export interface ApiRequest<Input = unknown> {
  method?: string;
  params?: Record<string, string | number>;
  query?: Record<string, string | number | boolean | undefined>;
  body?: Input;
}

export interface ApiClientOptions {
  baseUrl?: string;
  fetch?: (input: RequestInfo | URL, init?: RequestInit) => Promise<Response>;
}

/** Runtime used by generated API clients; throws a typed response error on non-2xx results. */
export function createApiClient(options: ApiClientOptions = {}) {
  const fetcher = options.fetch ?? globalThis.fetch;
  return async function call<Output, Input = unknown>(
    template: string,
    request: ApiRequest<Input> = {},
  ): Promise<Output> {
    let path = template;
    for (const [name, value] of Object.entries(request.params ?? {})) {
      path = path.replace(`[${name}]`, encodeURIComponent(String(value)));
    }
    const url = new URL(path, options.baseUrl ?? globalThis.location?.origin ?? "http://localhost");
    for (const [name, value] of Object.entries(request.query ?? {}))
      if (value !== undefined) url.searchParams.set(name, String(value));
    const response = await fetcher(url, {
      method: request.method ?? (request.body === undefined ? "GET" : "POST"),
      credentials: "same-origin",
      headers: request.body === undefined ? undefined : { "content-type": "application/json" },
      body: request.body === undefined ? undefined : JSON.stringify(request.body),
    });
    const data = response.status === 204 ? undefined : await response.json();
    if (!response.ok)
      throw Object.assign(
        new Error((data as { error?: string })?.error ?? `HTTP ${response.status}`),
        { status: response.status, data },
      );
    return data as Output;
  };
}