#!/usr/bin/env python3
"""
export-laptop-playlists.py — daily Navidrome → Traktor M3U export.

Lists every Navidrome playlist whose name starts with `dj-`, fetches each
playlist's tracks via Subsonic, looks up the real on-disk path of each
track in beets, and writes a `.m3u` for Syncthing → Traktor.

Output dir: $MUSIC_DATA_DIR/playlists-laptop/
  - One `dj-<name>.m3u` per Navidrome dj-* playlist (overwritten each run)
  - Exact format Traktor Pro 4 itself uses when you Export Playlist as M3U:
    one absolute Windows path per line (`C:\\Music\\Library\\...\\Track.flac`),
    UTF-8 encoded, LF line endings, NO `#EXTM3U` header. Traktor's M3U
    importer treats `#EXTM3U` as either a parse error or a phantom track
    path, which kicks the rest of the import into "treat-as-new" mode and
    the playlist ends up with unanalyzed records. With the header omitted,
    Traktor parses each line as a LOCATION, matches against the existing
    Collection by DIR+FILE+VOLUME, and the playlist inherits BPM, waveform,
    and key from the already-analyzed entries.

Why beets, not Subsonic, for paths: Navidrome's Subsonic `path` attribute
is a *synthesized* string like `Artist/Album/01 - Title.flac` even when
the real file is just `Artist/Album/Title.flac`. The track-number prefix
is generated from metadata, not read from disk. Traktor then can't find
the file. Beets stores the real path, so we look up each track by
(album, title) in a one-shot beets index, falling back to artist
disambiguation when multiple albums share the same album+title.

Reconciles deletes: any `dj-*.m3u` on disk whose stem is no longer a
current Navidrome playlist is removed; also sweeps legacy `.m3u8`/`.nml`
files from earlier experiments.

Existing M3U files in `$MUSIC_DATA_DIR/playlists/` (Navidrome's M3U
import source for the automated Spotify pipeline) are NOT touched.

Usage:
    export-laptop-playlists.py [--verbose]
"""

from __future__ import annotations

import argparse
import os
import re
import subprocess
import sys
import time
import urllib.parse
import urllib.request
import xml.etree.ElementTree as ET

_ALEMBIC_CONFIG_DIR = os.environ.get("ALEMBIC_CONFIG_DIR", "/config")
_MUSIC_DATA_DIR = os.environ.get("MUSIC_DATA_DIR", "/data/music")

OUT_DIR = f"{_MUSIC_DATA_DIR}/playlists-laptop"

# Absolute Windows path to the laptop's library root.
LIBRARY_LAPTOP_ROOT = r"C:\Music\Library"

# Beets stores paths with this prefix (the container-side mount of the
# library); strip it to get the path relative to the library root. This is
# still "/music/" through the migration's Stage 0-3 transitional mount;
# revisit at Stage 4 once beets' directory: becomes MUSIC_DATA_DIR/Library.
BEETS_LIBRARY_PREFIX = "/music/"

M3U_EXT = ".m3u"
# Older formats from earlier iterations of this script — swept by reconcile.
LEGACY_EXTS = (".m3u8", ".nml")


def _load_navidrome_env():
    path = f"{_ALEMBIC_CONFIG_DIR}/pipeline/navidrome/admin.env"
    env = {}
    if os.path.exists(path):
        for line in open(path):
            line = line.strip()
            if not line or line.startswith("#") or "=" not in line:
                continue
            k, v = line.split("=", 1)
            env[k] = v.strip().strip("'").strip('"')
    return env

_nd_env = _load_navidrome_env()
ND_BASE = _nd_env.get("ND_BASE", "http://navidrome:4533")
ND_USER = _nd_env.get("ND_USER", "")
ND_PASS = _nd_env.get("ND_PASS", "")
ND_API_VERSION = "1.16.0"
ND_CLIENT = "dj-export"

NS = "{http://subsonic.org/restapi}"

# ASCII Unit Separator — safe field separator for beets `-f` output.
SEP = "\x1f"


def _call(endpoint: str, params: dict[str, str]) -> ET.Element:
    qp = {
        "u": ND_USER, "p": ND_PASS,
        "v": ND_API_VERSION, "c": ND_CLIENT, "f": "xml",
        **params,
    }
    url = f"{ND_BASE}/rest/{endpoint}.view?{urllib.parse.urlencode(qp)}"
    with urllib.request.urlopen(url, timeout=60) as r:
        body = r.read()
    root = ET.fromstring(body)
    if root.attrib.get("status") != "ok":
        err = root.find(f"{NS}error")
        msg = err.attrib.get("message", "unknown") if err is not None else "?"
        raise RuntimeError(f"Subsonic {endpoint} failed: {msg}")
    return root


def list_dj_playlists() -> list[tuple[str, str]]:
    root = _call("getPlaylists", {})
    out: list[tuple[str, str]] = []
    for p in root.iter(f"{NS}playlist"):
        name = p.attrib.get("name", "")
        if name.startswith("dj-"):
            out.append((p.attrib["id"], name))
    return out


def get_playlist_tracks(pid: str) -> list[tuple[str, str, str]]:
    """Return (albumartist, album, title) tuples per playlist entry."""
    root = _call("getPlaylist", {"id": pid})
    out: list[tuple[str, str, str]] = []
    for entry in root.iter(f"{NS}entry"):
        aa = (entry.attrib.get("displayAlbumArtist")
              or entry.attrib.get("artist", ""))
        album = entry.attrib.get("album", "")
        title = entry.attrib.get("title", "")
        out.append((aa, album, title))
    return out


def _normkey(s: str) -> str:
    """Lowercase + normalize curly quotes to straight ASCII."""
    return (s.lower()
            .replace("’", "'").replace("‘", "'")
            .replace("“", '"').replace("”", '"'))


def build_beets_index() -> dict[tuple[str, str], list[tuple[str, str, str, str]]]:
    """Map (album, title) →
    [(albumartist, album, title, library-relative path), ...].

    Album and title are returned with original casing (not _normkey'd) so the
    NML COLLECTION entries can carry the real metadata for display."""
    fmt = SEP.join(["$albumartist", "$album", "$title", "$path"])
    res = subprocess.run(
        ["beet", "ls", "-f", fmt],
        capture_output=True, text=True, check=True
    )
    idx: dict[tuple[str, str], list[tuple[str, str, str, str]]] = {}
    for ln in res.stdout.splitlines():
        parts = ln.split(SEP)
        if len(parts) != 4:
            continue
        aa, alb, ti, path = parts
        if not path.startswith(BEETS_LIBRARY_PREFIX):
            continue
        rel = path[len(BEETS_LIBRARY_PREFIX):]
        idx.setdefault((_normkey(alb), _normkey(ti)), []).append((aa, alb, ti, rel))
    return idx


def resolve(idx: dict[tuple[str, str], list[tuple[str, str, str, str]]],
            aa_query: str, album: str, title: str
            ) -> tuple[str, str, str, str] | None:
    """Return (albumartist, album, title, rel_path) for a Subsonic track, or None."""
    candidates = idx.get((_normkey(album), _normkey(title)))
    if not candidates:
        return None
    if len(candidates) == 1:
        return candidates[0]
    q = _normkey(aa_query).replace(" • ", " ").replace(";", " ")
    for c in candidates:
        if _normkey(c[0]) in q:
            return c
    return candidates[0]


def to_windows_path(rel: str) -> str:
    """Library-relative POSIX path → absolute Windows path with backslashes."""
    return LIBRARY_LAPTOP_ROOT + "\\" + rel.replace("/", "\\")


def write_m3u(name: str, tracks: list[tuple[str, str, str, str]], verbose: bool) -> int:
    """Plain-path M3U, no `#EXTM3U` header — matches the format Traktor
    Pro 4 itself emits via Export Playlist → M3U. With this byte-exact
    format, Traktor's import re-uses existing analyzed Collection entries
    (matched by DIR+FILE+VOLUME) instead of creating fresh unanalyzed
    records."""
    target = os.path.join(OUT_DIR, f"{name}{M3U_EXT}")
    tmp = target + ".tmp"
    with open(tmp, "w", encoding="utf-8", newline="\n") as f:
        for _aa, _alb, _ti, rel in tracks:
            f.write(to_windows_path(rel) + "\n")
    os.replace(tmp, target)
    if verbose:
        print(f"  wrote {target} ({len(tracks)} tracks)")
    return len(tracks)


def reconcile(current_names: set[str], verbose: bool) -> int:
    """Delete dj-*.m3u files whose stem is no longer current, and sweep
    any legacy .m3u8/.nml leftovers from earlier iterations."""
    removed = 0
    if not os.path.isdir(OUT_DIR):
        return 0
    for entry in os.scandir(OUT_DIR):
        if not entry.is_file() or not entry.name.startswith("dj-"):
            continue
        if entry.name.endswith(M3U_EXT):
            stem = entry.name[:-len(M3U_EXT)]
            if stem in current_names:
                continue
        elif any(entry.name.endswith(e) for e in LEGACY_EXTS):
            pass  # always sweep
        else:
            continue
        os.remove(entry.path)
        removed += 1
        if verbose:
            print(f"  removed stale {entry.path}")
    return removed


def main() -> int:
    ap = argparse.ArgumentParser(description=__doc__)
    ap.add_argument("--verbose", action="store_true")
    args = ap.parse_args()

    os.makedirs(OUT_DIR, exist_ok=True)
    stamp = time.strftime("%Y-%m-%dT%H:%M:%S")
    print(f"[{stamp}] export-laptop-playlists starting")

    idx = build_beets_index()
    print(f"  beets index: {len(idx)} (album,title) keys")

    playlists = list_dj_playlists()
    print(f"  found {len(playlists)} dj-* playlists in Navidrome")

    # Safety guard: if Navidrome answers successfully but reports ZERO dj-*
    # playlists while exported files exist on disk, something is wrong on the
    # Navidrome side (fresh/restored DB, purge, renamed playlists). Running
    # reconcile() would delete every dj-*.m3u and Syncthing would propagate
    # the deletions to the laptop — the 2026-06-01 Traktor wipe through the
    # other door. Refuse and keep the files.
    if not playlists:
        existing = [e.name for e in os.scandir(OUT_DIR)
                    if e.is_file() and e.name.startswith("dj-")]
        if existing:
            print(f"  WARN: Navidrome returned 0 dj-* playlists but "
                  f"{len(existing)} dj-* file(s) exist in {OUT_DIR} — "
                  f"REFUSING to reconcile/delete. Check Navidrome before "
                  f"trusting this.")
            return 0

    total_tracks = 0
    total_unresolved = 0
    written = 0
    skipped = 0
    for pid, name in playlists:
        try:
            tracks = get_playlist_tracks(pid)
        except Exception as e:
            print(f"  WARN: failed to fetch {name}: {e}")
            continue
        resolved: list[tuple[str, str, str, str]] = []
        unresolved: list[tuple[str, str, str]] = []
        for aa, album, title in tracks:
            hit = resolve(idx, aa, album, title)
            if hit is None:
                unresolved.append((aa, album, title))
                continue
            resolved.append(hit)
        if unresolved:
            total_unresolved += len(unresolved)
            print(f"  WARN: {name}: {len(unresolved)} track(s) not in beets index "
                  f"(skipped). First: {unresolved[0]}")
        # Safety guard: never blow away a populated .m3u with an empty export.
        # On 2026-06-01 a PURGEMISSING scan emptied the Navidrome dj-* playlists
        # while the QNAP share was flaky; this script then overwrote every
        # laptop .m3u with 0 tracks, and the laptop's auto-merge wiped Traktor.
        # If Navidrome resolves to 0 tracks but a non-empty file already exists,
        # keep the file and warn loudly instead of trusting the empty result.
        if not resolved:
            target = os.path.join(OUT_DIR, f"{name}{M3U_EXT}")
            if os.path.exists(target) and os.path.getsize(target) > 0:
                print(f"  WARN: {name}: Navidrome returned 0 resolvable tracks but "
                      f"{target} is non-empty — REFUSING to overwrite (kept existing). "
                      f"Check Navidrome (likely a purge/scan glitch) before trusting this.")
                skipped += 1
                continue

        total_tracks += write_m3u(name, resolved, args.verbose)
        written += 1

    current_names = {name for _pid, name in playlists}
    removed = reconcile(current_names, args.verbose)

    print(f"[{stamp}] done. wrote {written} playlists, {total_tracks} total tracks, "
          f"{total_unresolved} unresolved, {skipped} kept (empty-guard), "
          f"removed {removed} stale files")
    return 0


if __name__ == "__main__":
    sys.exit(main())