"""
Music library helpers — read folder tree, delete files/folders.
File serving is handled directly in main.py via FastAPI's FileResponse.
"""

import shutil
from pathlib import Path
from typing import Any

from config import MUSIC_DIR


def get_library() -> list[dict[str, Any]]:
    """
    Walk the Music directory and return a nested structure:
    [
      {
        "artist": "Queen",
        "albums": [
          {
            "album": "A Night at the Opera",
            "tracks": [
              { "filename": "01 - Bohemian Rhapsody.mp3", "path": "Queen/A Night at the Opera/01 - Bohemian Rhapsody.mp3" }
            ]
          }
        ]
      }
    ]
    """
    artists: list[dict[str, Any]] = []

    if not MUSIC_DIR.exists():
        return artists

    for artist_dir in sorted(MUSIC_DIR.iterdir()):
        if not artist_dir.is_dir():
            continue

        albums: list[dict[str, Any]] = []
        for album_dir in sorted(artist_dir.iterdir()):
            if not album_dir.is_dir():
                continue

            tracks = []
            for track_file in sorted(album_dir.iterdir()):
                if track_file.suffix.lower() not in {".mp3", ".flac", ".m4a", ".ogg"}:
                    continue
                rel = track_file.relative_to(MUSIC_DIR)
                tracks.append({
                    "filename": track_file.name,
                    "path": rel.as_posix(),
                    "size": track_file.stat().st_size,
                })

            if tracks:
                albums.append({"album": album_dir.name, "tracks": tracks})

        if albums:
            artists.append({"artist": artist_dir.name, "albums": albums})

    return artists


def delete_path(rel_path: str) -> None:
    """
    Delete a file or directory relative to MUSIC_DIR.
    Raises ValueError if the resolved path escapes MUSIC_DIR (path traversal guard).
    """
    target = (MUSIC_DIR / rel_path).resolve()

    # Security: ensure target is inside MUSIC_DIR
    if not str(target).startswith(str(MUSIC_DIR)):
        raise ValueError("Path traversal detected.")

    if not target.exists():
        raise FileNotFoundError(f"Not found: {rel_path}")

    if target.is_dir():
        shutil.rmtree(target)
    else:
        target.unlink()

    # Clean up empty parent directories (album → artist)
    _remove_empty_parents(target.parent)


def _remove_empty_parents(directory: Path) -> None:
    """Walk up and remove directories that are now empty, stopping at MUSIC_DIR."""
    current = directory
    while current != MUSIC_DIR and current.is_dir():
        if not any(current.iterdir()):
            current.rmdir()
            current = current.parent
        else:
            break


def resolve_track_path(rel_path: str) -> Path:
    """
    Resolve a relative path (e.g. 'Artist/Album/track.mp3') to an absolute path
    inside MUSIC_DIR. Raises ValueError on path traversal.
    """
    target = (MUSIC_DIR / rel_path).resolve()
    if not str(target).startswith(str(MUSIC_DIR)):
        raise ValueError("Path traversal detected.")
    if not target.exists():
        raise FileNotFoundError(f"Not found: {rel_path}")
    return target