js.ts

import { buildSchema, execute, parse } from "graphql";
import { resolve } from "path";
import {
  ApolloIntrospection,
  GraphQLIntrospection,
  Introspection,
  SchemaLoader,
} from "../interface";
import { query as introspectionQuery } from "../utility";

export interface IJsSchemaLoaderOptions {
  schemaFile: string;
}

export const jsSchemaLoader: SchemaLoader = async (
  options: IJsSchemaLoaderOptions
) => {
  const schemaPath = resolve(options.schemaFile);
  let schemaModule = require(schemaPath);
  let schema: string;

  // check if exist default in module
  if (typeof schemaModule === "object") {
    schemaModule = schemaModule.default;
  }

  // check for array of definition
  if (Array.isArray(schemaModule)) {
    schema = schemaModule.join("");

    // check for array array wrapped in a function
  } else if (typeof schemaModule === "function") {
    schema = schemaModule().join("");
  } else {
    throw new Error(
      `Unexpected schema definition on "${schemaModule}", must be an array or function`
    );
  }

  const introspection = (await execute(
    buildSchema(schema),
    parse(introspectionQuery)
  )) as Introspection;

  return (
    (introspection as ApolloIntrospection).__schema ||
    (introspection as GraphQLIntrospection).data.__schema
  );
};