background.js

'use strict';

const APPLICABLE_PROTOCOLS = ["http:", "https:"];

function protocolIsApplicable(url) {
  var anchor =  document.createElement('a');
  anchor.href = url;
  return APPLICABLE_PROTOCOLS.includes(anchor.protocol);
}

function showPageActionOnTab(tabInfo){
  if (protocolIsApplicable(tabInfo.url)) {
    browser.pageAction.show(tabInfo.id);
  }
}

function translateCurrentPage() {
    browser.tabs.query({
        currentWindow: true,
        active: true
    }, function (foundTabs) {
        var currentTabId = foundTabs[0].id;
        var executing = browser.tabs.executeScript(currentTabId, {
            file: 'scripts/inject_google_translate_content.js'
        });
    });
}

if (browser.commands) {
  browser.commands.onCommand.addListener(function(action) {
    if (action == "translate-current-page") {
      translateCurrentPage();
    }
  });
}

if (browser.contextMenus) {
  browser.contextMenus.onClicked.addListener(function(info, tab) {
    if (info.menuItemId == "translate-current-page") {
      translateCurrentPage();
    }
  });
  browser.contextMenus.create({
    id: "translate-current-page",
    title: browser.i18n.getMessage("translateCurrentPage"),
    contexts: ["all"]
  });
}

if (browser.browserAction) {
  browser.browserAction.setIcon({
		"path": {
			"19": "images/icon-19.png",
			"38": "images/icon-38.png"
		}
  });
  browser.browserAction.onClicked.addListener(translateCurrentPage);
}


if (browser.pageAction) {
  browser.pageAction.onClicked.addListener(translateCurrentPage);
  browser.tabs.query({}).then((tabs) => {
    var tab;
    for (tab of tabs) {
      showPageActionOnTab(tab);
    }
  });

  browser.tabs.onUpdated.addListener((id, changeInfo, tab) => {
    showPageActionOnTab(tab);
  });
}