Add Azure cache implementation

Author: JimBobSquarePants

src/ImageSharp.Web.Providers.Azure/Caching/AzureBlobStorageCache.cs

@@ -0,0 +1,60 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System.IO;
+using System.Threading.Tasks;
+using Azure.Storage.Blobs;
+using Azure.Storage.Blobs.Models;
+using Microsoft.Extensions.Options;
+using SixLabors.ImageSharp.Web.Resolvers;
+using SixLabors.ImageSharp.Web.Resolvers.Azure;
+
+namespace SixLabors.ImageSharp.Web.Caching.Azure
+{
+    /// <summary>
+    /// Implements an Azure Blob Storage based cache.
+    /// </summary>
+    public class AzureBlobStorageCache : IImageCache
+    {
+        private readonly BlobContainerClient container;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AzureBlobStorageCache"/> class.
+        /// </summary>
+        /// <param name="cacheOptions">The cache options.</param>
+        public AzureBlobStorageCache(IOptions<AzureBlobStorageCacheOptions> cacheOptions)
+        {
+            Guard.NotNull(cacheOptions, nameof(cacheOptions));
+            AzureBlobStorageCacheOptions options = cacheOptions.Value;
+
+            this.container = new BlobContainerClient(options.ConnectionString, options.ContainerName);
+            this.container.CreateIfNotExistsAsync(PublicAccessType.None);
+        }
+
+        /// <inheritdoc/>
+        public async Task<IImageCacheResolver> GetAsync(string key)
+        {
+            BlobClient blob = this.container.GetBlobClient(key);
+
+            if (!await blob.ExistsAsync())
+            {
+                return null;
+            }
+
+            return new AzureBlobStorageCacheResolver(blob);
+        }
+
+        /// <inheritdoc/>
+        public Task SetAsync(string key, Stream stream, ImageCacheMetadata metadata)
+        {
+            BlobClient blob = this.container.GetBlobClient(key);
+
+            var headers = new BlobHttpHeaders
+            {
+                ContentType = metadata.ContentType,
+            };
+
+            return blob.UploadAsync(stream, httpHeaders: headers, metadata: metadata.ToDictionary());
+        }
+    }
+}

src/ImageSharp.Web.Providers.Azure/Caching/AzureBlobStorageCacheOptions.cs

@@ -0,0 +1,23 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+namespace SixLabors.ImageSharp.Web.Caching.Azure
+{
+    /// <summary>
+    /// Configuration options for the <see cref="AzureBlobStorageCache"/>.
+    /// </summary>
+    public class AzureBlobStorageCacheOptions
+    {
+        /// <summary>
+        /// Gets or sets the Azure Blob Storage connection string.
+        /// </summary>
+        public string ConnectionString { get; set; }
+
+        /// <summary>
+        /// Gets or sets the Azure Blob Storage container name.
+        /// Must conform to Azure Blob Storage containiner naming guidlines.
+        /// <see href="https://docs.microsoft.com/en-us/rest/api/storageservices/naming-and-referencing-containers--blobs--and-metadata#container-names"/>
+        /// </summary>
+        public string ContainerName { get; set; }
+    }
+}

src/ImageSharp.Web.Providers.Azure/Caching/AzureBlobStorageCacheResolver.cs

@@ -0,0 +1,39 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System.IO;
+using System.Threading.Tasks;
+using Azure.Storage.Blobs;
+using Azure.Storage.Blobs.Models;
+using SixLabors.ImageSharp.Web.Caching.Azure;
+
+namespace SixLabors.ImageSharp.Web.Resolvers.Azure
+{
+    /// <summary>
+    /// Provides means to manage image buffers within the <see cref="AzureBlobStorageCache"/>.
+    /// </summary>
+    public class AzureBlobStorageCacheResolver : IImageCacheResolver
+    {
+        private readonly BlobClient blob;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AzureBlobStorageCacheResolver"/> class.
+        /// </summary>
+        /// <param name="blob">The Azure blob.</param>
+        public AzureBlobStorageCacheResolver(BlobClient blob)
+            => this.blob = blob;
+
+        /// <inheritdoc/>
+        public async Task<ImageCacheMetadata> GetMetaDataAsync()
+        {
+            // I've had a good read through the SDK source and I believe we cannot get
+            // a 304 here since 'If-Modified-Since' header is not set by default.
+            BlobProperties properties = await this.blob.GetPropertiesAsync();
+            return ImageCacheMetadata.FromDictionary(properties.Metadata);
+        }
+
+        /// <inheritdoc/>
+        public async Task<Stream> OpenReadAsync()
+            => (await this.blob.DownloadAsync()).Value.Content;
+    }
+}

src/ImageSharp.Web.Providers.Azure/ImageSharp.Web.Providers.Azure.csproj

@@ -14,7 +14,7 @@
 
   <ItemGroup>
     <PackageReference Include="Azure.Storage.Blobs" />
-    <PackageReference Include="Microsoft.SourceLink.GitHub"/>
+    <PackageReference Include="Microsoft.SourceLink.GitHub" />
     <PackageReference Include="MinVer" PrivateAssets="All" />
   </ItemGroup>
 

src/ImageSharp.Web.Providers.Azure/Resolvers/AzureBlobStorageImageResolver.cs

@@ -1,9 +1,10 @@
 // Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
 using System.IO;
+using System.Net.Http.Headers;
 using System.Threading.Tasks;
-using Azure;
 using Azure.Storage.Blobs;
 using Azure.Storage.Blobs.Models;
 
@@ -20,15 +21,30 @@ public class AzureBlobStorageImageResolver : IImageResolver
         /// Initializes a new instance of the <see cref="AzureBlobStorageImageResolver"/> class.
         /// </summary>
         /// <param name="blob">The Azure blob.</param>
-        public AzureBlobStorageImageResolver(BlobClient blob) => this.blob = blob;
+        public AzureBlobStorageImageResolver(BlobClient blob)
+            => this.blob = blob;
 
         /// <inheritdoc/>
         public async Task<ImageMetadata> GetMetaDataAsync()
         {
             // I've had a good read through the SDK source and I believe we cannot get
             // a 304 here since 'If-Modified-Since' header is not set by default.
-            Response<BlobProperties> properties = await this.blob.GetPropertiesAsync();
-            return new ImageMetadata(properties.Value.LastModified.DateTime);
+            BlobProperties properties = (await this.blob.GetPropertiesAsync()).Value;
+
+            // Try to parse the max age from the source. If it's not zero then we pass it along
+            // to set the cache control headers for the response.
+            TimeSpan maxAge = TimeSpan.MinValue;
+            if (CacheControlHeaderValue.TryParse(properties.CacheControl, out CacheControlHeaderValue cacheControl))
+            {
+                // Weirdly passing null to TryParse returns true.
+                TimeSpan sourceMaxAge = cacheControl?.MaxAge.GetValueOrDefault() ?? TimeSpan.Zero;
+                if (sourceMaxAge != TimeSpan.Zero)
+                {
+                    maxAge = sourceMaxAge;
+                }
+            }
+
+            return new ImageMetadata(properties.LastModified.UtcDateTime, maxAge, properties.ContentLength);
         }
 
         /// <inheritdoc/>

src/ImageSharp.Web/Caching/PhysicalFileSystemCache.cs

@@ -47,7 +47,7 @@ public class PhysicalFileSystemCache : IImageCache
         /// <summary>
         /// Contains various format helper methods based on the current configuration.
         /// </summary>
-        private readonly FormatUtilities formatUtilies;
+        private readonly FormatUtilities formatUtilities;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="PhysicalFileSystemCache"/> class.
@@ -81,7 +81,7 @@ public PhysicalFileSystemCache(
             this.fileProvider = new PhysicalFileProvider(this.cacheRootPath);
             this.options = options.Value;
             this.cachedNameLength = (int)this.options.CachedNameLength;
-            this.formatUtilies = formatUtilities;
+            this.formatUtilities = formatUtilities;
         }
 
         /// <inheritdoc/>
@@ -143,7 +143,7 @@ public async Task SetAsync(string key, Stream stream, ImageCacheMetadata metadat
         /// <param name="metaData">The image metadata.</param>
         /// <returns>The <see cref="string"/>.</returns>
         private string ToImageFilePath(string path, in ImageCacheMetadata metaData)
-            => $"{path}.{this.formatUtilies.GetExtensionFromContentType(metaData.ContentType)}";
+            => $"{path}.{this.formatUtilities.GetExtensionFromContentType(metaData.ContentType)}";
 
         /// <summary>
         /// Gets the path to the image file based on the supplied root.

src/ImageSharp.Web/Caching/PhysicalFileSystemCacheResolver.cs

@@ -4,11 +4,12 @@
 using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.FileProviders;
+using SixLabors.ImageSharp.Web.Caching;
 
 namespace SixLabors.ImageSharp.Web.Resolvers
 {
     /// <summary>
-    /// Provides means to manage image buffers within the physical file system cache.
+    /// Provides means to manage image buffers within the <see cref="PhysicalFileSystemCache"/>.
     /// </summary>
     public class PhysicalFileSystemCacheResolver : IImageCacheResolver
     {