background.js

var pending = [];
var db;

function openDatabase() {
  console.log('openDatabase');
  indexedDB.open("dict", 1).onsuccess = function(e) {
    db = e.target.result;
    for (var i = 0; i < pending.length; ++i) {
      pending[i]();
    }
    pending = [];
  };
}

function closeDatabase() {
  console.log('closeDatabase');
  if (db == null) {
    return;
  }
  db.close();
  db = null;
}

function addToLocalStorage(entry, callback) {
  var str = localStorage['numEntries'];
  var numEntries = (str == undefined) ? 0 : parseInt(str);
  localStorage['entry[' + numEntries + ']'] = JSON.stringify(entry);
  localStorage['numEntries'] = numEntries + 1;
  callback('localStorage');
}

function addToAnki(entry, inCallback) {
  if (localStorage['use_anki'] == undefined) {
    addToLocalStorage(entry, inCallback);
    return;
  }

  var ankiweb = 'https://ankiweb.net/edit/';
  var message = {entry: entry,
                 config: {noteType: localStorage['note_type'],
                          deck: localStorage['deck']}};
  chrome.tabs.create({url: ankiweb, active: false}, function(tab) {
    // Wrap inCallback so that we can always close the tab.
    function callback(result) {
      chrome.tabs.remove(tab.id, function() { inCallback(result); });
    }

    // Cancel adding to Anki if it took more than 10 seconds. In that case add
    // to localStorage instead.
    var cancelled = false;
    var st = setTimeout(function() {
      cancelled = true;
      addToLocalStorage(entry, callback);
    }, 10000);

    chrome.tabs.executeScript(tab.id, {file: 'ankiweb.js'}, function(result) {
      if (cancelled) return;
      clearTimeout(st);

      // If executeScript was successfully performed, result should be an array
      // containing a string 'success'.
      if ((result instanceof Array) && result.length == 1 &&
          result[0] == 'success') {
        // executeScript succeeded. Proceed to adding the word to ankiweb.
        chrome.tabs.sendMessage(tab.id, message, function(result) {
          if (result == 'success') {
            callback('ankiweb');
          } else {
            // Sometimes Ankiweb does maintainance!
            addToLocalStorage(entry, callback);
          }
        });
      } else {
        // executeScript failed, probably offline. Add the word to
        // localStorage.
        addToLocalStorage(entry, callback);
      }
    });
  });
}

function respond(word, callback) {
  // Lookup the requested word from DB.
  var trans = db.transaction(["word"], "readonly");
  var index = trans.objectStore("word").index('key');
  index.count(word).onsuccess = function(e) {
    var count = e.target.result;
    if (count == 0) {
      callback([]);
      return;
    }
    var results = [];
    index.openCursor(word).onsuccess = function(e) {
      var cursor = e.target.result;
      results.push(cursor.value);
      if (results.length == count) {
        callback(results);
        return;
      }
      cursor.continue();
    };
  };
}

function onMessage(request, sender, callback) {
  switch (request.action) {
  case 'translateWord':
    if (db == null) {
      pending.push(function() { respond(request.word, callback); });
    } else {
      respond(request.word, callback);
    }
    return true;
  case 'beginDatabaseUpdate':
    closeDatabase();
    callback();
    break;
  case 'endDatabaseUpdate':
    openDatabase();
    callback();
    break;
  case 'addToAnki':
    addToAnki(request.entry, callback);
    return true;
  }
  return false;
}

chrome.runtime.onMessage.addListener(onMessage);

// Open DB.
openDatabase();