Add support of saving note revision and improve app start and stop procedure to ensure data integrity

5 files changed, 345 insertions, 11 deletions

diff --git a/lib/config.js b/lib/config.js
index 1ba1763c..3828e2dc 100644
--- a/lib/config.js
+++ b/lib/config.js
@@ -78,7 +78,7 @@ function getserverurl() {
 }
 
 var version = '0.4.2';
-var maintenance = config.maintenance || false;
+var maintenance = true;
 var cwd = path.join(__dirname, '..');
 
 module.exports = {
diff --git a/lib/migrations/20160607060246-support-revision.js b/lib/migrations/20160607060246-support-revision.js
new file mode 100644
index 00000000..9721d7fc
--- /dev/null
+++ b/lib/migrations/20160607060246-support-revision.js
@@ -0,0 +1,24 @@
+'use strict';
+
+module.exports = {
+  up: function (queryInterface, Sequelize) {
+    queryInterface.addColumn('Notes', 'savedAt', Sequelize.DATE);
+    queryInterface.createTable('Revisions', {
+      id: Sequelize.UUID,
+      noteId: Sequelize.UUID,
+      patch: Sequelize.TEXT,
+      lastContent: Sequelize.TEXT,
+      content: Sequelize.TEXT,
+      length: Sequelize.INTEGER,
+      createdAt: Sequelize.DATE,
+      updatedAt: Sequelize.DATE
+    });
+    return;
+  },
+
+  down: function (queryInterface, Sequelize) {
+    queryInterface.dropTable('Revisions');
+    queryInterface.removeColumn('Notes', 'savedAt');
+    return;
+  }
+};
diff --git a/lib/models/note.js b/lib/models/note.js
index 2b51c87c..ace072a3 100644
--- a/lib/models/note.js
+++ b/lib/models/note.js
@@ -52,6 +52,9 @@ module.exports = function (sequelize, DataTypes) {
         },
         lastchangeAt: {
             type: DataTypes.DATE
+        },
+        savedAt: {
+            type: DataTypes.DATE
         }
     }, {
         classMethods: {
@@ -66,6 +69,10 @@ module.exports = function (sequelize, DataTypes) {
                     as: "lastchangeuser",
                     constraints: false
                 });
+                Note.hasMany(models.Revision, {
+                    foreignKey: "noteId",
+                    constraints: false
+                });
             },
             checkFileExist: function (filePath) {
                 try {
@@ -100,11 +107,15 @@ module.exports = function (sequelize, DataTypes) {
                                     var dbModifiedTime = moment(note.lastchangeAt || note.createdAt);
                                     if (fsModifiedTime.isAfter(dbModifiedTime)) {
                                         var body = fs.readFileSync(filePath, 'utf8');
-                                        note.title = LZString.compressToBase64(Note.parseNoteTitle(body));
-                                        note.content = LZString.compressToBase64(body);
-                                        note.lastchangeAt = fsModifiedTime;
-                                        note.save().then(function (note) {
-                                            return callback(null, note.id);
+                                        note.update({
+                                            title: LZString.compressToBase64(Note.parseNoteTitle(body)),
+                                            content: LZString.compressToBase64(body),
+                                            lastchangeAt: fsModifiedTime
+                                        }).then(function (note) {
+                                            sequelize.models.Revision.saveNoteRevision(note, function (err, revision) {
+                                                if (err) return _callback(err, null);
+                                                return callback(null, note.id);
+                                            });
                                         }).catch(function (err) {
                                             return _callback(err, null);
                                         });
@@ -224,6 +235,11 @@ module.exports = function (sequelize, DataTypes) {
                     }
                 }
                 return callback(null, note);
+            },
+            afterCreate: function (note, options, callback) {
+                sequelize.models.Revision.saveNoteRevision(note, function (err, revision) {
+                    callback(err, note);
+                });
             }
         }
     });
diff --git a/lib/models/revision.js b/lib/models/revision.js
new file mode 100644
index 00000000..5300d725
--- /dev/null
+++ b/lib/models/revision.js
@@ -0,0 +1,276 @@
+"use strict";
+
+// external modules
+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();
+
+// core
+var config = require("../config.js");
+var logger = require("../logger.js");
+
+module.exports = function (sequelize, DataTypes) {
+    var Revision = sequelize.define("Revision", {
+        id: {
+            type: DataTypes.UUID,
+            primaryKey: true,
+            defaultValue: Sequelize.UUIDV4
+        },
+        patch: {
+            type: DataTypes.TEXT
+        },
+        lastContent: {
+            type: DataTypes.TEXT
+        },
+        content: {
+            type: DataTypes.TEXT
+        },
+        length: {
+            type: DataTypes.INTEGER
+        }
+    }, {
+        classMethods: {
+            associate: function (models) {
+                Revision.belongsTo(models.User, {
+                    foreignKey: "noteId",
+                    as: "note",
+                    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: {
+                        noteId: note.id
+                    },
+                    order: '"createdAt" DESC'
+                }).then(function (revisions) {
+                    var data = [];
+                    for (var i = 0, l = revisions.length; i < l; i++) {
+                        var revision = revisions[i];
+                        data.push({
+                            time: moment(revision.createdAt).valueOf(),
+                            length: revision.length
+                        });
+                    }
+                    callback(null, data);
+                }).catch(function (err) {
+                    callback(err, null);
+                });
+            },
+            getPatchedNoteRevisionByTime: function (note, time, callback) {
+                // find all revisions to prepare for all possible calculation
+                Revision.findAll({
+                    where: {
+                        noteId: note.id
+                    },
+                    order: '"createdAt" DESC'
+                }).then(function (revisions) {
+                    if (revisions.length <= 0) return callback(null, null);
+                    // measure target revision position 
+                    Revision.count({
+                        where: {
+                            noteId: note.id,
+                            createdAt: {
+                                $gte: time
+                            }
+                        },
+                        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 = [];
+                        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;
+                            }
+                            // 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);
+                                }
+                                if (revision.patch) {
+                                    var patch = dmp.patch_fromText(LZString.decompressFromBase64(revision.patch));
+                                    applyPatches = applyPatches.concat(patch);
+                                }
+                                lastPatch = revision.patch;
+                            }
+                        }
+                        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))
+                        };
+                        var ms_end = (new Date()).getTime();
+                        if (config.debug) {
+                            logger.info((ms_end - ms_start) + 'ms');
+                        }
+                        return callback(null, data);
+                    }).catch(function (err) {
+                        return callback(err, null);
+                    });
+                }).catch(function (err) {
+                    return callback(err, null);
+                });
+            },
+            checkAllNotesRevision: function (callback) {
+                Revision.saveAllNotesRevision(function (err, notes) {
+                    if (err) return callback(err, null);
+                    if (notes.length <= 0) {
+                        return callback(null, notes);
+                    } else {
+                        Revision.checkAllNotesRevision(callback);
+                    }
+                });
+            },
+            saveAllNotesRevision: function (callback) {
+                sequelize.models.Note.findAll({
+                    where: {
+                        $and: [
+                            {
+                                lastchangeAt: {
+                                    $or: {
+                                        $eq: null,
+                                        $and: {
+                                            $ne: null,
+                                            $gt: sequelize.col('createdAt')
+                                        }
+                                    }
+                                }
+                            },
+                            {
+                                savedAt: {
+                                    $or: {
+                                        $eq: null,
+                                        $lt: sequelize.col('lastchangeAt')
+                                    }
+                                }
+                            }
+                        ]
+                    }
+                }).then(function (notes) {
+                    if (notes.length <= 0) return callback(null, notes);
+                    async.each(notes, function (note, _callback) {
+                        Revision.saveNoteRevision(note, _callback);
+                    }, function (err) {
+                        if (err) return callback(err, null);
+                        return callback(null, notes);
+                    });
+                }).catch(function (err) {
+                    return callback(err, null);
+                });
+            },
+            saveNoteRevision: function (note, callback) {
+                Revision.findAll({
+                    where: {
+                        noteId: note.id
+                    },
+                    order: '"createdAt" DESC'
+                }).then(function (revisions) {
+                    if (revisions.length <= 0) {
+                        // if no revision available
+                        Revision.create({
+                            noteId: note.id,
+                            lastContent: note.content,
+                            length: LZString.decompressFromBase64(note.content).length
+                        }).then(function (revision) {
+                            Revision.finishSaveNoteRevision(note, revision, callback);
+                        }).catch(function (err) {
+                            return callback(err, null);
+                        });
+                    } else {
+                        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
+                            }).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);
+                });
+            },
+            finishSaveNoteRevision: function (note, revision, callback) {
+                note.update({
+                    savedAt: revision.updatedAt
+                }).then(function () {
+                    return callback(null, revision);
+                }).catch(function (err) {
+                    return callback(err, null);
+                });
+            }
+        }
+    });
+
+    return Revision;
+};
\ No newline at end of file
diff --git a/lib/realtime.js b/lib/realtime.js
index 1d142709..0edf647c 100644
--- a/lib/realtime.js
+++ b/lib/realtime.js
@@ -26,8 +26,7 @@ var realtime = {
     secure: secure,
     connection: connection,
     getStatus: getStatus,
-    users: users,
-    notes: notes
+    isReady: isReady
 };
 
 function onAuthorizeSuccess(data, accept) {
@@ -72,9 +71,8 @@ function emitCheck(note) {
 }
 
 //actions
-var users, notes;
-realtime.users = users = {};
-realtime.notes = notes = {};
+var users = {};
+var notes = {};
 //update when the note is dirty
 var updater = setInterval(function () {
     async.each(Object.keys(notes), function (key, callback) {
@@ -152,6 +150,7 @@ function finishUpdateNote(note, _note, callback) {
         lastchangeAt: Date.now()
     };
     _note.update(values).then(function (_note) {
+        saverSleep = false;
         return callback(null, _note);
     }).catch(function (err) {
         logger.error(err);
@@ -179,6 +178,18 @@ var cleaner = setInterval(function () {
         if (err) return logger.error('cleaner error', err);
     });
 }, 60000);
+var saverSleep = true;
+// save note revision in interval
+var saver = setInterval(function () {
+    if (saverSleep) return;
+    models.Revision.saveAllNotesRevision(function (err, notes) {
+        if (err) return logger.error('revision saver failed: ' + err);
+        if (notes.length <= 0) {
+            saverSleep = true;
+            return;
+        }
+    });
+}, 60000 * 5);
 
 function getStatus(callback) {
     models.Note.count().then(function (notecount) {
@@ -233,6 +244,13 @@ function getStatus(callback) {
     });
 }
 
+function isReady() {
+    return realtime.io 
+    && Object.keys(notes).length == 0 && Object.keys(users).length == 0 
+    && connectionSocketQueue.length == 0 && !isConnectionBusy
+    && disconnectSocketQueue.length == 0 && !isDisconnectBusy;
+}
+
 function extractNoteIdFromSocket(socket) {
     if (!socket || !socket.handshake || !socket.handshake.headers) {
         return false;