(function() {
    function isEscapeKey(e) {
        var isEscape = false;
        if (e.key == 'Escape' || e.key == 'Esc' || e.keyCode == 27) {
            isEscape = true;
        }
        return isEscape;
    }

    function _draggable(element, target) {
        var moveOffsetX;
        var moveOffsetY;

        function dragHandler(e) {
            moveElement(element, e.clientX - moveOffsetX, e.clientY - moveOffsetY);
        };

        function dragEndHandler(e) {
            document.body.removeEventListener('mousemove', dragHandler);
            document.body.removeEventListener('mouseup', dragEndHandler);
        };

        function dragStart(e) {
            var boundingRect = element.getBoundingClientRect();
            moveOffsetX = e.clientX - boundingRect.left;
            moveOffsetY = e.clientY - boundingRect.top;
            document.body.addEventListener('mousemove', dragHandler);
            document.body.addEventListener('mouseup', dragEndHandler);
        };

        target.addEventListener('mousedown', dragStart);
    }

    var dialogs = [];
    var focused;
    var focusedZIndex = 1000;

    function sortDialogs() {
        dialogs.sort(function(a, b) {
            var isOpen = b.isOpen() - a.isOpen();
            var elevationDelta = b.getElevation() - a.getElevation();
            return isOpen || elevationDelta;
        });
    }

    function Dialog(o) {
        var d = this;
        dialogs.push(d);
        d.element = o.element;
        d.access = {};
        d.actions = {};
        var drag = d.element.querySelector(o.drag);

        d.getElevation = function() {
            return parseInt(d.element.style.zIndex, 10);
        };

        d.setElevation = function(elevation) {
            d.element.style.zIndex = elevation;
        };

        d.isFocused = function() {
            return focused == d;
        };

        d.focus = function() {
            if (!d.isFocused()) {
                d.setElevation(focusedZIndex++);
                focused = d;
            }
        };

        d.isOpen = function() {
            return d.element.classList.contains('active');
        };

        d.close = function() {
            d.element.classList.remove('active');
        };

        d.open = function() {
            d.focus();
            d.element.classList.add('active');
        };

        d.move = moveElement.bind(d, d.element);
        d.size = resizeElement.bind(d, d.element);

        _draggable(d.element, drag);
        d.element.addEventListener('mousedown', d.focus);

        if (o.position) {
            d.move(o.position.x, o.position.y);
        } else {
            d.element.classList.add('measure');
            var boundingRect = d.element.getBoundingClientRect();
            d.element.classList.remove('measure');
            var x = (innerWidth - boundingRect.width) / 2;
            var y = (innerHeight - boundingRect.height) / 2;
            d.move(x, y);
        }

        if (o.trigger) {
            var target;
            var event;

            if (o.trigger instanceof Element) {
                target = o.trigger;
                event = 'click';
            } else {
                target = o.trigger.element;
                event = o.trigger.event;
            }

            target.addEventListener(event, d.open);
        }

        if (o.size) {
            d.size(o.size.width, o.size.height);
        }

        o.actions.forEach(function(a) {
            var target = d.element.querySelector(a.selector);
            if (!target) {
                console.log("No element matches action selector " + a.selector);
                return;
            }

            var callback;
            if (typeof a.callback == 'string') {
                callback = d[a.callback];
            } else {
                callback = function(e) {
                    a.callback.call(d, target, e);
                }
            }

            var event = a.event;
            if (!event) {
                event = 'click';
            }

            target.addEventListener(event, callback);

            if (a.id) {
                d.actions[a.id] = target;
            }
        });

        if (o.access) {
            Object.keys(o.access).forEach(function(key) {
                d.access[key] = d.element.querySelector(o.access[key]);
            });
        }
    }

    document.addEventListener('keydown', function(e) {
        if (isEscapeKey(e)) {
            sortDialogs();
            dialogs[0].close();
        }
    });

    window.Dialog = Dialog;
})();