const API_URL = import.meta.env.VITE_API_URL || '/api/v1';
const SESSION_KEY = 'compor_hub_session';

export type ApiRole = 'student' | 'instructor' | 'admin';

export interface ApiUser {
  id: string;
  email: string;
  name: string;
  role: ApiRole;
}

export interface ManagedUser {
  id: string;
  email: string;
  name: string;
  role: ApiRole;
  isActive: boolean;
  createdAt: string;
}

interface Session {
  token: string;
  user: ApiUser;
}

export class ApiError extends Error {
  constructor(message: string, public status: number) {
    super(message);
  }
}

export function getSession(): Session | null {
  const value = localStorage.getItem(SESSION_KEY);
  if (!value) return null;
  try {
    return JSON.parse(value) as Session;
  } catch {
    localStorage.removeItem(SESSION_KEY);
    return null;
  }
}

export function saveSession(session: Session) {
  localStorage.setItem(SESSION_KEY, JSON.stringify(session));
}

export function clearSession() {
  localStorage.removeItem(SESSION_KEY);
}

export async function apiRequest<T>(path: string, options: RequestInit = {}): Promise<T> {
  const session = getSession();
  const headers = new Headers(options.headers);
  if (options.body) headers.set('Content-Type', 'application/json');
  if (session) headers.set('Authorization', `Bearer ${session.token}`);

  const response = await fetch(`${API_URL}${path}`, { ...options, headers });
  if (response.status === 204) return undefined as T;

  const body = await response.json().catch(() => ({}));
  if (!response.ok) {
    throw new ApiError(body.error || 'The request could not be completed', response.status);
  }
  return body as T;
}

export const authApi = {
  async login(email: string, password: string) {
    return apiRequest<Session>('/auth/login', { method: 'POST', body: JSON.stringify({ email, password }) });
  },
  async register(name: string, email: string, password: string) {
    return apiRequest<Session>('/auth/register', { method: 'POST', body: JSON.stringify({ name, email, password }) });
  },
  async me() {
    return apiRequest<{ user: ApiUser }>('/auth/me');
  },
};

export const adminApi = {
  async listUsers() {
    return apiRequest<{ data: ManagedUser[] }>('/admin/users');
  },
  async updateUser(userId: string, update: Partial<Pick<ManagedUser, 'role' | 'isActive'>>) {
    return apiRequest<{ data: ManagedUser }>(`/admin/users/${userId}`, {
      method: 'PATCH',
      body: JSON.stringify(update),
    });
  },
};