import 'dart:convert';

import '../modelos/emisora.dart';
import '../modelos/grupo_favoritos.dart';
import '../modelos/preset_ecualizador.dart';

/// Owns the backup (export/import) JSON serialization (S4-R4).
///
/// The v2 envelope produced here is byte-compatible with the legacy format
/// previously assembled inline by `EstadoRadio.exportarConfig` and
/// pretty-printed by `pantalla_ajustes.dart`, so existing exports keep
/// round-tripping. State APPLICATION (writing favorites, EQ, alarms back
/// into the app) stays in `EstadoRadio.importarConfig` — this service only
/// owns serialization, parsing and the envelope shape.
class ServicioExportImport {
  const ServicioExportImport();

  /// Current backup schema version (v2 — full portability).
  static const int versionActual = 2;

  /// Builds the v2 export envelope. Key set and semantics must stay exactly
  /// as the legacy inline export so old backups remain importable:
  /// the `alarmas` block is the RAW JSON map persisted by ServicioAlarmas
  /// and passes through untouched (no re-parsing here).
  Map<String, dynamic> construirExportacion({
    required List<GrupoFavoritos> gruposFavoritos,
    required List<Emisora> favoritos,
    required List<Emisora> emisorasCustom,
    required PresetEcualizador presetPrincipal,
    required Map<String, PresetEcualizador> presetsPorEmisora,
    required Map<String, dynamic>? alarmas,
    required String? emisoraPreferidaUuid,
    required String ordenListas,
    required List<int> timerSuenoPresetsSegundos,
    DateTime? exportadoEn,
  }) {
    return {
      'version': versionActual,
      'exportedAt': (exportadoEn ?? DateTime.now()).toIso8601String(),
      // Favorites + groups (preserves grupo_id assignments per station).
      // The protected "sin asignar" group is implicit and never exported.
      'gruposFavoritos':
          gruposFavoritos
              .where((g) => !g.esSinAsignar)
              .map((g) => g.toMap())
              .toList(),
      'favoritos': favoritos.map((e) => e.toMap()).toList(),
      // Custom stations.
      'emisorasCustom': emisorasCustom.map((e) => e.toMap()).toList(),
      // Equalizer.
      'presetPrincipalEcualizador': presetPrincipal.toJson(),
      'presetsEcualizador': presetsPorEmisora.map(
        (uuid, preset) => MapEntry(uuid, preset.toJson()),
      ),
      // Full alarm block (alarms + vacations + exceptions) — raw passthrough.
      'alarmas': alarmas,
      // User preferences.
      'emisoraPreferidaUuid': emisoraPreferidaUuid,
      'ordenListas': ordenListas,
      'timerSuenoPresetsSegundos': timerSuenoPresetsSegundos,
    };
  }

  /// Serializes an export envelope to pretty-printed JSON (same formatting
  /// the legacy export shared as a file).
  String exportar(Map<String, dynamic> config) =>
      const JsonEncoder.withIndent('  ').convert(config);

  /// Parses a backup JSON string. Returns `null` on malformed input or when
  /// the document is not a JSON object — graceful, never throws (S4-R4).
  Map<String, dynamic>? importar(String raw) {
    try {
      final decoded = jsonDecode(raw);
      if (decoded is! Map) return null;
      return Map<String, dynamic>.from(decoded);
    } on FormatException {
      return null;
    }
  }
}