loopback-graphql-server/src/db/resolveConnection.js

Add Relay based Apollo Server or GraphQL queries on your Loopback server

'use strict';

const _ = require('lodash');
const utils = require('./utils');

function connectionFromPromisedArray(dataPromise, args, model) {
    return dataPromise.then(data => connectionFromArray(data, args, model));
}

function connectionFromArray(obj, args, model) {
    const idName = (model && model.getIdName()) ? model.getIdName() : 'id';

    const res = {
        totalCount: obj.count ? obj.count : obj.length,

        edges: _.map(obj.list, node => ({
            cursor: utils.idToCursor(node[idName]),
            node
        })),

        list: obj.list,

        pageInfo: {
            startCursor: null,
            endCursor: null,
            hasPreviousPage: false,
            hasNextPage: false
        }
    };

    if (obj.count > 0) {
        if (obj.list.length > 0) {
            res.pageInfo.startCursor = utils.idToCursor(obj.list[0][idName]);
            res.pageInfo.endCursor = utils.idToCursor(obj.list[obj.list.length - 1][idName]);
        }
        res.pageInfo.hasNextPage = Boolean(args.first && obj.count > args.first);
        res.pageInfo.hasPreviousPage = Boolean(args.last && obj.count > args.last);
    }

    return res;
}

module.exports = {
    connectionFromArray,
    connectionFromPromisedArray
};