import fetch from "isomorphic-unfetch";
import { buildClientSchema, ExecutionResult, getIntrospectionQuery } from "graphql";
import { GraphQLSchemaValidationOptions } from "graphql/type/schema";
import qs from "qs";

export interface SchemaFetcher {
  (query: string, fetchImpl: typeof fetch, qsImpl: typeof qs): Promise<ExecutionResult>;
}

export async function fetchSchema({
  endpoint,
  usePost = false,
  headers,
  options,
}: {
  endpoint: string;
  usePost: boolean;
  headers?: Record<string, string>;
  options?: GraphQLSchemaValidationOptions;
}) {
  const response = await fetch(
    usePost ? endpoint : `${endpoint}?${qs.stringify({ query: getIntrospectionQuery() })}`,
    usePost
      ? {
          method: usePost ? "POST" : "GET",
          body: JSON.stringify({ query: getIntrospectionQuery() }),
          headers: { ...headers, "Content-Type": "application/json" },
        }
      : {
          headers,
        }
  );
  if (!response.ok) {
    throw new Error("introspection query was not successful, " + response.statusText);
  }

  const result = await response.json().catch((e) => {
    const contentType = response.headers.get("Content-Type");
    console.log(`content type is ${contentType}`);
    throw new Error(
      `endpoint '${endpoint}' did not return valid json, check that your endpoint points to a valid graphql api`
    );
  });
  if (!result.data) {
    throw new Error("introspection request did not receive a valid response");
  }

  // console.log(result.data)
  // console.log(JSON.stringify(result.data, null, 4))

  return buildClientSchema(result.data, options);
}

export async function customFetchSchema(fetcher: SchemaFetcher, options?: GraphQLSchemaValidationOptions) {
  const result = await fetcher(getIntrospectionQuery(), fetch, qs);

  if (!result.data) {
    throw new Error("introspection request did not receive a valid response");
  }

  return buildClientSchema(result.data as any, options);
}