social-media/backend/Infrastructure/BlobStorage/Services/AzureBlobStorage.cs

using Azure;
using Azure.Storage.Blobs;
using Azure.Storage.Blobs.Models;
using Hutopy.Infrastructure.BlobStorage.Contracts;

namespace Hutopy.Infrastructure.BlobStorage.Services;

public class AzureBlobStorage : IBlobStorage
{
    private const long MaxUploadSize = 10 * 1024 * 1024; // 10 MB in bytes
    
    private readonly BlobServiceClient _blobServiceClient;
    private readonly ILogger<AzureBlobStorage> _logger;

    public AzureBlobStorage(IConfiguration configuration, ILogger<AzureBlobStorage> logger)
    {
        _logger = logger;
        var connectionString = configuration.GetConnectionString("AzureBlob");
        _blobServiceClient = new BlobServiceClient(connectionString);
    }

    /// <summary>
    /// Upload a file to microsoft azure blob storage.
    /// </summary>
    /// <param name="containerName">The name of the container where the file is stored.</param>
    /// <param name="blobName">The blob name (path within the container, include the file name).</param>
    /// <param name="stream"></param>
    /// <param name="contentType">The content type.</param>
    /// <param name="ct">The cancellation token</param>
    /// <returns></returns>
    public async Task<string> UploadFileAsync(
        string containerName, 
        string blobName, 
        Stream stream,
        string contentType,
        CancellationToken ct = default)
    {
        // Read the file stream into a memory stream to determine the length
        // WATCH FOR MEMORY USAGE USING THE MEMORY STREAM.
        stream.Position = 0;

        // Check if the file size exceeds the maximum upload size
        if (stream.Length > MaxUploadSize)
        {
            _logger.LogError(
                $"Blob storage: File size exceeds the maximum allowed size of {MaxUploadSize} bytes.");
            throw new InvalidOperationException(
                $"Blob storage: File size exceeds the maximum allowed size of {MaxUploadSize} bytes.");
        }

        // Validate content type
        if (!ContentTypes.IsAllowed(contentType, stream))
        {
            _logger.LogError(
                $"Blob storage: Unsupported file type {contentType}.");
            throw new InvalidOperationException("Unsupported file type.");
        }

        try
        {
            // Get a reference to a container
            var containerClient = _blobServiceClient.GetBlobContainerClient(containerName);

            // Create the container if it does not exist
            await containerClient.CreateIfNotExistsAsync(
                PublicAccessType.Blob,
                cancellationToken: ct);

            // Get a reference to a blob
            var blobClient = containerClient.GetBlobClient(blobName);

            // Define the BlobHttpHeaders to include the content type
            var blobHttpHeaders = new BlobHttpHeaders { ContentType = contentType };

            // Upload the file
            var response = await blobClient.UploadAsync(
                stream,
                new BlobUploadOptions { HttpHeaders = blobHttpHeaders },
                ct);

            var fileUri = blobClient.Uri.ToString();

            _logger.LogInformation(
                """
                Blob storage: Status [   {ResponseStatus}   ] 
                Uploaded [  {BlobName}  ] to the container [  {ContainerName}  ] 
                with contentType [  {ContentType}  ] 
                with a length of [   {StreamLength} bytes   ]
                with the uri [   {FileUri}   ]
                """,
                response.GetRawResponse().Status.ToString(),
                blobName,
                containerName,
                contentType,
                stream.Length,
                fileUri
            );

            // Return the URI of the uploaded blob
            return fileUri;
        }
        catch (RequestFailedException ex)
        {
            _logger.LogError($"Blob storage: Azure Storage request failed: {ex.Message}");
            throw;
        }
        catch (Exception ex)
        {
            _logger.LogError($"Blob storage: An error occurred: {ex.Message}");
            throw;
        }
    }

    /// <summary>
    /// Download a file to microsoft's azure blob storage.
    /// </summary>
    /// <param name="blobName">The blob name (path within the container).</param>
    /// <param name="containerName">The name of the container where the file is stored. (users)</param>
    /// <param name="ct">The cancellation token for the request</param>
    /// <returns></returns>
    public async Task<MemoryStream> DownloadFileAsync(
        string containerName,
        string blobName,
        CancellationToken ct = default)
    {
        try
        {
            // Get a reference to a container
            var containerClient = _blobServiceClient.GetBlobContainerClient(containerName);

            // Get a reference to a blob
            var blobClient = containerClient.GetBlobClient(blobName);

            // Download the blob to a stream
            BlobDownloadInfo download = await blobClient.DownloadAsync(ct);
            
            MemoryStream memoryStream = new();
            await download.Content.CopyToAsync(memoryStream, ct);
            memoryStream.Position = 0; // Ensure the stream is at the beginning

            return memoryStream;
        }
        catch (RequestFailedException ex)
        {
            _logger.LogError($"Azure Storage request failed: {ex.Message}");
            throw;
        }
        catch (Exception ex)
        {
            _logger.LogError($"An error occurred: {ex.Message}");
            throw;
        }
    }
}