/* Copyright 2014 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

'use strict';

(function(root, factory) {
    if (typeof define === 'function' && define.amd) {
        define('pdfjs-web/overlay_manager', ['exports'], factory);
    } else if (typeof exports !== 'undefined') {
        factory(exports);
    } else {
        factory((root.pdfjsWebOverlayManager = {}));
    }
}(this, function(exports) {

    var OverlayManager = {
        overlays : {},
        active   : null,

        /**
         * @param {string} name The name of the overlay that is registered.
         * @param {HTMLDivElement} element The overlay's DOM element.
         * @param {function} callerCloseMethod (optional) The method that, if present,
         *                   will call OverlayManager.close from the Object
         *                   registering the overlay. Access to this method is
         *                   necessary in order to run cleanup code when e.g.
         *                   the overlay is force closed. The default is null.
         * @param {boolean} canForceClose (optional) Indicates if opening the overlay
         *                  will close an active overlay. The default is false.
         * @returns {Promise} A promise that is resolved when the overlay has been
         *                    registered.
         */
        register : function overlayManagerRegister(name, element,
                                                   callerCloseMethod, canForceClose) {
            return new Promise(function(resolve) {
                var container;
                if (!name || !element || !(container = element.parentNode)) {
                    throw new Error('Not enough parameters.');
                } else if (this.overlays[name]) {
                    throw new Error('The overlay is already registered.');
                }
                this.overlays[name] = {
                    element           : element,
                    container         : container,
                    callerCloseMethod : (callerCloseMethod || null),
                    canForceClose     : (canForceClose || false)
                };
                resolve();
            }.bind(this));
        },

        /**
         * @param {string} name The name of the overlay that is unregistered.
         * @returns {Promise} A promise that is resolved when the overlay has been
         *                    unregistered.
         */
        unregister : function overlayManagerUnregister(name) {
            return new Promise(function(resolve) {
                if (!this.overlays[name]) {
                    throw new Error('The overlay does not exist.');
                } else if (this.active === name) {
                    throw new Error('The overlay cannot be removed while it is active.');
                }
                delete this.overlays[name];

                resolve();
            }.bind(this));
        },

        /**
         * @param {string} name The name of the overlay that should be opened.
         * @returns {Promise} A promise that is resolved when the overlay has been
         *                    opened.
         */
        open : function overlayManagerOpen(name) {
            return new Promise(function(resolve) {
                if (!this.overlays[name]) {
                    throw new Error('The overlay does not exist.');
                } else if (this.active) {
                    if (this.overlays[name].canForceClose) {
                        this._closeThroughCaller();
                    } else if (this.active === name) {
                        throw new Error('The overlay is already active.');
                    } else {
                        throw new Error('Another overlay is currently active.');
                    }
                }
                this.active = name;
                this.overlays[this.active].element.classList.remove('hidden');
                this.overlays[this.active].container.classList.remove('hidden');

                window.addEventListener('keydown', this._keyDown);
                resolve();
            }.bind(this));
        },

        /**
         * @param {string} name The name of the overlay that should be closed.
         * @returns {Promise} A promise that is resolved when the overlay has been
         *                    closed.
         */
        close : function overlayManagerClose(name) {
            return new Promise(function(resolve) {
                if (!this.overlays[name]) {
                    throw new Error('The overlay does not exist.');
                } else if (!this.active) {
                    throw new Error('The overlay is currently not active.');
                } else if (this.active !== name) {
                    throw new Error('Another overlay is currently active.');
                }
                this.overlays[this.active].container.classList.add('hidden');
                this.overlays[this.active].element.classList.add('hidden');
                this.active = null;

                window.removeEventListener('keydown', this._keyDown);
                resolve();
            }.bind(this));
        },

        /**
         * @private
         */
        _keyDown : function overlayManager_keyDown(evt) {
            var self = OverlayManager;
            if (self.active && evt.keyCode === 27) { // Esc key.
                self._closeThroughCaller();
                evt.preventDefault();
            }
        },

        /**
         * @private
         */
        _closeThroughCaller : function overlayManager_closeThroughCaller() {
            if (this.overlays[this.active].callerCloseMethod) {
                this.overlays[this.active].callerCloseMethod();
            }
            if (this.active) {
                this.close(this.active);
            }
        }
    };

    exports.OverlayManager = OverlayManager;
}));
