// ⏱️ 우리 학교 전용 "백품타" 공부 타이머 화면의 기능(서버 통신/상태) 담당 컨트롤러.
import 'dart:async';
import 'dart:convert';
import 'package:flutter/foundation.dart';
import 'package:http/http.dart' as http;
import '../config.dart';

enum StudyTimerState { idle, running, paused }

class StudyTimerController extends ChangeNotifier {
  final String studentId;
  final String studentName;

  StudyTimerController({required this.studentId, required this.studentName});

  bool _isLoading = true;
  bool _isBusy = false; // 시작/일시정지/재개/종료 버튼 눌러서 서버 응답 기다리는 중
  StudyTimerState _state = StudyTimerState.idle;
  int _elapsedSeconds = 0; // 지금 세션에서 "정지 상태"일 때 확정된 누적 초 (일시정지 구간 제외)
  DateTime? _lastResumedAt; // running일 때만 의미 있음 - 여기서부터 실시간으로 흐른다
  int _todaySeconds = 0;
  int _weekSeconds = 0;
  int _totalSeconds = 0;
  Timer? _ticker;
  bool _disposed = false;

  bool get isLoading => _isLoading;
  bool get isBusy => _isBusy;
  bool get isRunning => _state == StudyTimerState.running;
  bool get isPaused => _state == StudyTimerState.paused;
  bool get isIdle => _state == StudyTimerState.idle;

  /// 지금 세션 하나만의 경과 시간(타이머 화면 큰 숫자용). 일시정지 중엔 멈춰 있다.
  int get liveElapsedSeconds {
    if (_state != StudyTimerState.running || _lastResumedAt == null) {
      return _elapsedSeconds;
    }
    final diff = DateTime.now().difference(_lastResumedAt!).inSeconds;
    return _elapsedSeconds + (diff > 0 ? diff : 0);
  }

  /// 지금 진행 중인 세션까지 포함한 "오늘" 누적 초. running일 때만 실시간으로 늘어난다.
  int get todaySecondsLive => _todaySeconds + _liveDelta;
  int get weekSecondsLive => _weekSeconds + _liveDelta;
  int get totalSecondsLive => _totalSeconds + _liveDelta;

  int get _liveDelta => _state == StudyTimerState.idle ? 0 : liveElapsedSeconds;

  void _safeNotify() {
    if (!_disposed) notifyListeners();
  }

  Future<void> init() async {
    await _fetchStatus();
  }

  @override
  void dispose() {
    _disposed = true;
    _ticker?.cancel();
    super.dispose();
  }

  Future<void> _fetchStatus() async {
    try {
      final response = await http.get(
        Uri.parse('$baseUrl/api/study/status?studentId=$studentId'),
      );
      if (response.statusCode == 200) {
        final data = jsonDecode(utf8.decode(response.bodyBytes));
        _state = _parseState(data['state']);
        _elapsedSeconds = (data['elapsedSeconds'] as num?)?.toInt() ?? 0;
        _lastResumedAt = data['lastResumedAt'] != null
            ? DateTime.tryParse(data['lastResumedAt'])
            : null;
        _todaySeconds = (data['todaySeconds'] as num?)?.toInt() ?? 0;
        _weekSeconds = (data['weekSeconds'] as num?)?.toInt() ?? 0;
        _totalSeconds = (data['totalSeconds'] as num?)?.toInt() ?? 0;
        _restartTickerIfNeeded();
      }
    } catch (_) {
      // 조용히 무시 - 마지막으로 알던 상태를 유지한다.
    } finally {
      _isLoading = false;
      _safeNotify();
    }
  }

  StudyTimerState _parseState(dynamic raw) {
    switch (raw) {
      case 'running':
        return StudyTimerState.running;
      case 'paused':
        return StudyTimerState.paused;
      default:
        return StudyTimerState.idle;
    }
  }

  void _restartTickerIfNeeded() {
    _ticker?.cancel();
    if (_state == StudyTimerState.running) {
      _ticker = Timer.periodic(
        const Duration(seconds: 1),
        (_) => _safeNotify(),
      );
    }
  }

  Future<(bool success, String message)> start() async {
    return _action(
      '/api/study/start',
      body: {"studentId": studentId, "studentName": studentName},
      onSuccess: (_) async {
        await _fetchStatus();
        return '공부를 시작했습니다.';
      },
    );
  }

  Future<(bool success, String message)> pause() async {
    return _action(
      '/api/study/pause',
      onSuccess: (_) async {
        await _fetchStatus();
        return '일시정지했습니다.';
      },
    );
  }

  Future<(bool success, String message)> resume() async {
    return _action(
      '/api/study/resume',
      onSuccess: (_) async {
        await _fetchStatus();
        return '다시 시작했습니다.';
      },
    );
  }

  Future<(bool success, String message)> stop() async {
    return _action(
      '/api/study/stop',
      onSuccess: (result) async {
        await _fetchStatus(); // 오늘/이번주/전체 합계를 서버 값으로 다시 맞춘다.
        final minutes =
            ((result['durationSeconds'] as num?)?.toInt() ?? 0) ~/ 60;
        return '이번 공부 시간: $minutes분 기록 완료!';
      },
    );
  }

  Future<(bool success, String message)> _action(
    String path, {
    Map<String, dynamic> body = const {},
    required Future<String> Function(Map<String, dynamic> result) onSuccess,
  }) async {
    _isBusy = true;
    _safeNotify();
    try {
      final response = await http.post(
        Uri.parse('$baseUrl$path'),
        headers: {"Content-Type": "application/json"},
        body: jsonEncode({"studentId": studentId, ...body}),
      );
      final result = jsonDecode(utf8.decode(response.bodyBytes));
      if (response.statusCode == 200 && result['status'] == 'success') {
        final message = await onSuccess(result);
        return (true, message);
      }
      return (false, '${result['message'] ?? '처리 실패'}');
    } catch (e) {
      return (false, '네트워크 에러: $e');
    } finally {
      _isBusy = false;
      _safeNotify();
    }
  }
}