[offline] Make last sync date and query modification date optional in mirror settings

It’s cleaner than using the epoch.

Author: Clément Le Provost

Source/Offline/MirrorSettings.swift

@@ -10,9 +10,9 @@ import Foundation
 
 
 class MirrorSettings {
-    var lastSyncDate: NSDate = NSDate(timeIntervalSince1970: 0)
+    var lastSyncDate: NSDate?
     var queries : [DataSelectionQuery] = []
-    var queriesModificationDate: NSDate = NSDate(timeIntervalSince1970: 0)
+    var queriesModificationDate: NSDate?
 
     /// Serialize the settings to a plist and save them to disk.
     func save(filePath: String) {
@@ -23,11 +23,11 @@ class MirrorSettings {
                 "maxObjects": query.maxObjects
             ])
         }
-        let settings = [
-            "lastSyncDate": lastSyncDate,
-            "queries": queriesJson,
-            "queriesModificationDate": queriesModificationDate
+        var settings: [String: AnyObject] = [
+            "queries": queriesJson
         ]
+        settings["lastSyncDate"] = lastSyncDate
+        settings["queriesModificationDate"] = queriesModificationDate
         (settings as NSDictionary).writeToFile(filePath, atomically: true)
     }
 

Source/Offline/MirroredIndex.swift

@@ -240,11 +240,23 @@ import Foundation
 
     private func isSyncDelayExpired() -> Bool {
         let currentDate = NSDate()
-        return currentDate.timeIntervalSinceDate(self.mirrorSettings.lastSyncDate) > self.delayBetweenSyncs
+        if let lastSyncDate = mirrorSettings.lastSyncDate {
+            return currentDate.timeIntervalSinceDate(lastSyncDate) > self.delayBetweenSyncs
+        } else {
+            return true
+        }
     }
 
     private func isMirrorSettingsDirty() -> Bool {
-        return self.mirrorSettings.queriesModificationDate.compare(self.mirrorSettings.lastSyncDate) == .OrderedDescending
+        if let queriesModificationDate = mirrorSettings.queriesModificationDate {
+            if let lastSyncDate = lastSuccessfulSyncDate {
+                return queriesModificationDate.compare(lastSyncDate) == .OrderedDescending
+            } else {
+                return true
+            }
+        } else {
+            return false
+        }
     }
 
     /// Refresh the local mirror.