import 'dart:convert';
import 'dart:io';

import 'package:audio_service/audio_service.dart';
import 'package:path_provider/path_provider.dart';

import '../estado/orden_emisoras.dart';
import '../modelos/emisora.dart';
import 'persistencia_tolerante.dart';
import 'servicio_favoritos.dart';

/// URI of the bundled default station artwork, served from
/// `android/app/src/main/res/drawable` via `android.resource://` (Design
/// "default artwork delivery" — no per-URI grant needed, works offline, and
/// cannot 404 unlike a FileProvider content URI or a remote placeholder).
const String _defaultArtUri =
    'android.resource://es.freetimelab.pluriwave/drawable/default_station_art';

const _prefijoEmisora = 'emisora:';

/// Browse-source abstraction for the Android Auto media tree (Design
/// "getChildren data source, cold-start safe"). Kept separate from
/// `EstadoRadio` so a headless Auto bind (`main()` runs but the widget tree
/// — and therefore the lazily-created `EstadoRadio` — never builds) still
/// gets a valid, non-throwing tree.
abstract class FuenteEmisorasAuto {
  Future<List<Emisora>> favoritos();
  Future<List<Emisora>> misEmisoras();

  /// `populares` snapshot; may be empty on a cold bind (Design "which
  /// stations surface & ordering").
  Future<List<Emisora>> todas();
  Future<Emisora?> porUuid(String uuid);

  /// Live-snapshot push (Design "live snapshot the source prefers"):
  /// `EstadoRadio`, when alive, calls this unconditionally on every
  /// favorites/custom/populares mutation so a car and phone that are both
  /// live see identical lists. Default no-op — only implementations that
  /// actually buffer a snapshot (e.g. [FuenteEmisorasAutoLocal]) need to
  /// override it; a null field on `EstadoRadio` skips the call entirely via
  /// `?.`.
  void actualizarSnapshot({
    List<Emisora>? favoritos,
    List<Emisora>? misEmisoras,
    List<Emisora>? todas,
  }) {}
}

/// Pure builder for the Android Auto browse tree: folders, leaf items, id
/// resolution. No platform dependency — fully testable without a running
/// car or a real `AudioHandler`.
class ConstructorArbolAuto {
  /// Root folder ids (Design "media-id scheme"). The tree root itself is
  /// identified by [AudioService.browsableRootId], not by a constant here —
  /// the handler compares against it directly before calling [raiz].
  static const idFavoritos = 'favoritos';
  static const idTodas = 'todas';
  static const idMisEmisoras = 'mis_emisoras';

  static const _idsCarpetas = {idFavoritos, idTodas, idMisEmisoras};
  static const _maxItemsPorCarpeta = 50;

  /// Content-style extras (Design "content style", optional polish): list
  /// (1) for the root's folders, grid (2) for playable station items.
  static const _contentStyleLista = {
    'android.media.browse.CONTENT_STYLE_BROWSABLE_HINT': 1,
    'android.media.browse.CONTENT_STYLE_PLAYABLE_HINT': 1,
  };
  static const _contentStyleGrid = {
    'android.media.browse.CONTENT_STYLE_PLAYABLE_HINT': 2,
  };

  /// The 3 root folders (Favoritos, Todas las emisoras, Mis emisoras), all
  /// non-playable.
  List<MediaItem> raiz() => [
    _carpeta(idFavoritos, 'Favoritos'),
    _carpeta(idTodas, 'Todas las emisoras'),
    _carpeta(idMisEmisoras, 'Mis emisoras'),
  ];

  MediaItem _carpeta(String id, String titulo) => MediaItem(
    id: id,
    title: titulo,
    playable: false,
    extras: _contentStyleLista,
  );

  /// Leaf items for [parentId], sorted via [ordenarEmisoras] and capped at
  /// [_maxItemsPorCarpeta] (Design "which stations surface & ordering" —
  /// avoids driver distraction and Auto list limits). Unknown [parentId]
  /// (or an empty [emisoras]) returns an empty list instead of throwing.
  List<MediaItem> hijos(String parentId, {required List<Emisora> emisoras}) {
    if (!_idsCarpetas.contains(parentId)) return const [];
    if (emisoras.isEmpty) return const [];
    final ordenadas = ordenarEmisoras(emisoras, OrdenEmisoras.calidad);
    return ordenadas.take(_maxItemsPorCarpeta).map(itemEmisora).toList();
  }

  /// Maps a single [Emisora] to a playable `MediaItem`: id `emisora:<uuid>`
  /// (Design "media-id scheme"), title, and artUri with the default-art
  /// fallback (Design "default artwork delivery").
  MediaItem itemEmisora(Emisora e) => MediaItem(
    id: '$_prefijoEmisora${e.uuid}',
    title: e.nombre,
    playable: true,
    artUri: Uri.parse(_artUriPara(e)),
    extras: _contentStyleGrid,
  );

  String _artUriPara(Emisora e) {
    final favicon = e.favicon;
    return (favicon != null && favicon.isNotEmpty) ? favicon : _defaultArtUri;
  }

  /// Resolves `emisora:<uuid>` ids to the matching [Emisora] in [universo].
  /// Any other shape (no prefix, empty uuid, unmatched uuid) returns `null`
  /// instead of throwing (Spec "Media Item Resolution by ID").
  Emisora? resolver(String id, List<Emisora> universo) {
    if (!id.startsWith(_prefijoEmisora)) return null;
    final uuid = id.substring(_prefijoEmisora.length);
    if (uuid.isEmpty) return null;
    for (final emisora in universo) {
      if (emisora.uuid == uuid) return emisora;
    }
    return null;
  }
}

/// Routing seam between a car-tapped `emisora:<uuid>` media id and the
/// existing internal playback path (Design "playback coherence" — reuse
/// over duplication). Resolves the uuid via [fuente], builds the same
/// phone-shaped `MediaItem` (`id` = station url, `extras['uuid']`) that
/// [ServicioAudio.reproducir] builds, and delegates to [reproducir].
///
/// A stale/unknown id (or a malformed one) is a no-op: [reproducir] is
/// never called and no exception propagates (Spec "Unknown or stale media
/// id").
Future<void> reproducirPorMediaId(
  String id, {
  required FuenteEmisorasAuto fuente,
  required Future<void> Function(MediaItem) reproducir,
}) async {
  if (!id.startsWith(_prefijoEmisora)) return;
  final uuid = id.substring(_prefijoEmisora.length);
  if (uuid.isEmpty) return;

  final emisora = await fuente.porUuid(uuid);
  if (emisora == null) return;

  final item = MediaItem(
    id: emisora.url,
    title: emisora.nombre,
    artist: emisora.pais ?? '',
    album: 'PluriWave',
    artUri:
        emisora.favicon != null && emisora.favicon!.isNotEmpty
            ? Uri.tryParse(emisora.favicon!)
            : null,
    extras: {'uuid': emisora.uuid},
  );
  await reproducir(item);
}

/// Local, cold-start-safe implementation of [FuenteEmisorasAuto] (Design
/// "getChildren data source"). Reads favourites from SQLite and custom
/// stations from the tolerant JSON file directly — both loadable without
/// the network or a built widget tree, unlike `EstadoRadio._init()` (which
/// is lazy-created by `ChangeNotifierProvider.create:` and may never run on
/// a headless Auto bind). `EstadoRadio`, when alive, overrides these reads
/// with a live snapshot via [actualizarSnapshot].
class FuenteEmisorasAutoLocal implements FuenteEmisorasAuto {
  FuenteEmisorasAutoLocal({
    ServicioFavoritos? favoritosServicio,
    Future<String> Function()? resolverRutaCustom,
  }) : _favoritosServicio = favoritosServicio ?? ServicioFavoritos(),
       _resolverRutaCustom = resolverRutaCustom;

  final ServicioFavoritos _favoritosServicio;
  final Future<String> Function()? _resolverRutaCustom;

  List<Emisora>? _snapshotFavoritos;
  List<Emisora>? _snapshotMisEmisoras;
  List<Emisora>? _snapshotTodas;

  /// Overrides the next reads with `EstadoRadio`'s live in-memory lists
  /// (Design "live snapshot the source prefers"). Passing `null` for a
  /// field leaves its current override (or local read) untouched.
  @override
  void actualizarSnapshot({
    List<Emisora>? favoritos,
    List<Emisora>? misEmisoras,
    List<Emisora>? todas,
  }) {
    if (favoritos != null) _snapshotFavoritos = favoritos;
    if (misEmisoras != null) _snapshotMisEmisoras = misEmisoras;
    if (todas != null) _snapshotTodas = todas;
  }

  @override
  Future<List<Emisora>> favoritos() async {
    final snapshot = _snapshotFavoritos;
    if (snapshot != null) return snapshot;
    try {
      return await _favoritosServicio.obtenerTodos();
    } catch (_) {
      // Cold-start safety (Spec "Browse requested before app state is
      // loaded"): never throw out of a browse call.
      return const [];
    }
  }

  @override
  Future<List<Emisora>> misEmisoras() async {
    final snapshot = _snapshotMisEmisoras;
    if (snapshot != null) return snapshot;
    return _leerEmisorasCustom();
  }

  @override
  Future<List<Emisora>> todas() async {
    // No live network snapshot on a cold bind — populated only once
    // EstadoRadio pushes its populares list (Design "which stations
    // surface & ordering": degrades gracefully to empty-but-valid).
    return _snapshotTodas ?? const [];
  }

  @override
  Future<Emisora?> porUuid(String uuid) async {
    final listas = await Future.wait([favoritos(), misEmisoras(), todas()]);
    for (final lista in listas) {
      for (final emisora in lista) {
        if (emisora.uuid == uuid) return emisora;
      }
    }
    return null;
  }

  /// Mirrors `EstadoRadio._cargarEmisorasCustom()`'s tolerant JSON read:
  /// missing/corrupt files never throw, they degrade to an empty list.
  Future<List<Emisora>> _leerEmisorasCustom() async {
    try {
      final ruta = await _rutaArchivoCustom();
      final archivo = File(ruta);
      if (!await archivo.exists()) return const [];
      final contenido = await archivo.readAsString();
      final data = jsonDecode(contenido) as List;
      final resultado = parseListaTolerante<Emisora>(
        data,
        Emisora.fromMap,
        subsistema: 'emisoras_custom_auto',
        coleccion: 'emisoras_custom',
      );
      return resultado.validas;
    } catch (_) {
      return const [];
    }
  }

  Future<String> _rutaArchivoCustom() async {
    final resolver = _resolverRutaCustom;
    if (resolver != null) return resolver();
    final dir = await getApplicationDocumentsDirectory();
    return '${dir.path}/emisoras_custom.json';
  }
}