falcor/lib/response/get/GetResponse.js

A JavaScript library for efficient data fetching.

var ModelResponse = require("./../ModelResponse");
var checkCacheAndReport = require("./checkCacheAndReport");
var getRequestCycle = require("./getRequestCycle");
var empty = {dispose: function() {}};
var collectLru = require("./../../lru/collect");
var getSize = require("./../../support/getSize");

/**
 * The get response.  It takes in a model and paths and starts
 * the request cycle.  It has been optimized for cache first requests
 * and closures.
 * @param {Model} model -
 * @param {Array} paths -
 * @augments ModelResponse
 * @private
 */
var GetResponse = function GetResponse(model, paths, isJSONGraph,
                                       isProgressive, forceCollect) {
    this.model = model;
    this.currentRemainingPaths = paths;
    this.isJSONGraph = isJSONGraph || false;
    this.isProgressive = isProgressive || false;
    this.forceCollect = forceCollect || false;
};

GetResponse.prototype = Object.create(ModelResponse.prototype);

/**
 * Makes the output of a get response JSONGraph instead of json.
 * @private
 */
GetResponse.prototype._toJSONG = function _toJSONGraph() {
    return new GetResponse(this.model, this.currentRemainingPaths,
                           true, this.isProgressive, this.forceCollect);
};

/**
 * Progressively responding to data in the cache instead of once the whole
 * operation is complete.
 * @public
 */
GetResponse.prototype.progressively = function progressively() {
    return new GetResponse(this.model, this.currentRemainingPaths,
                           this.isJSONGraph, true, this.forceCollect);
};

/**
 * purely for the purposes of closure creation other than the initial
 * prototype created closure.
 *
 * @private
 */
GetResponse.prototype._subscribe = function _subscribe(observer) {
    var seed = [{}];
    var errors = [];
    var model = this.model;
    var isJSONG = observer.isJSONG = this.isJSONGraph;
    var isProgressive = this.isProgressive;
    var results = checkCacheAndReport(model, this.currentRemainingPaths,
                                      observer, isProgressive, isJSONG, seed,
                                      errors);

    // If there are no results, finish.
    if (!results) {
        if (this.forceCollect) {
            var modelRoot = model._root;
            var modelCache = modelRoot.cache;
            var currentVersion = modelCache.$_version;

            collectLru(modelRoot, modelRoot.expired, getSize(modelCache),
                    model._maxSize, model._collectRatio, currentVersion);
        }
        return empty;
    }

    // Starts the async request cycle.
    return getRequestCycle(this, model, results,
                           observer, errors, 1);
};

module.exports = GetResponse;