keep a guid when the snapshot is first generated and uplaoded to the server, and propagate it to all clients. this way we know if the server store gets completely wiped out

services/sync/nsBookmarksSyncService.js

@@ -110,10 +110,24 @@ BookmarksSyncService.prototype = {
   // DAVCollection object
   _dav: null,
 
-  // Last synced tree and version
+  // Last synced tree, version, and GUID (to detect if the store has
+  // been completely replaced and invalidate the snapshot)
   _snapshot: {},
   _snapshotVersion: 0,
 
+  __snapshotGuid: null,
+  get _snapshotGuid() {
+    if (!this.__snapshotGuid) {
+      let uuidgen = Cc["@mozilla.org/uuid-generator;1"].
+        getService(Ci.nsIUUIDGenerator);
+      this.__snapshotGuid = uuidgen.generateUUID().toString().replace(/[{}]/g, '');
+    }
+    return this.__snapshotGuid;
+  },
+  set _snapshotGuid(guid) {
+    this.__snapshotGuid = guid;
+  },
+
   get currentUser() {
     return this._dav.currentUser;
   },
@@ -172,7 +186,9 @@ BookmarksSyncService.prototype = {
     let flags = MODE_WRONLY | MODE_CREATE | MODE_TRUNCATE;
     fos.init(file, flags, PERMS_FILE, 0);
 
-    let out = {version: this._snapshotVersion, snapshot: this._snapshot};
+    let out = {version: this._snapshotVersion,
+               guid: this._snapshotGuid,
+               snapshot: this._snapshot};
     out = uneval(out);
     fos.write(out, out.length);
     fos.close();
@@ -202,9 +218,10 @@ BookmarksSyncService.prototype = {
     fis.close();
     json = eval(json);
 
-    if (json.snapshot && json.version) {
+    if (json && json.snapshot && json.version && json.guid) {
       this._snapshot = json.snapshot;
       this._snapshotVersion = json.version;
+      this._snapshotGuid = json.guid;
     }
   },
 
@@ -699,8 +716,9 @@ BookmarksSyncService.prototype = {
 
       this.notice("Server status: " + server.status);
       this.notice("Server version: " + server.version);
-      this.notice("Server version type: " + typeof server.version);
+      this.notice("Server guid: " + server.guid);
       this.notice("Local snapshot version: " + this._snapshotVersion);
+      this.notice("Local snapshot guid: " + this._snapshotGuid);
 
       for (version in server.deltas) {
         this.notice("Server delta " + version + ":\n" +
@@ -717,6 +735,13 @@ BookmarksSyncService.prototype = {
         return;
       }
 
+      if (this._snapshotGuid != server.guid) {
+        this.notice("Snapshot GUIDs differ, local snapshot is not valid");
+        this._snapshot = {};
+        this._snapshotVersion = -1;
+        this._snapshotGuid = server.guid;
+      }
+
       // 2) Generate local deltas from snapshot -> current client status
 
       let localUpdates = this._detectUpdates(this._snapshot, localJson);
@@ -799,7 +824,9 @@ BookmarksSyncService.prototype = {
         this._snapshot = this._getBookmarks();
         this._snapshotVersion = server['version'] + 1;
         server['deltas']['version ' + this._snapshotVersion] = serverChanges;
-        this._dav.PUT("bookmarks.delta", uneval(server['deltas']), handlers);
+
+        let out = {guid: this._snapshotGuid, deltas: server['deltas']};
+        this._dav.PUT("bookmarks.delta", uneval(out), handlers);
         data = yield;
 
         if (data.target.status >= 200 || data.target.status < 300) {
@@ -830,6 +857,9 @@ BookmarksSyncService.prototype = {
    *      2: ok, initial sync
    *   version:
    *     the latest version on the server
+   *   guid:
+   *     the guid that was created when the first snapshot was uploaded
+   *     (will only change if the server store is completely wiped)
    *   deltas:
    *     the individual deltas on the server
    *   updates:
@@ -840,7 +870,8 @@ BookmarksSyncService.prototype = {
     var generator = yield;
     var handlers = this._handlersForGenerator(generator);
 
-    var ret = {status: -1, version: -1, deltas: null, updates: null};
+    var ret = {status: -1, version: -1,
+      guid: null, deltas: null, updates: null};
 
     this.notice("Getting bookmarks delta from server");
     this._dav.GET("bookmarks.delta", handlers);
@@ -850,7 +881,9 @@ BookmarksSyncService.prototype = {
     case 200:
       this.notice("Got bookmarks delta from server");
 
-      ret.deltas = eval(data.target.responseText);
+      let resp = eval(data.target.responseText);
+      ret.guid = resp.guid;
+      ret.deltas = resp.deltas;
 
       let next = "version " + (this._snapshotVersion + 1);
       let cur = "version " + this._snapshotVersion;
@@ -858,7 +891,7 @@ BookmarksSyncService.prototype = {
       if (next in ret.deltas) {
         // Merge the matching deltas into one, find highest version
         let keys = [];
-        for (var vstr in ret.deltas) {
+        for (let vstr in ret.deltas) {
           let v = parseInt(vstr.replace(/^version /, ''));
           if (v > this._snapshotVersion)
             keys.push(vstr);
@@ -898,7 +931,7 @@ BookmarksSyncService.prototype = {
 
         // fixme: this is duplicated from above, need to do some refactoring
         let keys = [];
-        for (var vstr in ret.deltas) {
+        for (let vstr in ret.deltas) {
           let v = parseInt(vstr.replace(/^version /, ''));
           if (v > this._snapshotVersion)
             keys.push(vstr);
@@ -916,8 +949,9 @@ BookmarksSyncService.prototype = {
         ret.status = data.status;
         ret.updates = this._detectUpdates(this._snapshot, tmp);
         ret.version = data.version;
+        ret.guid = data.guid;
 
-        for (var vstr in ret.deltas) {
+        for (let vstr in ret.deltas) {
           let v = parseInt(vstr.replace(/^version /, ''));
           if (v > ret.version)
             ret.version = v;
@@ -950,7 +984,7 @@ BookmarksSyncService.prototype = {
     let generator = yield;
     let handlers = this._handlersForGenerator(generator);
 
-    var ret = {status: -1, version: -1, updates: null};
+    var ret = {status: -1, version: -1, guid: null, updates: null};
 
     this._dav.GET("bookmarks.json", handlers);
     data = yield;
@@ -962,6 +996,7 @@ BookmarksSyncService.prototype = {
       ret.status = 1;
       ret.updates = this._detectUpdates(this._snapshot, tmp.snapshot);
       ret.version = tmp.version;
+      ret.guid = tmp.guid;
       if (typeof ret.version != "number")
         this.notice("Error: version is not a number!  Full server response text:\n" +
                     data.target.responseText);
@@ -971,7 +1006,10 @@ BookmarksSyncService.prototype = {
 
       this._snapshot = localJson;
       this._snapshotVersion = 1;
-      this._dav.PUT("bookmarks.json", uneval({version: 1, snapshot: this._snapshot}), handlers);
+      this._dav.PUT("bookmarks.json", uneval({version: 1,
+                                              guid: this._snapshotGuid,
+                                              snapshot: this._snapshot}),
+                    handlers);
       data = yield;
 
       if (data.target.status >= 200 || data.target.status < 300) {