graphbrainz/src/schema.js

A GraphQL schema, Express server, and middleware for querying the MusicBrainz.

import createDebug from 'debug';
import GraphQL from 'graphql';
import GraphQLToolsSchema from '@graphql-tools/schema';
import { lookup, browse, search } from './queries/index.js';
import { nodeField } from './types/node.js';

const { GraphQLSchema, GraphQLObjectType, extendSchema, parse } = GraphQL;
const { addResolversToSchema } = GraphQLToolsSchema;

const debug = createDebug('graphbrainz:schema');

export function applyExtension(extension, schema, options = {}) {
  let outputSchema = schema;
  if (extension.extendSchema) {
    if (typeof extension.extendSchema === 'object') {
      debug(
        `Extending schema via an object from the “${extension.name}” extension.`
      );
      const { schemas = [], resolvers } = extension.extendSchema;
      outputSchema = schemas.reduce((updatedSchema, extensionSchema) => {
        if (typeof extensionSchema === 'string') {
          extensionSchema = parse(extensionSchema);
        }
        return extendSchema(updatedSchema, extensionSchema);
      }, outputSchema);
      if (resolvers) {
        outputSchema = addResolversToSchema({
          schema: outputSchema,
          resolvers,
        });
      }
    } else if (typeof extension.extendSchema === 'function') {
      debug(
        `Extending schema via a function from the “${extension.name}” extension.`
      );
      outputSchema = extension.extendSchema(schema, options);
    } else {
      throw new Error(
        `The “${extension.name}” extension contains an invalid ` +
          `\`extendSchema\` value: ${extension.extendSchema}`
      );
    }
  }

  // Fix for `graphql-tools` creating a new Query type with no description.
  if (outputSchema._queryType.description === undefined) {
    outputSchema._queryType.description = schema._queryType.description;
  }
  return outputSchema;
}

export function createSchema(schema, options = {}) {
  const { extensions = [] } = options;
  return extensions.reduce((updatedSchema, extension) => {
    return applyExtension(extension, updatedSchema, options);
  }, schema);
}

export const baseSchema = new GraphQLSchema({
  query: new GraphQLObjectType({
    name: 'Query',
    description: `The query root, from which multiple types of MusicBrainz
requests can be made.`,
    fields: () => ({
      lookup,
      browse,
      search,
      node: nodeField,
    }),
  }),
});