import { BACKEND_URL } from './config';

export type LoginResponse = {
  access_token: string;
  token_type: string;
};

export type Category = {
  id: number;
  name: string;
  description?: string | null;
};

export type Transaction = {
  id: number;
  amount: number;
  description?: string | null;
  category_ids: number[];
};

function getBaseUrl() {
  const base = BACKEND_URL?.replace(/\/$/, '') || '';
  return base || '';
}

function getHeaders(contentType: 'json' | 'form' | 'none' = 'json'): Record<string, string> {
  const token = localStorage.getItem('token');
  const headers: Record<string, string> = {};

  if (contentType === 'json') {
    headers['Content-Type'] = 'application/json';
  } else if (contentType === 'form') {
    headers['Content-Type'] = 'application/x-www-form-urlencoded';
  }

  if (token) {
    headers['Authorization'] = `Bearer ${token}`;
  }

  return headers;
}

export async function login(email: string, password: string): Promise<void> {
  const body = new URLSearchParams();
  body.set('username', email);
  body.set('password', password);

  const res = await fetch(`${getBaseUrl()}/auth/jwt/login`, {
    method: 'POST',
    headers: {
      'Content-Type': 'application/x-www-form-urlencoded',
    },
    body: body.toString(),
  });
  if (!res.ok) {
    const text = await res.text();
    throw new Error(text || 'Login failed');
  }
  const data: LoginResponse = await res.json();
  localStorage.setItem('token', data.access_token);
}

export async function register(email: string, password: string, first_name?: string, last_name?: string): Promise<void> {
  const res = await fetch(`${getBaseUrl()}/auth/register`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ email, password, first_name, last_name }),
  });
  if (!res.ok) {
    const text = await res.text();
    throw new Error(text || 'Registration failed');
  }
}

export async function getCategories(): Promise<Category[]> {
  const res = await fetch(`${getBaseUrl()}/categories/`, {
    headers: getHeaders(),
  });
  if (!res.ok) throw new Error('Failed to load categories');
  return res.json();
}

export type CreateTransactionInput = {
  amount: number;
  description?: string;
  category_ids?: number[];
};

export async function createTransaction(input: CreateTransactionInput): Promise<Transaction> {
  const res = await fetch(`${getBaseUrl()}/transactions/create`, {
    method: 'POST',
    headers: getHeaders(),
    body: JSON.stringify(input),
  });
  if (!res.ok) {
    const text = await res.text();
    throw new Error(text || 'Failed to create transaction');
  }
  return res.json();
}

export async function getTransactions(): Promise<Transaction[]> {
    const res = await fetch(`${getBaseUrl()}/transactions/`, {
    headers: getHeaders(),
  });
  if (!res.ok) throw new Error('Failed to load transactions');
  return res.json();
}

export type User = {
  id: string;
  email: string;
  first_name?: string | null;
  last_name?: string | null;
  is_active: boolean;
  is_superuser: boolean;
  is_verified: boolean;
};

export async function getMe(): Promise<User> {
  const res = await fetch(`${getBaseUrl()}/users/me`, {
    headers: getHeaders(),
  });
  if (!res.ok) throw new Error('Failed to load user');
  return res.json();
}

export type UpdateMeInput = Partial<Pick<User, 'first_name' | 'last_name'>> & { password?: string };
export async function updateMe(input: UpdateMeInput): Promise<User> {
  const res = await fetch(`${getBaseUrl()}/users/me`, {
    method: 'PATCH',
    headers: getHeaders(),
    body: JSON.stringify(input),
  });
  if (!res.ok) {
    const text = await res.text();
    throw new Error(text || 'Failed to update user');
  }
  return res.json();
}

export async function deleteMe(): Promise<void> {
  const res = await fetch(`${getBaseUrl()}/users/me`, {
    method: 'DELETE',
    headers: getHeaders(),
  });
  if (!res.ok) {
    const text = await res.text();
    throw new Error(text || 'Failed to delete account');
  }
}

export function logout() {
  localStorage.removeItem('token');
}