export interface ApiErrorShape {
  error: string;
  message: string;
  details?: unknown;
}

export class ApiError extends Error {
  readonly status: number;
  readonly code: string;
  readonly details?: unknown;
  constructor(status: number, body: ApiErrorShape) {
    super(body.message);
    this.status = status;
    this.code = body.error;
    this.details = body.details;
  }
}

interface RequestOptions<TBody = unknown> {
  method?: 'GET' | 'POST' | 'PATCH' | 'DELETE';
  body?: TBody;
  signal?: AbortSignal;
  formData?: FormData;
}

async function request<TResponse, TBody = unknown>(
  path: string,
  options: RequestOptions<TBody> = {},
): Promise<TResponse> {
  const headers: Record<string, string> = {};
  let body: BodyInit | undefined;

  if (options.formData) {
    body = options.formData;
  } else if (options.body !== undefined) {
    headers['content-type'] = 'application/json';
    body = JSON.stringify(options.body);
  }

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

  const isJson = response.headers.get('content-type')?.includes('application/json');
  const payload = isJson ? await response.json().catch(() => null) : null;

  if (!response.ok) {
    const errBody: ApiErrorShape =
      payload && typeof payload === 'object' && 'error' in payload
        ? (payload as ApiErrorShape)
        : { error: 'HTTP', message: response.statusText || 'Request failed' };
    throw new ApiError(response.status, errBody);
  }

  return payload as TResponse;
}

export const api = {
  get: <T>(path: string, signal?: AbortSignal) => request<T>(path, { signal }),
  post: <T, B = unknown>(path: string, body?: B) => request<T, B>(path, { method: 'POST', body }),
  patch: <T, B = unknown>(path: string, body?: B) =>
    request<T, B>(path, { method: 'PATCH', body }),
  delete: <T>(path: string) => request<T>(path, { method: 'DELETE' }),
  upload: <T>(path: string, formData: FormData) =>
    request<T>(path, { method: 'POST', formData }),
};