How to GraphQL and Relay

graphql-todos.task.js

const graphql = require('graphql');
const GraphQLRelay = require('graphql-relay');

state.graphql_todos = state.graphql_todos || {};

var nodeDefinitions = GraphQLRelay.nodeDefinitions(function(globalId) {
  var idInfo = GraphQLRelay.fromGlobalId(globalId);
  if (idInfo.type == 'Todo') return state.graphql_todos[idInfo];
  return null;
});

var todoType = new graphql.GraphQLObjectType({
  name: 'Todo',
  interfaces: [nodeDefinitions.nodeInterface],
  isTypeOf: 'Todo',
  fields: {
    id: { type: graphql.GraphQLInt },
    isDone: { type: graphql.GraphQLBoolean},
    description: { type: graphql.GraphQLString },
  }
});

var schema = new graphql.GraphQLSchema({
  query: new graphql.GraphQLObjectType({
    name: 'Query',
    node: nodeDefinitions.nodeField,
    fields: {
      todos:{
        type: new graphql.GraphQLList(todoType),
        resolve: () => Object.keys(state.graphql_todos).map(x => state.graphql_todos[x])
      },
      todo: {
        type: todoType,
        args: { id: { type: graphql.GraphQLInt } },
        resolve:  (_, args) => state.graphql_todos[args.id]
      }
    }
  }),
  mutation: new graphql.GraphQLObjectType({
    name: 'Mutation',
    fields: {
      upsertTodo: {
        type: todoType,
        args: { 
          description: { type: new graphql.GraphQLNonNull(graphql.GraphQLString) },
          isDone: { type: graphql.GraphQLBoolean }
        },
        resolve: (_, args) => {
          var key = args.id || Object.keys(state.graphql_todos).length + 1;
          state.graphql_todos[key] = { id: key, description: args.description, isDone: args.isDone || false};
          return state.graphql_todos[key];
        }
      }
    }
  })  
});

graphql.graphql(schema, req.query.query || req.body.query || req.body)
  .then(result => res.send(JSON.stringify(result, null, 4)));