9 files changed, 375 insertions, 413 deletions

diff --git a/lib/history.js b/lib/history.js
index bdc922d7..4a3bbe1e 100644
--- a/lib/history.js
+++ b/lib/history.js
@@ -2,7 +2,6 @@
 //external modules
 var async = require('async');
 var moment = require('moment');
-var childProcess = require('child_process');
 
 //core
 var config = require("./config.js");
@@ -10,9 +9,6 @@ var logger = require("./logger.js");
 var response = require("./response.js");
 var models = require("./models");
 
-// workers
-var historyUpdater = require("./workers/historyUpdater");
-
 //public
 var History = {
     historyGet: historyGet,
@@ -24,50 +20,49 @@ var History = {
 
 var caches = {};
 //update when the history is dirty
-var updaterIsBusy = false;
 var updater = setInterval(function () {
-    if (updaterIsBusy) return;
     var deleted = [];
-    var _caches = {};
-    Object.keys(caches).forEach(function (key) {
+    async.each(Object.keys(caches), function (key, callback) {
         var cache = caches[key];
         if (cache.isDirty) {
-            _caches[key] = cache.history;
-            cache.isDirty = false;
+            if (config.debug) logger.info("history updater found dirty history: " + key);
+            var history = parseHistoryToArray(cache.history);
+            finishUpdateHistory(key, history, function (err, count) {
+                if (err) return callback(err, null);
+                if (!count) return callback(null, null);
+                cache.isDirty = false;
+                cache.updateAt = Date.now();
+                return callback(null, null);
+            });
         } else {
             if (moment().isAfter(moment(cache.updateAt).add(5, 'minutes'))) {
                 deleted.push(key);
             }
+            return callback(null, null);
         }
+    }, function (err) {
+        if (err) return logger.error('history updater error', err);
     });
     // delete specified caches
     for (var i = 0, l = deleted.length; i < l; i++) {
         caches[deleted[i]].history = {};
         delete caches[deleted[i]];
     }
-    if (Object.keys(_caches).length <= 0) return;
-    updaterIsBusy = true;
-    var worker = childProcess.fork("./lib/workers/historyUpdater.js");
-    if (config.debug) logger.info('history updater worker process started');
-    worker.send({
-        msg: 'update history',
-        caches: _caches
-    });
-    worker.on('message', function (data) {
-        if (!data || !data.msg || !data.userid) return;
-        var cache = caches[data.userid];
-        if (!cache) return;
-        switch(data.msg) {
-            case 'check':
-                cache.updateAt = Date.now();
-                break;
+}, 1000);
+
+function finishUpdateHistory(userid, history, callback) {
+    models.User.update({
+        history: JSON.stringify(history)
+    }, {
+        where: {
+            id: userid
         }
+    }).then(function (count) {
+        return callback(null, count);
+    }).catch(function (err) {
+        return callback(err, null);
     });
-    worker.on('close', function (code) {
-        updaterIsBusy = false;
-        if (config.debug) logger.info('history updater worker process exited with code ' + code);
-    });
-}, 1000);
+}
 
 function isReady() {
     var dirtyCount = 0;
@@ -106,7 +101,7 @@ function getHistory(userid, callback) {
 }
 
 function setHistory(userid, history) {
-    if (Array.isArray(history)) history = historyUpdater.parseHistoryToObject(history);
+    if (Array.isArray(history)) history = parseHistoryToObject(history);
     if (!caches[userid]) {
         caches[userid] = {
             history: {},
@@ -135,13 +130,31 @@ function updateHistory(userid, noteId, document) {
     }
 }
 
+function parseHistoryToArray(history) {
+    var _history = [];
+    Object.keys(history).forEach(function (key) {
+        var item = history[key];
+        _history.push(item);
+    });
+    return _history;
+}
+
+function parseHistoryToObject(history) {
+    var _history = {};
+    for (var i = 0, l = history.length; i < l; i++) {
+        var item = history[i];
+        _history[item.id] = item;
+    }
+    return _history;
+}
+
 function historyGet(req, res) {
     if (req.isAuthenticated()) {
         getHistory(req.user.id, function (err, history) {
             if (err) return response.errorInternalError(res);
             if (!history) return response.errorNotFound(res);
             res.send({
-                history: historyUpdater.parseHistoryToArray(history)
+                history: parseHistoryToArray(history)
             });
         });
     } else {
diff --git a/lib/models/note.js b/lib/models/note.js
index 05ed04c0..5727046c 100644
--- a/lib/models/note.js
+++ b/lib/models/note.js
@@ -260,6 +260,9 @@ module.exports = function (sequelize, DataTypes) {
                 if (!title) title = "Untitled";
                 return title;
             },
+            generateDescription: function (markdown) {
+                return markdown.substr(0, 100).replace(/(?:\r\n|\r|\n)/g, ' ');
+            },
             decodeTitle: function (title) {
                 var decodedTitle = LZString.decompressFromBase64(title);
                 if (decodedTitle) title = decodedTitle;
diff --git a/lib/models/revision.js b/lib/models/revision.js
index 33fdd73c..8b8eba94 100644
--- a/lib/models/revision.js
+++ b/lib/models/revision.js
@@ -5,13 +5,53 @@ var Sequelize = require("sequelize");
 var LZString = require('lz-string');
 var async = require('async');
 var moment = require('moment');
-var DiffMatchPatch = require('diff-match-patch');
-var dmp = new DiffMatchPatch();
+var childProcess = require('child_process');
+var shortId = require('shortid');
 
 // core
 var config = require("../config.js");
 var logger = require("../logger.js");
 
+var dmpWorker = createDmpWorker();
+var dmpCallbackCache = {};
+
+function createDmpWorker() {
+    var worker = childProcess.fork("./lib/workers/dmpWorker.js", {
+        stdio: 'ignore'
+    });
+    if (config.debug) logger.info('dmp worker process started');
+    worker.on('message', function (data) {
+        if (!data || !data.msg || !data.cacheKey) {
+            return logger.error('dmp worker error: not enough data on message');
+        }
+        var cacheKey = data.cacheKey;
+        switch(data.msg) {
+            case 'error':
+                dmpCallbackCache[cacheKey](data.error, null);
+                break;
+            case 'check':
+                dmpCallbackCache[cacheKey](null, data.result);
+                break;
+        }
+        delete dmpCallbackCache[cacheKey];
+    });
+    worker.on('close', function (code) {
+        dmpWorker = null;
+        if (config.debug) logger.info('dmp worker process exited with code ' + code);
+    });
+    return worker;
+}
+
+function sendDmpWorker(data, callback) {
+    if (!dmpWorker) dmpWorker = createDmpWorker();
+    var cacheKey = Date.now() + '_' + shortId.generate();
+    dmpCallbackCache[cacheKey] = callback;
+    data = Object.assign(data, {
+        cacheKey: cacheKey
+    });
+    dmpWorker.send(data);
+}
+
 module.exports = function (sequelize, DataTypes) {
     var Revision = sequelize.define("Revision", {
         id: {
@@ -43,19 +83,6 @@ module.exports = function (sequelize, DataTypes) {
                     constraints: false
                 });
             },
-            createPatch: function (lastDoc, CurrDoc) {
-                var ms_start = (new Date()).getTime();
-                var diff = dmp.diff_main(lastDoc, CurrDoc);
-                dmp.diff_cleanupSemantic(diff);
-                var patch = dmp.patch_make(lastDoc, diff);
-                patch = dmp.patch_toText(patch);
-                var ms_end = (new Date()).getTime();
-                if (config.debug) {
-                    logger.info(patch);
-                    logger.info((ms_end - ms_start) + 'ms');
-                }
-                return patch;
-            },
             getNoteRevisions: function (note, callback) {
                 Revision.findAll({
                     where: {
@@ -96,67 +123,11 @@ module.exports = function (sequelize, DataTypes) {
                         order: '"createdAt" DESC'
                     }).then(function (count) {
                         if (count <= 0) return callback(null, null);
-                        var ms_start = (new Date()).getTime();
-                        var startContent = null;
-                        var lastPatch = [];
-                        var applyPatches = [];
-                        var authorship = [];
-                        if (count <= Math.round(revisions.length / 2)) {
-                            // start from top to target
-                            for (var i = 0; i < count; i++) {
-                                var revision = revisions[i];
-                                if (i == 0) {
-                                    startContent = LZString.decompressFromBase64(revision.content || revision.lastContent);
-                                }
-                                if (i != count - 1) {
-                                    var patch = dmp.patch_fromText(LZString.decompressFromBase64(revision.patch));
-                                    applyPatches = applyPatches.concat(patch);
-                                }
-                                lastPatch = revision.patch;
-                                authorship = revision.authorship;
-                            }
-                            // swap DIFF_INSERT and DIFF_DELETE to achieve unpatching
-                            for (var i = 0, l = applyPatches.length; i < l; i++) {
-                                for (var j = 0, m = applyPatches[i].diffs.length; j < m; j++) {
-                                    var diff = applyPatches[i].diffs[j];
-                                    if (diff[0] == DiffMatchPatch.DIFF_INSERT)
-                                        diff[0] = DiffMatchPatch.DIFF_DELETE;
-                                    else if (diff[0] == DiffMatchPatch.DIFF_DELETE)
-                                        diff[0] = DiffMatchPatch.DIFF_INSERT;
-                                }
-                            }
-                        } else {
-                            // start from bottom to target
-                            var l = revisions.length - 1;
-                            for (var i = l; i >= count - 1; i--) {
-                                var revision = revisions[i];
-                                if (i == l) {
-                                    startContent = LZString.decompressFromBase64(revision.lastContent);
-                                    authorship = revision.authorship;
-                                }
-                                if (revision.patch) {
-                                    var patch = dmp.patch_fromText(LZString.decompressFromBase64(revision.patch));
-                                    applyPatches = applyPatches.concat(patch);
-                                }
-                                lastPatch = revision.patch;
-                                authorship = revision.authorship;
-                            }
-                        }
-                        try {
-                            var finalContent = dmp.patch_apply(applyPatches, startContent)[0];
-                        } catch (err) {
-                            return callback(err, null);
-                        }
-                        var data = {
-                            content: finalContent,
-                            patch: dmp.patch_fromText(LZString.decompressFromBase64(lastPatch)),
-                            authorship: authorship ? JSON.parse(LZString.decompressFromBase64(authorship)) : null
-                        };
-                        var ms_end = (new Date()).getTime();
-                        if (config.debug) {
-                            logger.info((ms_end - ms_start) + 'ms');
-                        }
-                        return callback(null, data);
+                        sendDmpWorker({
+                            msg: 'get revision',
+                            revisions: revisions,
+                            count: count
+                        }, callback);
                     }).catch(function (err) {
                         return callback(err, null);
                     });
@@ -254,37 +225,43 @@ module.exports = function (sequelize, DataTypes) {
                         var latestRevision = revisions[0];
                         var lastContent = LZString.decompressFromBase64(latestRevision.content || latestRevision.lastContent);
                         var content = LZString.decompressFromBase64(note.content);
-                        var patch = Revision.createPatch(lastContent, content);
-                        if (!patch) {
-                            // if patch is empty (means no difference) then just update the latest revision updated time 
-                            latestRevision.changed('updatedAt', true); 
-                            latestRevision.update({
-                                updatedAt: Date.now()
-                            }).then(function (revision) {
-                                Revision.finishSaveNoteRevision(note, revision, callback);
-                            }).catch(function (err) {
-                                return callback(err, null);
-                            });
-                        } else {
-                            Revision.create({
-                                noteId: note.id,
-                                patch: LZString.compressToBase64(patch),
-                                content: note.content,
-                                length: LZString.decompressFromBase64(note.content).length,
-                                authorship: note.authorship
-                            }).then(function (revision) {
-                                // clear last revision content to reduce db size
+                        sendDmpWorker({
+                            msg: 'create patch',
+                            lastDoc: lastContent,
+                            currDoc: content,
+                        }, function (err, patch) {
+                            if (err) logger.error('save note revision error', err);
+                            if (!patch) {
+                                // if patch is empty (means no difference) then just update the latest revision updated time 
+                                latestRevision.changed('updatedAt', true); 
                                 latestRevision.update({
-                                    content: null
-                                }).then(function () {
+                                    updatedAt: Date.now()
+                                }).then(function (revision) {
                                     Revision.finishSaveNoteRevision(note, revision, callback);
                                 }).catch(function (err) {
                                     return callback(err, null);
                                 });
-                            }).catch(function (err) {
-                                return callback(err, null);
-                            });
-                        }
+                            } else {
+                                Revision.create({
+                                    noteId: note.id,
+                                    patch: LZString.compressToBase64(patch),
+                                    content: note.content,
+                                    length: LZString.decompressFromBase64(note.content).length,
+                                    authorship: note.authorship
+                                }).then(function (revision) {
+                                    // clear last revision content to reduce db size
+                                    latestRevision.update({
+                                        content: null
+                                    }).then(function () {
+                                        Revision.finishSaveNoteRevision(note, revision, callback);
+                                    }).catch(function (err) {
+                                        return callback(err, null);
+                                    });
+                                }).catch(function (err) {
+                                    return callback(err, null);
+                                });
+                            }
+                        });
                     }
                 }).catch(function (err) {
                     return callback(err, null);
diff --git a/lib/realtime.js b/lib/realtime.js
index 5d769e7d..b50e05b2 100644
--- a/lib/realtime.js
+++ b/lib/realtime.js
@@ -9,7 +9,6 @@ var randomcolor = require("randomcolor");
 var Chance = require('chance'),
     chance = new Chance();
 var moment = require('moment');
-var childProcess = require('child_process');
 
 //core
 var config = require("./config.js");
@@ -20,9 +19,6 @@ var models = require("./models");
 //ot
 var ot = require("./ot/index.js");
 
-// workers
-var noteUpdater = require("./workers/noteUpdater");
-
 //public
 var realtime = {
     io: null,
@@ -83,62 +79,97 @@ function emitCheck(note) {
 var users = {};
 var notes = {};
 //update when the note is dirty
-var updaterIsBusy = false;
 var updater = setInterval(function () {
-    if (updaterIsBusy) return;
-    var _notes = {};
-    Object.keys(notes).forEach(function (key) {
+    async.each(Object.keys(notes), function (key, callback) {
         var note = notes[key];
-        if (!note.server || !note.server.isDirty) return;
-        _notes[key] = {
-            id: note.id,
-            lastchangeuser: note.lastchangeuser,
-            authorship: note.authorship,
-            document: note.server.document
-        };
-        note.server.isDirty = false;
-    });
-    if (Object.keys(_notes).length <= 0) return;
-    updaterIsBusy = true;
-    var worker = childProcess.fork("./lib/workers/noteUpdater.js");
-    if (config.debug) logger.info('note updater worker process started');
-    worker.send({
-        msg: 'update note',
-        notes: _notes
-    });
-    worker.on('message', function (data) {
-        if (!data || !data.msg || !data.note) return;
-        var note = notes[data.note.id];
-        if (!note) return;
-        switch(data.msg) {
-            case 'error':
-                for (var i = 0, l = note.socks.length; i < l; i++) {
-                    var sock = note.socks[i];
-                    if (typeof sock !== 'undefined' && sock) {
-                        setTimeout(function () {
-                            sock.disconnect(true);
-                        }, 0);
+        if (note.server.isDirty) {
+            if (config.debug) logger.info("updater found dirty note: " + key);
+            updateNote(note, function(err, _note) {
+                // handle when note already been clean up
+                if (!notes[key] || !notes[key].server) return callback(null, null);
+                if (!_note) {
+                    realtime.io.to(note.id).emit('info', {
+                        code: 404
+                    });
+                    logger.error('note not found: ', note.id);
+                }
+                if (err || !_note) {
+                    for (var i = 0, l = note.socks.length; i < l; i++) {
+                        var sock = note.socks[i];
+                        if (typeof sock !== 'undefined' && sock) {
+                            setTimeout(function () {
+                                sock.disconnect(true);
+                            }, 0);
+                        }
                     }
+                    return callback(err, null);
                 }
-                break;
-            case 'note not found':
-                realtime.io.to(note.id).emit('info', {
-                    code: 404
-                });
-                break;
-            case 'check':
-                note.lastchangeuserprofile = data.note.lastchangeuserprofile;
-                note.updatetime = data.note.updatetime;
-                saverSleep = false;
+                note.server.isDirty = false;
+                note.updatetime = moment(_note.lastchangeAt).valueOf();
                 emitCheck(note);
-                break;
+                return callback(null, null);
+            });
+        } else {
+            return callback(null, null);
         }
-    });
-    worker.on('close', function (code) {
-        updaterIsBusy = false;
-        if (config.debug) logger.info('note updater worker process exited with code ' + code);
+    }, function (err) {
+        if (err) return logger.error('updater error', err);
     });
 }, 1000);
+function updateNote(note, callback) {
+    models.Note.findOne({
+        where: {
+            id: note.id
+        }
+    }).then(function (_note) {
+        if (!_note) return callback(null, null);
+        if (note.lastchangeuser) {
+            if (_note.lastchangeuserId != note.lastchangeuser) {
+                models.User.findOne({
+                    where: {
+                        id: note.lastchangeuser
+                    }
+                }).then(function (user) {
+                    if (!user) return callback(null, null);
+                    note.lastchangeuserprofile = models.User.parseProfile(user.profile);
+                    return finishUpdateNote(note, _note, callback);
+                }).catch(function (err) {
+                    logger.error(err);
+                    return callback(err, null);
+                });
+            } else {
+                return finishUpdateNote(note, _note, callback);
+            }
+        } else {
+            note.lastchangeuserprofile = null;
+            return finishUpdateNote(note, _note, callback);
+        }
+    }).catch(function (err) {
+        logger.error(err);
+        return callback(err, null);
+    });
+}
+function finishUpdateNote(note, _note, callback) {
+    if (!note || !note.server) return callback(null, null);
+    var body = note.server.document;
+    var title = note.title = models.Note.parseNoteTitle(body);
+    title = LZString.compressToBase64(title);
+    body = LZString.compressToBase64(body);
+    var values = {
+        title: title,
+        content: body,
+        authorship: LZString.compressToBase64(JSON.stringify(note.authorship)),
+        lastchangeuserId: note.lastchangeuser,
+        lastchangeAt: Date.now()
+    };
+    _note.update(values).then(function (_note) {
+        saverSleep = false;
+        return callback(null, _note);
+    }).catch(function (err) {
+        logger.error(err);
+        return callback(err, null);
+    });
+}
 //clean when user not in any rooms or user not in connected list
 var cleaner = setInterval(function () {
     async.each(Object.keys(users), function (key, callback) {
@@ -161,28 +192,16 @@ var cleaner = setInterval(function () {
     });
 }, 60000);
 var saverSleep = false;
-var saverIsBusy = false;
 // save note revision in interval
 var saver = setInterval(function () {
-    if (saverSleep || saverIsBusy) return;
-    saverIsBusy = true;
-    var worker = childProcess.fork("./lib/workers/noteRevisionSaver.js");
-    if (config.debug) logger.info('note revision saver worker process started');
-    worker.send({
-        msg: 'save note revision'
-    });
-    worker.on('message', function (data) {
-        if (!data || !data.msg) return;
-        switch(data.msg) {
-            case 'empty':
-                saverSleep = true;
-                break;
+    if (saverSleep) return;
+    models.Revision.saveAllNotesRevision(function (err, notes) {
+        if (err) return logger.error('revision saver failed: ' + err);
+        if (notes && notes.length <= 0) {
+            saverSleep = true;
+            return;
         }
     });
-    worker.on('close', function (code) {
-        saverIsBusy = false;
-        if (config.debug) logger.info('note revision saver worker process exited with code ' + code);
-    });
 }, 60000 * 5);
 
 function getStatus(callback) {
@@ -524,7 +543,7 @@ function disconnect(socket) {
         // remove note in notes if no user inside
         if (Object.keys(note.users).length <= 0) {
             if (note.server.isDirty) {
-                noteUpdater.updateNote(note, function (err, _note) {
+                updateNote(note, function (err, _note) {
                     if (err) return logger.error('disconnect note failed: ' + err);
                     // clear server before delete to avoid memory leaks
                     note.server.document = "";
diff --git a/lib/response.js b/lib/response.js
index fa97f157..0004f824 100755
--- a/lib/response.js
+++ b/lib/response.js
@@ -16,15 +16,6 @@ var config = require("./config.js");
 var logger = require("./logger.js");
 var models = require("./models");
 
-//slides
-var md = require('reveal.js/plugin/markdown/markdown');
-
-//reveal.js
-var slideOptions = {
-    separator: '^(\r\n?|\n)---(\r\n?|\n)$',
-    verticalSeparator: '^(\r\n?|\n)----(\r\n?|\n)$'
-};
-
 //public
 var response = {
     errorForbidden: function (res) {
@@ -187,26 +178,28 @@ function showPublishNote(req, res, next) {
             }
             var body = LZString.decompressFromBase64(note.content);
             var meta = null;
+            var markdown = null;
             try {
-                meta = models.Note.parseMeta(metaMarked(body).meta);
+                var obj = metaMarked(body);
+                markdown = obj.markdown;
+                meta = models.Note.parseMeta(obj.meta);
             } catch(err) {
                 //na
             }
             if (!meta) meta = {};
             var createtime = note.createdAt;
             var updatetime = note.lastchangeAt;
-            var text = S(body).escapeHTML().s;
             var title = models.Note.decodeTitle(note.title);
             title = models.Note.generateWebTitle(meta.title || title);
             var origin = config.serverurl;
             var data = {
                 title: title,
-                description: meta.description,
+                description: meta.description || markdown ? models.Note.generateDescription(markdown) : null,
                 viewcount: note.viewcount,
                 createtime: createtime,
                 updatetime: updatetime,
                 url: origin,
-                body: text,
+                body: body,
                 useCDN: config.usecdn,
                 owner: note.owner ? note.owner.id : null,
                 ownerprofile: note.owner ? models.User.parseProfile(note.owner.profile) : null,
@@ -259,19 +252,21 @@ function actionDownload(req, res, note) {
 function actionInfo(req, res, note) {
     var body = LZString.decompressFromBase64(note.content);
     var meta = null;
+    var markdown = null;
     try {
-        meta = models.Note.parseMeta(metaMarked(body).meta);
+        var obj = metaMarked(body);
+        markdown = obj.markdown;
+        meta = models.Note.parseMeta(obj.meta);
     } catch(err) {
         //na
     }
     if (!meta) meta = {};
     var createtime = note.createdAt;
     var updatetime = note.lastchangeAt;
-    var text = S(body).escapeHTML().s;
     var title = models.Note.decodeTitle(note.title);
     var data = {
         title: meta.title || title,
-        description: meta.description,
+        description: meta.description || markdown ? models.Note.generateDescription(markdown) : null,
         viewcount: note.viewcount,
         createtime: createtime,
         updatetime: updatetime
@@ -571,9 +566,10 @@ function showPublishSlide(req, res, next) {
             }
             var body = LZString.decompressFromBase64(note.content);
             var meta = null;
+            var markdown = null;
             try {
                 var obj = metaMarked(body);
-                body = obj.markdown;
+                markdown = obj.markdown;
                 meta = models.Note.parseMeta(obj.meta);
             } catch(err) {
                 //na
@@ -581,19 +577,17 @@ function showPublishSlide(req, res, next) {
             if (!meta) meta = {};
             var createtime = note.createdAt;
             var updatetime = note.lastchangeAt;
-            var text = S(body).escapeHTML().s;
             var title = models.Note.decodeTitle(note.title);
             title = models.Note.generateWebTitle(meta.title || title);
-            var slides = md.slidify(text, slideOptions);
             var origin = config.serverurl;
             var data = {
                 title: title,
-                description: meta.description,
+                description: meta.description || markdown ? models.Note.generateDescription(markdown) : null,
                 viewcount: note.viewcount,
                 createtime: createtime,
                 updatetime: updatetime,
                 url: origin,
-                slides: slides,
+                body: markdown,
                 meta: JSON.stringify(obj.meta || {}),
                 useCDN: config.usecdn,
                 owner: note.owner ? note.owner.id : null,
diff --git a/lib/workers/dmpWorker.js b/lib/workers/dmpWorker.js
new file mode 100644
index 00000000..fae36191
--- /dev/null
+++ b/lib/workers/dmpWorker.js
@@ -0,0 +1,142 @@
+// external modules
+var LZString = require('lz-string');
+var DiffMatchPatch = require('diff-match-patch');
+var dmp = new DiffMatchPatch();
+
+// core
+var config = require("../config.js");
+var logger = require("../logger.js");
+
+process.on('message', function(data) {
+    if (!data || !data.msg || !data.cacheKey) {
+        return logger.error('dmp worker error: not enough data');
+    }
+    switch (data.msg) {
+        case 'create patch':
+            if (!data.hasOwnProperty('lastDoc') || !data.hasOwnProperty('currDoc')) {
+                return logger.error('dmp worker error: not enough data on create patch');
+            }
+            try {
+                var patch = createPatch(data.lastDoc, data.currDoc);
+                process.send({
+                    msg: 'check',
+                    result: patch,
+                    cacheKey: data.cacheKey
+                });
+            } catch (err) {
+                logger.error('dmp worker error', err);
+                process.send({
+                    msg: 'error',
+                    error: err,
+                    cacheKey: data.cacheKey
+                });
+            }
+            break;
+        case 'get revision':
+            if (!data.hasOwnProperty('revisions') || !data.hasOwnProperty('count')) {
+                return logger.error('dmp worker error: not enough data on get revision');
+            }
+            try {
+                var result = getRevision(data.revisions, data.count);
+                process.send({
+                    msg: 'check',
+                    result: result,
+                    cacheKey: data.cacheKey
+                });
+            } catch (err) {
+                logger.error('dmp worker error', err);
+                process.send({
+                    msg: 'error',
+                    error: err,
+                    cacheKey: data.cacheKey
+                });
+            }
+            break;
+    }
+});
+
+function createPatch(lastDoc, currDoc) {
+    var ms_start = (new Date()).getTime();
+    var diff = dmp.diff_main(lastDoc, currDoc);
+    dmp.diff_cleanupSemantic(diff);
+    var patch = dmp.patch_make(lastDoc, diff);
+    patch = dmp.patch_toText(patch);
+    var ms_end = (new Date()).getTime();
+    if (config.debug) {
+        logger.info(patch);
+        logger.info((ms_end - ms_start) + 'ms');
+    }
+    return patch;
+}
+
+function getRevision(revisions, count) {
+    var ms_start = (new Date()).getTime();
+    var startContent = null;
+    var lastPatch = [];
+    var applyPatches = [];
+    var authorship = [];
+    if (count <= Math.round(revisions.length / 2)) {
+        // start from top to target
+        for (var i = 0; i < count; i++) {
+            var revision = revisions[i];
+            if (i == 0) {
+                startContent = LZString.decompressFromBase64(revision.content || revision.lastContent);
+            }
+            if (i != count - 1) {
+                var patch = dmp.patch_fromText(LZString.decompressFromBase64(revision.patch));
+                applyPatches = applyPatches.concat(patch);
+            }
+            lastPatch = revision.patch;
+            authorship = revision.authorship;
+        }
+        // swap DIFF_INSERT and DIFF_DELETE to achieve unpatching
+        for (var i = 0, l = applyPatches.length; i < l; i++) {
+            for (var j = 0, m = applyPatches[i].diffs.length; j < m; j++) {
+                var diff = applyPatches[i].diffs[j];
+                if (diff[0] == DiffMatchPatch.DIFF_INSERT)
+                    diff[0] = DiffMatchPatch.DIFF_DELETE;
+                else if (diff[0] == DiffMatchPatch.DIFF_DELETE)
+                    diff[0] = DiffMatchPatch.DIFF_INSERT;
+            }
+        }
+    } else {
+        // start from bottom to target
+        var l = revisions.length - 1;
+        for (var i = l; i >= count - 1; i--) {
+            var revision = revisions[i];
+            if (i == l) {
+                startContent = LZString.decompressFromBase64(revision.lastContent);
+                authorship = revision.authorship;
+            }
+            if (revision.patch) {
+                var patch = dmp.patch_fromText(LZString.decompressFromBase64(revision.patch));
+                applyPatches = applyPatches.concat(patch);
+            }
+            lastPatch = revision.patch;
+            authorship = revision.authorship;
+        }
+    }
+    try {
+        var finalContent = dmp.patch_apply(applyPatches, startContent)[0];
+    } catch (err) {
+        throw new Error(err);
+    }
+    var data = {
+        content: finalContent,
+        patch: dmp.patch_fromText(LZString.decompressFromBase64(lastPatch)),
+        authorship: authorship ? JSON.parse(LZString.decompressFromBase64(authorship)) : null
+    };
+    var ms_end = (new Date()).getTime();
+    if (config.debug) {
+        logger.info((ms_end - ms_start) + 'ms');
+    }
+    return data;
+}
+
+// log uncaught exception
+process.on('uncaughtException', function (err) {
+    logger.error('An uncaught exception has occured.');
+    logger.error(err);
+    logger.error('Process will exit now.');
+    process.exit(1);
+});
\ No newline at end of file
diff --git a/lib/workers/historyUpdater.js b/lib/workers/historyUpdater.js
deleted file mode 100644
index df80e92d..00000000
--- a/lib/workers/historyUpdater.js
+++ /dev/null
@@ -1,66 +0,0 @@
-// external modules
-var async = require('async');
-
-// core
-var config = require("../config.js");
-var logger = require("../logger.js");
-var models = require("../models");
-
-process.on('message', function (data) {
-    if (!data || !data.msg || data.msg !== 'update history' || !data.caches) return process.exit();
-    var caches = data.caches;
-    async.each(Object.keys(caches), function (key, callback) {
-        var cache = caches[key];
-        if (config.debug) logger.info("history updater found dirty history: " + key);
-        var history = parseHistoryToArray(cache);
-        finishUpdateHistory(key, history, function (err, count) {
-            if (err) return callback(err, null);
-            if (!count) return callback(null, null);
-            process.send({
-                msg: 'check',
-                userid: key
-            });
-            return callback(null, null);
-        });
-    }, function (err) {
-        if (err) logger.error('history updater error', err);
-        process.exit();
-    });
-});
-
-function finishUpdateHistory(userid, history, callback) {
-    models.User.update({
-        history: JSON.stringify(history)
-    }, {
-        where: {
-            id: userid
-        }
-    }).then(function (count) {
-        return callback(null, count);
-    }).catch(function (err) {
-        return callback(err, null);
-    });
-}
-
-function parseHistoryToArray(history) {
-    var _history = [];
-    Object.keys(history).forEach(function (key) {
-        var item = history[key];
-        _history.push(item);
-    });
-    return _history;
-}
-
-function parseHistoryToObject(history) {
-    var _history = {};
-    for (var i = 0, l = history.length; i < l; i++) {
-        var item = history[i];
-        _history[item.id] = item;
-    }
-    return _history;
-}
-
-module.exports = {
-    parseHistoryToArray: parseHistoryToArray,
-    parseHistoryToObject: parseHistoryToObject
-};
\ No newline at end of file
diff --git a/lib/workers/noteRevisionSaver.js b/lib/workers/noteRevisionSaver.js
deleted file mode 100644
index b6b117a3..00000000
--- a/lib/workers/noteRevisionSaver.js
+++ /dev/null
@@ -1,19 +0,0 @@
-// core
-var logger = require("../logger.js");
-var models = require("../models");
-
-process.on('message', function (data) {
-    if (!data || !data.msg || data.msg !== 'save note revision') return process.exit();
-    models.Revision.saveAllNotesRevision(function (err, notes) {
-        if (err) {
-            logger.error('note revision saver failed: ' + err);
-            return process.exit();
-        }
-        if (notes && notes.length <= 0) {
-            process.send({
-                msg: 'empty'
-            });
-        }
-        process.exit();
-    });
-});
\ No newline at end of file
diff --git a/lib/workers/noteUpdater.js b/lib/workers/noteUpdater.js
deleted file mode 100644
index 3fc4b1eb..00000000
--- a/lib/workers/noteUpdater.js
+++ /dev/null
@@ -1,101 +0,0 @@
-// external modules
-var async = require('async');
-var moment = require('moment');
-var LZString = require('lz-string');
-
-// core
-var config = require("../config.js");
-var logger = require("../logger.js");
-var models = require("../models");
-
-process.on('message', function (data) {
-    if (!data || !data.msg || data.msg !== 'update note' || !data.notes) return process.exit();
-    var notes = data.notes;
-    async.each(Object.keys(notes), function (key, callback) {
-        var note = notes[key];
-        if (config.debug) logger.info("note updater found dirty note: " + key);
-        updateNote(note, function(err, _note) {
-            if (!_note) {
-                process.send({
-                    msg: 'note not found',
-                    note: note
-                });
-                logger.error('note not found: ', note.id);
-            }
-            if (err || !_note) {
-                process.send({
-                    msg: 'error',
-                    note: note
-                });
-                return callback(err, null);
-            }
-            note.updatetime = moment(_note.lastchangeAt).valueOf();
-            process.send({
-                msg: 'check',
-                note: note
-            });
-            return callback(null, null);
-        });
-    }, function (err) {
-        if (err) logger.error('note updater error', err);
-        process.exit();
-    });
-});
-
-function updateNote(note, callback) {
-    models.Note.findOne({
-        where: {
-            id: note.id
-        }
-    }).then(function (_note) {
-        if (!_note) return callback(null, null);
-        if (note.lastchangeuser) {
-            if (_note.lastchangeuserId != note.lastchangeuser) {
-                models.User.findOne({
-                    where: {
-                        id: note.lastchangeuser
-                    }
-                }).then(function (user) {
-                    if (!user) return callback(null, null);
-                    note.lastchangeuserprofile = models.User.parseProfile(user.profile);
-                    return finishUpdateNote(note, _note, callback);
-                }).catch(function (err) {
-                    logger.error(err);
-                    return callback(err, null);
-                });
-            } else {
-                return finishUpdateNote(note, _note, callback);
-            }
-        } else {
-            note.lastchangeuserprofile = null;
-            return finishUpdateNote(note, _note, callback);
-        }
-    }).catch(function (err) {
-        logger.error(err);
-        return callback(err, null);
-    });
-}
-
-function finishUpdateNote(note, _note, callback) {
-    var body = note.document;
-    var title = note.title = models.Note.parseNoteTitle(body);
-    title = LZString.compressToBase64(title);
-    body = LZString.compressToBase64(body);
-    var values = {
-        title: title,
-        content: body,
-        authorship: LZString.compressToBase64(JSON.stringify(note.authorship)),
-        lastchangeuserId: note.lastchangeuser,
-        lastchangeAt: Date.now()
-    };
-    _note.update(values).then(function (_note) {
-        return callback(null, _note);
-    }).catch(function (err) {
-        logger.error(err);
-        return callback(err, null);
-    });
-}
-
-module.exports = {
-    updateNote: updateNote
-};
\ No newline at end of file