// ─────────────────────────────────────────────────────────────────────────────
//  src/lib/api/studentsapi.ts
//  Uses the same TOKEN_KEY + request() pattern as studentApi.ts
// ─────────────────────────────────────────────────────────────────────────────

import { ApiError } from './studentApi';

import { getApiBaseUrl } from './config';

const BASE_URL = getApiBaseUrl();
const SHEIKH_URL = `${BASE_URL}/api/sheikh/my-students`;
const TOKEN_KEY = 'authToken';   // must match studentApi.ts

// ─── Types ────────────────────────────────────────────────────────────────────

/** Shape returned by list endpoints (all / active / top / search) */
export interface StudentListItem {
  id: number;
  fullName: string;
  quranLevel: string;
  currentStreak: number;
  email: string;
  country: string;
  sessionCount: number;
  lastSessionDate: string | null;
  totalEarnings: number;
  averageRate: number;
}

/** Shape returned by View-Student endpoint */
export interface StudentDetail {
  id: number;
  fullName: string;
  quranLevel: string;
  currentStreak: number;
  email: string;
  country: string;
  phone: string | null;
  goal: string | null;
  membershipDate: string | null;
  sessionCount: number;
  completedSessions: number;
  canceledSessions: number;
  lastSessionDate: string | null;
  totalEarnings: number;
  totalTimeMinutes: number;
  averageRate: number;
  avgRating: number | null;
  totalHoursSpent: number;
  totalRevenue: number;
  cancelledSessions: number;
  completionRate: number;
}

/** Shape returned by /stats endpoint */
export interface StudentsStats {
  totalStudents: number;
  activeStudentsLast7Days: number;
  totalEarnings: number;
  averageRating: number;
}

/** Stats for a specific student's sessions with this sheikh */
export interface StudentSessionStats {
  avgRating: number | null;
  totalMinutesSpent: number;
  totalRevenue: number;
  completedSessions: number;
  cancelledSessions: number;
  totalSessions: number;
  completionRate: number;
  lastSessionDate: string | null;
}

/** Normalised student shape used by the UI */
export interface Student {
  id: string;
  name: string;
  email: string;
  phone?: string;
  location?: string;
  joinedDate: string | null;
  totalSessions: number;
  completedSessions: number;
  cancelledSessions: number;
  totalMinutes: number;
  totalSpent: number;
  averageRating: number;
  lastSession: string | null;
  currentStreak: number;
  progress: number;
  level: string;
  goals: string[];
}

/** Session shape (backend doesn't expose history yet) */
export interface Session {
  id?: string;
  date: string | null;
  duration: number;
  status: 'completed' | 'cancelled' | 'upcoming';
  rating?: number;
  feedback?: string;
  price: number;
  topic: string;
}

// ─── Shared request helper (mirrors studentApi.ts) ────────────────────────────

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

async function request<T>(path: string): Promise<T> {
  const url = `${SHEIKH_URL}${path}`;

  // Guard: check token expiry before sending
  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;
      localStorage.removeItem(TOKEN_KEY); // malformed token
    }
  }

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

    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}`);
  }
}

// ─── Mappers ──────────────────────────────────────────────────────────────────

function capitalise(str: string): string {
  if (!str) return '';
  return str.charAt(0).toUpperCase() + str.slice(1).toLowerCase();
}

function mapListItem(item: StudentListItem): Student {
  return {
    id: String(item.id),
    name: item.fullName,
    email: item.email,
    phone: undefined,
    location: item.country,
    joinedDate: null,
    totalSessions: item.sessionCount,
    completedSessions: item.sessionCount, // list endpoint has no split
    cancelledSessions: 0,
    totalMinutes: 0,
    totalSpent: item.totalEarnings,
    averageRating: item.averageRate,
    lastSession: item.lastSessionDate,
    currentStreak: item.currentStreak,
    progress: 0,
    level: capitalise(item.quranLevel),
    goals: [],
  };
}

function mapDetail(d: StudentDetail): Student {
  const progress =
    d.sessionCount > 0
      ? Math.min(100, Math.round((d.completedSessions / d.sessionCount) * 100))
      : 0;

  return {
    id: String(d.id),
    name: d.fullName,
    email: d.email,
    phone: d.phone ?? undefined,
    location: d.country,
    joinedDate: d.membershipDate,
    totalSessions: d.sessionCount,
    completedSessions: d.completedSessions,
    cancelledSessions: d.canceledSessions,
    totalMinutes: d.totalTimeMinutes,
    totalSpent: d.totalEarnings,
    averageRating: d.averageRate,
    lastSession: d.lastSessionDate,
    currentStreak: d.currentStreak,
    progress,
    level: capitalise(d.quranLevel),
    goals: d.goal ? [d.goal] : [],
  };
}

// ─── Public API functions ─────────────────────────────────────────────────────

/** GET /api/sheikh/my-students */
export async function getAllStudents(): Promise<Student[]> {
  const data = await request<StudentListItem[]>('');
  return data.map(mapListItem);
}

/** GET /api/sheikh/my-students/active-last-7-days */
export async function getActiveStudents(): Promise<Student[]> {
  const data = await request<StudentListItem[]>('/active-last-7-days');
  return data.map(mapListItem);
}

/** GET /api/sheikh/my-students/top-students */
export async function getTopStudents(): Promise<Student[]> {
  const data = await request<StudentListItem[]>('/top-students');
  return data.map(mapListItem);
}

/** GET /api/sheikh/my-students/search?keyword=… */
export async function searchStudents(keyword: string): Promise<Student[]> {
  const data = await request<StudentListItem[]>(
    `/search?keyword=${encodeURIComponent(keyword)}`,
  );
  return data.map(mapListItem);
}

/** GET /api/sheikh/my-students/View-Student?id=… */
export async function getStudentDetails(
  id: number,
): Promise<{ student: Student; sessionHistory: Session[]; sessionStats: StudentSessionStats }> {
  const data = await request<StudentDetail>(`/View-Student?id=${id}`);
  const completed = data.completedSessions ?? 0;
  const cancelled = data.canceledSessions ?? 0;
  const total = data.sessionCount ?? 0;
  const completionRate = total > 0 ? Math.round((completed / total) * 1000) / 10 : 0;

  return {
    student: mapDetail(data),
    sessionHistory: [],
    sessionStats: {
      avgRating: data.averageRate ?? null,
      totalMinutesSpent: data.totalTimeMinutes ?? 0,
      totalRevenue: data.totalEarnings ?? 0,
      completedSessions: completed,
      cancelledSessions: cancelled,
      totalSessions: total,
      completionRate,
      lastSessionDate: data.lastSessionDate ?? null,
    },
  };
}

/** GET /api/sheikh/my-students/stats */
export async function getStudentsStats(): Promise<StudentsStats> {
  return request<StudentsStats>('/stats');
}

/** GET /api/sheikh/my-students/student-session-stats?studentId=… */
export async function getStudentSessionStats(studentId: number): Promise<StudentSessionStats> {
  return request<StudentSessionStats>(`/student-session-stats?studentId=${studentId}`);
}