falcor/lib/deref/index.js

A JavaScript library for efficient data fetching.

var InvalidDerefInputError = require("./../errors/InvalidDerefInputError");
var getCachePosition = require("./../get/getCachePosition");
var CONTAINER_DOES_NOT_EXIST = "e";
var $ref = require("./../types/ref");

module.exports = function deref(boundJSONArg) {

    var absolutePath = boundJSONArg && boundJSONArg.$__path;
    var refPath = boundJSONArg && boundJSONArg.$__refPath;
    var toReference = boundJSONArg && boundJSONArg.$__toReference;
    var referenceContainer;

    // We deref and then ensure that the reference container is attached to
    // the model.
    if (absolutePath) {
        var validContainer = CONTAINER_DOES_NOT_EXIST;

        if (toReference) {
            validContainer = false;
            referenceContainer = getCachePosition(this, toReference);

            // If the reference container is still a sentinel value then compare
            // the reference value with refPath.  If they are the same, then the
            // model is still valid.
            if (refPath && referenceContainer &&
                referenceContainer.$type === $ref) {

                var containerPath = referenceContainer.value;
                var i = 0;
                var len = refPath.length;

                validContainer = true;
                for (; validContainer && i < len; ++i) {
                    if (containerPath[i] !== refPath[i]) {
                        validContainer = false;
                    }
                }
            }
        }

        // Signal to the deref'd model that it has been disconnected from the
        // graph or there is no _fromWhenceYouCame
        if (!validContainer) {
            referenceContainer = false;
        }

        // The container did not exist, therefore there is no reference
        // container and fromWhenceYouCame should always return true.
        else if (validContainer === CONTAINER_DOES_NOT_EXIST) {
            referenceContainer = true;
        }

        return this._clone({
            _path: absolutePath,
            _referenceContainer: referenceContainer
        });
    }

    throw new InvalidDerefInputError();
};