dmc/app/lib/services/sharing/mission_share_codec.dart

import 'dart:convert';

import '../../app_info.dart';
import '../../domain/waypoint/flat_waypoint_list.dart';
import '../database/waypoint_json_codec.dart';

/// Missionsdaten fuer den Export - unabhaengig von der Drift-Zeilenklasse,
/// damit dieser Codec ohne Datenbankzugriff testbar bleibt.
class MissionExportData {
  const MissionExportData({
    required this.name,
    this.placeName,
    required this.createdAt,
    required this.waypoints,
  });

  final String name;
  final String? placeName;
  final DateTime createdAt;
  final List<Waypoint> waypoints;
}

/// Baut die Export-Datei fuer eine Mission (Doku 3.6, analog
/// buildMissionExportObject()/shareMission() im HTML-Demonstrator) - ein
/// mit `appVersion`/`exportedAt` umschlossenes JSON-Dokument, damit ein
/// Import spaeter erkennen kann, aus welcher App-Version die Datei stammt.
String buildMissionExportJson(MissionExportData mission) {
  final map = {
    'appVersion': kAppVersion,
    'exportedAt': DateTime.now().toUtc().toIso8601String(),
    'mission': {
      'name': mission.name,
      'placeName': mission.placeName,
      'createdAt': mission.createdAt.toUtc().toIso8601String(),
      'waypoints': [for (final w in mission.waypoints) waypointToJson(w)],
    },
  };
  return const JsonEncoder.withIndent('  ').convert(map);
}

/// Vorschlagsname fuer die geteilte Datei (Doku 3.6, analog
/// `'mission-' + safeName + '.json'` im HTML-Demonstrator).
String missionExportFilename(String label) {
  final safeName = label.replaceAll(RegExp(r'[^a-zA-Z0-9]'), '_');
  return 'mission-$safeName.json';
}

class ParsedMissionImport {
  const ParsedMissionImport({
    required this.name,
    this.placeName,
    required this.waypoints,
    this.versionMismatch,
  });

  final String name;
  final String? placeName;
  final List<Waypoint> waypoints;

  /// Enthaelt die appVersion der Datei, falls sie sich von [kAppVersion] in
  /// der Hauptversionsnummer unterscheidet - sonst null (analog der
  /// "Imported from a different app version"-Warnung im HTML-Demonstrator).
  final String? versionMismatch;
}

/// Parst eine importierte Missionsdatei - wirft [FormatException] bei
/// ungueltigem JSON oder fehlenden Wegpunkten (Doku 3.6, analog dem
/// `change`-Handler von importMissionInput im HTML-Demonstrator).
ParsedMissionImport parseMissionImportJson(String jsonText) {
  final Object? decoded;
  try {
    decoded = jsonDecode(jsonText);
  } on FormatException {
    throw const FormatException('Invalid mission file');
  }
  if (decoded is! Map<String, dynamic>) {
    throw const FormatException('Invalid mission file');
  }
  final missionData = decoded['mission'] ?? decoded;
  if (missionData is! Map<String, dynamic>) {
    throw const FormatException('Invalid mission file');
  }
  final waypointsRaw = missionData['waypoints'];
  if (waypointsRaw is! List || waypointsRaw.isEmpty) {
    throw const FormatException('File has no waypoints');
  }

  final waypoints = [
    for (final w in waypointsRaw) waypointFromJson(w as Map<String, dynamic>),
  ];
  final name = (missionData['name'] as String?) ??
      (missionData['placeName'] as String?) ??
      'Imported mission';
  final placeName =
      (missionData['placeName'] as String?) ?? (missionData['name'] as String?);

  final appVersion = decoded['appVersion'] as String?;
  final mismatch = appVersion != null &&
          appVersion.split('.').first != kAppVersion.split('.').first
      ? appVersion
      : null;

  return ParsedMissionImport(
    name: name,
    placeName: placeName,
    waypoints: waypoints,
    versionMismatch: mismatch,
  );
}