background.js

'use strict';

//part 1. activating/deactivating the debugger via the browserAction button.
const activeTabs = {};

function updateIcon(tabId) {
  const color = activeTabs[tabId] ? 'red' : 'black';
  chrome.browserAction.setIcon({path: `images/${color}_16.png`});
}

function detachTab(tabId) {
  chrome.debugger.detach({tabId: tabId}, function () {
    console.log("detached debugger to tab: " + tabId);
    delete activeTabs[tabId];
    updateIcon(tabId);
  });
}

function attachTab(tabId) {
  chrome.debugger.attach({tabId: tabId}, "1.3", function () {
    console.log("attached debugger to tab: " + tabId);
    activeTabs[tabId] = true;
    updateIcon(tabId);
  });
}

chrome.browserAction.onClicked.addListener(function callback(data) {
  console.log("BrowserAction icon clicked. Attaching/detaching the tab.");
  const tabId = data.id;
  activeTabs[tabId] ? detachTab(tabId) : attachTab(tabId);
});

chrome.tabs.onActivated.addListener(function callback(data) {
  // console.log("A tab activated. Updating icon.");
  updateIcon(data.tabId);
})

chrome.runtime.onMessage.addListener(function handleMessage(request, sender, sendResponse) {
  //filtering out inactive tabs
  var tabId = sender.tab.id;
  if (!activeTabs[tabId])
    return;
  console.log("received request from clientScript on active tab", request);
  dispatchNativeEvent(request, tabId);
});

//part 2. turning messages into native events for active tabs.
function dispatchNativeEvent(event, tabId) {
  //convert the command into an approved native event here.
  let cmd;
  if (event.type.startsWith("mouse"))
    cmd = "Input.dispatchMouseEvent";
  else if (event.type.startsWith("touch"))
    cmd = "Input.dispatchTouchEvent";
  else if (event.type === "keyDown" || event.type === "keyUp" || event.type === "char" || event.type === "rawKeyDown")
    cmd = "Input.dispatchKeyEvent";
  else if (event.type === "beforeinput-is-trusted")
    cmd = "Input.insertText";
  else
    throw new Error("Illegal native event: ", event);
  chrome.debugger.sendCommand({tabId: tabId}, cmd, event, function () {
    console.log("sendCommand", cmd, event);
  });
}