might as well add cache control

Author: thefringeninja

src/SqlStreamStore.HAL.DevServer/SqlStreamStore.HAL.DevServer.csproj

@@ -2,9 +2,9 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>netcoreapp2.1</TargetFramework>
-    <LangVersion>latest</LangVersion>
     <RuntimeIdentifiers>alpine.3.7-x64</RuntimeIdentifiers>
     <TargetLatestRuntimePatch>true</TargetLatestRuntimePatch>
+    <LangVersion>7.3</LangVersion>
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.AspNetCore.Hosting" Version="2.1.1" />

src/SqlStreamStore.HAL.Tests/SqlStreamStore.HAL.Tests.csproj

@@ -14,6 +14,7 @@
     <DebugSymbols>true</DebugSymbols>
     <GenerateRuntimeConfigurationFiles>true</GenerateRuntimeConfigurationFiles>
     <NoWarn>1591</NoWarn>
+    <LangVersion>7.3</LangVersion>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\SqlStreamStore.HAL\SqlStreamStore.HAL.csproj" />

src/SqlStreamStore.HAL/Constants.cs

@@ -10,6 +10,7 @@ public static class Headers
             public const string Location = "Location";
             public const string ETag = "ETag";
             public const string IfNoneMatch = "If-None-Match";
+            public const string CacheControl = "Cache-Control";
 
             public static class ContentTypes
             {

src/SqlStreamStore.HAL/Response.cs

@@ -14,10 +14,7 @@ public Response(HALResponse hal, int statusCode = 200)
         {
             Hal = hal;
             StatusCode = statusCode;
-            Headers = new Dictionary<string, string[]>(StringComparer.OrdinalIgnoreCase)
-            {
-                ["Cache-Control"] = new[] { "max-age=0" }
-            };
+            Headers = new Dictionary<string, string[]>(StringComparer.OrdinalIgnoreCase);
         }
     }
 }

src/SqlStreamStore.HAL/SqlStreamStore.HAL.csproj

@@ -6,7 +6,7 @@
     <AssemblyTitle>Stream Store - HAL Server</AssemblyTitle>    
     <DebugSymbols>true</DebugSymbols>
     <NoWarn>1701;1702;1705;1591</NoWarn>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>7.3</LangVersion>
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Halcyon" Version="2.5.1" />

src/SqlStreamStore.HAL/SqlStreamStoreHalMiddleware.cs

@@ -16,6 +16,18 @@
 
     public static class SqlStreamStoreHalMiddleware
     {
+        private static readonly string[] s_NoCache =
+        {
+            "max-age=0",
+            "no-cache",
+            "must-revalidate"
+        };
+
+        private static readonly string[] s_CacheForOneYear =
+        {
+            "max-age=31536000"
+        };
+
         private static MidFunc CaseSensitiveQueryStrings => (context, next) =>
         {
             if(context.Request.QueryString != QueryString.Empty)
@@ -67,6 +79,23 @@ private static MidFunc MethodsNotAllowed(params string[] methods) => (context, n
             }
         };
 
+        private static MidFunc CacheControl => (context, next) =>
+        {
+            Task AddCacheControlHeaders()
+            {
+                context.Response.Headers[Constants.Headers.CacheControl] =
+                    context.Response.Headers.ContainsKey(Constants.Headers.ETag)
+                        ? s_NoCache
+                        : s_CacheForOneYear;
+
+                return Task.CompletedTask;
+            }
+
+            context.Response.OnStarting(AddCacheControlHeaders);
+
+            return next();
+        };
+
         public static IApplicationBuilder UseSqlStreamStoreHal(
             this IApplicationBuilder builder,
             IStreamStore streamStore)
@@ -81,6 +110,7 @@ public static IApplicationBuilder UseSqlStreamStoreHal(
                 .Use(CaseSensitiveQueryStrings)
                 .Use(AcceptHalJson)
                 .Use(HeadRequests)
+                .Use(CacheControl)
                 .UseIndex()
                 .Map("/stream", UseAllStream(streamStore))
                 .Map("/streams", UseStream(streamStore));