// 學習會話服務
const API_BASE = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:5008';

// 類型定義
export interface StudySession {
  sessionId: string;
  totalCards: number;
  totalTests: number;
  currentCardIndex: number;
  currentTestType?: string;
  startedAt: string;
}

export interface CurrentTest {
  sessionId: string;
  testType: string;
  card: Card;
  progress: ProgressSummary;
}

export interface Card {
  id: string;
  word: string;
  translation: string;
  definition: string;
  example: string;
  exampleTranslation: string;
  pronunciation: string;
  difficultyLevel: string;
}

export interface ProgressSummary {
  currentCardIndex: number;
  totalCards: number;
  completedTests: number;
  totalTests: number;
  completedCards: number;
}

export interface TestResult {
  testType: string;
  isCorrect: boolean;
  userAnswer?: string;
  confidenceLevel?: number;
  responseTimeMs: number;
}

export interface SubmitTestResponse {
  success: boolean;
  isCardCompleted: boolean;
  progress: ProgressSummary;
  message: string;
}

export interface NextTest {
  hasNextTest: boolean;
  testType?: string;
  sameCard: boolean;
  message: string;
}

export interface Progress {
  sessionId: string;
  status: string;
  currentCardIndex: number;
  totalCards: number;
  completedTests: number;
  totalTests: number;
  completedCards: number;
  cards: CardProgress[];
}

export interface CardProgress {
  cardId: string;
  word: string;
  plannedTests: string[];
  completedTestsCount: number;
  isCompleted: boolean;
  tests: TestProgress[];
}

export interface TestProgress {
  testType: string;
  isCorrect: boolean;
  completedAt: string;
}

export class StudySessionService {
  private async makeRequest<T>(endpoint: string, options: RequestInit = {}): Promise<{ success: boolean; data: T | null; error?: string }> {
    try {
      const token = localStorage.getItem('auth_token');

      const response = await fetch(`${API_BASE}${endpoint}`, {
        headers: {
          'Content-Type': 'application/json',
          'Authorization': token ? `Bearer ${token}` : '',
          ...options.headers,
        },
        ...options,
      });

      if (!response.ok) {
        const errorData = await response.json().catch(() => ({ error: 'Network error' }));
        return { success: false, data: null, error: errorData.error || `HTTP ${response.status}` };
      }

      const result = await response.json();
      return { success: result.Success || false, data: result.Data || null, error: result.Error };
    } catch (error) {
      console.error('API request failed:', error);
      return { success: false, data: null, error: 'Network error' };
    }
  }

  /**
   * 開始新的學習會話
   */
  async startSession(): Promise<{ success: boolean; data: StudySession | null; error?: string }> {
    return await this.makeRequest<StudySession>('/api/study/sessions/start', {
      method: 'POST'
    });
  }

  /**
   * 獲取當前測驗
   */
  async getCurrentTest(sessionId: string): Promise<{ success: boolean; data: CurrentTest | null; error?: string }> {
    return await this.makeRequest<CurrentTest>(`/api/study/sessions/${sessionId}/current-test`);
  }

  /**
   * 提交測驗結果
   */
  async submitTest(sessionId: string, result: TestResult): Promise<{ success: boolean; data: SubmitTestResponse | null; error?: string }> {
    return await this.makeRequest<SubmitTestResponse>(`/api/study/sessions/${sessionId}/submit-test`, {
      method: 'POST',
      body: JSON.stringify(result)
    });
  }

  /**
   * 獲取下一個測驗
   */
  async getNextTest(sessionId: string): Promise<{ success: boolean; data: NextTest | null; error?: string }> {
    return await this.makeRequest<NextTest>(`/api/study/sessions/${sessionId}/next-test`);
  }

  /**
   * 獲取詳細進度
   */
  async getProgress(sessionId: string): Promise<{ success: boolean; data: Progress | null; error?: string }> {
    return await this.makeRequest<Progress>(`/api/study/sessions/${sessionId}/progress`);
  }

  /**
   * 完成學習會話
   */
  async completeSession(sessionId: string): Promise<{ success: boolean; data: any | null; error?: string }> {
    return await this.makeRequest(`/api/study/sessions/${sessionId}/complete`, {
      method: 'PUT'
    });
  }
}

// 導出服務實例
export const studySessionService = new StudySessionService();