AzureBlobStorageCache.cs

// Copyright (c) Six Labors.
// Licensed under the Apache License, Version 2.0.

using System.IO;
using System.Threading.Tasks;
using Azure;
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);
        }

        /// <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());
        }

        /// <summary>
        /// Creates a new container under the specified account if a container
        /// with the same name does not already exist.
        /// </summary>
        /// <param name="options">The Azure Blob Storage cache options.</param>
        /// <param name="accessType">
        /// Optionally specifies whether data in the container may be accessed publicly and
        /// the level of access. <see cref="PublicAccessType.BlobContainer"/>
        /// specifies full public read access for container and blob data. Clients can enumerate
        /// blobs within the container via anonymous request, but cannot enumerate containers
        /// within the storage account. <see cref="PublicAccessType.Blob"/>
        /// specifies public read access for blobs. Blob data within this container can be
        /// read via anonymous request, but container data is not available. Clients cannot
        /// enumerate blobs within the container via anonymous request. <see cref="PublicAccessType.None"/>
        /// specifies that the container data is private to the account owner.
        /// </param>
        /// <returns>
        /// If the container does not already exist, a <see cref="Response{T}"/> describing the newly
        /// created container. If the container already exists, <see langword="null"/>.
        /// </returns>
        public static Response<BlobContainerInfo> CreateIfNotExists(
            AzureBlobStorageCacheOptions options,
            PublicAccessType accessType)
            => new BlobContainerClient(options.ConnectionString, options.ContainerName).CreateIfNotExists(accessType);
    }
}