From cc2f9fa2045bf56f0c733566dfe62d9eeda5febd Mon Sep 17 00:00:00 2001
From: benweet <benoit.schweblin@gmail.com>
Date: Fri, 25 Aug 2017 11:37:46 +0100
Subject: [PATCH] Added gdrive app data provider

---
 src/components/NavigationBar.vue              |  42 +-
 src/components/SideBar.vue                    |  17 +-
 src/components/Toc.vue                        |   6 +-
 src/components/common/app.scss                |  11 +
 src/data/emptyContent.js                      |   3 +-
 src/data/emptyContentState.js                 |   2 +-
 src/data/emptyFile.js                         |   1 +
 src/data/emptyFolder.js                       |   1 +
 src/data/emptySyncContent.js                  |   7 -
 src/data/emptySyncLocation.js                 |   6 +
 src/data/emptySyncedContent.js                |   7 +
 src/extensions/markdownExt.js                 |   4 +-
 src/icons/Sync.vue                            |   5 +
 src/icons/SyncOff.vue                         |   5 +
 src/icons/index.js                            |   4 +
 src/services/diffUtils.js                     | 128 +++---
 src/services/editorEngineSvc.js               | 102 ++---
 src/services/editorSvc.js                     |  74 ++--
 src/services/localDbSvc.js                    |  56 ++-
 src/services/markdownConversionSvc.js         |   2 +-
 .../providers/gdriveAppDataProvider.js        | 102 ++++-
 src/services/providers/gdriveProvider.js      |  30 ++
 .../{ => providers}/helpers/googleHelper.js   | 217 +++++-----
 src/services/providers/providerUtils.js       |  48 +++
 src/services/syncSvc.js                       | 371 ++++++++++++------
 src/services/utils.js                         |  51 ++-
 src/store/index.js                            |  29 +-
 src/store/modules/contentState.js             |   2 +-
 src/store/modules/data.js                     |  19 +-
 src/store/modules/moduleTemplate.js           |  15 +-
 src/store/modules/syncContent.js              |  12 -
 src/store/modules/syncLocation.js             |  21 +
 src/store/modules/syncedContent.js            |  12 +
 33 files changed, 916 insertions(+), 496 deletions(-)
 delete mode 100644 src/data/emptySyncContent.js
 create mode 100644 src/data/emptySyncLocation.js
 create mode 100644 src/data/emptySyncedContent.js
 create mode 100644 src/icons/Sync.vue
 create mode 100644 src/icons/SyncOff.vue
 create mode 100644 src/services/providers/gdriveProvider.js
 rename src/services/{ => providers}/helpers/googleHelper.js (51%)
 create mode 100644 src/services/providers/providerUtils.js
 delete mode 100644 src/store/modules/syncContent.js
 create mode 100644 src/store/modules/syncLocation.js
 create mode 100644 src/store/modules/syncedContent.js

diff --git a/src/components/NavigationBar.vue b/src/components/NavigationBar.vue
index 0d188b4c..fbb434c3 100644
--- a/src/components/NavigationBar.vue
+++ b/src/components/NavigationBar.vue
@@ -17,6 +17,12 @@
       <div class="navigation-bar__title navigation-bar__title--fake text-input"></div>
       <div class="navigation-bar__title navigation-bar__title--text text-input" v-bind:style="{maxWidth: styles.titleMaxWidth + 'px'}">{{title}}</div>
       <input class="navigation-bar__title navigation-bar__title--input text-input" :class="{'navigation-bar__title--focus': titleFocus, 'navigation-bar__title--scrolling': titleScrolling}" v-bind:style="{width: titleWidth + 'px'}" @focus="editTitle(true)" @blur="editTitle(false)" @keyup.enter="submitTitle()" @keyup.esc="submitTitle(true)" v-on:mouseenter="titleHover = true" v-on:mouseleave="titleHover = false" v-model="title">
+      <button v-if="!offline && isSyncPossible" class="navigation-bar__button button" :disabled="isSyncRequested" @click="requestSync">
+        <icon-sync></icon-sync>
+      </button>
+      <button v-if="offline && isSyncPossible" class="navigation-bar__button navigation-bar__button--sync-off button" disabled="disabled">
+        <icon-sync-off></icon-sync-off>
+      </button>
     </div>
     <div class="navigation-bar__inner navigation-bar__inner--edit-buttons">
       <button class="navigation-bar__button button" @click="pagedownClick('bold')">
@@ -60,8 +66,9 @@
 </template>
 
 <script>
-import { mapGetters, mapActions } from 'vuex';
+import { mapState, mapGetters, mapActions } from 'vuex';
 import editorSvc from '../services/editorSvc';
+import syncSvc from '../services/syncSvc';
 import animationSvc from '../services/animationSvc';
 
 export default {
@@ -72,9 +79,19 @@ export default {
     titleHover: false,
   }),
   computed: {
+    ...mapState([
+      'offline',
+    ]),
+    ...mapState('queue', [
+      'isSyncRequested',
+    ]),
     ...mapGetters('layout', [
       'styles',
     ]),
+    isSyncPossible() {
+      return this.$store.getters['data/loginToken'] ||
+        this.$store.getters['syncLocation/current'].length;
+    },
     showSpinner() {
       return !this.$store.state.queue.isEmpty;
     },
@@ -112,6 +129,11 @@ export default {
       'toggleExplorer',
       'toggleSideBar',
     ]),
+    requestSync() {
+      if (!this.isSyncRequested) {
+        syncSvc.requestSync();
+      }
+    },
     pagedownClick(name) {
       editorSvc.pagedownEditor.uiManager.doClick(name);
     },
@@ -203,6 +225,24 @@ export default {
   font-size: 22px;
 }
 
+.navigation-bar__button[disabled] {
+  &,
+  &:active,
+  &:focus,
+  &:hover {
+    color: $navbar-color;
+  }
+}
+
+.navigation-bar__button--sync-off[disabled] {
+  &,
+  &:active,
+  &:focus,
+  &:hover {
+    color: #f20;
+  }
+}
+
 .navigation-bar__title--input,
 .navigation-bar__button {
   &:active,
diff --git a/src/components/SideBar.vue b/src/components/SideBar.vue
index 7bf326bd..311ff9e7 100644
--- a/src/components/SideBar.vue
+++ b/src/components/SideBar.vue
@@ -15,14 +15,15 @@
       <div v-if="panel === 'menu'" class="side-bar__panel side-bar__panel--menu">
         <side-bar-item v-if="!loginToken" @click.native="signin">
           <icon-login slot="icon"></icon-login>
-          <div>Sign in</div>
+          <div>Sign in with Google</div>
           <span>Have all your files and settings backed up and synced.</span>
         </side-bar-item>
         <!-- <side-bar-item @click.native="signin">
-                <icon-login slot="icon"></icon-login>
-                <div>Sign in on CouchDB</div>
-                <span>Save and collaborate on a CouchDB hosted by you.</span>
-              </side-bar-item> -->
+                  <icon-login slot="icon"></icon-login>
+                  <div>Sign in on CouchDB</div>
+                  <span>Save and collaborate on a CouchDB hosted by you.</span>
+                </side-bar-item> -->
+        <hr v-if="!loginToken">
         <side-bar-item @click.native="panel = 'toc'">
           <icon-toc slot="icon"></icon-toc>
           Table of contents
@@ -49,7 +50,7 @@ import Toc from './Toc';
 import SideBarItem from './SideBarItem';
 import markdownSample from '../data/markdownSample.md';
 import markdownConversionSvc from '../services/markdownConversionSvc';
-import googleHelper from '../services/helpers/googleHelper';
+import googleHelper from '../services/providers/helpers/googleHelper';
 import syncSvc from '../services/syncSvc';
 
 const panelNames = {
@@ -100,6 +101,10 @@ export default {
 .side-bar {
   overflow: hidden;
   height: 100%;
+
+  hr {
+    margin: 5px 10px;
+  }
 }
 
 .side-bar__inner {
diff --git a/src/components/Toc.vue b/src/components/Toc.vue
index e695d9bd..fc83ec82 100644
--- a/src/components/Toc.vue
+++ b/src/components/Toc.vue
@@ -59,7 +59,7 @@ export default {
   color: rgba(0, 0, 0, 0.75);
   cursor: pointer;
   font-size: 10px;
-  padding: 10px 20px;
+  padding: 5px 20px 40px;
   white-space: nowrap;
   -webkit-user-select: none;
   -moz-user-select: none;
@@ -73,8 +73,8 @@ export default {
 
   .cl-toc-section {
     * {
-      margin: 0.25em 0;
-      padding: 0.25em 0;
+      margin: 0.2em 0;
+      padding: 0.2em 0;
     }
 
     h2 {
diff --git a/src/components/common/app.scss b/src/components/common/app.scss
index 3c2086de..f25649fb 100644
--- a/src/components/common/app.scss
+++ b/src/components/common/app.scss
@@ -83,6 +83,17 @@ textarea {
     background-color: rgba(0, 0, 0, 0.1);
     outline: 0;
   }
+
+  &[disabled] {
+    &,
+    &:active,
+    &:focus,
+    &:hover {
+      opacity: 0.5;
+      background-color: transparent;
+      cursor: inherit;
+    }
+  }
 }
 
 .flex {
diff --git a/src/data/emptyContent.js b/src/data/emptyContent.js
index 1784f4f9..c8806e28 100644
--- a/src/data/emptyContent.js
+++ b/src/data/emptyContent.js
@@ -5,6 +5,5 @@ export default () => ({
   properties: '\n',
   discussions: {},
   comments: {},
-  syncLocations: [],
-  updated: 0,
+  hash: 0,
 });
diff --git a/src/data/emptyContentState.js b/src/data/emptyContentState.js
index 2c88edde..6266625d 100644
--- a/src/data/emptyContentState.js
+++ b/src/data/emptyContentState.js
@@ -4,5 +4,5 @@ export default () => ({
   selectionStart: 0,
   selectionEnd: 0,
   scrollPosition: null,
-  updated: 0,
+  hash: 0,
 });
diff --git a/src/data/emptyFile.js b/src/data/emptyFile.js
index 9910598b..9e5d2146 100644
--- a/src/data/emptyFile.js
+++ b/src/data/emptyFile.js
@@ -3,4 +3,5 @@ export default () => ({
   type: 'file',
   name: '',
   parentId: null,
+  hash: 0,
 });
diff --git a/src/data/emptyFolder.js b/src/data/emptyFolder.js
index 8419d417..15fd5e34 100644
--- a/src/data/emptyFolder.js
+++ b/src/data/emptyFolder.js
@@ -3,4 +3,5 @@ export default () => ({
   type: 'folder',
   name: '',
   parentId: null,
+  hash: 0,
 });
diff --git a/src/data/emptySyncContent.js b/src/data/emptySyncContent.js
deleted file mode 100644
index cb9b7cf1..00000000
--- a/src/data/emptySyncContent.js
+++ /dev/null
@@ -1,7 +0,0 @@
-export default () => ({
-  id: null,
-  type: 'syncContent',
-  historyData: {},
-  syncLocationData: {},
-  updated: 0,
-});
diff --git a/src/data/emptySyncLocation.js b/src/data/emptySyncLocation.js
new file mode 100644
index 00000000..80c68268
--- /dev/null
+++ b/src/data/emptySyncLocation.js
@@ -0,0 +1,6 @@
+export default () => ({
+  id: null,
+  type: 'syncLocation',
+  fileId: null,
+  hash: 0,
+});
diff --git a/src/data/emptySyncedContent.js b/src/data/emptySyncedContent.js
new file mode 100644
index 00000000..4950e3b8
--- /dev/null
+++ b/src/data/emptySyncedContent.js
@@ -0,0 +1,7 @@
+export default () => ({
+  id: null,
+  type: 'syncedContent',
+  historyData: {},
+  syncHistory: {},
+  hash: 0,
+});
diff --git a/src/extensions/markdownExt.js b/src/extensions/markdownExt.js
index 723c8a9e..3f3be3a3 100644
--- a/src/extensions/markdownExt.js
+++ b/src/extensions/markdownExt.js
@@ -110,7 +110,7 @@ extensionSvc.onInitConverter(0, (markdown, options) => {
     const anchorHash = {};
     let headingOpenToken;
     let headingContent;
-    state.tokens.cl_each((token) => {
+    state.tokens.forEach((token) => {
       if (token.type === 'heading_open') {
         headingContent = '';
         headingOpenToken = token;
@@ -148,7 +148,7 @@ extensionSvc.onInitConverter(0, (markdown, options) => {
         ];
         headingOpenToken = undefined;
       } else if (headingOpenToken) {
-        headingContent += token.children.cl_reduce((result, child) => {
+        headingContent += token.children.reduce((result, child) => {
           if (child.type !== 'footnote_ref') {
             return result + child.content;
           }
diff --git a/src/icons/Sync.vue b/src/icons/Sync.vue
new file mode 100644
index 00000000..171b7577
--- /dev/null
+++ b/src/icons/Sync.vue
@@ -0,0 +1,5 @@
+<template>
+  <svg xmlns="http://www.w3.org/2000/svg" class="icon" width="100%" height="100%" viewBox="0 0 24.00 24.00">
+    <path d="M12,18C8.69,18 6,15.31 6,12C6,11 6.25,10.03 6.7,9.2L5.24,7.74C4.46,8.97 4,10.43 4,12C4,16.42 7.58,20 12,20V23L16,19L12,15M12,4V1L8,5L12,9V6C15.31,6 18,8.69 18,12C18,13 17.75,13.97 17.3,14.8L18.76,16.26C19.54,15.03 20,13.57 20,12C20,7.58 16.42,4 12,4Z" />
+  </svg>
+</template>
diff --git a/src/icons/SyncOff.vue b/src/icons/SyncOff.vue
new file mode 100644
index 00000000..0c586268
--- /dev/null
+++ b/src/icons/SyncOff.vue
@@ -0,0 +1,5 @@
+<template>
+  <svg xmlns="http://www.w3.org/2000/svg" class="icon" width="100%" height="100%" viewBox="0 0 24.00 24.00">
+    <path d="M20,4H14V10L16.24,7.76C17.32,8.85 18,10.34 18,12C18,13 17.75,13.94 17.32,14.77L18.78,16.23C19.55,15 20,13.56 20,12C20,9.79 19.09,7.8 17.64,6.36L20,4M2.86,5.41L5.22,7.77C4.45,9 4,10.44 4,12C4,14.21 4.91,16.2 6.36,17.64L4,20H10V14L7.76,16.24C6.68,15.15 6,13.66 6,12C6,11 6.25,10.06 6.68,9.23L14.76,17.31C14.5,17.44 14.26,17.56 14,17.65V19.74C14.79,19.53 15.54,19.2 16.22,18.78L18.58,21.14L19.85,19.87L4.14,4.14L2.86,5.41M10,6.35V4.26C9.2,4.47 8.45,4.8 7.77,5.22L9.23,6.68C9.5,6.56 9.73,6.44 10,6.35Z" />
+  </svg>
+</template>
diff --git a/src/icons/index.js b/src/icons/index.js
index 1d299704..2451120c 100644
--- a/src/icons/index.js
+++ b/src/icons/index.js
@@ -28,6 +28,8 @@ import ArrowLeft from './ArrowLeft';
 import HelpCircle from './HelpCircle';
 import Toc from './Toc';
 import Login from './Login';
+import Sync from './Sync';
+import SyncOff from './SyncOff';
 
 Vue.component('iconFormatBold', FormatBold);
 Vue.component('iconFormatItalic', FormatItalic);
@@ -58,3 +60,5 @@ Vue.component('iconArrowLeft', ArrowLeft);
 Vue.component('iconHelpCircle', HelpCircle);
 Vue.component('iconToc', Toc);
 Vue.component('iconLogin', Login);
+Vue.component('iconSync', Sync);
+Vue.component('iconSyncOff', SyncOff);
diff --git a/src/services/diffUtils.js b/src/services/diffUtils.js
index 6fa2fbc4..99954cff 100644
--- a/src/services/diffUtils.js
+++ b/src/services/diffUtils.js
@@ -2,13 +2,12 @@ import DiffMatchPatch from 'diff-match-patch';
 import utils from './utils';
 
 const diffMatchPatch = new DiffMatchPatch();
-const diffMatchPatchStrict = new DiffMatchPatch();
-diffMatchPatchStrict.Match_Threshold = 0;
-diffMatchPatchStrict.Patch_DeleteThreshold = 0;
-const diffMatchPatchPermissive = new DiffMatchPatch();
-diffMatchPatchPermissive.Match_Distance = 999999999;
+diffMatchPatch.Match_Distance = 10000;
 
 function makePatchableText(content, markerKeys, markerIdxMap) {
+  if (!content || !content.discussions) {
+    return null;
+  }
   const markers = [];
   // Sort keys to have predictable marker positions in case of same offset
   const discussionKeys = Object.keys(content.discussions).sort();
@@ -58,6 +57,9 @@ function makePatchableText(content, markerKeys, markerIdxMap) {
 }
 
 function stripDiscussionOffsets(objectMap) {
+  if (objectMap == null) {
+    return objectMap;
+  }
   const result = {};
   Object.keys(objectMap).forEach((id) => {
     result[id] = {
@@ -85,72 +87,58 @@ function restoreDiscussionOffsets(content, markerKeys) {
   }
 }
 
-function serializeObject(obj) {
-  if (!obj) {
-    return obj;
+function mergeText(serverText, clientText, lastMergedText) {
+  const serverClientDiffs = diffMatchPatch.diff_main(serverText, clientText);
+  diffMatchPatch.diff_cleanupSemantic(serverClientDiffs);
+  // Fusion text is a mix of both server and client contents
+  const fusionText = serverClientDiffs.map(diff => diff[1]).join('');
+  if (!lastMergedText) {
+    return fusionText;
   }
-  return JSON.stringify(obj, (key, value) => {
-    if (Object.prototype.toString.call(value) !== '[object Object]') {
-      return value;
-    }
-    return Object.keys(value).sort().reduce((sorted, valueKey) => {
-      sorted[valueKey] = value[valueKey];
-      return sorted;
-    }, {});
-  });
+  // Let's try to find out what text has to be removed from fusion
+  const intersectionText = serverClientDiffs
+    // Keep only equalities
+    .filter(diff => diff[0] === DiffMatchPatch.DIFF_EQUAL)
+    .map(diff => diff[1]).join('');
+  const lastMergedTextDiffs = diffMatchPatch.diff_main(lastMergedText, intersectionText)
+    // Keep only equalities and deletions
+    .filter(diff => diff[0] !== DiffMatchPatch.DIFF_INSERT);
+  diffMatchPatch.diff_cleanupSemantic(serverClientDiffs);
+  // Make a patch with deletions only
+  const patches = diffMatchPatch.patch_make(lastMergedText, lastMergedTextDiffs);
+  // Apply patch to fusion text
+  return diffMatchPatch.patch_apply(patches, fusionText)[0];
 }
 
-function mergeText(oldText, newText, serverText) {
-  let diffs = diffMatchPatch.diff_main(oldText, newText);
-  diffMatchPatch.diff_cleanupSemantic(diffs);
-  const patches = diffMatchPatch.patch_make(oldText, diffs);
-  const patchResult = diffMatchPatch.patch_apply(patches, serverText);
-  if (!patchResult[1].some(changeApplied => !changeApplied)) {
-    return patchResult[0];
+function mergeValues(serverValue, clientValue, lastMergedValue) {
+  if (!lastMergedValue) {
+    return serverValue || clientValue; // Take the server value in priority
   }
-
-  diffs = diffMatchPatchStrict.diff_main(patchResult[0], newText);
-  diffMatchPatch.diff_cleanupSemantic(diffs);
-  return diffs.map(diff => diff[1]).join('');
-}
-
-function quickPatch(oldStr, newStr, destStr, strict) {
-  const dmp = strict ? diffMatchPatchStrict : diffMatchPatch;
-  const diffs = dmp.diff_main(oldStr, newStr);
-  const patches = dmp.patch_make(oldStr, diffs);
-  const patchResult = dmp.patch_apply(patches, destStr);
-  return patchResult[0];
-}
-
-function mergeValue(oldValue, newValue, serverValue) {
-  if (!oldValue) {
-    return serverValue; // There might be conflict, keep the server value
-  }
-  const newSerializedValue = serializeObject(newValue);
-  const serverSerializedValue = serializeObject(serverValue);
+  const newSerializedValue = utils.serializeObject(clientValue);
+  const serverSerializedValue = utils.serializeObject(serverValue);
   if (newSerializedValue === serverSerializedValue) {
     return serverValue; // no conflict
   }
-  const oldSerializedValue = serializeObject(oldValue);
+  const oldSerializedValue = utils.serializeObject(lastMergedValue);
   if (oldSerializedValue !== newSerializedValue && !serverValue) {
-    return newValue; // Removed on server but changed on client
+    return clientValue; // Removed on server but changed on client
   }
-  if (oldSerializedValue !== serverSerializedValue && !newValue) {
+  if (oldSerializedValue !== serverSerializedValue && !clientValue) {
     return serverValue; // Removed on client but changed on server
   }
   if (oldSerializedValue !== newSerializedValue && oldSerializedValue === serverSerializedValue) {
-    return newValue; // Take the client value
+    return clientValue; // Take the client value
   }
-  return serverValue; // Take the server value otherwise
+  return serverValue; // Take the server value
 }
 
-function mergeObjects(oldObject, newObject, serverObject) {
+function mergeObjects(serverObject, clientObject, lastMergedObject = {}) {
   const mergedObject = {};
   Object.keys({
-    ...newObject,
+    ...clientObject,
     ...serverObject,
   }).forEach((key) => {
-    const mergedValue = mergeValue(oldObject[key], newObject[key], serverObject[key]);
+    const mergedValue = mergeValues(serverObject[key], clientObject[key], lastMergedObject[key]);
     if (mergedValue != null) {
       mergedObject[key] = mergedValue;
     }
@@ -158,47 +146,41 @@ function mergeObjects(oldObject, newObject, serverObject) {
   return utils.deepCopy(mergedObject);
 }
 
-function mergeContent(oldContent, newContent, serverContent) {
+function mergeContent(serverContent, clientContent, lastMergedContent = {}) {
   const markerKeys = [];
   const markerIdxMap = Object.create(null);
-  const oldText = makePatchableText(oldContent, markerKeys, markerIdxMap);
+  const lastMergedText = makePatchableText(lastMergedContent, markerKeys, markerIdxMap);
   const serverText = makePatchableText(serverContent, markerKeys, markerIdxMap);
-  const localText = makePatchableText(newContent, markerKeys, markerIdxMap);
-  const isServerTextChanges = oldText !== serverText;
-  const isTextSynchronized = serverText === localText;
+  const clientText = makePatchableText(clientContent, markerKeys, markerIdxMap);
+  const isServerTextChanges = lastMergedText !== serverText;
+  const isTextSynchronized = serverText === clientText;
 
   const result = {
     text: isTextSynchronized || !isServerTextChanges
-      ? localText
-      : mergeText(oldText, serverText, localText),
-    properties: mergeValue(
-      oldContent.properties,
-      newContent.properties,
+      ? clientText
+      : mergeText(serverText, clientText, lastMergedText),
+    properties: mergeValues(
       serverContent.properties,
+      clientContent.properties,
+      lastMergedContent.properties,
     ),
     discussions: mergeObjects(
-      stripDiscussionOffsets(oldContent.discussions),
-      stripDiscussionOffsets(newContent.discussions),
       stripDiscussionOffsets(serverContent.discussions),
+      stripDiscussionOffsets(clientContent.discussions),
+      stripDiscussionOffsets(lastMergedContent.discussions),
     ),
     comments: mergeObjects(
-      oldContent.comments,
-      newContent.comments,
       serverContent.comments,
+      clientContent.comments,
+      lastMergedContent.comments,
     ),
   };
   restoreDiscussionOffsets(result, markerKeys);
-  return result
+  return result;
 }
 
 export default {
-  serializeObject,
   makePatchableText,
   restoreDiscussionOffsets,
-  applyContentChanges,
-  getTextPatches,
-  getObjectPatches,
-  quickPatch,
-  mergeObjects,
   mergeContent,
 };
diff --git a/src/services/editorEngineSvc.js b/src/services/editorEngineSvc.js
index 0c906376..85ed0534 100644
--- a/src/services/editorEngineSvc.js
+++ b/src/services/editorEngineSvc.js
@@ -1,6 +1,7 @@
 import DiffMatchPatch from 'diff-match-patch';
 import cledit from '../libs/cledit';
-import clDiffUtils from '../libs/cldiffutils';
+import utils from './utils';
+import diffUtils from './diffUtils';
 import store from '../store';
 
 let clEditor;
@@ -34,26 +35,35 @@ function getDiscussionMarkers(discussion, discussionId, onMarker) {
   getMarker('offset1');
 }
 
-function syncDiscussionMarkers() {
-  const content = store.getters['content/current'];
-  Object.keys(discussionMarkers)
-    .forEach((markerKey) => {
-      const marker = discussionMarkers[markerKey];
-      // Remove marker if discussion was removed
-      const discussion = content.discussions[marker.discussionId];
-      if (!discussion || discussion[marker.offsetName] === undefined) {
-        clEditor.removeMarker(marker);
-        delete discussionMarkers[markerKey];
-      }
-    });
+function syncDiscussionMarkers(content, writeOffsets) {
+  Object.keys(discussionMarkers).forEach((markerKey) => {
+    const marker = discussionMarkers[markerKey];
+    // Remove marker if discussion was removed
+    const discussion = content.discussions[marker.discussionId];
+    if (!discussion || discussion[marker.offsetName] === undefined) {
+      clEditor.removeMarker(marker);
+      delete discussionMarkers[markerKey];
+    }
+  });
 
-  Object.keys(content.discussions)
-    .forEach((discussionId) => {
-      const discussion = content.discussions[discussionId];
-      getDiscussionMarkers(discussion, discussionId, (marker) => {
+  Object.keys(content.discussions).forEach((discussionId) => {
+    const discussion = content.discussions[discussionId];
+    getDiscussionMarkers(discussion, discussionId, writeOffsets
+      ? (marker) => {
         discussion[marker.offsetName] = marker.offset;
+      }
+      : (marker) => {
+        marker.offset = discussion[marker.offsetName];
       });
-    });
+  });
+}
+
+function removeDiscussionMarkers() {
+  Object.keys(discussionMarkers).forEach((markerKey) => {
+    const marker = discussionMarkers[markerKey];
+    clEditor.removeMarker(marker);
+    delete discussionMarkers[markerKey];
+  });
 }
 
 const diffMatchPatch = new DiffMatchPatch();
@@ -91,8 +101,6 @@ function reversePatches(patches) {
 
 export default {
   clEditor: null,
-  lastChange: 0,
-  lastExternalChange: 0,
   createClEditor(editorElt) {
     this.clEditor = cledit(editorElt, editorElt.parentNode);
     clEditor = this.clEditor;
@@ -100,42 +108,38 @@ export default {
     markerIdxMap = Object.create(null);
     discussionMarkers = {};
     clEditor.on('contentChanged', (text) => {
-      store.dispatch('content/patchCurrent', { text });
-      syncDiscussionMarkers();
-      const content = store.getters['content/current'];
+      const oldContent = store.getters['content/current'];
+      const newContent = {
+        ...oldContent,
+        discussions: utils.deepCopy(oldContent.discussions),
+        text,
+      };
+      syncDiscussionMarkers(newContent, true);
       if (!isChangePatch) {
         previousPatchableText = currentPatchableText;
-        currentPatchableText = clDiffUtils.makePatchableText(content, markerKeys, markerIdxMap);
+        currentPatchableText = diffUtils.makePatchableText(newContent, markerKeys, markerIdxMap);
       } else {
         // Take a chance to restore discussion offsets on undo/redo
-        content.text = currentPatchableText;
-        clDiffUtils.restoreDiscussionOffsets(content, markerKeys);
-        content.discussions.cl_each((discussion, discussionId) => {
-          getDiscussionMarkers(discussion, discussionId, (marker) => {
-            marker.offset = discussion[marker.offsetName];
-          });
-        });
+        diffUtils.restoreDiscussionOffsets(newContent, markerKeys);
+        syncDiscussionMarkers(newContent, false);
       }
+      store.dispatch('content/patchCurrent', newContent);
       isChangePatch = false;
-      this.lastChange = Date.now();
     });
     clEditor.addMarker(newDiscussionMarker0);
     clEditor.addMarker(newDiscussionMarker1);
   },
-  initClEditor(opts, reinit) {
+  initClEditor(opts) {
     const content = store.getters['content/current'];
-    const contentState = store.getters['contentState/current'];
     if (content) {
       const options = Object.assign({}, opts);
 
       if (contentId !== content.id) {
         contentId = content.id;
-        currentPatchableText = clDiffUtils.makePatchableText(content, markerKeys, markerIdxMap);
+        currentPatchableText = diffUtils.makePatchableText(content, markerKeys, markerIdxMap);
         previousPatchableText = currentPatchableText;
-        syncDiscussionMarkers();
-      }
-
-      if (reinit) {
+        syncDiscussionMarkers(content, false);
+        const contentState = store.getters['contentState/current'];
         options.content = content.text;
         options.selectionStart = contentState.selectionStart;
         options.selectionEnd = contentState.selectionEnd;
@@ -143,21 +147,21 @@ export default {
 
       options.patchHandler = {
         makePatches,
-        applyPatches: patches => applyPatches(patches),
+        applyPatches,
         reversePatches,
       };
       clEditor.init(options);
     }
   },
-  applyContent(isExternal) {
-    if (!clEditor) {
-      return null;
+  applyContent() {
+    if (clEditor) {
+      const content = store.getters['content/current'];
+      if (clEditor.setContent(content.text, true).range) {
+        // Marker will be recreated on contentChange
+        removeDiscussionMarkers();
+      } else {
+        syncDiscussionMarkers(content, false);
+      }
     }
-    if (isExternal) {
-      this.lastExternalChange = Date.now();
-    }
-    syncDiscussionMarkers();
-    const content = store.getters['content/current'];
-    return clEditor.setContent(content.text, isExternal);
   },
 };
diff --git a/src/services/editorSvc.js b/src/services/editorSvc.js
index 19bd71ed..ed96f349 100644
--- a/src/services/editorSvc.js
+++ b/src/services/editorSvc.js
@@ -29,7 +29,6 @@ const allowDebounce = (action, wait) => {
 
 const diffMatchPatch = new DiffMatchPatch();
 let lastContentId = null;
-let reinitClEditor = true;
 let instantPreview = true;
 let tokens;
 const anchorHash = {};
@@ -185,12 +184,11 @@ const editorSvc = Object.assign(new Vue(), { // Use a vue instance as an event b
         return 0.15;
       },
     };
-    editorEngineSvc.initClEditor(options, reinitClEditor);
+    editorEngineSvc.initClEditor(options);
     editorEngineSvc.clEditor.toggleEditable(true);
     const contentId = store.getters['content/current'].id;
     // Switch off the editor when no content is loaded
     editorEngineSvc.clEditor.toggleEditable(!!contentId);
-    reinitClEditor = false;
     this.restoreScrollPosition();
   },
 
@@ -573,30 +571,26 @@ const editorSvc = Object.assign(new Vue(), { // Use a vue instance as an event b
 
     const debouncedRefreshPreview = debounce(refreshPreview, 20);
 
-    let newSectionList;
-    let newSelectionRange;
-    const onEditorChanged = () => {
-      if (this.sectionList !== newSectionList) {
-        this.sectionList = newSectionList;
-        this.$emit('sectionList', this.sectionList);
-        if (instantPreview) {
-          refreshPreview();
-        } else {
-          debouncedRefreshPreview();
+    const onEditorChanged =
+      (sectionList = this.sectionList, selectionRange = this.selectionRange) => {
+        if (this.sectionList !== sectionList) {
+          this.sectionList = sectionList;
+          this.$emit('sectionList', this.sectionList);
+          if (instantPreview) {
+            refreshPreview();
+          } else {
+            debouncedRefreshPreview();
+          }
         }
-      }
-      if (this.selectionRange !== newSelectionRange) {
-        this.selectionRange = newSelectionRange;
-        this.$emit('selectionRange', this.selectionRange);
-      }
-      this.saveContentState();
-    };
-    const debouncedEditorChanged = debounce(onEditorChanged, 10);
+        if (this.selectionRange !== selectionRange) {
+          this.selectionRange = selectionRange;
+          this.$emit('selectionRange', this.selectionRange);
+        }
+        this.saveContentState();
+      };
 
-    editorEngineSvc.clEditor.selectionMgr.on('selectionChanged', (start, end, selectionRange) => {
-      newSelectionRange = selectionRange;
-      debouncedEditorChanged();
-    });
+    editorEngineSvc.clEditor.selectionMgr.on('selectionChanged',
+      (start, end, selectionRange) => onEditorChanged(undefined, selectionRange));
 
     /* -----------------------------
      * Inline images
@@ -684,14 +678,8 @@ const editorSvc = Object.assign(new Vue(), { // Use a vue instance as an event b
       triggerImgCacheGc();
     });
 
-    editorEngineSvc.clEditor.on('contentChanged', (content, diffs, sectionList) => {
-      newSectionList = sectionList;
-      if (instantPreview) {
-        onEditorChanged();
-      } else {
-        debouncedEditorChanged();
-      }
-    });
+    editorEngineSvc.clEditor.on('contentChanged',
+      (content, diffs, sectionList) => onEditorChanged(sectionList));
 
     this.$emit('inited');
 
@@ -716,20 +704,20 @@ const editorSvc = Object.assign(new Vue(), { // Use a vue instance as an event b
     //   }
     // })
 
-    // Watch file content properties changes
+    // Watch file content changes
     store.watch(
-      () => store.getters['content/current'].properties,
-      (properties) => {
-        // Track ID changes at the same time
-        const contentId = store.getters['content/current'].id;
+      () => store.getters['content/current'].hash,
+      () => {
+        const content = store.getters['content/current'];
+        // Track ID changes
         let initClEditor = false;
-        if (contentId !== lastContentId) {
-          reinitClEditor = true;
+        if (content.id !== lastContentId) {
           instantPreview = true;
-          lastContentId = contentId;
+          lastContentId = content.id;
           initClEditor = true;
         }
-        const options = extensionSvc.getOptions(properties, true);
+        // Track properties changes
+        const options = extensionSvc.getOptions(content.properties, true);
         if (JSON.stringify(options) !== JSON.stringify(editorSvc.options)) {
           editorSvc.options = options;
           editorSvc.initPrism();
@@ -739,6 +727,8 @@ const editorSvc = Object.assign(new Vue(), { // Use a vue instance as an event b
         if (initClEditor) {
           editorSvc.initClEditor();
         }
+        // Apply possible text and discussion changes
+        editorEngineSvc.applyContent();
       }, {
         immediate: true,
       });
diff --git a/src/services/localDbSvc.js b/src/services/localDbSvc.js
index 5a118900..a2732881 100644
--- a/src/services/localDbSvc.js
+++ b/src/services/localDbSvc.js
@@ -1,16 +1,15 @@
 import 'babel-polyfill';
-import 'indexeddbshim';
+import 'indexeddbshim/dist/indexeddbshim';
 import utils from './utils';
 import store from '../store';
 
-let indexedDB = window.indexedDB;
+const indexedDB = window.indexedDB;
 const localStorage = window.localStorage;
 const dbVersion = 1;
 const dbStoreName = 'objects';
 
-// Use the shim on Safari or when indexedDB is not available
-if (window.shimIndexedDB && (!indexedDB || (navigator.userAgent.indexOf('Chrome') === -1 && navigator.userAgent.indexOf('Safari') !== -1))) {
-  indexedDB = window.shimIndexedDB;
+if (!indexedDB) {
+  throw new Error('Your browser is not supported. Please upgrade to the latest version.');
 }
 
 const deleteMarkerMaxAge = 1000;
@@ -81,20 +80,20 @@ class Connection {
   }
 }
 
-const updatedMap = {};
+const hashMap = {};
 utils.types.forEach((type) => {
-  updatedMap[type] = Object.create(null);
+  hashMap[type] = Object.create(null);
 });
 
 const contentTypes = {
   content: true,
   contentState: true,
-  syncContent: true,
+  syncedContent: true,
 };
 
 export default {
   lastTx: 0,
-  updatedMap,
+  hashMap,
   connection: new Connection(),
 
   /**
@@ -145,7 +144,7 @@ export default {
         changes.forEach((item) => {
           this.readDbItem(item, storeItemMap);
           // If item is an old delete marker, remove it from the DB
-          if (!item.updated && lastTx - item.tx > deleteMarkerMaxAge) {
+          if (!item.hash && lastTx - item.tx > deleteMarkerMaxAge) {
             dbStore.delete(item.id);
           }
         });
@@ -163,7 +162,7 @@ export default {
     const incrementedTx = this.lastTx + 1;
 
     // Remove deleted store items
-    Object.keys(this.updatedMap).forEach((type) => {
+    Object.keys(this.hashMap).forEach((type) => {
       // Remove this type only if file is deleted
       let checker = cb => id => !storeItemMap[id] && cb(id);
       if (contentTypes[type]) {
@@ -177,14 +176,14 @@ export default {
           }
         };
       }
-      Object.keys(this.updatedMap[type]).forEach(checker((id) => {
+      Object.keys(this.hashMap[type]).forEach(checker((id) => {
         // Put a delete marker to notify other tabs
         dbStore.put({
           id,
           type,
           tx: incrementedTx,
         });
-        delete this.updatedMap[type][id];
+        delete this.hashMap[type][id];
         this.lastTx = incrementedTx; // No need to read what we just wrote
       }));
     });
@@ -193,13 +192,13 @@ export default {
     Object.keys(storeItemMap).forEach((id) => {
       const storeItem = storeItemMap[id];
       // Store object has changed
-      if (this.updatedMap[storeItem.type][storeItem.id] !== storeItem.updated) {
+      if (this.hashMap[storeItem.type][storeItem.id] !== storeItem.hash) {
         const item = {
           ...storeItem,
           tx: incrementedTx,
         };
         dbStore.put(item);
-        this.updatedMap[item.type][item.id] = item.updated;
+        this.hashMap[item.type][item.id] = item.hash;
         this.lastTx = incrementedTx; // No need to read what we just wrote
       }
     });
@@ -210,20 +209,21 @@ export default {
    */
   readDbItem(dbItem, storeItemMap) {
     const existingStoreItem = storeItemMap[dbItem.id];
-    if (!dbItem.updated) {
+    if (!dbItem.hash) {
       // DB item is a delete marker
-      delete this.updatedMap[dbItem.type][dbItem.id];
+      delete this.hashMap[dbItem.type][dbItem.id];
       if (existingStoreItem) {
         // Remove item from the store
         store.commit(`${existingStoreItem.type}/deleteItem`, existingStoreItem.id);
         delete storeItemMap[existingStoreItem.id];
       }
-    } else if (this.updatedMap[dbItem.type][dbItem.id] !== dbItem.updated) {
+    } else if (this.hashMap[dbItem.type][dbItem.id] !== dbItem.hash) {
       // DB item is different from the corresponding store item
-      this.updatedMap[dbItem.type][dbItem.id] = dbItem.updated;
+      this.hashMap[dbItem.type][dbItem.id] = dbItem.hash;
       // Update content only if it exists in the store
       if (existingStoreItem || !contentTypes[dbItem.type]) {
         // Put item in the store
+        dbItem.tx = undefined;
         store.commit(`${dbItem.type}/setItem`, dbItem);
         storeItemMap[dbItem.id] = dbItem;
       }
@@ -248,13 +248,14 @@ export default {
         const request = dbStore.get(id);
         request.onsuccess = () => {
           const dbItem = request.result;
-          if (!dbItem || !dbItem.updated) {
+          if (!dbItem || !dbItem.hash) {
             onError();
           } else {
-            this.updatedMap[dbItem.type][dbItem.id] = dbItem.updated;
+            this.hashMap[dbItem.type][dbItem.id] = dbItem.hash;
             // Put item in the store
+            dbItem.tx = undefined;
             store.commit(`${dbItem.type}/setItem`, dbItem);
-            resolve(dbItem);
+            resolve();
           }
         };
       }, () => onError());
@@ -265,15 +266,12 @@ export default {
    * Unload from the store contents that haven't been opened recently
    */
   unloadContents() {
-    const lastOpenedFileIds = store.getters['data/lastOpenedIds']
-      .slice(0, 10).reduce((result, id) => {
-        result[id] = true;
-        return result;
-      }, {});
+    // Keep only last opened files in memory
+    const lastOpenedFileIds = new Set(store.getters['data/lastOpenedIds']);
     Object.keys(contentTypes).forEach((type) => {
-      store.getters(`${type}/items`).forEach((item) => {
+      store.getters[`${type}/items`].forEach((item) => {
         const [fileId] = item.id.split('/');
-        if (!lastOpenedFileIds[fileId]) {
+        if (!lastOpenedFileIds.has(fileId)) {
           // Remove item from the store
           store.commit(`${type}/deleteItem`, item.id);
         }
diff --git a/src/services/markdownConversionSvc.js b/src/services/markdownConversionSvc.js
index 4b294a6e..4bbf1eae 100644
--- a/src/services/markdownConversionSvc.js
+++ b/src/services/markdownConversionSvc.js
@@ -93,7 +93,7 @@ const deflistBlockTypeMap = createFlagMap([
 
 function hashArray(arr, valueHash, valueArray) {
   const hash = [];
-  arr.cl_each((str) => {
+  arr.forEach((str) => {
     let strHash = valueHash[str];
     if (strHash === undefined) {
       strHash = valueArray.length;
diff --git a/src/services/providers/gdriveAppDataProvider.js b/src/services/providers/gdriveAppDataProvider.js
index f48344de..eb51561f 100644
--- a/src/services/providers/gdriveAppDataProvider.js
+++ b/src/services/providers/gdriveAppDataProvider.js
@@ -1,24 +1,108 @@
 import store from '../../store';
-import googleHelper from '../helpers/googleHelper';
+import googleHelper from './helpers/googleHelper';
 
 export default {
-  downloadContent(token, fileId) {
-    const syncData = store.getters['data/syncDataByItemId'][`${fileId}/content`];
+  getChanges(token) {
+    return googleHelper.getChanges(token)
+      .then((result) => {
+        const changes = result.changes.filter((change) => {
+          if (change.file) {
+            try {
+              change.item = JSON.parse(change.file.name);
+            } catch (e) {
+              return false;
+            }
+            // Build sync data
+            change.syncData = {
+              id: change.fileId,
+              itemId: change.item.id,
+              type: change.item.type,
+              hash: change.item.hash,
+            };
+            change.file = undefined;
+          }
+          return true;
+        });
+        changes.nextPageToken = result.nextPageToken;
+        return changes;
+      });
+  },
+  setAppliedChanges(token, changes) {
+    const lastToken = store.getters['data/googleTokens'][token.sub];
+    if (changes.nextPageToken !== lastToken.nextPageToken) {
+      store.dispatch('data/setGoogleToken', {
+        ...lastToken,
+        nextPageToken: changes.nextPageToken,
+      });
+    }
+  },
+  saveItem(token, item, syncData, ifNotTooLate) {
+    return googleHelper.saveFile(
+      token,
+      JSON.stringify(item),
+      ['appDataFolder'],
+      null,
+      syncData && syncData.id,
+      ifNotTooLate,
+    )
+      .then(file => ({
+        // Build sync data
+        id: file.id,
+        itemId: item.id,
+        type: item.type,
+        hash: item.hash,
+      }));
+  },
+  removeItem(token, syncData, ifNotTooLate) {
+    return googleHelper.removeAppDataFile(token, syncData.id, ifNotTooLate)
+      .then(() => syncData);
+  },
+  downloadContent(token, syncLocation) {
+    const syncData = store.getters['data/syncDataByItemId'][`${syncLocation.fileId}/content`];
+    if (!syncData) {
+      return Promise.resolve();
+    }
     return googleHelper.downloadAppDataFile(token, syncData.id)
       .then((content) => {
-        if (content.updated !== syncData.updated) {
+        const item = JSON.parse(content);
+        if (item.hash !== syncData.hash) {
           store.dispatch('data/setSyncData', {
             ...store.getters['data/syncData'],
             [syncData.id]: {
               ...syncData,
-              updated: content.updated,
+              hash: item.hash,
             },
           });
         }
-        return {
-          history: [],
-          ...content,
-        };
+        return item;
       });
   },
+  uploadContent(token, item, syncLocation, ifNotTooLate) {
+    const syncData = store.getters['data/syncDataByItemId'][`${syncLocation.fileId}/content`];
+    if (syncData && syncData.hash === item.hash) {
+      return Promise.resolve();
+    }
+    return googleHelper.saveAppDataFile(
+      token,
+      JSON.stringify({
+        id: item.id,
+        type: item.type,
+        hash: item.hash,
+      }),
+      ['appDataFolder'],
+      JSON.stringify(item),
+      syncData && syncData.id,
+      ifNotTooLate,
+    )
+      .then(file => store.dispatch('data/setSyncData', {
+        ...store.getters['data/syncData'],
+        [file.id]: {
+          // Build sync data
+          id: file.id,
+          itemId: item.id,
+          type: item.type,
+          hash: item.hash,
+        },
+      }));
+  },
 };
diff --git a/src/services/providers/gdriveProvider.js b/src/services/providers/gdriveProvider.js
new file mode 100644
index 00000000..6e67e22f
--- /dev/null
+++ b/src/services/providers/gdriveProvider.js
@@ -0,0 +1,30 @@
+import store from '../../store';
+import googleHelper from './helpers/googleHelper';
+import providerUtils from './providerUtils';
+
+export default {
+  downloadContent(token, syncLocation) {
+    return googleHelper.downloadFile(token, syncLocation.gdriveFileId)
+      .then(content => providerUtils.parseContent(content));
+  },
+  uploadContent(token, item, syncLocation, ifNotTooLate) {
+    const file = store.state.file.itemMap[syncLocation.fileId];
+    const name = (file && file.name) || 'Untitled';
+    const parents = [];
+    if (syncLocation.gdriveParentId) {
+      parents.push(syncLocation.gdriveParentId);
+    }
+    return googleHelper.saveFile(
+      token,
+      name,
+      parents,
+      providerUtils.serializeContent(item),
+      syncLocation && syncLocation.gdriveId,
+      ifNotTooLate,
+    )
+      .then(gdriveFile => ({
+        ...syncLocation,
+        gdriveId: gdriveFile.id,
+      }));
+  },
+};
diff --git a/src/services/helpers/googleHelper.js b/src/services/providers/helpers/googleHelper.js
similarity index 51%
rename from src/services/helpers/googleHelper.js
rename to src/services/providers/helpers/googleHelper.js
index 95c9ea2a..3b7b4fa3 100644
--- a/src/services/helpers/googleHelper.js
+++ b/src/services/providers/helpers/googleHelper.js
@@ -1,9 +1,9 @@
-import utils from '../utils';
-import store from '../../store';
+import utils from '../../utils';
+import store from '../../../store';
 
 const clientId = '241271498917-t4t7d07qis7oc0ahaskbif3ft6tk63cd.apps.googleusercontent.com';
 const appsDomain = null;
-const tokenExpirationMargin = 10 * 60 * 1000; // 10 min
+const tokenExpirationMargin = 5 * 60 * 1000; // 5 min (Google tokens expire after 1h)
 
 // const scopeMap = {
 //   profile: [
@@ -23,6 +23,11 @@ const tokenExpirationMargin = 10 * 60 * 1000; // 10 min
 //   ],
 // };
 
+const gdriveAppDataScopes = ['https://www.googleapis.com/auth/drive.appdata'];
+const getGdriveScopes = () => [store.getters['data/settings'].gdriveFullAccess === true
+  ? 'https://www.googleapis.com/auth/drive'
+  : 'https://www.googleapis.com/auth/drive.file'];
+
 const request = (token, options) => utils.request({
   ...options,
   headers: {
@@ -31,17 +36,76 @@ const request = (token, options) => utils.request({
   },
 });
 
+function saveFile(refreshedToken, name, parents, media = null, fileId = null,
+  ifNotTooLate = cb => res => cb(res),
+) {
+  return Promise.resolve()
+    // Refreshing a token can take a while if an oauth window pops up, so check if it's too late
+    .then(ifNotTooLate(() => {
+      const options = {
+        method: 'POST',
+        url: 'https://www.googleapis.com/drive/v3/files',
+      };
+      const metadata = { name };
+      if (fileId) {
+        options.method = 'PATCH';
+        options.url = `https://www.googleapis.com/drive/v3/files/${fileId}`;
+      } else if (parents) {
+        // Parents field is not patchable
+        metadata.parents = parents;
+      }
+      if (media) {
+        const boundary = `-------${utils.uid()}`;
+        const delimiter = `\r\n--${boundary}\r\n`;
+        const closeDelimiter = `\r\n--${boundary}--`;
+        let multipartRequestBody = '';
+        multipartRequestBody += delimiter;
+        multipartRequestBody += 'Content-Type: application/json; charset=UTF-8\r\n\r\n';
+        multipartRequestBody += JSON.stringify(metadata);
+        multipartRequestBody += delimiter;
+        multipartRequestBody += 'Content-Type: text/plain; charset=UTF-8\r\n\r\n';
+        multipartRequestBody += media;
+        multipartRequestBody += closeDelimiter;
+        options.url = options.url.replace(
+          'https://www.googleapis.com/',
+          'https://www.googleapis.com/upload/');
+        return request(refreshedToken, {
+          ...options,
+          params: {
+            uploadType: 'multipart',
+          },
+          headers: {
+            'Content-Type': `multipart/mixed; boundary="${boundary}"`,
+          },
+          body: multipartRequestBody,
+        }).then(res => res.body);
+      }
+      return request(refreshedToken, {
+        ...options,
+        body: metadata,
+      }).then(res => res.body);
+    }));
+}
+
+function downloadFile(refreshedToken, id) {
+  return request(refreshedToken, {
+    method: 'GET',
+    url: `https://www.googleapis.com/drive/v3/files/${id}?alt=media`,
+    raw: true,
+  }).then(res => res.body);
+}
+
 export default {
   startOauth2(scopes, sub = null, silent = false) {
     return utils.startOauth2(
-        'https://accounts.google.com/o/oauth2/v2/auth', {
-          client_id: clientId,
-          response_type: 'token',
-          scope: scopes.join(' '),
-          hd: appsDomain,
-          login_hint: sub,
-          prompt: silent ? 'none' : null,
-        }, silent)
+      'https://accounts.google.com/o/oauth2/v2/auth', {
+        client_id: clientId,
+        response_type: 'token',
+        scope: scopes.join(' '),
+        hd: appsDomain,
+        login_hint: sub,
+        prompt: silent ? 'none' : null,
+      }, silent)
       // Call the tokeninfo endpoint
       .then(data => utils.request({
         method: 'POST',
@@ -116,8 +180,10 @@ export default {
       });
   },
   getChanges(token) {
-    let changes = [];
-    return this.refreshToken(['https://www.googleapis.com/auth/drive.appdata'], token)
+    const result = {
+      changes: [],
+    };
+    return this.refreshToken(gdriveAppDataScopes, token)
       .then((refreshedToken) => {
         const getPage = (pageToken = '1') => request(refreshedToken, {
           method: 'GET',
@@ -129,122 +195,39 @@ export default {
             fields: 'nextPageToken,newStartPageToken,changes(fileId,removed,file/name,file/properties)',
           },
         }).then((res) => {
-          changes = changes.concat(res.body.changes.filter(item => item.fileId));
+          result.changes = result.changes.concat(res.body.changes.filter(item => item.fileId));
           if (res.body.nextPageToken) {
             return getPage(res.body.nextPageToken);
           }
-          changes.forEach((change) => {
-            if (change.file) {
-              change.item = {
-                name: change.file.name,
-              };
-              if (change.file.properties) {
-                Object.keys(change.file.properties).forEach((key) => {
-                  change.item[key] = JSON.parse(change.file.properties[key]);
-                });
-              }
-              change.syncData = {
-                id: change.fileId,
-                itemId: change.item.id,
-                updated: change.item.updated,
-              };
-              change.file = undefined;
-            }
-          });
-          changes.nextPageToken = res.body.newStartPageToken;
-          return changes;
+          result.nextPageToken = res.body.newStartPageToken;
+          return result;
         });
 
         return getPage(refreshedToken.nextPageToken);
       });
   },
-  updateNextPageToken(token, changes) {
-    const lastToken = store.getters['data/googleTokens'][token.sub];
-    if (changes.nextPageToken !== lastToken.nextPageToken) {
-      store.dispatch('data/setGoogleToken', {
-        ...lastToken,
-        nextPageToken: changes.nextPageToken,
-      });
-    }
+  saveFile(token, name, parents, media, fileId, ifNotTooLate) {
+    return this.refreshToken(getGdriveScopes(), token)
+      .then(refreshedToken => saveFile(refreshedToken, name, parents, media, fileId, ifNotTooLate));
   },
-  saveItem(token, item, syncData, ifNotTooLate = cb => res => cb(res)) {
-    return this.refreshToken(['https://www.googleapis.com/auth/drive.appdata'], token)
-      // Refreshing a token can take a while if an oauth window pops up, so check if it's too late
-      .then(ifNotTooLate((refreshedToken) => {
-        const options = {
-          method: 'POST',
-          url: 'https://www.googleapis.com/drive/v3/files',
-        };
-        const metadata = {
-          name: item.name,
-          properties: {},
-        };
-        if (syncData) {
-          options.method = 'PATCH';
-          options.url = `https://www.googleapis.com/drive/v3/files/${syncData.id}`;
-        } else {
-          // Parents field is not patchable
-          metadata.parents = ['appDataFolder'];
-        }
-        Object.keys(item).forEach((key) => {
-          if (key !== 'name' && key !== 'tx') {
-            metadata.properties[key] = JSON.stringify(item[key]);
-          }
-        });
-        const media = null;
-        const boundary = `-------${utils.uid()}`;
-        const delimiter = `\r\n--${boundary}\r\n`;
-        const closeDelimiter = `\r\n--${boundary}--`;
-        if (media) {
-          let multipartRequestBody = '';
-          multipartRequestBody += delimiter;
-          multipartRequestBody += 'Content-Type: application/json\r\n\r\n';
-          multipartRequestBody += JSON.stringify(metadata);
-          multipartRequestBody += delimiter;
-          multipartRequestBody += 'Content-Type: application/json\r\n\r\n';
-          multipartRequestBody += JSON.stringify(media);
-          multipartRequestBody += closeDelimiter;
-          options.url = options.url.replace(
-            'https://www.googleapis.com/',
-            'https://www.googleapis.com/upload/');
-          return request(refreshedToken, {
-            ...options,
-            params: {
-              uploadType: 'multipart',
-            },
-            headers: {
-              'Content-Type': `multipart/mixed; boundary="${boundary}"`,
-            },
-            body: multipartRequestBody,
-          });
-        }
-        return request(refreshedToken, {
-          ...options,
-          body: metadata,
-        }).then(res => ({
-          // Build sync data
-          id: res.body.id,
-          itemId: item.id,
-          updated: item.updated,
-        }));
-      }));
+  saveAppDataFile(token, name, parents, media, fileId, ifNotTooLate) {
+    return this.refreshToken(gdriveAppDataScopes, token)
+      .then(refreshedToken => saveFile(refreshedToken, name, parents, media, fileId, ifNotTooLate));
   },
-  removeItem(token, syncData, ifNotTooLate = cb => res => cb(res)) {
-    return this.refreshToken(['https://www.googleapis.com/auth/drive.appdata'], token)
+  downloadFile(token, id) {
+    return this.refreshToken(getGdriveScopes(), token)
+      .then(refreshedToken => downloadFile(refreshedToken, id));
+  },
+  downloadAppDataFile(token, id) {
+    return this.refreshToken(gdriveAppDataScopes, token)
+      .then(refreshedToken => downloadFile(refreshedToken, id));
+  },
+  removeAppDataFile(token, id, ifNotTooLate = cb => res => cb(res)) {
+    return this.refreshToken(gdriveAppDataScopes, token)
       // Refreshing a token can take a while if an oauth window pops up, so check if it's too late
       .then(ifNotTooLate(refreshedToken => request(refreshedToken, {
         method: 'DELETE',
-        url: `https://www.googleapis.com/drive/v3/files/${syncData.id}`,
-      })).then(() => syncData));
-  },
-  downloadFile(refreshedToken, id) {
-    return request(refreshedToken, {
-      method: 'GET',
-      url: `https://www.googleapis.com/drive/v3/files/${id}?alt=media`,
-    }).then(res => res.body);
-  },
-  downloadAppDataFile(token, id) {
-    return this.refreshToken(['https://www.googleapis.com/auth/drive.appdata'], token)
-      .then(refreshedToken => this.downloadFile(refreshedToken, id));
+        url: `https://www.googleapis.com/drive/v3/files/${id}`,
+      })));
   },
 };
diff --git a/src/services/providers/providerUtils.js b/src/services/providers/providerUtils.js
new file mode 100644
index 00000000..9f47ff81
--- /dev/null
+++ b/src/services/providers/providerUtils.js
@@ -0,0 +1,48 @@
+import emptyContent from '../../data/emptyContent';
+
+const dataExtractor = /<!--stackedit_data:([A-Za-z0-9+/=\s]+)-->$/;
+
+// https://developer.mozilla.org/en/docs/Web/API/WindowBase64/Base64_encoding_and_decoding
+const b64Encode = str => btoa(encodeURIComponent(str).replace(/%([0-9A-F]{2})/g,
+  (match, p1) => String.fromCharCode(`0x${p1}`)));
+const b64Decode = str => decodeURIComponent(atob(str).split('').map(
+  c => `%${`00${c.charCodeAt(0).toString(16)}`.slice(-2)}`).join(''));
+
+export default {
+  serializeContent(content) {
+    let result = content.text;
+    const data = {};
+    if (content.properties.length > 1) {
+      data.properties = content.properties;
+    }
+    if (Object.keys(content.discussions).length) {
+      data.discussions = content.discussions;
+    }
+    if (Object.keys(content.comments).length) {
+      data.comments = content.comments;
+    }
+    if (content.history && content.history.length) {
+      data.history = content.history;
+    }
+    if (Object.keys(data).length) {
+      const serializedData = b64Encode(JSON.stringify(data)).replace(/(.{50})/g, '$1\n');
+      result += `<!--stackedit_data:\n${serializedData}-->`;
+    }
+    return result;
+  },
+  parseContent(serializedContent) {
+    const result = emptyContent();
+    result.text = serializedContent;
+    const extractedData = dataExtractor.exec(serializedContent);
+    if (extractedData) {
+      try {
+        const serializedData = extractedData[1].replace(/\s/g, '');
+        Object.assign(result, JSON.parse(b64Decode(serializedData)));
+        result.text = serializedContent.slice(0, extractedData.index);
+      } catch (e) {
+        // Ignore
+      }
+    }
+    return result;
+  },
+};
diff --git a/src/services/syncSvc.js b/src/services/syncSvc.js
index a46d0f64..25e090ed 100644
--- a/src/services/syncSvc.js
+++ b/src/services/syncSvc.js
@@ -2,18 +2,22 @@ import localDbSvc from './localDbSvc';
 import store from '../store';
 import welcomeFile from '../data/welcomeFile.md';
 import utils from './utils';
+import diffUtils from './diffUtils';
 import userActivitySvc from './userActivitySvc';
 import gdriveAppDataProvider from './providers/gdriveAppDataProvider';
-import googleHelper from './helpers/googleHelper';
 
 const lastSyncActivityKey = 'lastSyncActivity';
 let lastSyncActivity;
 const getStoredLastSyncActivity = () => parseInt(localStorage[lastSyncActivityKey], 10) || 0;
 const inactivityThreshold = 3 * 1000; // 3 sec
 const restartSyncAfter = 30 * 1000; // 30 sec
-const autoSyncAfter = utils.randomize(restartSyncAfter);
-const isSyncAvailable = () => window.navigator.onLine !== false &&
-  !!store.getters['data/loginToken'];
+const autoSyncAfter = utils.randomize(60 * 1000); // 60 sec
+
+const isDataSyncPossible = () => !!store.getters['data/loginToken'];
+const hasCurrentFileSyncLocations = () => !!store.getters['syncLocation/current'].length;
+
+const isSyncPossible = () => !store.state.offline &&
+  (isDataSyncPossible() || hasCurrentFileSyncLocations());
 
 function isSyncWindow() {
   const storedLastSyncActivity = getStoredLastSyncActivity();
@@ -48,13 +52,31 @@ function getSyncToken(syncLocation) {
   }
 }
 
+function cleanSyncedContent(syncedContent) {
+  // Clean syncHistory from removed syncLocations
+  Object.keys(syncedContent.syncHistory).forEach((syncLocationId) => {
+    if (syncLocationId !== 'main' && !store.state.syncLocation.itemMap[syncLocationId]) {
+      delete syncedContent.syncHistory[syncLocationId];
+    }
+  });
+  const allSyncLocationHashes = new Set([].concat(
+    ...Object.keys(syncedContent.syncHistory).map(
+      id => syncedContent.syncHistory[id])));
+  // Clean historyData from unused contents
+  Object.keys(syncedContent.historyData).map(hash => parseInt(hash, 10)).forEach((hash) => {
+    if (!allSyncLocationHashes.has(hash)) {
+      delete syncedContent.historyData[hash];
+    }
+  });
+}
+
 const loader = type => fileId => localDbSvc.loadItem(`${fileId}/${type}`)
   // Item does not exist, create it
   .catch(() => store.commit(`${type}/setItem`, {
     id: `${fileId}/${type}`,
   }));
 const loadContent = loader('content');
-const loadSyncContent = loader('syncContent');
+const loadSyncedContent = loader('syncedContent');
 const loadContentState = loader('contentState');
 
 function applyChanges(changes) {
@@ -73,9 +95,9 @@ function applyChanges(changes) {
       }
       delete syncData[change.fileId];
       syncDataChanged = true;
-    } else if (!change.removed && change.item && change.item.updated) {
-      if (!existingSyncData || (existingSyncData.updated !== change.item.updated && (
-        !existingItem || existingItem.updated !== change.item.updated
+    } else if (!change.removed && change.item && change.item.hash) {
+      if (!existingSyncData || (existingSyncData.hash !== change.item.hash && (
+        !existingItem || existingItem.hash !== change.item.hash
       ))) {
         // Put object in the store
         if (change.item.type !== 'content') { // Merge contents later
@@ -93,33 +115,184 @@ function applyChanges(changes) {
   }
 }
 
+const LAST_SENT = 0;
+const LAST_MERGED = 1;
+
+function syncFile(fileId) {
+  return loadSyncedContent(fileId)
+    .then(() => loadContent(fileId))
+    .then(() => {
+      const getContent = () => store.state.content.itemMap[`${fileId}/content`];
+      const getSyncedContent = () => store.state.syncedContent.itemMap[`${fileId}/syncedContent`];
+      const getSyncHistoryItem = syncLocationId => getSyncedContent().syncHistory[syncLocationId];
+      const downloadedLocations = {};
+
+      const isLocationSynced = syncLocation =>
+        getSyncHistoryItem(syncLocation.id)[LAST_SENT] === getContent().hash;
+
+      const syncOneContentLocation = () => {
+        const syncLocations = [
+          ...store.getters['syncLocation/groupedByFileId'][fileId] || [],
+        ];
+        if (isDataSyncPossible()) {
+          syncLocations.push({ id: 'main', provider: 'gdriveAppData', fileId });
+        }
+        let result;
+        syncLocations.some((syncLocation) => {
+          if (!downloadedLocations[syncLocation.id] || !isLocationSynced(syncLocation)) {
+            const provider = getSyncProvider(syncLocation);
+            const token = getSyncToken(syncLocation);
+            result = provider && token && provider.downloadContent(token, syncLocation)
+              .then((serverContent = null) => {
+                downloadedLocations[syncLocation.id] = true;
+
+                const syncedContent = getSyncedContent();
+                const syncHistoryItem = getSyncHistoryItem(syncLocation.id);
+                let mergedContent = (() => {
+                  const clientContent = utils.deepCopy(getContent());
+                  if (!serverContent) {
+                    // Sync location has not been created yet
+                    return clientContent;
+                  }
+                  if (serverContent.hash === clientContent.hash) {
+                    // Server and client contents are synced
+                    return clientContent;
+                  }
+                  if (syncedContent.historyData[serverContent.hash]) {
+                    // Server content has not changed or has already been merged
+                    return clientContent;
+                  }
+                  // Perform a merge with last merged content if any, or a simple fusion otherwise
+                  let lastMergedContent;
+                  serverContent.history.some((hash) => {
+                    lastMergedContent = syncedContent.historyData[hash];
+                    return lastMergedContent;
+                  });
+                  if (!lastMergedContent && syncHistoryItem) {
+                    lastMergedContent = syncedContent.historyData[syncHistoryItem[LAST_MERGED]];
+                  }
+                  return diffUtils.mergeContent(serverContent, clientContent, lastMergedContent);
+                })();
+
+                // Update content in store
+                store.commit('content/patchItem', {
+                  id: `${fileId}/content`,
+                  ...mergedContent,
+                });
+
+                // Retrieve content with new `hash` value and freeze it
+                mergedContent = utils.deepCopy(getContent());
+
+                // Make merged content history
+                const mergedContentHistory = serverContent ? serverContent.history.slice() : [];
+                let skipUpload = true;
+                if (mergedContentHistory[0] !== mergedContent.hash) {
+                  // Put merged content hash at the beginning of history
+                  mergedContentHistory.unshift(mergedContent.hash);
+                  // Server content is either out of sync or its history is incomplete, do upload
+                  skipUpload = false;
+                }
+                if (syncHistoryItem && syncHistoryItem[0] !== mergedContent.hash) {
+                  // Clean up by removing the hash we've previously added
+                  const idx = mergedContentHistory.indexOf(syncHistoryItem[LAST_SENT]);
+                  if (idx !== -1) {
+                    mergedContentHistory.splice(idx, 1);
+                  }
+                }
+
+                // Store server content if any, and merged content which will be sent if different
+                const newSyncedContent = utils.deepCopy(syncedContent);
+                const newSyncHistoryItem = newSyncedContent.syncHistory[syncLocation.id] || [];
+                newSyncedContent.syncHistory[syncLocation.id] = newSyncHistoryItem;
+                if (serverContent && (serverContent.hash === newSyncHistoryItem[LAST_SENT] ||
+                  serverContent.history.indexOf(newSyncHistoryItem[LAST_SENT]) !== -1)
+                ) {
+                  // The server has accepted the content we previously sent
+                  newSyncHistoryItem[LAST_MERGED] = newSyncHistoryItem[LAST_SENT];
+                }
+                newSyncHistoryItem[LAST_SENT] = mergedContent.hash;
+                newSyncedContent.historyData[mergedContent.hash] = mergedContent;
+
+                // Clean synced content from unused revisions
+                cleanSyncedContent(newSyncedContent);
+                // Store synced content
+                store.commit('syncedContent/patchItem', newSyncedContent);
+
+                if (skipUpload) {
+                  // Server content and merged content are equal, skip content upload
+                  return null;
+                }
+
+                // Prevent from sending new content too long after old content has been fetched
+                const syncStartTime = Date.now();
+                const ifNotTooLate = cb => (res) => {
+                  // No time to refresh a token...
+                  if (syncStartTime + 500 < Date.now()) {
+                    throw new Error('TOO_LATE');
+                  }
+                  return cb(res);
+                };
+
+                // Upload merged content
+                return provider.uploadContent(token, {
+                  ...mergedContent,
+                  history: mergedContentHistory,
+                }, syncLocation, ifNotTooLate);
+              })
+              .then(() => syncOneContentLocation());
+          }
+          return result;
+        });
+        return result;
+      };
+
+      return syncOneContentLocation();
+    })
+    .then(() => localDbSvc.unloadContents(), (err) => {
+      localDbSvc.unloadContents();
+      throw err;
+    })
+    .catch((err) => {
+      if (err && err.message === 'TOO_LATE') {
+        // Restart sync
+        return syncFile(fileId);
+      }
+      throw err;
+    });
+}
+
 function sync() {
   const googleToken = store.getters['data/loginToken'];
-  return googleHelper.getChanges(googleToken)
+  return gdriveAppDataProvider.getChanges(googleToken)
     .then((changes) => {
       // Apply changes
       applyChanges(changes);
-      googleHelper.updateNextPageToken(googleToken, changes);
+      gdriveAppDataProvider.setAppliedChanges(googleToken, changes);
 
       // Prevent from sending items too long after changes have been retrieved
       const syncStartTime = Date.now();
       const ifNotTooLate = cb => (res) => {
         if (syncStartTime + restartSyncAfter < Date.now()) {
-          throw new Error('too_late');
+          throw new Error('TOO_LATE');
         }
         return cb(res);
       };
 
       // Called until no item to save
       const saveNextItem = ifNotTooLate(() => {
-        const storeItemMap = store.getters.syncedItemMap;
+        const storeItemMap = {
+          ...store.state.file.itemMap,
+          ...store.state.folder.itemMap,
+          ...store.state.syncLocation.itemMap,
+          // Deal with contents later
+        };
         const syncDataByItemId = store.getters['data/syncDataByItemId'];
         let result;
         Object.keys(storeItemMap).some((id) => {
           const item = storeItemMap[id];
           const existingSyncData = syncDataByItemId[id];
-          if (!existingSyncData || existingSyncData.updated !== item.updated) {
-            result = googleHelper.saveItem(
+          if (!existingSyncData || existingSyncData.hash !== item.hash) {
+            result = gdriveAppDataProvider.saveItem(
               googleToken,
               // Use deepCopy to freeze objects
               utils.deepCopy(item),
@@ -138,15 +311,23 @@ function sync() {
 
       // Called until no item to remove
       const removeNextItem = ifNotTooLate(() => {
-        const storeItemMap = store.getters.syncedItemMap;
+        const storeItemMap = {
+          ...store.state.file.itemMap,
+          ...store.state.folder.itemMap,
+          ...store.state.syncLocation.itemMap,
+          ...store.state.content.itemMap, // Deal with contents now
+        };
         const syncData = store.getters['data/syncData'];
         let result;
         Object.keys(syncData).some((id) => {
           const existingSyncData = syncData[id];
-          if (!storeItemMap[existingSyncData.itemId]) {
+          if (!storeItemMap[existingSyncData.itemId] &&
+            // Remove content only if file has been removed
+            (existingSyncData.type !== 'content' || !storeItemMap[existingSyncData.itemId.split('/')[0]])
+          ) {
             // Use deepCopy to freeze objects
             const syncDataToRemove = utils.deepCopy(existingSyncData);
-            result = googleHelper.removeItem(googleToken, syncDataToRemove, ifNotTooLate)
+            result = gdriveAppDataProvider.removeItem(googleToken, syncDataToRemove, ifNotTooLate)
               .then(() => {
                 const syncDataCopy = { ...store.getters['data/syncData'] };
                 delete syncDataCopy[syncDataToRemove.id];
@@ -159,98 +340,45 @@ function sync() {
         return result;
       });
 
-      // Get content `updated` field from itemMap or from localDbSvc if not loaded
-      const getContentUpdated = (contentId) => {
-        const loadedContent = store.state.content.itemMap[contentId];
-        return loadedContent ? loadedContent.updated : localDbSvc.updatedMap.content[contentId];
+      const getOneFileIdToSync = () => {
+        const allContentIds = Object.keys({
+          ...store.state.content.itemMap,
+          ...store.getters['data/syncDataByType'].content,
+        });
+        let fileId;
+        allContentIds.some((contentId) => {
+          // Get content hash from itemMap or from localDbSvc if not loaded
+          const loadedContent = store.state.content.itemMap[contentId];
+          const hash = loadedContent ? loadedContent.hash : localDbSvc.hashMap.content[contentId];
+          const syncData = store.getters['data/syncDataByItemId'][contentId];
+          // Sync if item hash and syncData hash are different
+          if (!hash || !syncData || hash !== syncData.hash) {
+            [fileId] = contentId.split('/');
+          }
+          return fileId;
+        });
+        return fileId;
       };
 
-      // Download current file content and contents that have changed
-      const forceContentIds = { [`${store.getters['file/current'].id}/content`]: true };
-      store.getters['file/items'].forEach((file) => {
-        const contentId = `${file.id}/content`;
-        const updated = getContentUpdated(contentId);
-        const existingSyncData = store.getters['data/syncDataByItemId'][contentId];
-      });
-
-      const syncOneContent = fileId => loadSyncContent(fileId)
-        .then(() => loadContent(fileId))
-        .then(() => {
-          const getContent = () => store.state.content.itemMap[`${fileId}/content`];
-          const getSyncContent = () => store.state.content.itemMap[`${fileId}/syncContent`];
-
-          const syncLocations = [
-            { id: 'main', provider: 'gdriveAppData' },
-            ...getContent().syncLocations.filter(syncLocation => getSyncToken(syncLocation),
-          )];
-          const downloadedLocations = {};
-
-          const syncOneContentLocation = () => {
-            let result;
-            syncLocations.some((syncLocation) => {
-              if (!downloadedLocations[syncLocation.id]) {
-                const provider = getSyncProvider(syncLocation);
-                const token = getSyncToken(syncLocation);
-                result = provider && token && provider.downloadContent(fileId, syncLocation)
-                  .then((content) => {
-                    const syncContent = getSyncContent();
-                    const syncLocationData = syncContent.syncLocationData[syncLocation.id] || {
-                      history: [],
-                    };
-                    let lastMergedContent;
-                    syncLocationData.history.some((updated) => {
-                      if (content.history.indexOf(updated) !== -1) {
-
-                      }
-                      return lastMergedContent;
-                    });
-                  })
-                  .then(() => syncOneContentLocation());
-              }
-              return result;
-            });
-            return result;
-          };
-
-          return syncOneContentLocation();
-        })
-        .then(() => localDbSvc.unloadContents(), (err) => {
-          localDbSvc.unloadContents();
-          throw err;
-        });
-
-      // Called until no content to save
-      const saveNextContent = ifNotTooLate(() => {
-        let saveContentPromise;
-        const getSaveContentPromise = (contentId) => {
-          const updated = getContentUpdated(contentId);
-          const existingSyncData = store.getters['data/syncDataByItemId'][contentId];
-          if (!existingSyncData || existingSyncData.updated !== updated) {
-            saveContentPromise = localDbSvc.loadItem(contentId)
-              .then(content => googleHelper.saveItem(
-                googleToken,
-                // Use deepCopy to freeze objects
-                utils.deepCopy(content),
-                utils.deepCopy(existingSyncData),
-                ifNotTooLate,
-              ))
-              .then(resultSyncData => store.dispatch('data/patchSyncData', {
-                [resultSyncData.id]: resultSyncData,
-              }))
-              .then(() => saveNextContent());
-          }
-          return saveContentPromise;
-        };
-        Object.keys(localDbSvc.updatedMap.content)
-          .some(id => getSaveContentPromise(id, syncDataByItemId));
-        return saveContentPromise;
-      });
+      const syncNextFile = () => {
+        const fileId = getOneFileIdToSync();
+        return fileId && syncFile(fileId)
+          .then(() => syncNextFile());
+      };
 
       return Promise.resolve()
         .then(() => saveNextItem())
         .then(() => removeNextItem())
+        .then(() => {
+          if (store.getters['content/current'].id) {
+            // Sync current file first
+            return syncFile(store.getters['file/current'].id)
+              .then(() => syncNextFile());
+          }
+          return syncNextFile();
+        })
         .catch((err) => {
-          if (err && err.message === 'too_late') {
+          if (err && err.message === 'TOO_LATE') {
             // Restart sync
             return sync();
           }
@@ -266,19 +394,30 @@ function requestSync() {
       // Only start syncing when these conditions are met
       if (userActivitySvc.isActive() && isSyncWindow()) {
         clearInterval(intervalId);
-        if (!isSyncAvailable()) {
+        if (!isSyncPossible()) {
           // Cancel sync
           reject();
-        } else {
-          // Call setLastSyncActivity periodically
-          intervalId = utils.setInterval(() => setLastSyncActivity(), 1000);
-          setLastSyncActivity();
-          const cleaner = cb => (res) => {
-            clearInterval(intervalId);
-            cb(res);
-          };
-          sync().then(cleaner(resolve), cleaner(reject));
+          return;
         }
+
+        // Call setLastSyncActivity periodically
+        intervalId = utils.setInterval(() => setLastSyncActivity(), 1000);
+        setLastSyncActivity();
+        const cleaner = cb => (res) => {
+          clearInterval(intervalId);
+          cb(res);
+        };
+        Promise.resolve()
+          .then(() => {
+            if (isDataSyncPossible()) {
+              return sync();
+            }
+            if (hasCurrentFileSyncLocations()) {
+              return syncFile(store.getters['file/current'].id);
+            }
+            return null;
+          })
+          .then(cleaner(resolve), cleaner(reject));
       }
     };
     intervalId = utils.setInterval(() => attempt(), 1000);
@@ -288,7 +427,7 @@ function requestSync() {
 
 // Sync periodically
 utils.setInterval(() => {
-  if (isSyncAvailable() &&
+  if (isSyncPossible() &&
     userActivitySvc.isActive() &&
     isSyncWindow() &&
     isAutoSyncReady()
@@ -337,8 +476,8 @@ localDbSvc.sync()
         return Promise.resolve()
           // Load contentState from DB
           .then(() => loadContentState(currentFile.id))
-          // Load syncContent from DB
-          .then(() => loadSyncContent(currentFile.id))
+          // Load syncedContent from DB
+          .then(() => loadSyncedContent(currentFile.id))
           // Load content from DB
           .then(() => localDbSvc.loadItem(`${currentFile.id}/content`));
       }),
@@ -358,6 +497,6 @@ utils.setInterval(() => {
 }, 5000);
 
 export default {
-  isSyncAvailable,
+  isSyncPossible,
   requestSync,
 };
diff --git a/src/services/utils.js b/src/services/utils.js
index 80543509..ba241d49 100644
--- a/src/services/utils.js
+++ b/src/services/utils.js
@@ -14,14 +14,36 @@ const scriptLoadingPromises = Object.create(null);
 const origin = `${location.protocol}//${location.host}`;
 
 export default {
-  types: ['contentState', 'syncContent', 'content', 'file', 'folder', 'data'],
+  types: ['contentState', 'syncedContent', 'content', 'file', 'folder', 'syncLocation', 'data'],
   deepCopy(obj) {
-    return obj === undefined ? obj : JSON.parse(JSON.stringify(obj));
+    return obj == null ? obj : JSON.parse(JSON.stringify(obj));
+  },
+  serializeObject(obj) {
+    return obj === undefined ? obj : JSON.stringify(obj, (key, value) => {
+      if (Object.prototype.toString.call(value) !== '[object Object]') {
+        return value;
+      }
+      // Sort keys to have a predictable result
+      return Object.keys(value).sort().reduce((sorted, valueKey) => {
+        sorted[valueKey] = value[valueKey];
+        return sorted;
+      }, {});
+    });
   },
   uid() {
     crypto.getRandomValues(array);
     return array.cl_map(value => alphabet[value % radix]).join('');
   },
+  hash(str) {
+    let hash = 0;
+    if (!str) return hash;
+    for (let i = 0; i < str.length; i += 1) {
+      const char = str.charCodeAt(i);
+      hash = ((hash << 5) - hash) + char; // eslint-disable-line no-bitwise
+      hash |= 0; // eslint-disable-line no-bitwise
+    }
+    return hash;
+  },
   randomize(value) {
     return Math.floor((1 + (Math.random() * 0.2)) * value);
   },
@@ -73,6 +95,7 @@ export default {
       oauth2Context.iframeElt.onload = () => {
         oauth2Context.closeTimeout = setTimeout(() => oauth2Context.clean(), 5 * 1000);
       };
+      oauth2Context.iframeElt.onerror = () => oauth2Context.clean();
       oauth2Context.iframeElt.src = authorizeUrl;
       document.body.appendChild(oauth2Context.iframeElt);
       oauth2Context.wnd = oauth2Context.iframeElt.contentWindow;
@@ -96,7 +119,9 @@ export default {
         }
         clearTimeout(oauth2Context.closeTimeout);
         window.removeEventListener('message', oauth2Context.msgHandler);
-        oauth2Context.clean = () => { }; // Prevent from cleaning several times
+        oauth2Context.clean = () => {
+          // Prevent from cleaning several times
+        };
         if (errorMsg) {
           reject(new Error(errorMsg));
         }
@@ -130,9 +155,11 @@ export default {
     let retryAfter = 500; // 500 ms
     const maxRetryAfter = 30 * 1000; // 30 sec
     const config = Object.assign({}, configParam);
-    config.headers = Object.assign({
-      'Content-Type': 'application/json',
-    }, config.headers);
+    config.headers = Object.assign({}, config.headers);
+    if (config.body && typeof config.body === 'object') {
+      config.body = JSON.stringify(config.body);
+      config.headers['Content-Type'] = 'application/json';
+    }
 
     function parseHeaders(xhr) {
       const pairs = xhr.getAllResponseHeaders().trim().split('\n');
@@ -174,10 +201,12 @@ export default {
             headers: parseHeaders(xhr),
             body: xhr.responseText,
           };
-          try {
-            result.body = JSON.parse(result.body);
-          } catch (e) {
-            // ignore
+          if (!config.raw) {
+            try {
+              result.body = JSON.parse(result.body);
+            } catch (e) {
+              // ignore
+            }
           }
           if (result.status >= 200 && result.status < 300) {
             resolve(result);
@@ -202,7 +231,7 @@ export default {
         Object.keys(config.headers).forEach((key) => {
           xhr.setRequestHeader(key, config.headers[key]);
         });
-        xhr.send(config.body ? JSON.stringify(config.body) : null);
+        xhr.send(config.body || null);
       })
         .catch((err) => {
           // Try again later in case of retriable error
diff --git a/src/store/index.js b/src/store/index.js
index b2c5211d..d1af4c3e 100644
--- a/src/store/index.js
+++ b/src/store/index.js
@@ -3,10 +3,11 @@ import Vue from 'vue';
 import Vuex from 'vuex';
 import utils from '../services/utils';
 import contentState from './modules/contentState';
-import syncContent from './modules/syncContent';
+import syncedContent from './modules/syncedContent';
 import content from './modules/content';
 import file from './modules/file';
 import folder from './modules/folder';
+import syncLocation from './modules/syncLocation';
 import data from './modules/data';
 import layout from './modules/layout';
 import editor from './modules/editor';
@@ -18,9 +19,10 @@ Vue.use(Vuex);
 
 const debug = process.env.NODE_ENV !== 'production';
 
-export default new Vuex.Store({
+const store = new Vuex.Store({
   state: {
     ready: false,
+    offline: false,
   },
   getters: {
     allItemMap: (state) => {
@@ -28,23 +30,22 @@ export default new Vuex.Store({
       utils.types.forEach(type => Object.assign(result, state[type].itemMap));
       return result;
     },
-    syncedItemMap: (state) => {
-      const result = {};
-      ['file', 'folder'].forEach(type => Object.assign(result, state[type].itemMap));
-      return result;
-    },
   },
   mutations: {
     setReady: (state) => {
       state.ready = true;
     },
+    setOffline: (state, value) => {
+      state.offline = value;
+    },
   },
   modules: {
     contentState,
-    syncContent,
+    syncedContent,
     content,
     file,
     folder,
+    syncLocation,
     data,
     layout,
     editor,
@@ -55,3 +56,15 @@ export default new Vuex.Store({
   strict: debug,
   plugins: debug ? [createLogger()] : [],
 });
+
+function checkOffline() {
+  const isOffline = window.navigator.onLine === false;
+  if (isOffline !== store.state.offline) {
+    store.commit('setOffline', isOffline);
+  }
+}
+utils.setInterval(checkOffline, 1000);
+window.addEventListener('online', checkOffline);
+window.addEventListener('offline', checkOffline);
+
+export default store;
diff --git a/src/store/modules/contentState.js b/src/store/modules/contentState.js
index c022d7d9..1f13f3a8 100644
--- a/src/store/modules/contentState.js
+++ b/src/store/modules/contentState.js
@@ -1,7 +1,7 @@
 import moduleTemplate from './moduleTemplate';
 import empty from '../../data/emptyContentState';
 
-const module = moduleTemplate(empty);
+const module = moduleTemplate(empty, true);
 
 module.getters = {
   ...module.getters,
diff --git a/src/store/modules/data.js b/src/store/modules/data.js
index 4df49dd1..99ca5f00 100644
--- a/src/store/modules/data.js
+++ b/src/store/modules/data.js
@@ -1,7 +1,8 @@
 import moduleTemplate from './moduleTemplate';
+import utils from '../../services/utils';
 import defaultLocalSettings from '../../data/defaultLocalSettings';
 
-const itemTemplate = (id, data = {}) => ({ id, type: 'data', data, updated: 0 });
+const itemTemplate = (id, data = {}) => ({ id, type: 'data', data, hash: 0 });
 
 const empty = (id) => {
   switch (id) {
@@ -11,7 +12,7 @@ const empty = (id) => {
       return itemTemplate(id);
   }
 };
-const module = moduleTemplate(empty);
+const module = moduleTemplate(empty, true);
 
 const getter = id => state => (state.itemMap[id] || empty(id)).data;
 const setter = id => ({ commit }, data) => commit('setItem', itemTemplate(id, data));
@@ -73,6 +74,20 @@ module.getters.syncDataByItemId = (state, getters) => {
   });
   return result;
 };
+module.getters.syncDataByType = (state, getters) => {
+  const result = {};
+  utils.types.forEach((type) => {
+    result[type] = {};
+  });
+  const syncData = getters.syncData;
+  Object.keys(syncData).forEach((id) => {
+    const item = syncData[id];
+    if (result[item.type]) {
+      result[item.type][item.itemId] = item;
+    }
+  });
+  return result;
+};
 module.actions.patchSyncData = patcher('syncData');
 module.actions.setSyncData = setter('syncData');
 
diff --git a/src/store/modules/moduleTemplate.js b/src/store/modules/moduleTemplate.js
index 3de1b196..4c0928ac 100644
--- a/src/store/modules/moduleTemplate.js
+++ b/src/store/modules/moduleTemplate.js
@@ -1,10 +1,17 @@
 import Vue from 'vue';
+import utils from '../../services/utils';
+
+export default (empty, simpleHash = false) => {
+  // Use Date.now as a simple hash function, which is ok for not-synced types
+  const hashFunc = simpleHash ? Date.now : item => utils.hash(utils.serializeObject({
+    ...item,
+    hash: undefined,
+  }));
 
-export default (empty) => {
   function setItem(state, value) {
     const item = Object.assign(empty(value.id), value);
-    if (!item.updated) {
-      item.updated = Date.now();
+    if (!item.hash) {
+      item.hash = hashFunc(item);
     }
     Vue.set(state.itemMap, item.id, item);
   }
@@ -13,7 +20,7 @@ export default (empty) => {
     const item = state.itemMap[patch.id];
     if (item) {
       Object.assign(item, patch);
-      item.updated = Date.now(); // Trigger sync
+      item.hash = hashFunc(item);
       Vue.set(state.itemMap, item.id, item);
       return true;
     }
diff --git a/src/store/modules/syncContent.js b/src/store/modules/syncContent.js
deleted file mode 100644
index 6033f80f..00000000
--- a/src/store/modules/syncContent.js
+++ /dev/null
@@ -1,12 +0,0 @@
-import moduleTemplate from './moduleTemplate';
-import empty from '../../data/emptySyncContent';
-
-const module = moduleTemplate(empty);
-
-module.getters = {
-  ...module.getters,
-  current: (state, getters, rootState, rootGetters) =>
-    state.itemMap[`${rootGetters['file/current'].id}/syncContent`] || empty(),
-};
-
-export default module;
diff --git a/src/store/modules/syncLocation.js b/src/store/modules/syncLocation.js
new file mode 100644
index 00000000..7a0d823d
--- /dev/null
+++ b/src/store/modules/syncLocation.js
@@ -0,0 +1,21 @@
+import moduleTemplate from './moduleTemplate';
+import empty from '../../data/emptySyncLocation';
+
+const module = moduleTemplate(empty);
+
+module.getters = {
+  ...module.getters,
+  groupedByFileId: (state, getters) => {
+    const result = {};
+    getters.items.forEach((item) => {
+      const list = result[item.fileId] || [];
+      list.push(item);
+      result[item.fileId] = list;
+    });
+    return result;
+  },
+  current: (state, getters, rootState, rootGetters) =>
+    getters.groupedByFileId[rootGetters['file/current'].id] || [],
+};
+
+export default module;
diff --git a/src/store/modules/syncedContent.js b/src/store/modules/syncedContent.js
new file mode 100644
index 00000000..8e722702
--- /dev/null
+++ b/src/store/modules/syncedContent.js
@@ -0,0 +1,12 @@
+import moduleTemplate from './moduleTemplate';
+import empty from '../../data/emptySyncedContent';
+
+const module = moduleTemplate(empty, true);
+
+module.getters = {
+  ...module.getters,
+  current: (state, getters, rootState, rootGetters) =>
+    state.itemMap[`${rootGetters['file/current'].id}/syncedContent`] || empty(),
+};
+
+export default module;