// ─────────────────────────────────────────────────────────────────────────────
// src/lib/api/adminUserManagementApi.ts
// User Management API for Admin Dashboard
// Based on the official API documentation - completely independent from adminApi
// ─────────────────────────────────────────────────────────────────────────────

import { getApiBaseUrl } from './config';

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

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

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

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

// ─── 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: 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 UserManagementApiError(401, 'Session expired — please log in again', path);
      }
    } catch (e) {
      if (e instanceof UserManagementApiError) throw e;
      localStorage.removeItem(TOKEN_KEY);
    }
  }

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

    // Handle 204 No Content
    if (res.status === 204) {
      return null as T;
    }

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

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

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

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

export interface UserManagementStatsDto {
  totalUsers: number;
  totalSheikhs: number;
  totalStudents: number;
  blockedUsers: number;
}

export interface StudentDtoAdmin {
  id: number;
  name: string;
  email: string;
  registrationDate: string;
  streak: number;
  totalSessions: number;
  status: 'ACTIVE' | 'BLOCKED' | 'INACTIVE';
}

export interface SheikhDtoAdmin {
  id: number;
  name: string;
  email: string;
  registrationDate: string;
  numberOfSessions: number;
  totalRevenue: number;
  averageRating: number;
  status: 'ACTIVE' | 'BLOCKED' | 'PENDING' | 'APPROVED' | 'REJECTED';
}

export type UserDtoAdmin = StudentDtoAdmin | SheikhDtoAdmin;

export interface DetailedStudentView {
  id: number;
  name: string;
  email: string;
  registrationDate: string;
  streak: number;
  sessionCount: number;
  country: string;
  numberOfCompletedSessions: number;
  totalSpentTime: number;
}

export interface DetailedSheikhView {
  id: number;
  name: string;
  email: string;
  country: string;
  experienceYears: number;
  bio: string;
  specialization: string;
  hourlyRate: number;
  status: 'PENDING' | 'APPROVED' | 'REJECTED' | 'ACTIVE' | 'BLOCKED';
  registrationDate: string;
  averageRating: number;
  numberOfCompletedSessions: number;
  numberOfStudents: number;
  numberofReviews: number;
  sessionCount: number;
  totalEarnings: number;
}

export interface SessionHistoryDto {
  sessionId: number;
  sheikhName: string;
  studentName: string;
  date: string;
  status: 'COMPLETED' | 'CANCELLED' | 'PENDING' | 'SCHEDULED';
  price: number;
  durationInMinutes: number;
  rate: number;
}

export interface SheikhProfileResponse {
  sheikhProfile: DetailedSheikhView;
  sessionHistories: SessionHistoryDto[];
}

export interface StudentProfileResponse {
  studentProfile: DetailedStudentView;
  sessionHistories: SessionHistoryDto[];
}

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

/**
 * GET /api/admin/user-management/stats
 * Retrieves comprehensive statistics about all users in the platform.
 */
export async function fetchUserManagementStats(): Promise<UserManagementStatsDto> {
  return request<UserManagementStatsDto>('/api/admin/user-management/stats');
}

/**
 * GET /api/admin/user-management/students
 * Retrieves a list of all students with basic information.
 */
export async function fetchAllStudents(): Promise<StudentDtoAdmin[]> {
  return request<StudentDtoAdmin[]>('/api/admin/user-management/students');
}

/**
 * GET /api/admin/user-management/sheikhs
 * Retrieves a list of all sheikhs with basic information.
 */
export async function fetchAllSheikhs(): Promise<SheikhDtoAdmin[]> {
  return request<SheikhDtoAdmin[]>('/api/admin/user-management/sheikhs');
}

/**
 * GET /api/admin/user-management/users
 * Retrieves a combined list of all users (students and sheikhs).
 */
export async function fetchAllUsers(): Promise<UserDtoAdmin[]> {
  return request<UserDtoAdmin[]>('/api/admin/user-management/users');
}

/**
 * POST /api/admin/user-management/block-user
 * Blocks a user account, preventing them from accessing the platform.
 * @param userId - ID of the user to block
 */
export async function blockUser(userId: number): Promise<void> {
  return request<void>(`/api/admin/user-management/block-user?userId=${userId}`, {
    method: 'POST',
  });
}

/**
 * POST /api/admin/user-management/unblock-user
 * Unblocks a previously blocked user account.
 * @param userId - ID of the user to unblock
 */
export async function unblockUser(userId: number): Promise<void> {
  return request<void>(`/api/admin/user-management/unblock-user?userId=${userId}`, {
    method: 'POST',
  });
}

/**
 * GET /api/admin/user-management/sheikh-profile
 * Retrieves detailed profile information for a specific sheikh including session history.
 * @param userId - Sheikh's ID
 */
export async function fetchSheikhProfile(userId: number): Promise<SheikhProfileResponse> {
  return request<SheikhProfileResponse>(`/api/admin/user-management/sheikh-profile?userId=${userId}`);
}

/**
 * GET /api/admin/user-management/student-profile
 * Retrieves detailed profile information for a specific student including session history.
 * @param userId - Student's ID
 */
export async function fetchStudentProfile(userId: number): Promise<StudentProfileResponse> {
  return request<StudentProfileResponse>(`/api/admin/user-management/student-profile?userId=${userId}`);
}

// ─── Convenience: load all user management data ───────────────────────────────

export interface UserManagementData {
  stats: UserManagementStatsDto;
  students: StudentDtoAdmin[];
  sheikhs: SheikhDtoAdmin[];
  users: UserDtoAdmin[];
}

export async function fetchUserManagementData(): Promise<{
  data: Partial<UserManagementData>;
  errors: Record<string, string>;
}> {
  const [statsResult, studentsResult, sheikhsResult, usersResult] = await Promise.allSettled([
    fetchUserManagementStats(),
    fetchAllStudents(),
    fetchAllSheikhs(),
    fetchAllUsers(),
  ]);

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

  if (statsResult.status === 'fulfilled') {
    data.stats = statsResult.value;
  } else {
    errors.stats = statsResult.reason?.message ?? 'Failed to load statistics';
  }

  if (studentsResult.status === 'fulfilled') {
    data.students = studentsResult.value;
  } else {
    errors.students = studentsResult.reason?.message ?? 'Failed to load students';
  }

  if (sheikhsResult.status === 'fulfilled') {
    data.sheikhs = sheikhsResult.value;
  } else {
    errors.sheikhs = sheikhsResult.reason?.message ?? 'Failed to load sheikhs';
  }

  if (usersResult.status === 'fulfilled') {
    data.users = usersResult.value;
  } else {
    errors.users = usersResult.reason?.message ?? 'Failed to load users';
  }

  return { data, errors };
}

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

const adminUserManagementApi = {
  fetchUserManagementStats,
  fetchAllStudents,
  fetchAllSheikhs,
  fetchAllUsers,
  blockUser,
  unblockUser,
  fetchSheikhProfile,
  fetchStudentProfile,
  fetchUserManagementData,
  UserManagementApiError,
};

export default adminUserManagementApi;