PowderCoatingLogix/src/PowderCoating.Application/Services/AzureBlobStorageService.cs

using Azure.Storage.Blobs;
using Azure.Storage.Blobs.Models;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using PowderCoating.Application.Configuration;
using PowderCoating.Application.Interfaces;

namespace PowderCoating.Application.Services;

/// <summary>
/// Azure Blob Storage wrapper that provides a uniform, result-tuple API for blob operations used
/// throughout the application (company logos, quote photos, documents). Containers are created
/// on first use with private access so blobs are never publicly URL-accessible; all serving goes
/// through controller actions that perform authorization checks before streaming bytes.
/// All methods catch exceptions and return a failure result rather than propagating so that blob
/// storage errors degrade gracefully without crashing the request pipeline.
/// </summary>
public class AzureBlobStorageService : IAzureBlobStorageService
{
    private readonly BlobServiceClient _blobServiceClient;
    private readonly ILogger<AzureBlobStorageService> _logger;

    /// <summary>
    /// Initializes the service using the storage connection string from <see cref="StorageSettings"/>.
    /// The <see cref="BlobServiceClient"/> is created once and reused across requests because it is
    /// registered as a singleton in DI, matching the thread-safe design of the Azure SDK client.
    /// </summary>
    public AzureBlobStorageService(
        IOptions<StorageSettings> settings,
        ILogger<AzureBlobStorageService> logger)
    {
        _blobServiceClient = new BlobServiceClient(settings.Value.ConnectionString);
        _logger = logger;
    }

    /// <summary>
    /// Uploads a stream to the specified blob path, setting the Content-Type header so that the
    /// Azure portal and download responses report the correct MIME type. The container is created
    /// with private access if it does not already exist, preventing accidental public exposure.
    /// </summary>
    public async Task<(bool Success, string ErrorMessage)> UploadAsync(
        string containerName,
        string blobName,
        Stream content,
        string contentType)
    {
        try
        {
            var containerClient = _blobServiceClient.GetBlobContainerClient(containerName);
            await containerClient.CreateIfNotExistsAsync(PublicAccessType.None);

            var blobClient = containerClient.GetBlobClient(blobName);
            var uploadOptions = new BlobUploadOptions
            {
                HttpHeaders = new BlobHttpHeaders { ContentType = contentType }
            };

            await blobClient.UploadAsync(content, uploadOptions);

            _logger.LogInformation("Uploaded blob {BlobName} to container {Container}", blobName, containerName);
            return (true, string.Empty);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error uploading blob {BlobName} to container {Container}", blobName, containerName);
            return (false, "An error occurred while uploading the file.");
        }
    }

    /// <summary>
    /// Downloads a blob's full content into memory and returns the byte array along with the
    /// stored Content-Type. Checks blob existence before attempting download to return a clean
    /// "not found" failure rather than surfacing an Azure SDK exception to the caller.
    /// </summary>
    public async Task<(bool Success, byte[] Content, string ContentType, string ErrorMessage)> DownloadAsync(
        string containerName,
        string blobName)
    {
        try
        {
            var containerClient = _blobServiceClient.GetBlobContainerClient(containerName);
            var blobClient = containerClient.GetBlobClient(blobName);

            if (!await blobClient.ExistsAsync())
            {
                return (false, Array.Empty<byte>(), string.Empty, "File not found.");
            }

            var response = await blobClient.DownloadContentAsync();
            var content = response.Value.Content.ToArray();
            var contentType = response.Value.Details.ContentType ?? "application/octet-stream";

            return (true, content, contentType, string.Empty);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error downloading blob {BlobName} from container {Container}", blobName, containerName);
            return (false, Array.Empty<byte>(), string.Empty, "An error occurred while retrieving the file.");
        }
    }

    /// <summary>
    /// Deletes a blob if it exists, returning success in both the deleted and not-found cases.
    /// Using <c>DeleteIfExistsAsync</c> makes the operation idempotent so callers do not need to
    /// check existence before deleting (e.g., during temp photo cleanup after quote promotion).
    /// </summary>
    public async Task<(bool Success, string ErrorMessage)> DeleteAsync(
        string containerName,
        string blobName)
    {
        try
        {
            var containerClient = _blobServiceClient.GetBlobContainerClient(containerName);
            var blobClient = containerClient.GetBlobClient(blobName);

            var deleted = await blobClient.DeleteIfExistsAsync();

            if (deleted)
                _logger.LogInformation("Deleted blob {BlobName} from container {Container}", blobName, containerName);

            return (true, string.Empty);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error deleting blob {BlobName} from container {Container}", blobName, containerName);
            return (false, "An error occurred while deleting the file.");
        }
    }

    /// <summary>
    /// Checks whether a blob exists without downloading its content.
    /// Used by controllers to determine whether to show a file download link or a
    /// "no file available" placeholder, avoiding a full download just for an existence check.
    /// Returns <c>false</c> on exception so that storage errors do not surface as unhandled faults.
    /// </summary>
    public async Task<bool> ExistsAsync(string containerName, string blobName)
    {
        try
        {
            var containerClient = _blobServiceClient.GetBlobContainerClient(containerName);
            var blobClient = containerClient.GetBlobClient(blobName);
            var response = await blobClient.ExistsAsync();
            return response.Value;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error checking existence of blob {BlobName} in container {Container}", blobName, containerName);
            return false;
        }
    }

    /// <summary>
    /// Lists all blob names in a container that share the given prefix, used by
    /// <see cref="QuotePhotoService"/> to enumerate all photos belonging to a temp session or a
    /// specific quote. Returns an empty enumerable on exception so callers can safely iterate
    /// without null checks.
    /// </summary>
    public async Task<IEnumerable<string>> ListBlobsByPrefixAsync(string containerName, string prefix)
    {
        try
        {
            var containerClient = _blobServiceClient.GetBlobContainerClient(containerName);
            var names = new List<string>();
            await foreach (var item in containerClient.GetBlobsAsync(prefix: prefix))
                names.Add(item.Name);
            return names;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error listing blobs with prefix {Prefix} in container {Container}", prefix, containerName);
            return [];
        }
    }
}