refactor

Author: thefringeninja

src/SqlStreamStore.HAL.Tests/StreamMessageTests.cs

@@ -26,7 +26,7 @@ public async Task read_single_message_stream()
             using(var response = await _fixture.HttpClient.GetAsync("/streams/a-stream/0"))
             {
                 response.StatusCode.ShouldBe(HttpStatusCode.OK);
-                response.Headers.ETag.ShouldBe(new EntityTagHeaderValue($@"""{writeResult.CurrentVersion};{writeResult.CurrentPosition}"""));
+                response.Headers.ETag.ShouldBe(new EntityTagHeaderValue($@"""{writeResult.CurrentVersion}"""));
 
                 var resource = await response.AsHal();
 

src/SqlStreamStore.HAL/ETag.cs

@@ -0,0 +1,33 @@
+namespace SqlStreamStore.HAL
+{
+    using System;
+
+    internal struct ETag : IEquatable<ETag>
+    {
+        private readonly string _value;
+        
+        public static ETag FromPosition(long position) => new ETag($@"""{position}""");
+        public static ETag FromStreamVersion(int streamVersion) => new ETag($@"""{streamVersion}""");
+        
+        private ETag(string value)
+        {
+            if(value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            if(value[0] != '"' || value[value.Length - 1] != '"')
+            {
+                throw new ArgumentException("ETags bust be enclosed in double quotes.", nameof(value));
+            }
+
+            _value = value;
+        }
+
+        public bool Equals(ETag other) => string.Equals(_value, other._value);
+        public override bool Equals(object obj) => obj is ETag other && Equals(other);
+        public override int GetHashCode() => _value.GetHashCode();
+        public static bool operator ==(ETag left, ETag right) => left.Equals(right);
+        public static bool operator !=(ETag left, ETag right) => !left.Equals(right);
+        public static implicit operator string(ETag etag) => etag._value;
+    }
+}

src/SqlStreamStore.HAL/Resources/StreamMessageResource.cs

@@ -81,7 +81,13 @@ public async Task<Response> Get(
                     .AddLinks(Links.Message(operation))
                     .AddLinks(Links.Find()))
             {
-                Headers = { [Constants.Headers.ETag] = new[] { $@"""{message.StreamVersion};{message.Position}""" } }
+                Headers =
+                {
+                    [Constants.Headers.ETag] = new string[]
+                    {
+                        ETag.FromStreamVersion(message.StreamVersion)
+                    }
+                }
             };
         }
 

src/SqlStreamStore.HAL/Resources/StreamMetadataResource.cs

@@ -48,7 +48,13 @@ public async Task<Response> Get(
                         Schemas.SetStreamMetadata),
                 result.MetadataStreamVersion >= 0 ? 200 : 404)
             {
-                Headers = { [Constants.Headers.ETag] = new[] { $@"""{result.MetadataStreamVersion}""" } }
+                Headers =
+                {
+                    [Constants.Headers.ETag] = new string[]
+                    {
+                        ETag.FromStreamVersion(result.MetadataStreamVersion)
+                    }
+                }
             };
 
             return response;