.dry_run, "actions": rec.actions, "counts": rec.counts}

    if album_paths:
        wanted = {str(Path(p)) for p in album_paths}
        folders = [Path(p) for p in album_paths] if all(Path(p).exists() for p in album_paths) else [
            f for f in _iter_album_folders(root) if str(f) in wanted
        ]
    else:
        folders = list(_iter_album_folders(root))

    rec.emit(
        "info",
        "start",
        f"{'Dry run' if options.dry_run else 'Applying'} across {len(folders)} album(s)",
    )
    for album_folder in folders:
        try:
            _process_album(album_folder, root, options, rec)
        except OSError as exc:
            rec.emit("warn", "album", f"Error processing {album_folder.name}: {exc}")

    rec.emit("info", "done", "Finished")
    return {
        "root": str(root),
        "dry_run": options.dry_run,
        "actions": rec.actions,
        "counts": rec.counts,
    }