//This file is a copy of https://github.com/AnalyticalGraphicsInc/cesium/blob/master/Specs/equalsMethodEqualityTester.js
/*global define*/
define([
        'Cesium/Core/defined'
    ], function(
        defined) {
    'use strict';

    return function(a, b) {
        var to_run;
        // if either a or b have an equals method, call it.
        if (a !== null && defined(a)) {
            if (typeof a.equals === 'function') {
                return a.equals(b);
            } else if(a instanceof Object) {
                // Check if the current object has a static function named 'equals'
                to_run = Object.getPrototypeOf(a).constructor.equals;
                if( typeof to_run === 'function') {
                    return to_run(a, b);
                }
            }
        }

        if (b !== null && defined(b)) {
            if (typeof b.equals === 'function') {
                return b.equals(a);
            } else if(b instanceof Object) {
                // Check if the current object has a static function named 'equals'
                to_run = Object.getPrototypeOf(b).constructor.equals;
                if( typeof to_run === 'function') {
                    return to_run(b, a);
                }
            }
        }

        // fall back to default equality checks.
        return undefined;
    };
});