pluriwave/lib/servicios/servicio_export_import.dart

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).
///
/// v3 extends v2 with `presetsPorDispositivo`, `presetsMatriz`, and
/// `eqMultiDeviceEnabled`. When those optional parameters are omitted the
/// export stays at v2 for backward compat with the old app. 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 (v3 — multi-device EQ).
  static const int versionActual = 3;

  /// Legacy v2 version constant kept for clarity.
  static const int versionV2 = 2;

  /// Builds the export envelope.
  ///
  /// When [presetsPorDispositivo] or [presetsMatriz] are provided (non-null),
  /// [versionActual] (3) is written. When both are omitted the call behaves
  /// identically to the original v2 format (version key stays 2) so old
  /// backups keep round-tripping without version bumps.
  ///
  /// 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,
    // v3 extensions — omitting these produces a v2-compatible export.
    Map<String, PresetEcualizador>? presetsPorDispositivo,
    Map<String, PresetEcualizador>? presetsMatriz,
    bool? eqMultiDeviceEnabled,
  }) {
    final tieneExtensionesV3 =
        presetsPorDispositivo != null ||
        presetsMatriz != null ||
        eqMultiDeviceEnabled != null;

    final envelope = <String, dynamic>{
      'version': tieneExtensionesV3 ? versionActual : versionV2,
      '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 (base fields — present in all versions).
      '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,
    };

    // v3 extensions: only written when explicitly provided.
    if (tieneExtensionesV3) {
      envelope['presetsPorDispositivo'] = (presetsPorDispositivo ?? {}).map(
        (deviceId, preset) => MapEntry(deviceId, preset.toJson()),
      );
      envelope['presetsMatriz'] = (presetsMatriz ?? {}).map(
        (clave, preset) => MapEntry(clave, preset.toJson()),
      );
      envelope['eqMultiDeviceEnabled'] = eqMultiDeviceEnabled ?? false;
    }

    return envelope;
  }

  /// 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;
    }
  }
}