import {
  GraphQLOptions,
  HttpQueryError,
  runHttpQuery,
} from 'apollo-server-core';

import { Request, Response, URL } from 'apollo-server-env';
import type { ValueOrPromise } from 'apollo-server-types';

// Design principles:
// - You can issue a GET or POST with your query.
// - simple, fast and secure
//

export interface CloudflareOptionsFunction {
  (req?: Request): ValueOrPromise<GraphQLOptions>;
}

export function graphqlCloudflare(
  options: GraphQLOptions | CloudflareOptionsFunction,
  csrfPreventionRequestHeaders?: string[] | null,
) {
  if (!options) {
    throw new Error('Apollo Server requires options.');
  }

  const graphqlHandler = async (req: Request): Promise<Response> => {
    const url = new URL(req.url);
    const query =
      req.method === 'POST'
        ? await req.json()
        : {
            query: url.searchParams.get('query'),
            variables: url.searchParams.get('variables'),
            operationName: url.searchParams.get('operationName'),
            extensions: url.searchParams.get('extensions'),
          };

    return runHttpQuery(
      [req],
      {
        method: req.method,
        options: options,
        query,
        request: req as Request,
      },
      csrfPreventionRequestHeaders,
    ).then(
      ({ graphqlResponse, responseInit }) =>
        new Response(graphqlResponse, responseInit),
      (error: HttpQueryError) => {
        if ('HttpQueryError' !== error.name) throw error;

        const res = new Response(error.message, {
          status: error.statusCode,
          headers: error.headers,
        });

        return res;
      },
    );
  };

  return graphqlHandler;
}