feat(id_generator): swap params (#76)

Author: peterdeme

src/Utils/ActivityIdGenerator.cs

@@ -15,15 +15,22 @@ public static class ActivityIdGenerator
         private static long UuidEpochDifference = 122192928000000000;
 
         /// <summary>Generates an Activity ID for the given epoch timestamp and foreign ID.</summary>
-        public static Guid GenerateId(int epoch, string foreignId)
+        public static Guid GenerateId(string foreignId, int epoch)
         {
-            return GenerateId(Epoch.AddSeconds(epoch), foreignId);
+            return GenerateId(foreignId, Epoch.AddSeconds(epoch));
         }
 
-        /// <summary>Generates an Activity ID for the given timestamp and foreign ID.</summary>
-        public static Guid GenerateId(DateTime timestamp, string foreignId)
+        /// <summary>
+        /// Generates an Activity ID for the given timestamp and foreign ID.
+        /// <paramref name="timestamp"/> must be UTC.
+        /// </summary>
+        /// <exception cref="ArgumentException">Raised if the timestamp kind if not UTC.</exception>
+        public static Guid GenerateId(string foreignId, DateTime timestamp)
         {
-            var unixNano = timestamp.Ticks - EpochTicks;
+            // The backend doesn't care about milliseconds, so we truncate the date here.
+            var truncatedDate = new DateTime(timestamp.Year, timestamp.Month, timestamp.Day, timestamp.Hour, timestamp.Minute, timestamp.Second, DateTimeKind.Utc);
+
+            var unixNano = truncatedDate.Ticks - EpochTicks;
             var t = (ulong)(UuidEpochDifference + unixNano);
 
             long signedDigest;

tests/UtilsTests.cs

@@ -13,42 +13,43 @@ public class UtilsTests : TestBase
         public void TestIdGenerator()
         {
             // All these test cases are copied from the backend Go implementation
-            var first = ActivityIdGenerator.GenerateId(1451260800, "123sdsd333}}}");
+            var first = ActivityIdGenerator.GenerateId("123sdsd333}}}", 1451260800);
             Assert.AreEqual("f01c0000-acf5-11e5-8080-80006a8b5bc2", first.ToString());
 
-            var second = ActivityIdGenerator.GenerateId(1452862482, "6621934");
+            var second = ActivityIdGenerator.GenerateId("6621934", 1452862482);
             Assert.AreEqual("24f9d500-bb87-11e5-8080-80012ce3cc51", second.ToString());
 
-            var third = ActivityIdGenerator.GenerateId(1452862489, "6621938");
+            var third = ActivityIdGenerator.GenerateId("6621938", 1452862489);
             Assert.AreEqual("2925f280-bb87-11e5-8080-8001597d791f", third.ToString());
 
-            var fourth = ActivityIdGenerator.GenerateId(1452862492, "6621941");
+            var fourth = ActivityIdGenerator.GenerateId("6621941", 1452862492);
             Assert.AreEqual("2aefb600-bb87-11e5-8080-8001226fe2f2", fourth.ToString());
 
-            var fifth = ActivityIdGenerator.GenerateId(1452862496, "6621945");
+            var fifth = ActivityIdGenerator.GenerateId("6621945", 1452862496);
             Assert.AreEqual("2d521000-bb87-11e5-8080-800026259780", fifth.ToString());
 
-            var sixth = ActivityIdGenerator.GenerateId(1463914800, "top_issues_summary_557dc1d9e46fea0a4c000002");
+            var sixth = ActivityIdGenerator.GenerateId("top_issues_summary_557dc1d9e46fea0a4c000002", 1463914800);
             Assert.AreEqual("53dbf800-200c-11e6-8080-800023ec2877", sixth.ToString());
 
-            var seventh = ActivityIdGenerator.GenerateId(1452866055, "6625387");
+            var seventh = ActivityIdGenerator.GenerateId("6625387", 1452866055);
             Assert.AreEqual("76a65d80-bb8f-11e5-8080-8000530672db", seventh.ToString());
 
-            var eight = ActivityIdGenerator.GenerateId(1480174117, "UserPrediction:11127278");
+            var eight = ActivityIdGenerator.GenerateId("UserPrediction:11127278", 1480174117);
             Assert.AreEqual("00000080-b3ed-11e6-8080-8000444ef374", eight.ToString());
 
-            var nineth = ActivityIdGenerator.GenerateId(1481475921, "467791-42-follow");
+            var nineth = ActivityIdGenerator.GenerateId("467791-42-follow", 1481475921);
             Assert.AreEqual("ffa65e80-bfc3-11e6-8080-800027086507", nineth.ToString());
         }
 
         [Test]
         public async Task TestActivityIdSameAsBackend()
         {
+            var time = DateTime.UtcNow;
             var foreignId = Guid.NewGuid().ToString();
-            var inputAct = new Activity("1", "test", "1") { Time = DateTime.UtcNow, ForeignId = foreignId };
+            var inputAct = new Activity("1", "test", "1") { Time = time, ForeignId = foreignId };
             var activity = await this.UserFeed.AddActivityAsync(inputAct);
 
-            Assert.AreEqual(ActivityIdGenerator.GenerateId(activity.Time.Value, foreignId).ToString(), activity.Id);
+            Assert.AreEqual(ActivityIdGenerator.GenerateId(activity.ForeignId, time).ToString(), activity.Id);
         }
     }
 }