mail/src/js/util/backbutton-handler.js

'use strict';

var axe = require('axe-logger'),
    DEBUG_TAG = 'backbutton handler';

/**
 * The back button handler introduces meaningful behavior fo rthe back button:
 * if there's an open lightbox, close it;
 * if the reader is open in mobile mode, close it;
 * if the navigation is open, close it;
 * if there's nothing else open, shut down the app;
 *
 * @type {Object}
 */
var backBtnHandler = {
    attachHandler: function(scope) {
        this.scope = scope;
    },
    start: function() {
        document.addEventListener("backbutton", handleBackButton, false);
    },
    stop: function() {
        document.removeEventListener("backbutton", handleBackButton, false);
    }
};

function handleBackButton(event) {
    axe.debug(DEBUG_TAG, 'back button pressed');

    // this disarms the default behavior which we NEVER want
    event.preventDefault();
    event.stopPropagation();

    if (backBtnHandler.scope.state.lightbox) {
        // closes the lightbox (error msgs, writer, ...)
        backBtnHandler.scope.state.lightbox = undefined;
        axe.debug(DEBUG_TAG, 'lightbox closed');
        backBtnHandler.scope.$apply();
    } else if (backBtnHandler.scope.state.read && backBtnHandler.scope.state.read.open) {
        // closes the reader
        backBtnHandler.scope.state.read.toggle(false);
        axe.debug(DEBUG_TAG, 'reader closed');
        backBtnHandler.scope.$apply();
    } else if (backBtnHandler.scope.state.nav && backBtnHandler.scope.state.nav.open) {
        // closes the navigation
        backBtnHandler.scope.state.nav.toggle(false);
        axe.debug(DEBUG_TAG, 'navigation closed');
        backBtnHandler.scope.$apply();
    } else {
        // exits the app
        navigator.app.exitApp();
    }
}

module.exports = backBtnHandler;