import 'dart:async';
import 'dart:convert';

import 'package:dio/dio.dart';

import '../../../../core/logging/logger.dart';
import '../../../../core/network/api_problem.dart';
import '../../../../data/network/api_client.dart';
import '../models/divination_backend_models.dart';
import '../models/divination_params.dart';
import '../models/divination_result.dart';

class DivinationApi {
  const DivinationApi({required ApiClient apiClient}) : _apiClient = apiClient;

  final ApiClient _apiClient;
  static final Logger _logger = getLogger('features.divination.api');

  Future<PointsBalanceData> getPointsBalance() async {
    final json = await _apiClient.getJson('/api/v1/points/balance');
    return PointsBalanceData.fromJson(json);
  }

  Future<RunAcceptedData> enqueueRun({
    required DivinationParams params,
    required List<YaoType> yaoStates,
    required String threadId,
    required String runId,
  }) async {
    final payload = buildDivinationRunPayload(
      params: params,
      yaoStates: yaoStates,
      threadId: threadId,
      runId: runId,
      clientNow: DateTime.now(),
    );
    final json = await _apiClient.postJson('/api/v1/agent/runs', data: payload);
    return RunAcceptedData.fromJson(json);
  }

  Future<List<DivinationResultData>> getHistoryRecords({
    required String userId,
  }) async {
    final json = await _apiClient.getJson('/api/v1/agent/history');
    final messagesRaw = json['messages'];
    if (messagesRaw is! List<dynamic>) {
      return const <DivinationResultData>[];
    }

    final records = <DivinationResultData>[];
    for (final raw in messagesRaw) {
      if (raw is! Map<String, dynamic>) {
        continue;
      }
      if (raw['role'] != 'assistant') {
        continue;
      }
      final agentOutputRaw = raw['agent_output'];
      if (agentOutputRaw is! Map<String, dynamic>) {
        continue;
      }
      final derivedRaw = agentOutputRaw['divination_derived'];
      if (derivedRaw is! Map<String, dynamic>) {
        continue;
      }
      try {
        final derived = DerivedDivinationData.fromJson(derivedRaw);
        final divinationTime = _resolveHistoryTime(raw, derived);
        final params = DivinationParams(
          method: _methodFromText(derived.divinationMethod),
          questionType: _questionTypeFromText(derived.questionType),
          question: derived.question,
          divinationTime: divinationTime,
          coinBalance: 0,
          userId: userId,
        );
        final aggregate = DivinationRunAggregate(
          derived: derived,
          signLevel: _asString(agentOutputRaw['sign_level']),
          conclusion: _asStringList(agentOutputRaw['conclusion']),
          focusPoints: _asStringList(agentOutputRaw['focus_points']),
          advice: _asStringList(agentOutputRaw['advice']),
          keywords: _asStringList(agentOutputRaw['keywords']),
          answer: _asString(agentOutputRaw['answer']),
        );
        records.add(aggregate.toViewData(params));
      } catch (error, stackTrace) {
        _logger.warning(
          message: 'Skip malformed history assistant message',
          extra: <String, dynamic>{
            'error': error.toString(),
            'stackTrace': stackTrace.toString(),
          },
        );
        continue;
      }
    }
    return records;
  }

  Stream<Map<String, dynamic>> streamEvents({
    required String threadId,
    required String runId,
  }) async* {
    Response<ResponseBody> response;
    try {
      response = await _apiClient.rawDio.get<ResponseBody>(
        '/api/v1/agent/runs/$threadId/events',
        queryParameters: <String, dynamic>{'runId': runId},
        options: Options(responseType: ResponseType.stream),
      );
    } on DioException catch (error, stackTrace) {
      _logger.error(
        message: 'Failed to open SSE stream for divination run',
        error: error,
        stackTrace: stackTrace,
        extra: <String, dynamic>{'threadId': threadId, 'runId': runId},
      );
      throw _mapProblem(error);
    }

    final body = response.data;
    if (body == null) {
      return;
    }

    String buffer = '';
    try {
      await for (final textChunk in utf8.decoder.bind(body.stream)) {
        buffer += textChunk.replaceAll('\r\n', '\n');
        while (true) {
          final splitAt = buffer.indexOf('\n\n');
          if (splitAt < 0) {
            break;
          }
          final frame = buffer.substring(0, splitAt);
          buffer = buffer.substring(splitAt + 2);
          final event = _parseSseFrame(frame);
          if (event != null) {
            yield event;
          }
        }
      }
    } on FormatException catch (error, stackTrace) {
      _logger.error(
        message: 'Failed to decode SSE stream chunk',
        error: error,
        stackTrace: stackTrace,
        extra: <String, dynamic>{
          'threadId': threadId,
          'runId': runId,
          'bufferLength': buffer.length,
        },
      );
      throw ApiProblem(
        status: 502,
        title: 'SSE parse error',
        detail: error.message,
      );
    }

    if (buffer.trim().isNotEmpty) {
      final event = _parseSseFrame(buffer);
      if (event != null) {
        yield event;
      }
    }
  }

  ApiProblem _mapProblem(DioException error) {
    final status = error.response?.statusCode ?? 500;
    final data = error.response?.data;
    if (data is Map<String, dynamic>) {
      return ApiProblem(
        status: status,
        title: (data['title'] as String?) ?? 'Request failed',
        detail: (data['detail'] as String?) ?? '',
        code: data['code'] as String?,
      );
    }
    return ApiProblem(
      status: status,
      title: 'Network error',
      detail: error.message ?? 'Request failed',
    );
  }

  Map<String, dynamic>? _parseSseFrame(String frame) {
    if (frame.startsWith(':')) {
      return null;
    }
    final lines = frame.split('\n');
    String eventType = '';
    final dataLines = <String>[];
    for (final raw in lines) {
      final line = raw.trimRight();
      if (line.startsWith('event:')) {
        eventType = line.substring(6).trim();
        continue;
      }
      if (line.startsWith('data:')) {
        dataLines.add(line.substring(5).trimLeft());
      }
    }
    if (dataLines.isEmpty) {
      return null;
    }
    final dataText = dataLines.join('\n');
    if (dataText.trim().isEmpty) {
      return null;
    }
    final decoded = jsonDecode(dataText);
    if (decoded is! Map<String, dynamic>) {
      return null;
    }
    if (!decoded.containsKey('type') && eventType.isNotEmpty) {
      decoded['type'] = eventType;
    }
    return decoded;
  }
}

Map<String, dynamic> buildDivinationRunPayload({
  required DivinationParams params,
  required List<YaoType> yaoStates,
  required String threadId,
  required String runId,
  required DateTime clientNow,
}) {
  if (yaoStates.length != 6) {
    throw ArgumentError('yaoStates must contain exactly 6 items');
  }

  return <String, dynamic>{
    'threadId': threadId,
    'runId': runId,
    'state': <String, dynamic>{},
    'messages': [
      {'id': 'msg_${runId}_user_0', 'role': 'user', 'content': params.question},
    ],
    'tools': const <Map<String, dynamic>>[],
    'context': const <Map<String, dynamic>>[],
    'forwardedProps': {
      'runtime_mode': 'chat',
      'client_time': {
        'device_timezone': 'Asia/Shanghai',
        'client_now_iso': _toRfc3339Utc(clientNow),
        'client_epoch_ms': clientNow.millisecondsSinceEpoch,
      },
      'divinationPayload': {
        'divinationMethod': params.method == DivinationMethod.manual
            ? '手动起卦'
            : '自动起卦',
        'questionType': _questionTypeToText(params.questionType),
        'question': params.question,
        'divinationTimeIso': _toRfc3339Utc(params.divinationTime),
        'yaoLines': yaoStates.map(_yaoTypeToText).toList(growable: false),
      },
    },
  };
}

String _toRfc3339Utc(DateTime value) {
  return value.toUtc().toIso8601String();
}

String _questionTypeToText(QuestionType type) {
  return switch (type) {
    QuestionType.career => '事业',
    QuestionType.love => '情感',
    QuestionType.wealth => '财富',
    QuestionType.fortune => '运势',
    QuestionType.dream => '解梦',
    QuestionType.health => '健康',
    QuestionType.study => '学业',
    QuestionType.search => '寻物',
    QuestionType.other => '其他',
  };
}

QuestionType _questionTypeFromText(String raw) {
  return switch (raw) {
    '事业' => QuestionType.career,
    '情感' => QuestionType.love,
    '财富' => QuestionType.wealth,
    '运势' => QuestionType.fortune,
    '解梦' => QuestionType.dream,
    '健康' => QuestionType.health,
    '学业' => QuestionType.study,
    '寻物' => QuestionType.search,
    _ => QuestionType.other,
  };
}

DivinationMethod _methodFromText(String raw) {
  return raw == '自动起卦' ? DivinationMethod.auto : DivinationMethod.manual;
}

DateTime _resolveHistoryTime(
  Map<String, dynamic> message,
  DerivedDivinationData derived,
) {
  final timestamp = message['timestamp'];
  if (timestamp is String) {
    final parsed = DateTime.tryParse(timestamp);
    if (parsed != null) {
      return parsed.toLocal();
    }
  }

  final derivedTime = DateTime.tryParse(derived.divinationTime);
  if (derivedTime != null) {
    return derivedTime.toLocal();
  }

  return DateTime.now();
}

String _asString(Object? value) {
  return value is String ? value : '';
}

List<String> _asStringList(Object? value) {
  if (value is! List<dynamic>) {
    return const <String>[];
  }
  return value.whereType<String>().toList(growable: false);
}

String _yaoTypeToText(YaoType type) {
  return switch (type) {
    YaoType.youngYang => '少阳',
    YaoType.youngYin => '少阴',
    YaoType.oldYang => '老阳',
    YaoType.oldYin => '老阴',
    YaoType.undetermined => throw ArgumentError(
      'yaoStates contains undetermined line',
    ),
  };
}