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

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

var strip = require('./strip');
var catAndSlice = require('./../../support/catAndSlice');

/**
 * Takes in the matched path and virtual path and creates the
 * set of paths that represent the virtualPath being stripped
 * from the matchedPath.
 *
 * @example
 * Terms:
 * * Relative Complement: Of sets A and B the relative complement of A in B is
 * the parts of B that A do not contain.  In our example its virtualPath (A) in
 * matchedPath (B).
 *
 * Example:
 * matchedInput = [[A, D], [B, E], [C, F]]
 * virtualIntput = [A, Keys, C]
 *
 * This will produce 2 arrays from the matched operation.
 * [
 *   [D, [B, E], [C, F]],
 *   [A, [B, E], [F]]
 * ]
 *
 *
 * All the complexity of this function is hidden away in strip and its inner
 * stripping functions.
 * @param {PathSet} matchedPath
 * @param {PathSet} virtualPath
 */
module.exports = function stripPath(matchedPath, virtualPath) {
    var relativeComplement = [];
    var exactMatch = [];
    var current = [];

    // Always use virtual path because it can be shorter.
    for (var i = 0, len = virtualPath.length; i < len; ++i) {
        var matchedAtom = matchedPath[i];
        var virtualAtom = virtualPath[i];
        var stripResults = strip(matchedAtom, virtualAtom);
        var innerMatch = stripResults[0];
        var innerComplement = stripResults[1];
        var hasComplement = innerComplement.length > 0;

        // using the algorithm partially described above we need to split and
        // combine output depending on what comes out of the split function.
        // 1.  If there is no relative complement do no copying / slicing.
        // 2.  If there is both the catAndslice.

        if (hasComplement) {
            var flattendIC = innerComplement.length === 1 ?
                innerComplement[0] : innerComplement;
            current[i] = flattendIC;
            relativeComplement[relativeComplement.length] =
                catAndSlice(current, matchedPath, i + 1);
        }

        // The exact match needs to be produced for calling function.
        exactMatch[i] = innerMatch;
        current[i] = innerMatch;
    }

    return [exactMatch, relativeComplement];
};