const apiBase = (): string => import.meta.env.PUBLIC_API_URL || '';

export function apiUrl(path: string): string {
  return path.startsWith('http') ? path : `${apiBase()}${path}`;
}

export class ApiError extends Error {
  status: number;
  code?: string;
  detail?: string;

  constructor(status: number, title: string, code?: string, detail?: string) {
    super(title);
    this.name = 'ApiError';
    this.status = status;
    this.code = code;
    this.detail = detail;
  }
}

export async function toApiError(res: Response): Promise<ApiError> {
  try {
    const body = await res.json();
    return new ApiError(
      res.status,
      body.title || body.detail || `Request failed (${res.status})`,
      body.code,
      body.detail,
    );
  } catch {
    return new ApiError(res.status, `Request failed (${res.status})`);
  }
}

export function jsonHeaders(options?: RequestInit): Headers {
  const headers = new Headers(options?.headers);
  if (!headers.has('Content-Type') && !(options?.body instanceof FormData)) {
    headers.set('Content-Type', 'application/json');
  }
  return headers;
}

export async function apiRequest<T>(path: string, options?: RequestInit): Promise<T> {
  const res = await fetch(apiUrl(path), {
    ...options,
    headers: jsonHeaders(options),
  });
  if (!res.ok) throw await toApiError(res);
  if (res.status === 204) return undefined as T;
  return res.json() as Promise<T>;
}