// ─────────────────────────────────────────────────────────────────────────────
//  src/lib/api/studentApi.ts
//  Centralised API layer for the Student Dashboard.
//  All fetch calls, types, and error handling live here.
// ─────────────────────────────────────────────────────────────────────────────

import { getApiBaseUrl } from './config';

const BASE_URL = getApiBaseUrl();
const TOKEN_KEY = 'authToken';

// ─── Custom Error Class ───────────────────────────────────────────────────────

export class ApiError extends Error {
  public readonly status: number;
  public readonly path: string;

  constructor(status: number, message: string, path: string) {
    super(`[${status}] ${path} → ${message}`);
    this.status = status;
    this.path = path;
    this.name = 'ApiError';
  }
}


// ─── Shared helper ────────────────────────────────────────────────────────────

function getHeaders(): HeadersInit {
  const token = localStorage.getItem(TOKEN_KEY) ?? '';
  return {
    'Content-Type': 'application/json',
    ...(token ? { Authorization: `Bearer ${token}` } : {}),
  };
}

async function request<T>(path: string, options?: RequestInit): Promise<T> {
  const url = `${BASE_URL}${path}`;

  // Guard: if token exists but is expired, clear it and throw immediately
  // instead of sending a request that will always return 401/403
  const token = localStorage.getItem(TOKEN_KEY);
  if (token) {
    try {
      const payload = JSON.parse(atob(token.split('.')[1]));
      if (payload?.exp && payload.exp * 1000 < Date.now()) {
        localStorage.removeItem(TOKEN_KEY);
        throw new ApiError(401, 'Session expired — please log in again', path);
      }
    } catch (e) {
      if (e instanceof ApiError) throw e;
      // malformed token — remove and continue (server will reject)
      localStorage.removeItem(TOKEN_KEY);
    }
  }

  try {
    const res = await fetch(url, {
      ...options,
      headers: { ...getHeaders(), ...options?.headers },
    });

    if (!res.ok) {
      const message = await res.text().catch(() => res.statusText);
      throw new ApiError(res.status, message, path);
    }

    const text = await res.text();
    if (!text) return {} as T;

    try {
      return JSON.parse(text) as T;
    } catch {
      return text as unknown as T;
    }
  } catch (error) {
    if (error instanceof ApiError) throw error;
    throw new Error(`Network error while calling ${path}`);
  }
}

// ─── Response Types ───────────────────────────────────────────────────────────

export interface StreakDto {
  userId: number;
  currentStreak: number;
  longestStreak: number;
  lastActivityDate: string;
}

export interface PracticeStatsDto {
  userId: number;
  totalRecitations: number;
  addedRecitationThisWeek: number;
  averageAccuracy: number;
  progressTrend: string | null;
}

export interface RecitationStatsDto {
  userId: number;
  totalRecitations: number;
  addedRecitationThisWeek: number | null;
  averageAccuracy: number;
  progressTrend: number;
}

export interface RecentRecitationDto {
  recitationId: number;
  name?: string;
  surahName?: string;
  ayahStart?: number;
  ayahEnd?: number;
  createdAt: string;
  wordScore: number;
  tashkeelScore: number;
  overallScore?: number;
}
export interface totalRecitationDto {
  recitationId: number;
  name?: string;
  surahName?: string;
  ayahStart?: number;
  ayahEnd?: number;
  createdAt: string;
  wordScore: number;
  tashkeelScore: number;
  overallScore?: number;
}

export interface RecitationDetailDto {
  recitationId: number;
  surahName: string;
  startAyah: number;
  endAyah: number;
  recitationText: string;
  userText?: string;
  wordScore: number;
  tashkeelScore: number;
  overallScore: number;
  wordMistakesCount: number;
  tashkeelMistakesCount: number;
  tajweedMistakesCount?: number;
  incorrectWords: string[];
  tashkeelMistakes: string[];
  tajweedMistakes?: string[];
  feedback?: string;
  createdAt: string;
}

export interface SubmitRecitationDto {
  surahName: string;
  ayahStart: number;
  ayahEnd: number;
  userText: string; // kept for backward compat
}

export interface SubmitRecitationAudioDto {
  surahName: string;
  surahNumber: number;
  audio: Blob | File; // actual audio file sent as FormData
}



export interface DashboardData {
  streak: StreakDto;
  practiceStats: PracticeStatsDto;
  monthCount: number;
  recitationStats: RecitationStatsDto;
  recentRecitations: RecentRecitationDto[];
}

export interface UserInfo {
  role?: string;
  userType?: string;
  authorities?: Array<string | { authority: string }>;
  userId?: number;
  id?: number;          // backend sends "id" not "userId"
  email?: string;
  sub?: string;
  exp?: number;         // expiry unix timestamp
  iat?: number;
}

// ─── Helper Functions ─────────────────────────────────────────────────────────

export function getUserInfoFromToken(): UserInfo | null {
  const token = localStorage.getItem(TOKEN_KEY);
  if (!token) return null;
  try {
    const parts = token.split('.');
    if (parts.length !== 3) return null;
    const payload = JSON.parse(atob(parts[1]));
    return payload;
  } catch {
    return null;
  }
}

export function isStudent(): boolean {
  const userInfo = getUserInfoFromToken();
  if (!userInfo) return false;

  // Check role / userType fields
  const role = userInfo.role || userInfo.userType;
  if (role && role.toString().toUpperCase().includes('STUDENT')) return true;

  // Check Spring-Security-style authorities array
  if (Array.isArray(userInfo.authorities)) {
    return userInfo.authorities.some((a) => {
      const str = typeof a === 'string' ? a : a?.authority ?? '';
      return str.toUpperCase().includes('STUDENT');
    });
  }

  return false;
}

/**
 * Check if the stored token is expired
 */
export function isTokenExpired(): boolean {
  const userInfo = getUserInfoFromToken();
  if (!userInfo?.exp) return true;
  // exp is in seconds, Date.now() is in milliseconds
  return userInfo.exp * 1000 < Date.now();
}

export function isAuthenticated(): boolean {
  if (!localStorage.getItem(TOKEN_KEY)) return false;
  if (isTokenExpired()) {
    // Auto-clean expired token
    removeToken();
    return false;
  }
  return true;
}

export function getToken(): string | null {
  return localStorage.getItem(TOKEN_KEY);
}

export function setToken(token: string): void {
  localStorage.setItem(TOKEN_KEY, token);
}

export function removeToken(): void {
  localStorage.removeItem(TOKEN_KEY);
}

// ─── API Functions ────────────────────────────────────────────────────────────

export async function fetchStreak(): Promise<StreakDto> {
  try {
    return await request<StreakDto>('/api/student/streak');
  } catch {
    return { userId: 0, currentStreak: 0, longestStreak: 0, lastActivityDate: new Date().toISOString() };
  }
}

export async function fetchPracticeStats(): Promise<PracticeStatsDto> {
  try {
    return await request<PracticeStatsDto>('/api/student/practice/stats');
  } catch {
    return { userId: 0, totalRecitations: 0, addedRecitationThisWeek: 0, averageAccuracy: 0, progressTrend: null };
  }
}

export async function fetchMonthCount(): Promise<number> {
  try {
    const result = await request<number | string>('/api/student/practice/month-count');
    // Backend might return a plain number or a JSON-wrapped number
    return typeof result === 'number' ? result : parseInt(String(result), 10) || 0;
  } catch {
    return 0;
  }
}

export async function fetchRecitationStats(): Promise<RecitationStatsDto> {
  try {
    return await request<RecitationStatsDto>('/api/student/recitations/stats');
  } catch {
    return { userId: 0, totalRecitations: 0, addedRecitationThisWeek: 0, averageAccuracy: 0, progressTrend: 0 };
  }
}

export async function fetchTotalRecitations(): Promise<RecentRecitationDto[]> {
  try {
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    const raw = await request<any[]>('/api/student/recitations');
    if (!raw || !Array.isArray(raw)) return [];

    return raw.map((r) => {
      const wordScore     = Number(r.wordScore     ?? 0);
      const tashkeelScore = Number(r.tashkeelScore ?? 0);
      const overallScore  = r.overallScore != null
        ? Number(r.overallScore)
        : Math.round(((wordScore + tashkeelScore) / 2) * 100) / 100;

      return {
        ...r,
        recitationId: r.recitationId ?? r.reciattionId ?? r.id,
        name: r.name || r.surahName || undefined,
        wordScore,
        tashkeelScore,
        overallScore,
        createdAt: r.createdAt || r.evaluatedAt || new Date().toISOString(),
      } as RecentRecitationDto;
    });
  } catch {
    return [];
  }
}
export async function fetchRecentRecitations(): Promise<RecentRecitationDto[]> {
  try {
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    const raw = await request<any[]>('/api/student/recitations/recent');
    if (!raw || !Array.isArray(raw)) return [];

    return raw.map((r) => {
      const wordScore     = Number(r.wordScore     ?? 0);
      const tashkeelScore = Number(r.tashkeelScore ?? 0);
      const overallScore  = r.overallScore != null
        ? Number(r.overallScore)
        : Math.round(((wordScore + tashkeelScore) / 2) * 100) / 100;

      return {
        ...r,
        recitationId: r.recitationId ?? r.reciattionId ?? r.id,
        name: r.name || r.surahName || undefined,
        wordScore,
        tashkeelScore,
        overallScore,
        createdAt: r.createdAt || r.evaluatedAt || new Date().toISOString(),
      } as RecentRecitationDto;
    });
  } catch {
    return [];
  }
}

export async function fetchRecitationDetail(id: number): Promise<RecitationDetailDto | null> {
  try {
    return await request<RecitationDetailDto>(`/api/student/recitations/${id}`);
  } catch {
    return null;
  }
}

export async function submitRecitation(body: SubmitRecitationDto): Promise<RecitationDetailDto | null> {
  try {
    return await request<RecitationDetailDto>('/api/student/recitations', {
      method: 'POST',
      body: JSON.stringify(body),
    });
  } catch {
    return null;
  }
}

/**
 * POST /api/student/recitations
 * Submit audio file for evaluation (multipart/form-data).
 * Throws ApiError so the caller can show meaningful error messages.
 */
export async function submitRecitationAudio(
  dto: SubmitRecitationAudioDto,
): Promise<RecitationDetailDto> {
  // Guard: expired token
  const token = localStorage.getItem(TOKEN_KEY);
  if (token) {
    try {
      const payload = JSON.parse(atob(token.split('.')[1]));
      if (payload?.exp && payload.exp * 1000 < Date.now()) {
        localStorage.removeItem(TOKEN_KEY);
        throw new ApiError(401, 'Session expired — please log in again', '/api/student/recitations');
      }
    } catch (e) {
      if (e instanceof ApiError) throw e;
    }
  }

  const form = new FormData();
  // Determine file extension from mime type
  const mime = dto.audio instanceof File ? dto.audio.type : (dto.audio as Blob).type;
  const ext = mime.includes('wav') ? 'wav' : mime.includes('mpeg') || mime.includes('mp3') ? 'mp3' : mime.includes('m4a') ? 'm4a' : 'webm';
  const filename = dto.audio instanceof File ? dto.audio.name : `recording.${ext}`;

  form.append('audio', dto.audio, filename);
  form.append('surahNumber', String(dto.surahNumber));

  const authToken = localStorage.getItem(TOKEN_KEY) ?? '';
  const res = await fetch(`${BASE_URL}/api/student/recitations`, {
    method: 'POST',
    headers: authToken ? { Authorization: `Bearer ${authToken}` } : {},
    body: form,
  });

  if (!res.ok) {
    const message = await res.text().catch(() => res.statusText);
    throw new ApiError(res.status, message, '/api/student/recitations');
  }

  const text = await res.text();
  if (!text) throw new ApiError(500, 'Empty response from server', '/api/student/recitations');
  return JSON.parse(text) as RecitationDetailDto;
}



export async function fetchStatistics(
  timeRange: 'week' | 'month' | 'year' = 'month',
  // eslint-disable-next-line @typescript-eslint/no-explicit-any
): Promise<any> {
  try {
    return await request(`/api/student/statistics?range=${timeRange}`);
  } catch {
    return { labels: [], accuracyData: [], countData: [] };
  }
}

// ─── Convenience: load everything for the dashboard in one call ───────────────

export async function fetchDashboardData(): Promise<{
  data: Partial<DashboardData>;
  errors: Record<string, string>;
}> {
  const [streak, practiceStats, monthCount, recitationStats, recentRecitations] =
    await Promise.allSettled([
      fetchStreak(),
      fetchPracticeStats(),
      fetchMonthCount(),
      fetchRecitationStats(),
      fetchRecentRecitations(),
    ]);

  const data: Partial<DashboardData> = {};
  const errors: Record<string, string> = {};

  const resolve = <K extends keyof DashboardData>(
    key: K,
    result: PromiseSettledResult<DashboardData[K]>,
  ) => {
    if (result.status === 'fulfilled') {
      data[key] = result.value;
    } else {
      const msg = result.reason?.message ?? 'Unknown error';
      // Only surface real errors (not auth-related ones) to the UI
      const isAuthError =
        result.reason instanceof ApiError &&
        (result.reason.status === 401 || result.reason.status === 403);
      if (!isAuthError) errors[key] = msg;

      // Safe defaults
      if (key === 'recentRecitations') {
        (data as any)[key] = [];
      } else if (key === 'monthCount') {
        (data as any)[key] = 0;
      }
    }
  };

  resolve('streak', streak);
  resolve('practiceStats', practiceStats);
  resolve('monthCount', monthCount);
  resolve('recitationStats', recitationStats);
  resolve('recentRecitations', recentRecitations);

  // Defensive normalization: backend may return a paginated object instead of a plain array.
  if (data.recentRecitations !== undefined && !Array.isArray(data.recentRecitations)) {
    const raw = data.recentRecitations as unknown;
    if (raw && typeof raw === 'object' && Array.isArray((raw as Record<string, unknown>)['content'])) {
      data.recentRecitations = (raw as Record<string, unknown[]>)['content'] as RecentRecitationDto[];
    } else {
      data.recentRecitations = [];
    }
  }


  // Normalise overallScore on each recitation
  if (Array.isArray(data.recentRecitations)) {
    data.recentRecitations = data.recentRecitations.map((rec) => ({
      ...rec,
      overallScore:
        rec.overallScore ??
        Math.round(((rec.wordScore + rec.tashkeelScore + (rec.totalScore ?? 0)) / 3) * 100) / 100,
    }));
  }

  return { data, errors };
}


// ─── Default export ───────────────────────────────────────────────────────────

const studentApi = {
  fetchStreak,
  fetchPracticeStats,
  fetchMonthCount,
  fetchRecitationStats,
  fetchRecentRecitations,
  fetchRecitationDetail,
  submitRecitation,
  submitRecitationAudio,
  fetchStatistics,
  fetchDashboardData,
  getUserInfoFromToken,
  isStudent,
  isAuthenticated,
  getToken,
  setToken,
  removeToken,
  ApiError,
};

export default studentApi;