from __future__ import annotations

import re
import sys
from pathlib import Path
from typing import Optional, List, Dict, Tuple

from models import AlbumScan, AlbumHints, TrackHints

try:
    from mutagen import File as MutagenFile
    HAS_MUTAGEN = True
except ImportError:
    HAS_MUTAGEN = False

try:
    from bs4 import BeautifulSoup
    HAS_BS4 = True
except ImportError:
    HAS_BS4 = False

_NATSORT_RE = re.compile(r"(\d+)")
_BAD_VALUES = {"unknown", "unknown artist", "unknown album", "untitled", "track", "va", "various"}

# Filename patterns: most specific first
_FILENAME_PATTERNS = [
    re.compile(r"^(?P<disc>\d{1,2})[- _]+(?P<track>\d{1,3})\s*[-._ ]+\s*(?P<artist>.+?)\s*[-–]\s*(?P<title>.+)$"),
    re.compile(r"^(?P<disc>\d{1,2})[- _]+(?P<track>\d{1,3})\s*[-._ ]+\s*(?P<title>.+)$"),
    re.compile(r"^(?P<track>\d{1,3})\s*[-._ ]+\s*(?P<artist>.+?)\s*[-–]\s*(?P<title>.+)$"),
    re.compile(r"^(?P<track>\d{1,3})\s*[-._ ]+\s*(?P<title>.+)$"),
    re.compile(r"^(?P<artist>.+?)\s*[-–]\s*(?P<title>.+)$"),
]

# Directory name patterns
_DIR_PATTERNS = [
    re.compile(r"^(?P<artist>.+?)[_ -]+[-–][_ -]+(?P<album>.+?)(?:[_ -]+(?P<year>\d{4}))?$"),
    re.compile(r"^(?P<artist>.+?)[_ ]+(?P<year>\d{4})[._ -]+(?P<album>.+)$"),
    re.compile(r"^(?P<album>.+?)[_ -]+(?P<year>\d{4})$"),
]

# Tracklist line patterns
_TRACKLIST_PATTERNS = [
    re.compile(r"^(?P<disc>\d{1,2})[- _](?P<track>\d{1,3})\s+(?P<title>.+?)(?:\s+\d+:\d{2})?$"),
    re.compile(r"^(?P<track>\d{1,3})[.):\s]+(?P<title>.+?)(?:\s+\d+:\d{2})?$"),
    re.compile(r"^(?P<track>[A-Z]\d{1,2})[.):\s]+(?P<title>.+?)(?:\s+\d+:\d{2})?$"),
]

_DISC_SECTION_RE = re.compile(r"(?i)(?:cd|disc|disk|side)[_ \-]*(\d{1,2})")


def _clean(s: Optional[str]) -> str:
    if not s:
        return ""
    # BOM (U+FEFF), Zero-Width-Space (U+200B), Soft-Hyphen (U+00AD) entfernen
    s = re.sub(r"[​­]", "", s)
    return re.sub(r"\s+", " ", s.replace("_", " ")).strip(" -._")


def _is_good(v: Optional[str]) -> bool:
    if not v:
        return False
    return _clean(v).casefold() not in _BAD_VALUES


def _parse_dirname(name: str) -> Tuple[Optional[str], Optional[str], Optional[str]]:
    name_clean = _clean(name)
    for pat in _DIR_PATTERNS:
        m = pat.match(name_clean)
        if m:
            d = m.groupdict()
            artist = _clean(d.get("artist")) or None
            album = _clean(d.get("album")) or None
            year = d.get("year")
            if _is_good(artist) or _is_good(album):
                return artist, album, year
    # No pattern matched — treat whole name as album
    return None, _clean(name_clean), None


def _parse_filename(stem: str) -> Dict[str, str]:
    stem_clean = _clean(stem)
    for pat in _FILENAME_PATTERNS:
        m = pat.match(stem_clean)
        if m:
            return {k: _clean(v) for k, v in m.groupdict().items() if v}
    return {"title": stem_clean}


def _read_tags(path: Path) -> Tuple[Dict[str, str], Optional[float]]:
    if not HAS_MUTAGEN:
        return {}, None
    try:
        audio = MutagenFile(str(path), easy=True)
        if not audio:
            return {}, None
        tags: Dict[str, str] = {}
        for k in ("title", "artist", "album", "albumartist", "tracknumber",
                  "discnumber", "date", "year", "genre", "label", "organization"):
            v = audio.get(k)
            if v:
                tags[k] = str(v[0]).strip()
        if "year" in tags and "date" not in tags:
            tags["date"] = tags["year"]
        duration = None
        if hasattr(audio, "info") and audio.info and hasattr(audio.info, "length"):
            duration = audio.info.length
        return tags, duration
    except Exception as e:
        print(f"  ⚠️ Tag-Lesefehler {path.name}: {e}", file=sys.stderr)
        return {}, None


def _parse_tracklist(text: str) -> List[Dict[str, str]]:
    tracks: List[Dict[str, str]] = []
    current_disc = 1

    for line in text.splitlines():
        line = line.strip()
        if not line:
            continue

        disc_m = _DISC_SECTION_RE.match(line)
        if disc_m and len(line) < 30:
            current_disc = int(disc_m.group(1))
            continue

        for pat in _TRACKLIST_PATTERNS:
            m = pat.match(line)
            if m:
                d = m.groupdict()
                entry: Dict[str, str] = {"title": _clean(d.get("title", ""))}
                raw_track = d.get("track", "")
                if raw_track and raw_track.isdigit():
                    entry["track"] = raw_track.lstrip("0") or "0"
                elif raw_track:
                    entry["track"] = raw_track
                if "disc" in d and d["disc"]:
                    entry["disc"] = d["disc"]
                else:
                    entry["disc"] = str(current_disc)
                if entry.get("title"):
                    tracks.append(entry)
                break

    return tracks


def _parse_m3u(text: str) -> List[Dict[str, str]]:
    """M3U/M3U8 → geordnete Liste: [{filename, title, position}].
    Reihenfolge der Einträge = gewünschte Trackreihenfolge.
    """
    tracks: List[Dict[str, str]] = []
    pending_title: Optional[str] = None
    position = 0
    for line in text.splitlines():
        line = line.strip()
        if not line:
            continue
        if line.upper().startswith("#EXTINF:"):
            parts = line.split(",", 1)
            pending_title = parts[1].strip() if len(parts) > 1 else None
        elif not line.startswith("#"):
            filename = Path(line.replace("\\", "/")).name
            if not filename:
                continue
            position += 1
            tracks.append({
                "position": str(position),
                "filename": filename,
                "title": pending_title or "",
            })
            pending_title = None
    return tracks


def _read_tracklist_file(path: Path) -> Optional[str]:
    try:
        if path.suffix.lower() in (".htm", ".html"):
            raw = path.read_bytes()
            encoding = "utf-8"
            for enc in ("utf-8", "latin-1", "cp1252"):
                try:
                    raw.decode(enc)
                    encoding = enc
                    break
                except UnicodeDecodeError:
                    continue
            text = raw.decode(encoding, errors="replace")
            if HAS_BS4:
                soup = BeautifulSoup(text, "html.parser")
                return soup.get_text(separator="\n")
            # Fallback: strip HTML tags
            return re.sub(r"<[^>]+>", " ", text)
        else:
            for enc in ("utf-8", "latin-1", "cp1252"):
                try:
                    return path.read_text(encoding=enc)
                except UnicodeDecodeError:
                    continue
    except Exception as e:
        print(f"  ⚠️ Tracklist-Lesefehler {path.name}: {e}", file=sys.stderr)
    return None


def _check_cover_images(paths: List[Path]) -> List[Path]:
    good: List[Path] = []
    for p in paths:
        name_lower = p.name.lower()
        # Prefer front covers
        if any(kw in name_lower for kw in ("front", "folder", "cover", "album")):
            good.insert(0, p)
        else:
            good.append(p)
    return good


def extract_hints(scan: AlbumScan) -> AlbumHints:
    hints = AlbumHints(album_dir=scan.album_dir)

    # Directory name
    hints.dir_artist, hints.dir_album, hints.dir_year = _parse_dirname(scan.album_dir.name)

    # Cover images
    hints.cover_images = _check_cover_images(scan.image_files)

    # Tracklist files
    texts: List[str] = []
    for tf in scan.tracklist_files:
        txt = _read_tracklist_file(tf)
        if txt:
            texts.append(txt)
    hints.tracklist_text = "\n\n".join(texts) if texts else None

    parsed_tracklist = _parse_tracklist(hints.tracklist_text) if hints.tracklist_text else []

    # M3U/Playlist-Reihenfolge: filename (stem, normalisiert) → Tracknummer
    m3u_order: Dict[str, int] = {}
    m3u_titles: Dict[str, str] = {}
    for pf in scan.playlist_files:
        try:
            text = pf.read_text(encoding="utf-8", errors="replace")
            for entry in _parse_m3u(text):
                stem = _clean(Path(entry["filename"]).stem).casefold()
                pos = int(entry["position"])
                if stem and stem not in m3u_order:
                    m3u_order[stem] = pos
                    if entry.get("title"):
                        m3u_titles[stem] = entry["title"]
        except Exception as e:
            print(f"  ⚠️ Playlist-Lesefehler {pf.name}: {e}", file=sys.stderr)

    # Tracklist-Lookup: normalisierter Titel → Eintrag (für titelbasiertes Matching)
    tl_by_title: Dict[str, Dict[str, str]] = {}
    for entry in parsed_tracklist:
        key = _clean(entry.get("title", "")).casefold()
        if key:
            tl_by_title[key] = entry

    # Build TrackHints per audio file
    for audio_path in sorted(scan.audio_files):
        tags, duration = _read_tags(audio_path)
        fn_hints = _parse_filename(audio_path.stem)

        track_num: Optional[int] = None
        disc_num: Optional[int] = None

        # Track number: tag > filename
        raw_tn = tags.get("tracknumber") or fn_hints.get("track")
        if raw_tn:
            try:
                tn_int = int(str(raw_tn).split("/")[0])
                if tn_int > 0:   # 0 gilt als "keine Nummer"
                    track_num = tn_int
            except ValueError:
                pass

        # Track number aus M3U-Reihenfolge (Vorrang vor Dateiname, aber nicht vor Tag)
        if track_num is None:
            stem_key = _clean(audio_path.stem).casefold()
            if stem_key in m3u_order:
                track_num = m3u_order[stem_key]

        # Disc number: tag > filename > path segment
        raw_dn = tags.get("discnumber") or fn_hints.get("disc")
        if raw_dn:
            try:
                disc_num = int(str(raw_dn).split("/")[0])
            except ValueError:
                pass
        if not disc_num:
            for part in audio_path.relative_to(scan.album_dir).parts[:-1]:
                dm = _DISC_SECTION_RE.search(part)
                if dm:
                    disc_num = int(dm.group(1))
                    break

        title = tags.get("title") or fn_hints.get("title")
        artist = tags.get("artist") or fn_hints.get("artist")

        # Tracklist: erst nach Nummer, dann nach Titel
        if parsed_tracklist:
            matched_tl: Optional[Dict[str, str]] = None
            if track_num:
                for tl_entry in parsed_tracklist:
                    tl_track = tl_entry.get("track")
                    tl_disc = tl_entry.get("disc", "1")
                    if (tl_track and int(tl_track) == track_num
                            and int(tl_disc) == (disc_num or 1)):
                        matched_tl = tl_entry
                        break
            if matched_tl is None and title:
                matched_tl = tl_by_title.get(_clean(title).casefold())
            if matched_tl and not _is_good(title) and _is_good(matched_tl.get("title")):
                title = matched_tl["title"]

        # M3U-Titel als Fallback (enthält "Composer - Title" — nur nutzen wenn kein besserer Titel)
        if not _is_good(title):
            stem_key = _clean(audio_path.stem).casefold()
            if stem_key in m3u_titles:
                title = m3u_titles[stem_key]

        hints.tracks.append(TrackHints(
            path=audio_path,
            track_number=track_num,
            disc_number=disc_num,
            title=_clean(title) if title else None,
            artist=_clean(artist) if artist else None,
            duration=duration,
            existing_tags=tags,
        ))

    return hints