import type { ApiError } from '@family-budget/shared';

let onUnauthorized: (() => void) | null = null;

export function setOnUnauthorized(cb: () => void) {
  onUnauthorized = cb;
}

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

async function request<T>(url: string, options: RequestInit = {}): Promise<T> {
  const res = await fetch(url, {
    ...options,
    headers: {
      'Content-Type': 'application/json',
      ...(options.headers as Record<string, string>),
    },
    credentials: 'include',
  });

  if (res.status === 401) {
    let body: ApiError;
    try {
      body = await res.json();
    } catch {
      body = { error: 'UNAUTHORIZED', message: 'Сессия истекла' };
    }
    if (!url.includes('/api/auth/login')) {
      onUnauthorized?.();
    }
    throw new ApiException(401, body);
  }

  if (!res.ok) {
    let body: ApiError;
    try {
      body = await res.json();
    } catch {
      body = { error: 'UNKNOWN', message: res.statusText };
    }
    throw new ApiException(res.status, body);
  }

  if (res.status === 204) return undefined as T;

  return res.json();
}

async function requestFormData<T>(url: string, formData: FormData): Promise<T> {
  const res = await fetch(url, {
    method: 'POST',
    body: formData,
    credentials: 'include',
    // Do not set Content-Type — browser sets multipart/form-data with boundary
  });

  if (res.status === 401) {
    let body: ApiError;
    try {
      body = await res.json();
    } catch {
      body = { error: 'UNAUTHORIZED', message: 'Сессия истекла' };
    }
    if (!url.includes('/api/auth/login')) {
      onUnauthorized?.();
    }
    throw new ApiException(401, body);
  }

  if (!res.ok) {
    let body: ApiError;
    try {
      body = await res.json();
    } catch {
      body = { error: 'UNKNOWN', message: res.statusText };
    }
    throw new ApiException(res.status, body);
  }

  return res.json();
}

export const api = {
  get: <T>(url: string) => request<T>(url),

  post: <T>(url: string, body?: unknown) =>
    request<T>(url, {
      method: 'POST',
      body: body != null ? JSON.stringify(body) : undefined,
    }),

  postFormData: <T>(url: string, formData: FormData) =>
    requestFormData<T>(url, formData),

  put: <T>(url: string, body: unknown) =>
    request<T>(url, { method: 'PUT', body: JSON.stringify(body) }),

  patch: <T>(url: string, body: unknown) =>
    request<T>(url, { method: 'PATCH', body: JSON.stringify(body) }),

  delete: <T>(url: string) =>
    request<T>(url, { method: 'DELETE' }),
};