Use incrementing version to reconcile setting sync conflicts instead of timestamp

www/assets/js/storage.js

@@ -1,4 +1,4 @@
-/* 
+/*
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
@@ -9,7 +9,7 @@
  * Save something to persistent storage.
  * @param {string} key
  * @param {string} value non-string values are converted to strings.
- * @param {bool} nochangeupdate If true, the lastchange setting won't be updated.
+ * @param {bool} nochangeupdate If true, the settings version won't be updated.
  * @returns {undefined}
  */
 function setStorage(key, value, nochangeupdate) {
@@ -18,7 +18,8 @@ function setStorage(key, value, nochangeupdate) {
     }
     localStorage.setItem(key, value);
     if (!nochangeupdate && !SETTINGS.synckeyblacklist.includes(key)) {
-        localStorage.setItem("lastchange", Date.now() / 1000);
+        var version = getStorage("syncstateversion") == null ? 0 : getStorage("syncstateversion");
+        localStorage.setItem("syncstateversion", Number(version) + 1);
     }
 }
 

www/assets/js/sync.js

@@ -6,15 +6,13 @@
 
 
 function gatherSyncData() {
+    if (getStorage("syncstateversion") == null) {
+        setStorage("syncstateversion", 0);
+    }
     var data = {
         localStorage: {},
-        changed: getStorage("lastchange") == null ? 0 : getStorage("lastchange"),
+        stateversion: getStorage("syncstateversion") == null ? 0 : getStorage("syncstateversion")
     };
-    if (!inStorage("lastsync")) {
-        // first time syncing to the server, let's make sure
-        // the server settings take precedence
-        data.changed = 1;
-    }
     var allitems = getAllStorage();
     for (var i = 0; i < allitems.length; i++) {
         var key = allitems[i].key;
@@ -27,33 +25,30 @@ function gatherSyncData() {
     return data;
 }
 
-function syncDataToLocalStorage(data) {
+function syncDataToLocalStorage(data, stateversion) {
     for (var key in data.localStorage) {
         if (data.localStorage.hasOwnProperty(key)) {
             setStorage(key, data.localStorage[key], true);
         }
     }
+    setStorage("syncstateversion", stateversion);
 }
 
-function resolveSync(remotedata) {
-    var localchangetime = getStorage("lastchange");
-    if (remotedata.changed == null) {
-        // The server has nothing, this is the first sync
-        return true;
-    }
-    if (localchangetime == null) {
-        // No local setting changes but since we've gotten this far,
-        // the server has stuff for us
-        syncDataToLocalStorage(remotedata);
+function resolveSync(remotedata, remotestateversion) {
+    var localstateversion = getStorage("syncstateversion");
+    console.log("Resolving sync: remote state: " + remotestateversion, "local state: " + localstateversion);
+    if (localstateversion == remotestateversion) {
+        // Server and client both have same version
+        console.log("Sync: server is same as client");
         return true;
-    }
-    if (localchangetime < remotedata.changed) {
-        // The server has newer stuff for us
-        syncDataToLocalStorage(remotedata);
+    } else if (Number(localstateversion) < Number(remotestateversion)) {
+        // Server has newer version
+        console.log("Sync: server is newer than client");
+        syncDataToLocalStorage(remotedata, remotestateversion);
         return true;
-    }
-    if (localchangetime >= remotedata.changed) {
-        // Our local data is newer or the same as the server copy
+    } else {
+        // We have the newer version
+        console.log("Sync: client is newer than server.");
         return true;
     }
     return false;
@@ -70,10 +65,11 @@ function syncNow(callback) {
     $.post(SETTINGS.syncapi, {
         username: username,
         password: password,
-        data: JSON.stringify(data)
+        data: JSON.stringify(data),
+        stateversion: data.stateversion
     }, function (resp) {
         if (resp.status == "OK") {
-            resolveSync(resp.data);
+            resolveSync(resp.data, resp.stateversion);
             setStorage("lastsync", Date.now() / 1000);
             if (typeof callback == "function") {
                 callback();

www/settings.js

@@ -367,7 +367,7 @@ var SETTINGS = {
     synckeyblacklist: [
         "username", "password", "trackingcodehistory", "packages",
         "user_latitude", "user_longitude", "geocode_cache", "scanevents",
-        "lastsync", "lastchange"
+        "lastsync", "lastchange", "syncstateversion"
     ],
     geocodecacheexpiry: 604800, // One week
     geocodeapi: "https://apis.netsyms.net/packagehelper/geocode.php",
@@ -377,7 +377,7 @@ var SETTINGS = {
     geoipapi: "https://data.netsyms.net/v1/net/geoip/key=packagehelper1/",
     sharelistapi: "https://apis.netsyms.net/packagehelper/sharepackagelist.php",
     loginurl: "https://apis.netsyms.net/packagehelper/login/",
-    syncapi: "https://apis.netsyms.net/packagehelper/sync.php",
+    syncapi: "https://apis.netsyms.net/packagehelper/sync_1.7.php",
     mapfixapi: "https://apis.netsyms.net/packagehelper/contribgeocode.php",
     addrlookupapi: "https://apis.netsyms.net/packagehelper/addresslookup.php"
 }