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//     (c) 2012 Onsi Fakhouri
//     Cocktail.js may be freely distributed under the MIT license.
//     http://github.com/onsi/cocktail
(function(factory) {
    if (typeof require === 'function' && typeof module !== 'undefined' && module.exports) {
        module.exports = factory(require('underscore'));
    } else if (typeof define === 'function') {
        define(['underscore'], factory);
    } else {
        this.Cocktail = factory(_);
    }
}(function (_) {

    var Cocktail = {};

    Cocktail.mixins = {};

    Cocktail.mixin = function mixin(klass) {
        var mixins = _.chain(arguments).toArray().rest().flatten().value();
        // Allows mixing into the constructor's prototype or the dynamic instance
        var obj = klass.prototype || klass;

        var collisions = {};

        _.each(mixins, function(mixin) {
            if (_.isString(mixin)) {
                mixin = Cocktail.mixins[mixin];
            }
            _.each(mixin, function(value, key) {
                if (_.isFunction(value)) {
                    // If the mixer already has that exact function reference
                    // Note: this would occur on an accidental mixin of the same base
                    if (obj[key] === value) return;

                    if (obj[key]) {
                        // Avoid accessing built-in properties like constructor (#39)
                        collisions[key] = collisions.hasOwnProperty(key) ? collisions[key] : [obj[key]];
                        collisions[key].push(value);
                    }
                    obj[key] = value;
                } else if (_.isArray(value)) {
                    obj[key] = _.union(value, obj[key] || []);
                } else if (_.isObject(value)) {
                    obj[key] = _.extend({}, value, obj[key] || {});
                } else if (!(key in obj)) {
                    obj[key] = value;
                }
            });
        });

        _.each(collisions, function(propertyValues, propertyName) {
            obj[propertyName] = function() {
                var that = this,
                    args = arguments,
                    returnValue;

                _.each(propertyValues, function(value) {
                    var returnedValue = _.isFunction(value) ? value.apply(that, args) : value;
                    returnValue = (typeof returnedValue === 'undefined' ? returnValue : returnedValue);
                });

                return returnValue;
            };
        });

        return klass;
    };

    var originalExtend;

    Cocktail.patch = function patch(Backbone) {
        originalExtend = Backbone.Model.extend;

        var extend = function(protoProps, classProps) {
            var klass = originalExtend.call(this, protoProps, classProps);

            var mixins = klass.prototype.mixins;
            if (mixins && klass.prototype.hasOwnProperty('mixins')) {
                Cocktail.mixin(klass, mixins);
            }

            return klass;
        };

        _.each([Backbone.Model, Backbone.Collection, Backbone.Router, Backbone.View], function(klass) {
            klass.mixin = function mixin() {
                Cocktail.mixin(this, _.toArray(arguments));
            };

            klass.extend = extend;
        });
    };

    Cocktail.unpatch = function unpatch(Backbone) {
        _.each([Backbone.Model, Backbone.Collection, Backbone.Router, Backbone.View], function(klass) {
            klass.mixin = undefined;
            klass.extend = originalExtend;
        });
    };

    return Cocktail;
}));