/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Bookmarks Sync.
 *
 * The Initial Developer of the Original Code is Mozilla.
 * Portions created by the Initial Developer are Copyright (C) 2007
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *  Dan Mills <thunder@mozilla.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

const EXPORTED_SYMBOLS = ['Utils', 'Svc', 'Str'];

const Cc = Components.classes;
const Ci = Components.interfaces;
const Cr = Components.results;
const Cu = Components.utils;

Cu.import("resource://services-sync/constants.js");
Cu.import("resource://services-sync/ext/Observers.js");
Cu.import("resource://services-sync/ext/Preferences.js");
Cu.import("resource://services-sync/ext/StringBundle.js");
Cu.import("resource://services-sync/ext/Sync.js");
Cu.import("resource://services-sync/log4moz.js");

/*
 * Utility functions
 */

let Utils = {
  /**
   * Wrap a function to catch all exceptions and log them
   *
   * @usage MyObj._catch = Utils.catch;
   *        MyObj.foo = function() { this._catch(func)(); }
   */
  catch: function Utils_catch(func) {
    let thisArg = this;
    return function WrappedCatch() {
      try {
        return func.call(thisArg);
      }
      catch(ex) {
        thisArg._log.debug("Exception: " + Utils.exceptionStr(ex));
      }
    };
  },

  /**
   * Wrap a function to call lock before calling the function then unlock.
   *
   * @usage MyObj._lock = Utils.lock;
   *        MyObj.foo = function() { this._lock(func)(); }
   */
  lock: function Utils_lock(func) {
    let thisArg = this;
    return function WrappedLock() {
      if (!thisArg.lock())
        throw "Could not acquire lock";

      try {
        return func.call(thisArg);
      }
      finally {
        thisArg.unlock();
      }
    };
  },

  /**
   * Wrap functions to notify when it starts and finishes executing or if it got
   * an error. The message is a combination of a provided prefix and local name
   * with the current state and the subject is the provided subject.
   *
   * @usage function MyObj() { this._notify = Utils.notify("prefix:"); }
   *        MyObj.foo = function() { this._notify(name, subject, func)(); }
   */
  notify: function Utils_notify(prefix) {
    return function NotifyMaker(name, subject, func) {
      let thisArg = this;
      let notify = function(state) {
        let mesg = prefix + name + ":" + state;
        thisArg._log.trace("Event: " + mesg);
        Observers.notify(mesg, subject);
      };

      return function WrappedNotify() {
        try {
          notify("start");
          let ret = func.call(thisArg);
          notify("finish");
          return ret;
        }
        catch(ex) {
          notify("error");
          throw ex;
        }
      };
    };
  },

  batchSync: function batchSync(service, engineType) {
    return function batchedSync() {
      let engine = this;
      let batchEx = null;

      // Try running sync in batch mode
      Svc[service].runInBatchMode({
        runBatched: function wrappedSync() {
          try {
            engineType.prototype._sync.call(engine);
          }
          catch(ex) {
            batchEx = ex;
          }
        }
      }, null);

      // Expose the exception if something inside the batch failed
      if (batchEx!= null)
        throw batchEx;
    };
  },

  queryAsync: function(query, names) {
    // Allow array of names, single name, and no name
    if (!Utils.isArray(names))
      names = names == null ? [] : [names];

    // Synchronously asyncExecute fetching all results by name
    let [exec, execCb] = Sync.withCb(query.executeAsync, query);
    return exec({
      items: [],
      handleResult: function handleResult(results) {
        let row;
        while ((row = results.getNextRow()) != null) {
          this.items.push(names.reduce(function(item, name) {
            item[name] = row.getResultByName(name);
            return item;
          }, {}));
        }
      },
      handleError: function handleError(error) {
        execCb.throw(error);
      },
      handleCompletion: function handleCompletion(reason) {
        execCb(this.items);
      }
    });
  },

  // Generates a brand-new globally unique identifier (GUID).
  makeGUID: function makeGUID() {
    // 70 characters that are not-escaped URL-friendly
    const code =
      "!()*-.0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz~";

    let guid = "";
    let num = 0;
    let val;

    // Generate ten 70-value characters for a 70^10 (~61.29-bit) GUID
    for (let i = 0; i < 10; i++) {
      // Refresh the number source after using it a few times
      if (i == 0 || i == 5)
        num = Math.random();

      // Figure out which code to use for the next GUID character
      num *= 70;
      val = Math.floor(num);
      guid += code[val];
      num -= val;
    }

    return guid;
  },

  anno: function anno(id, anno, val, expire) {
    // Figure out if we have a bookmark or page
    let annoFunc = (typeof id == "number" ? "Item" : "Page") + "Annotation";

    // Convert to a nsIURI if necessary
    if (typeof id == "string")
      id = Utils.makeURI(id);

    if (id == null)
      throw "Null id for anno! (invalid uri)";

    switch (arguments.length) {
      case 2:
        // Get the annotation with 2 args
        return Svc.Annos["get" + annoFunc](id, anno);
      case 3:
        expire = "NEVER";
        // Fallthrough!
      case 4:
        // Convert to actual EXPIRE value
        expire = Svc.Annos["EXPIRE_" + expire];

        // Set the annotation with 3 or 4 args
        return Svc.Annos["set" + annoFunc](id, anno, val, 0, expire);
    }
  },

  ensureOneOpen: let (windows = {}) function ensureOneOpen(window) {
    // Close the other window if it exists
    let url = window.location.href;
    let other = windows[url];
    if (other != null)
      other.close();

    // Save the new window for future closure
    windows[url] = window;

    // Actively clean up when the window is closed
    window.addEventListener("unload", function() windows[url] = null, false);
  },

  // Returns a nsILocalFile representing a file relative to the
  // current user's profile directory.  If the argument is a string,
  // it should be a string with unix-style slashes for directory names
  // (these slashes are automatically converted to platform-specific
  // path separators).
  //
  // Alternatively, if the argument is an object, it should contain
  // the following attributes:
  //
  //   path: the path to the file, relative to the current user's
  //   profile dir.
  //
  //   autoCreate: whether or not the file should be created if it
  //   doesn't already exist.
  getProfileFile: function getProfileFile(arg) {
    if (typeof arg == "string")
      arg = {path: arg};

    let pathParts = arg.path.split("/");
    let file = Svc.Directory.get("ProfD", Ci.nsIFile);
    file.QueryInterface(Ci.nsILocalFile);
    for (let i = 0; i < pathParts.length; i++)
      file.append(pathParts[i]);
    if (arg.autoCreate && !file.exists())
      file.create(file.NORMAL_FILE_TYPE, PERMS_FILE);
    return file;
  },

  /**
   * Add a simple getter/setter to an object that defers access of a property
   * to an inner property.
   *
   * @param obj
   *        Object to add properties to defer in its prototype
   * @param defer
   *        Hash property of obj to defer to (dot split each level)
   * @param prop
   *        Property name to defer (or an array of property names)
   */
  deferGetSet: function Utils_deferGetSet(obj, defer, prop) {
    if (Utils.isArray(prop))
      return prop.map(function(prop) Utils.deferGetSet(obj, defer, prop));

    // Split the defer into each dot part for each level to dereference
    let parts = defer.split(".");
    let deref = function(base) Utils.deref(base, parts);

    let prot = obj.prototype;

    // Create a getter if it doesn't exist yet
    if (!prot.__lookupGetter__(prop))
      prot.__defineGetter__(prop, function() deref(this)[prop]);

    // Create a setter if it doesn't exist yet
    if (!prot.__lookupSetter__(prop))
      prot.__defineSetter__(prop, function(val) deref(this)[prop] = val);
  },

  /**
   * Dereference an array of properties starting from a base object
   *
   * @param base
   *        Base object to start dereferencing
   * @param props
   *        Array of properties to dereference (one for each level)
   */
  deref: function Utils_deref(base, props) props.reduce(function(curr, prop)
    curr[prop], base),

  /**
   * Determine if some value is an array
   *
   * @param val
   *        Value to check (can be null, undefined, etc.)
   * @return True if it's an array; false otherwise
   */
  isArray: function Utils_isArray(val) val != null && typeof val == "object" &&
    val.constructor.name == "Array",

  // lazy load objects from a constructor on first access.  It will
  // work with the global object ('this' in the global context).
  lazy: function Weave_lazy(dest, prop, ctr) {
    delete dest[prop];
    dest.__defineGetter__(prop, Utils.lazyCb(dest, prop, ctr));
  },
  lazyCb: function Weave_lazyCb(dest, prop, ctr) {
    return function() {
      delete dest[prop];
      dest[prop] = new ctr();
      return dest[prop];
    };
  },

  // like lazy, but rather than new'ing the 3rd arg we use its return value
  lazy2: function Weave_lazy2(dest, prop, fn) {
    delete dest[prop];
    dest.__defineGetter__(prop, Utils.lazyCb2(dest, prop, fn));
  },
  lazyCb2: function Weave_lazyCb2(dest, prop, fn) {
    return function() {
      delete dest[prop];
      return dest[prop] = fn();
    };
  },

  lazySvc: function Weave_lazySvc(dest, prop, cid, iface) {
    let getter = function() {
      delete dest[prop];
      let svc = null;

      // Use the platform's service if it exists
      if (cid in Cc && iface in Ci)
        svc = Cc[cid].getService(Ci[iface]);
      else {
        svc = FakeSvc[cid];

        let log = Log4Moz.repository.getLogger("Service.Util");
        if (svc == null)
          log.warn("Component " + cid + " doesn't exist on this platform.");
        else
          log.debug("Using a fake svc object for " + cid);
      }

      return dest[prop] = svc;
    };
    dest.__defineGetter__(prop, getter);
  },

  lazyStrings: function Weave_lazyStrings(name) {
    let bundle = "chrome://weave/locale/services/" + name + ".properties";
    return function() new StringBundle(bundle);
  },

  deepEquals: function eq(a, b) {
    // If they're triple equals, then it must be equals!
    if (a === b)
      return true;

    // If they weren't equal, they must be objects to be different
    if (typeof a != "object" || typeof b != "object")
      return false;

    // But null objects won't have properties to compare
    if (a === null || b === null)
      return false;

    // Make sure all of a's keys have a matching value in b
    for (let k in a)
      if (!eq(a[k], b[k]))
        return false;

    // Do the same for b's keys but skip those that we already checked
    for (let k in b)
      if (!(k in a) && !eq(a[k], b[k]))
        return false;

    return true;
  },

  deepCopy: function Weave_deepCopy(thing, noSort) {
    if (typeof(thing) != "object" || thing == null)
      return thing;
    let ret;

    if (Utils.isArray(thing)) {
      ret = [];
      for (let i = 0; i < thing.length; i++)
        ret.push(Utils.deepCopy(thing[i], noSort));

    } else {
      ret = {};
      let props = [p for (p in thing)];
      if (!noSort)
        props = props.sort();
      props.forEach(function(k) ret[k] = Utils.deepCopy(thing[k], noSort));
    }

    return ret;
  },

  // Works on frames or exceptions, munges file:// URIs to shorten the paths
  // FIXME: filename munging is sort of hackish, might be confusing if
  // there are multiple extensions with similar filenames
  formatFrame: function Utils_formatFrame(frame) {
    let tmp = "<file:unknown>";

    let file = frame.filename || frame.fileName;
    if (file)
      tmp = file.replace(/^(?:chrome|file):.*?([^\/\.]+\.\w+)$/, "$1");

    if (frame.lineNumber)
      tmp += ":" + frame.lineNumber;
    if (frame.name)
      tmp = frame.name + "()@" + tmp;

    return tmp;
  },

  exceptionStr: function Weave_exceptionStr(e) {
    let message = e.message ? e.message : e;
    return message + " " + Utils.stackTrace(e);
 },

  stackTraceFromFrame: function Weave_stackTraceFromFrame(frame) {
    let output = [];
    while (frame) {
      let str = Utils.formatFrame(frame);
      if (str)
        output.push(str);
      frame = frame.caller;
    }
    return output.join(" < ");
  },

  stackTrace: function Weave_stackTrace(e) {
    // Wrapped nsIException
    if (e.location)
      return "Stack trace: " + Utils.stackTraceFromFrame(e.location);

    // Standard JS exception
    if (e.stack)
      return "JS Stack trace: " + e.stack.trim().replace(/\n/g, " < ").
        replace(/@[^@]*?([^\/\.]+\.\w+:)/g, "@$1");

    return "No traceback available";
  },

  checkStatus: function Weave_checkStatus(code, msg, ranges) {
    if (!ranges)
      ranges = [[200,300]];

    for (let i = 0; i < ranges.length; i++) {
      var rng = ranges[i];
      if (typeof(rng) == "object" && code >= rng[0] && code < rng[1])
        return true;
      else if (typeof(rng) == "number" && code == rng) {
        return true;
      }
    }

    if (msg) {
      let log = Log4Moz.repository.getLogger("Service.Util");
      log.error(msg + " Error code: " + code);
    }

    return false;
  },

  ensureStatus: function Weave_ensureStatus(args) {
    if (!Utils.checkStatus.apply(Utils, arguments))
      throw 'checkStatus failed';
  },

  digest: function digest(message, hasher) {
    let converter = Cc["@mozilla.org/intl/scriptableunicodeconverter"].
      createInstance(Ci.nsIScriptableUnicodeConverter);
    converter.charset = "UTF-8";

    let data = converter.convertToByteArray(message, {});
    hasher.update(data, data.length);

    // Convert each hashed byte into 2-hex strings then combine them
    return [("0" + byte.charCodeAt().toString(16)).slice(-2) for each (byte in
      hasher.finish(false))].join("");
  },

  sha1: function sha1(message) {
    let hasher = Cc["@mozilla.org/security/hash;1"].
      createInstance(Ci.nsICryptoHash);
    hasher.init(hasher.SHA1);
    return Utils.digest(message, hasher);
  },

  /**
   * Generate a sha256 HMAC for a string message and a given nsIKeyObject
   */
  sha256HMAC: function sha256HMAC(message, key) {
    let hasher = Cc["@mozilla.org/security/hmac;1"].
      createInstance(Ci.nsICryptoHMAC);
    hasher.init(hasher.SHA256, key);
    return Utils.digest(message, hasher);
  },

  makeURI: function Weave_makeURI(URIString) {
    if (!URIString)
      return null;
    try {
      return Svc.IO.newURI(URIString, null, null);
    } catch (e) {
      let log = Log4Moz.repository.getLogger("Service.Util");
      log.debug("Could not create URI: " + Utils.exceptionStr(e));
      return null;
    }
  },

  makeURL: function Weave_makeURL(URIString) {
    let url = Utils.makeURI(URIString);
    url.QueryInterface(Ci.nsIURL);
    return url;
  },

  xpath: function Weave_xpath(xmlDoc, xpathString) {
    let root = xmlDoc.ownerDocument == null ?
      xmlDoc.documentElement : xmlDoc.ownerDocument.documentElement;
    let nsResolver = xmlDoc.createNSResolver(root);

    return xmlDoc.evaluate(xpathString, xmlDoc, nsResolver,
                           Ci.nsIDOMXPathResult.ANY_TYPE, null);
  },

  getTmp: function Weave_getTmp(name) {
    let tmp = Svc.Directory.get("ProfD", Ci.nsIFile);
    tmp.QueryInterface(Ci.nsILocalFile);

    tmp.append("weave");
    tmp.append("tmp");
    if (!tmp.exists())
      tmp.create(tmp.DIRECTORY_TYPE, PERMS_DIRECTORY);

    if (name)
      tmp.append(name);

    return tmp;
  },

  /**
   * Load a json object from disk
   *
   * @param filePath
   *        Json file path load from weave/[filePath].json
   * @param that
   *        Object to use for logging and "this" for callback
   * @param callback
   *        Function to process json object as its first parameter
   */
  jsonLoad: function Utils_jsonLoad(filePath, that, callback) {
    filePath = "weave/" + filePath + ".json";
    if (that._log)
      that._log.trace("Loading json from disk: " + filePath);

    let file = Utils.getProfileFile(filePath);
    if (!file.exists())
      return;

    try {
      let [is] = Utils.open(file, "<");
      let json = Utils.readStream(is);
      is.close();
      callback.call(that, JSON.parse(json));
    }
    catch (ex) {
      if (that._log)
        that._log.debug("Failed to load json: " + Utils.exceptionStr(ex));
    }
  },

  /**
   * Save a json-able object to disk
   *
   * @param filePath
   *        Json file path save to weave/[filePath].json
   * @param that
   *        Object to use for logging and "this" for callback
   * @param callback
   *        Function to provide json-able object to save. If this isn't a
   *        function, it'll be used as the object to make a json string.
   */
  jsonSave: function Utils_jsonSave(filePath, that, callback) {
    filePath = "weave/" + filePath + ".json";
    if (that._log)
      that._log.trace("Saving json to disk: " + filePath);

    let file = Utils.getProfileFile({ autoCreate: true, path: filePath });
    let json = typeof callback == "function" ? callback.call(that) : callback;
    let out = JSON.stringify(json);
    let [fos] = Utils.open(file, ">");
    fos.writeString(out);
    fos.close();
  },

  /**
   * Return a timer that is scheduled to call the callback after waiting the
   * provided time or as soon as possible. The timer will be set as a property
   * of the provided object with the given timer name.
   */
  delay: function delay(callback, wait, thisObj, name) {
    // Default to running right away
    wait = wait || 0;

    // Use a dummy object if one wasn't provided
    thisObj = thisObj || {};

    // Delay an existing timer if it exists
    if (name in thisObj && thisObj[name] instanceof Ci.nsITimer) {
      thisObj[name].delay = wait;
      return;
    }

    // Create a special timer that we can add extra properties
    let timer = {};
    timer.__proto__ = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);

    // Provide an easy way to clear out the timer
    timer.clear = function() {
      thisObj[name] = null;
      timer.cancel();
    };

    // Initialize the timer with a smart callback
    timer.initWithCallback({
      notify: function notify() {
        // Clear out the timer once it's been triggered
        timer.clear();
        callback.call(thisObj, timer);
      }
    }, wait, timer.TYPE_ONE_SHOT);

    return thisObj[name] = timer;
  },

  open: function open(pathOrFile, mode, perms) {
    let stream, file;

    if (pathOrFile instanceof Ci.nsIFile) {
      file = pathOrFile;
    } else {
      file = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsILocalFile);
      dump("PATH IS" + pathOrFile + "\n");
      file.initWithPath(pathOrFile);
    }

    if (!perms)
      perms = PERMS_FILE;

    switch(mode) {
    case "<": {
      if (!file.exists())
        throw "Cannot open file for reading, file does not exist";
      let fis = Cc["@mozilla.org/network/file-input-stream;1"].
        createInstance(Ci.nsIFileInputStream);
      fis.init(file, MODE_RDONLY, perms, 0);
      stream = Cc["@mozilla.org/intl/converter-input-stream;1"].
        createInstance(Ci.nsIConverterInputStream);
      stream.init(fis, "UTF-8", 4096,
                  Ci.nsIConverterInputStream.DEFAULT_REPLACEMENT_CHARACTER);
    } break;

    case ">": {
      let fos = Cc["@mozilla.org/network/file-output-stream;1"].
        createInstance(Ci.nsIFileOutputStream);
      fos.init(file, MODE_WRONLY | MODE_CREATE | MODE_TRUNCATE, perms, 0);
      stream = Cc["@mozilla.org/intl/converter-output-stream;1"]
        .createInstance(Ci.nsIConverterOutputStream);
      stream.init(fos, "UTF-8", 4096, 0x0000);
    } break;

    case ">>": {
      let fos = Cc["@mozilla.org/network/file-output-stream;1"].
        createInstance(Ci.nsIFileOutputStream);
      fos.init(file, MODE_WRONLY | MODE_CREATE | MODE_APPEND, perms, 0);
      stream = Cc["@mozilla.org/intl/converter-output-stream;1"]
        .createInstance(Ci.nsIConverterOutputStream);
      stream.init(fos, "UTF-8", 4096, 0x0000);
    } break;

    default:
      throw "Illegal mode to open(): " + mode;
    }

    return [stream, file];
  },

  getIcon: function(iconUri, defaultIcon) {
    try {
      let iconURI = Utils.makeURI(iconUri);
      return Svc.Favicon.getFaviconLinkForIcon(iconURI).spec;
    }
    catch(ex) {}

    // Just give the provided default icon or the system's default
    return defaultIcon || Svc.Favicon.defaultFavicon.spec;
  },

  getErrorString: function Utils_getErrorString(error, args) {
    try {
      return Str.errors.get(error, args || null);
    } catch (e) {}

    // basically returns "Unknown Error"
    return Str.errors.get("error.reason.unknown");
  },

  // assumes an nsIConverterInputStream
  readStream: function Weave_readStream(is) {
    let ret = "", str = {};
    while (is.readString(4096, str) != 0) {
      ret += str.value;
    }
    return ret;
  },

  /**
   * Create an array like the first but without elements of the second
   */
  arraySub: function arraySub(minuend, subtrahend) {
    return minuend.filter(function(i) subtrahend.indexOf(i) == -1);
  },

  bind2: function Async_bind2(object, method) {
    return function innerBind() { return method.apply(object, arguments); };
  },

  mpLocked: function mpLocked() {
    let modules = Cc["@mozilla.org/security/pkcs11moduledb;1"].
                  getService(Ci.nsIPKCS11ModuleDB);
    let sdrSlot = modules.findSlotByName("");
    let status  = sdrSlot.status;
    let slots = Ci.nsIPKCS11Slot;

    if (status == slots.SLOT_READY || status == slots.SLOT_LOGGED_IN)
      return false;

    if (status == slots.SLOT_NOT_LOGGED_IN)
      return true;
    
    // something wacky happened, pretend MP is locked
    return true;
  },

  __prefs: null,
  get prefs() {
    if (!this.__prefs) {
      this.__prefs = Cc["@mozilla.org/preferences-service;1"]
        .getService(Ci.nsIPrefService);
      this.__prefs = this.__prefs.getBranch(PREFS_BRANCH);
      this.__prefs.QueryInterface(Ci.nsIPrefBranch2);
    }
    return this.__prefs;
  }
};

let FakeSvc = {
  // Private Browsing
  "@mozilla.org/privatebrowsing;1": {
    autoStarted: false,
    privateBrowsingEnabled: false
  },
  // Session Restore
  "@mozilla.org/browser/sessionstore;1": {
    setTabValue: function(tab, key, value) {
      if (!tab.__SS_extdata)
        tab.__SS_extdata = {};
      tab.__SS_extData[key] = value;
    },
    getBrowserState: function() {
      // Fennec should have only one window. Not more, not less.
      let state = { windows: [{ tabs: [] }] };
      let window = Svc.WinMediator.getMostRecentWindow("navigator:browser");

      // Extract various pieces of tab data
      window.Browser._tabs.forEach(function(tab) {
        let tabState = { entries: [{}] };
        let browser = tab.browser;

        // Cases when we want to skip the tab. Could come up if we get
        // state as a tab is opening or closing.
        if (!browser || !browser.currentURI || !browser.sessionHistory)
          return;

        let history = browser.sessionHistory;
        if (history.count > 0) {
          // We're only grabbing the current history entry for now.
          let entry = history.getEntryAtIndex(history.index, false);
          tabState.entries[0].url = entry.URI.spec;
          // Like SessionStore really does it...
          if (entry.title && entry.title != entry.url)
            tabState.entries[0].title = entry.title;
        }
        // index is 1-based
        tabState.index = 1;

        // Get the image for the tab. Fennec doesn't quite work the same
        // way as Firefox, so we'll just get this from the browser object.
        tabState.attributes = { image: browser.mIconURL };

        // Collect the extdata
        if (tab.__SS_extdata) {
          tabState.extData = {};
          for (let key in tab.__SS_extdata)
            tabState.extData[key] = tab.__SS_extdata[key];
        }

        // Add the tab to the window
        state.windows[0].tabs.push(tabState);
      });
      return JSON.stringify(state);
    }
  },
  // A fake service only used for testing
  "@labs.mozilla.com/Fake/Thing;1": {
    isFake: true
  }
};

// Use the binary WeaveCrypto (;1) if the js-ctypes version (;2) fails to load
// by adding an alias on FakeSvc from ;2 to ;1
Utils.lazySvc(FakeSvc, "@labs.mozilla.com/Weave/Crypto;2",
              "@labs.mozilla.com/Weave/Crypto;1", "IWeaveCrypto");

/*
 * Commonly-used services
 */
let Svc = {};
Svc.Prefs = new Preferences(PREFS_BRANCH);
Svc.DefaultPrefs = new Preferences({branch: PREFS_BRANCH, defaultBranch: true});
Svc.Obs = Observers;
[["Annos", "@mozilla.org/browser/annotation-service;1", "nsIAnnotationService"],
 ["AppInfo", "@mozilla.org/xre/app-info;1", "nsIXULAppInfo"],
 ["Bookmark", "@mozilla.org/browser/nav-bookmarks-service;1", "nsINavBookmarksService"],
 ["Crypto", "@labs.mozilla.com/Weave/Crypto;2", "IWeaveCrypto"],
 ["Directory", "@mozilla.org/file/directory_service;1", "nsIProperties"],
 ["Env", "@mozilla.org/process/environment;1", "nsIEnvironment"],
 ["Favicon", "@mozilla.org/browser/favicon-service;1", "nsIFaviconService"],
 ["Form", "@mozilla.org/satchel/form-history;1", "nsIFormHistory2"],
 ["History", "@mozilla.org/browser/nav-history-service;1", "nsPIPlacesDatabase"],
 ["Idle", "@mozilla.org/widget/idleservice;1", "nsIIdleService"],
 ["IO", "@mozilla.org/network/io-service;1", "nsIIOService"],
 ["KeyFactory", "@mozilla.org/security/keyobjectfactory;1", "nsIKeyObjectFactory"],
 ["Login", "@mozilla.org/login-manager;1", "nsILoginManager"],
 ["Memory", "@mozilla.org/xpcom/memory-service;1", "nsIMemory"],
 ["Private", "@mozilla.org/privatebrowsing;1", "nsIPrivateBrowsingService"],
 ["Profiles", "@mozilla.org/toolkit/profile-service;1", "nsIToolkitProfileService"],
 ["Prompt", "@mozilla.org/embedcomp/prompt-service;1", "nsIPromptService"],
 ["Script", "@mozilla.org/moz/jssubscript-loader;1", "mozIJSSubScriptLoader"],
 ["SysInfo", "@mozilla.org/system-info;1", "nsIPropertyBag2"],
 ["Version", "@mozilla.org/xpcom/version-comparator;1", "nsIVersionComparator"],
 ["WinMediator", "@mozilla.org/appshell/window-mediator;1", "nsIWindowMediator"],
 ["WinWatcher", "@mozilla.org/embedcomp/window-watcher;1", "nsIWindowWatcher"],
 ["Session", "@mozilla.org/browser/sessionstore;1", "nsISessionStore"],
].forEach(function(lazy) Utils.lazySvc(Svc, lazy[0], lazy[1], lazy[2]));

let Str = {};
["errors", "sync"]
  .forEach(function(lazy) Utils.lazy2(Str, lazy, Utils.lazyStrings(lazy)));
