export type ApiErrorPayload = {
  error?: {
    code?: string;
    title?: string;
    message?: string;
    meta?: Record<string, unknown>;
  };
  code?: string;
  message?: string;
};

export type ApiError = Error & {
  status?: number;
  code?: string;
  meta?: Record<string, unknown>;
};

export type FetchJsonResult<T> = {
  data: T | null;
  etag: string | null;
  notModified: boolean;
  status: number;
};

type FetchJsonOptions = {
  method?: string;
  headers?: HeadersInit;
  body?: BodyInit | null;
  signal?: AbortSignal;
  etag?: string | null;
  noStore?: boolean;
};

export async function fetchJson<T>(url: string, options: FetchJsonOptions = {}): Promise<FetchJsonResult<T>> {
  const headers: Record<string, string> = {
    Accept: 'application/json',
  };

  if (options.noStore) {
    headers['Cache-Control'] = 'no-store';
  }

  if (options.etag) {
    headers['If-None-Match'] = options.etag;
  }

  if (options.headers) {
    Object.assign(headers, options.headers as Record<string, string>);
  }

  const response = await fetch(url, {
    method: options.method ?? 'GET',
    headers,
    body: options.body ?? null,
    signal: options.signal,
    credentials: 'include',
  });

  if (response.status === 304) {
    return {
      data: null,
      etag: response.headers.get('ETag') ?? options.etag ?? null,
      notModified: true,
      status: response.status,
    };
  }

  if (!response.ok) {
    const errorPayload = await safeParseError(response);
    const error: ApiError = new Error(errorPayload?.error?.message ?? errorPayload?.message ?? `Request failed (${response.status})`);
    error.status = response.status;
    error.code = errorPayload?.error?.code ?? errorPayload?.code;
    if (errorPayload?.error?.meta) {
      error.meta = errorPayload.error.meta;
    }
    throw error;
  }

  const data = (await response.json()) as T;
  return {
    data,
    etag: response.headers.get('ETag'),
    notModified: false,
    status: response.status,
  };
}

async function safeParseError(response: Response): Promise<ApiErrorPayload | null> {
  try {
    const payload = (await response.clone().json()) as ApiErrorPayload;
    return payload;
  } catch (error) {
    return null;
  }
}