falcor-router/src/operations/strip/strip.js

A router DataSource constructor for falcor that allows you to model all your cloud data sources as a single JSON resource.

var isArray = Array.isArray;
var stripFromArray = require('./stripFromArray');
var stripFromRange = require('./stripFromRange');

/**
 *  Takes a virtual atom and the matched atom and returns an
 * array of results that is relative complement with matchedAtom
 * as the rhs.  I believe the proper set syntax is virutalAtom \ matchedAtom.
 *
 * 1) An assumption made is that the matched atom and virtual atom have
 * an intersection.  This makes the algorithm easier since if the matched
 * atom is a primitive and the virtual atom is an object
 * then there is no relative complement to create.  This also means if
 * the direct equality test fails and matchedAtom is not an object
 * then virtualAtom is an object.  The inverse applies.
 *
 *
 * @param {String|Number|Array|Object} matchedAtom
 * @param {String|Number|Array|Object} virtualAtom
 * @return {Array} the tuple of what was matched and the relative complenment.
 */
module.exports = function strip(matchedAtom, virtualAtom) {
    var relativeComplement = [];
    var matchedResults;
    var typeOfMatched = typeof matchedAtom;
    var isArrayMatched = isArray(matchedAtom);
    var isObjectMatched = typeOfMatched === 'object';

    // Lets assume they are not objects  This covers the
    // string / number cases.
    if (matchedAtom === virtualAtom ||
       String(matchedAtom) === String(virtualAtom)) {

        matchedResults = [matchedAtom];
    }

    // See function comment 1)
    else if (!isObjectMatched) {
        matchedResults = [matchedAtom];
    }

    // Its a complex object set potentially.  Let the
    // subroutines handle the cases.
    else {
        var results;

        // The matchedAtom needs to reduced to everything that is not in
        // the virtualAtom.
        if (isArrayMatched) {
            results = stripFromArray(virtualAtom, matchedAtom);
            matchedResults = results[0];
            relativeComplement = results[1];
        } else {
            results = stripFromRange(virtualAtom, matchedAtom);
            matchedResults = results[0];
            relativeComplement = results[1];
        }
    }

    if (matchedResults.length === 1) {
        matchedResults = matchedResults[0];
    }

    return [matchedResults, relativeComplement];
};