Function.prototype.bind = Function.prototype.bind || function (target) {
    var self = this;
    return function (args) {
        if (!(args instanceof Array)) {
            args = [args];
        }
        self.apply(target, args);
    };
};
(function () {
    if (typeof window.Element === "undefined" ||
      "classList" in document.documentElement) {
        return;
    }

    var prototype = Array.prototype,
      push = prototype.push,
      splice = prototype.splice,
      join = prototype.join;

    function DOMTokenList(el) {
        this.el = el;
        // The className needs to be trimmed and split on whitespace
        // to retrieve a list of classes.
        var classes = el.className.replace(/^\s+|\s+$/g, ‘‘).split(/\s+/);
        for (var i = 0; i < classes.length; i++) {
            push.call(this, classes[i]);
        }
    }

    DOMTokenList.prototype = {
        add: function (token) {
            if (this.contains(token)) return;
            push.call(this, token);
            this.el.className = this.toString();
        },
        contains: function (token) {
            return this.el.className.indexOf(token) != -1;
        },
        item: function (index) {
            return this[index] || null;
        },
        remove: function (token) {
            if (!this.contains(token)) return;
            for (var i = 0; i < this.length; i++) {
                if (this[i] == token) break;
            }
            splice.call(this, i, 1);
            this.el.className = this.toString();
        },
        toString: function () {
            return join.call(this, ‘ ‘);
        },
        toggle: function (token) {
            if (!this.contains(token)) {
                this.add(token);
            } else {
                this.remove(token);
            }

            return this.contains(token);
        }
    };

    window.DOMTokenList = DOMTokenList;

    function defineElementGetter(obj, prop, getter) {
        if (Object.defineProperty) {
            Object.defineProperty(obj, prop, {
                get: getter
            });
        } else {
            obj.__defineGetter__(prop, getter);
        }
    }

    defineElementGetter(HTMLElement.prototype, ‘classList‘, function () {
        return new DOMTokenList(this);
    });
})();

function KeyboardInputManager() {
    this.events = {};

    if (window.navigator.msPointerEnabled) {
        //Internet Explorer 10 style
        this.eventTouchstart = "MSPointerDown";
        this.eventTouchmove = "MSPointerMove";
        this.eventTouchend = "MSPointerUp";
    } else {
        this.eventTouchstart = "touchstart";
        this.eventTouchmove = "touchmove";
        this.eventTouchend = "touchend";
    }

    this.listen();
}

KeyboardInputManager.prototype.on = function (event, callback) {
    if (!this.events[event]) {
        this.events[event] = [];
    }
    this.events[event].push(callback);
};

KeyboardInputManager.prototype.emit = function (event, data) {
    var callbacks = this.events[event];
    if (callbacks) {
        callbacks.forEach(function (callback) {
            callback(data);
        });
    }
};

KeyboardInputManager.prototype.listen = function () {
    var self = this;

    var map = {
        38: 0, // Up
        39: 1, // Right
        40: 2, // Down
        37: 3, // Left
        75: 0, // Vim up
        76: 1, // Vim right
        74: 2, // Vim down
        72: 3, // Vim left
        87: 0, // W
        68: 1, // D
        83: 2, // S
        65: 3  // A
    };

    // Respond to direction keys
    document.addEventListener("keydown", function (event) {
        var modifiers = event.altKey || event.ctrlKey || event.metaKey ||
                    event.shiftKey;
        var mapped = map[event.which];

        // Ignore the event if it‘s happening in a text field
        if (self.targetIsInput(event)) return;

        if (!modifiers) {
            if (mapped !== undefined) {
                event.preventDefault();
                self.emit("move", mapped);
            }
        }

        // R key restarts the game
        if (!modifiers && event.which === 82) {
            self.restart.call(self, event);
        }
    });

    // Respond to button presses
    this.bindButtonPress(".retry-button", this.restart);
    this.bindButtonPress(".restart-button", this.restart);
    this.bindButtonPress(".keep-playing-button", this.keepPlaying);

    // Respond to swipe events
    var touchStartClientX, touchStartClientY;
    var gameContainer = document.getElementsByClassName("game-container")[0];

    gameContainer.addEventListener(this.eventTouchstart, function (event) {
        if ((!window.navigator.msPointerEnabled && event.touches.length > 1) ||
        event.targetTouches > 1 ||
        self.targetIsInput(event)) {
            return; // Ignore if touching with more than 1 finger or touching input
        }

        if (window.navigator.msPointerEnabled) {
            touchStartClientX = event.pageX;
            touchStartClientY = event.pageY;
        } else {
            touchStartClientX = event.touches[0].clientX;
            touchStartClientY = event.touches[0].clientY;
        }

        event.preventDefault();
    });

    gameContainer.addEventListener(this.eventTouchmove, function (event) {
        event.preventDefault();
    });