// The one door to the server. Mutations carry the anti-CSRF header the server
// requires; errors come back as a stable code the interface translates.

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

async function call<T>(method: string, path: string, body?: unknown): Promise<T> {
  const headers: Record<string, string> = { 'x-requested-with': 'libredecision' };
  if (body !== undefined) headers['content-type'] = 'application/json';
  let res: Response;
  try {
    res = await fetch(`/api${path}`, {
      method,
      headers,
      credentials: 'same-origin',
      body: body === undefined ? undefined : JSON.stringify(body),
    });
  } catch {
    throw new ApiError(0, 'network');
  }
  const data = await res.json().catch(() => null);
  if (!res.ok) throw new ApiError(res.status, (data && typeof data.error === 'string' && data.error) || 'internal');
  return data as T;
}

export const api = {
  get: <T>(path: string) => call<T>('GET', path),
  post: <T>(path: string, body: unknown = {}) => call<T>('POST', path, body),
  patch: <T>(path: string, body: unknown) => call<T>('PATCH', path, body),
  put: <T>(path: string, body: unknown) => call<T>('PUT', path, body),
  del: <T>(path: string) => call<T>('DELETE', path),
};