background.js

/*
 * Copyright 2015 Boris Smus. All Rights Reserved.
 * 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.
 */
 
var tabsState = {};
var controllableTabs = {};
var playingTabs = {};
var lastPlayingTab = -1;
var activeTab = -1;

function togglePlaying(tabId, state) {
    if(state === undefined) {
        state = !playingTabs[tabId];
    }
    
    if (playingTabs.hasOwnProperty(tabId) && !state) {
        delete playingTabs[tabId];
    } else if (!playingTabs.hasOwnProperty(tabId) && state) {
        playingTabs[tabId] = true;
    }
}

function sendCommand(tabId, command) {
    
    if (command === 'play-pause') {
        togglePlaying(tabId);
    }
    
    chrome.tabs.sendMessage(tabId, {command: command});
}

function registerTab(tabId) {
    if (!controllableTabs.hasOwnProperty(tabId)) {
        controllableTabs[tabId] = true;
        
        chrome.tabs.get(tabId, function(tab) {
            if (tab.audible) {
                togglePlaying(tabId, true);
            }
        });

        chrome.pageAction.show(tabId);
        //TODO: save state in local storage
        tabsPluginState(tabId, true);
    }
}

function unregisterTab(tabId) {
    if (controllableTabs.hasOwnProperty(tabId)) {
        delete controllableTabs[tabId];
        delete tabsPluginState[tabId];
        togglePlaying(tabId, false);
    }
}

function checkAudible(tabId, changeInfo) {
    if (!changeInfo.hasOwnProperty('audible')) {
        return;
    }
    
    if (!controllableTabs.hasOwnProperty(tabId)) {
        console.log('ignore unregistered', tabId);
        return;
    }
    
    if (changeInfo.audible) {
        playingTabs[tabId] = true;
        lastPlayingTab = tabId;
        console.log('update playingTabs', playingTabs);
    } else {
        togglePlaying(tabId, false);
        lastPlayingTab = tabId;
    }
}

function tabsPluginState(tabId, state) {
    tabId = tabId.id || tabId
    tabsState[tabId] = state !== undefined && state || !tabsState[tabId]
    postfix = ''
    
    if (!tabsState[tabId]) {
        postfix = '-inactive'
    }
    
    chrome.pageAction.setIcon({
        tabId: tabId,
        path: {
            '19': 'icons/icon19' + postfix + '.png',
            '38': 'icons/icon38' + postfix + '.png'
        }
    });

}

function processAction(command) {
    console.log('Command:', command);
    var isPlaying = false;
    
    for (tabId in playingTabs) {
        
        if (playingTabs.hasOwnProperty(tabId) && tabsState[tabId]) {
            isPlaying = true;
            sendCommand(+tabId, command);
            console.log('control playing', tabId);
        }
        
    }
    
    if (isPlaying) {
        return;
    }
    
    if (controllableTabs[activeTab] && tabsState[activeTab]){
        console.log('control active', activeTab);
        sendCommand(activeTab, command)
    } else if (lastPlayingTab !== -1 && tabsState[lastPlayingTab]) {
        console.log('control lastPlayingTab', lastPlayingTab)
        sendCommand(lastPlayingTab, command);
    }
}

function processRegisterMessage(request, sender, sendResponse) {
    console.log('Received tab message: ', request);

    if (request.command == 'registerTab' && sender.tab) {
        registerTab(sender.tab.id);
    } else if (request.command == 'unregisterTab' && sender.tab) {
        unregisterTab(sender.tab.id);
    }
}

function switchActiveTab(evt) {
    activeTab = evt.tabId;
}

chrome.commands.onCommand.addListener(processAction);
chrome.tabs.onRemoved.addListener(unregisterTab);
chrome.tabs.onUpdated.addListener(checkAudible);
chrome.pageAction.onClicked.addListener(tabsPluginState);
chrome.runtime.onMessage.addListener(processRegisterMessage);
chrome.tabs.onActivated.addListener(switchActiveTab);