From 8833b4eb1e65dda51abd24b453b86531b3f5f7a8 Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Fri, 13 Mar 2020 17:05:03 +0800
Subject: Abstract out data cache helper.

---
 Timeline/Helpers/DataCacheHelper.cs | 108 ++++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 Timeline/Helpers/DataCacheHelper.cs

(limited to 'Timeline/Helpers/DataCacheHelper.cs')

diff --git a/Timeline/Helpers/DataCacheHelper.cs b/Timeline/Helpers/DataCacheHelper.cs
new file mode 100644
index 00000000..c13aaddb
--- /dev/null
+++ b/Timeline/Helpers/DataCacheHelper.cs
@@ -0,0 +1,108 @@
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Microsoft.Net.Http.Headers;
+using System;
+using System.Linq;
+using System.Threading.Tasks;
+using Timeline.Models.Http;
+using static Timeline.Resources.Helper.DataCacheHelper;
+
+namespace Timeline.Helpers
+{
+    public interface ICacheableData
+    {
+        string Type { get; }
+#pragma warning disable CA1819 // Properties should not return arrays
+        byte[] Data { get; }
+#pragma warning restore CA1819 // Properties should not return arrays
+        DateTime? LastModified { get; }
+    }
+
+    public class CacheableData : ICacheableData
+    {
+        public CacheableData(string type, byte[] data, DateTime? lastModified)
+        {
+            Type = type;
+            Data = data;
+            LastModified = lastModified;
+        }
+
+        public string Type { get; set; }
+#pragma warning disable CA1819 // Properties should not return arrays
+        public byte[] Data { get; set; }
+#pragma warning restore CA1819 // Properties should not return arrays
+        public DateTime? LastModified { get; set; }
+    }
+
+    public interface ICacheableDataProvider
+    {
+        Task<string> GetDataETag();
+        Task<ICacheableData> GetData();
+    }
+
+    public class DelegateCacheableDataProvider : ICacheableDataProvider
+    {
+        private readonly Func<Task<string>> _getDataETagDelegate;
+        private readonly Func<Task<ICacheableData>> _getDataDelegate;
+
+        public DelegateCacheableDataProvider(Func<Task<string>> getDataETagDelegate, Func<Task<ICacheableData>> getDataDelegate)
+        {
+            _getDataETagDelegate = getDataETagDelegate;
+            _getDataDelegate = getDataDelegate;
+        }
+
+        public Task<ICacheableData> GetData()
+        {
+            return _getDataDelegate();
+        }
+
+        public Task<string> GetDataETag()
+        {
+            return _getDataETagDelegate();
+        }
+    }
+
+    public static class DataCacheHelper
+    {
+        public static async Task<ActionResult> GenerateActionResult(Controller controller, ICacheableDataProvider provider)
+        {
+            const string IfNonMatchHeaderKey = "If-None-Match";
+            const string ETagHeaderKey = "ETag";
+
+            var loggerFactory = controller.HttpContext.RequestServices.GetRequiredService<ILoggerFactory>();
+            var logger = loggerFactory.CreateLogger(typeof(DataCacheHelper));
+
+            var eTagValue = await provider.GetDataETag();
+            eTagValue = '"' + eTagValue + '"';
+            var eTag = new EntityTagHeaderValue(eTagValue);
+
+
+            if (controller.Request.Headers.TryGetValue(IfNonMatchHeaderKey, out var value))
+            {
+                if (!EntityTagHeaderValue.TryParseStrictList(value, out var eTagList))
+                {
+                    logger.LogInformation(Log.Format(LogBadIfNoneMatch, ("Header Value", value)));
+                    return controller.BadRequest(ErrorResponse.Common.Header.IfNonMatch_BadFormat());
+                }
+
+                if (eTagList.FirstOrDefault(e => e.Equals(eTag)) != null)
+                {
+                    controller.Response.Headers.Add(ETagHeaderKey, eTagValue);
+                    logger.LogInformation(LogResultNotModified);
+                    return controller.StatusCode(StatusCodes.Status304NotModified);
+                }
+            }
+
+            var data = await provider.GetData();
+            logger.LogInformation(LogResultData);
+            return controller.File(data.Data, data.Type, data.LastModified, eTag);
+        }
+
+        public static Task<ActionResult> GenerateActionResult(Controller controller, Func<Task<string>> getDataETagDelegate, Func<Task<ICacheableData>> getDataDelegate)
+        {
+            return GenerateActionResult(controller, new DelegateCacheableDataProvider(getDataETagDelegate, getDataDelegate));
+        }
+    }
+}
-- 
cgit v1.2.3