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using Api.Services.Contracts;
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using Api.Settings;
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using Microsoft.AspNetCore.Cors;
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using Microsoft.AspNetCore.Mvc;
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using Microsoft.AspNetCore.StaticFiles;
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using Microsoft.Extensions.Options;
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using Microsoft.Net.Http.Headers;
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namespace Api.Controllers
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{
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/// <summary>
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/// Controller for handling file downloads with support for resume and chunked transfers.
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/// Routes are prefixed with "api/filedownload".
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/// </summary>
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[ApiController]
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[Route("api/[controller]")]
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[EnableCors("FrontendOnly")]
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public sealed class FileDownloadController : ControllerBase
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{
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private readonly ILogger<FileDownloadController> _logger;
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private readonly FileStorageSettings _fileStorageSettings;
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private readonly IContentTypeProvider _contentTypeProvider;
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private readonly IEmailSender _emailSender;
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private const int BufferSize = 81920; // 80 KB buffer for optimal streaming performance
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public FileDownloadController(
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ILogger<FileDownloadController> logger,
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IOptions<FileStorageSettings> fileStorageSettings,
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IContentTypeProvider contentTypeProvider,
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IEmailSender emailSender)
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{
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_logger = logger;
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_fileStorageSettings = fileStorageSettings.Value;
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_contentTypeProvider = contentTypeProvider;
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_emailSender = emailSender;
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}
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/// <summary>
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/// Downloads a file with support for resume (range requests) and chunked transfer.
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/// Supports HTTP 206 Partial Content for efficient downloads and resume capability.
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/// Sends email notification when download starts.
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/// </summary>
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/// <param name="fileName">The name of the file to download (optional - uses default from settings if not provided)</param>
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/// <returns>File stream with appropriate headers for resumable downloads</returns>
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/// <response code="200">Full file content</response>
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/// <response code="206">Partial file content (range request)</response>
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/// <response code="404">File not found</response>
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/// <response code="416">Requested range not satisfiable</response>
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[HttpGet("{fileName?}")]
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[ProducesResponseType(StatusCodes.Status200OK)]
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[ProducesResponseType(StatusCodes.Status206PartialContent)]
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[ProducesResponseType(StatusCodes.Status404NotFound)]
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[ProducesResponseType(StatusCodes.Status416RangeNotSatisfiable)]
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public async Task<IActionResult> DownloadFile(string? fileName = null)
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{
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try
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{
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// Use default file name from settings if not provided
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if (string.IsNullOrWhiteSpace(fileName))
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{
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fileName = _fileStorageSettings.DefaultFileName;
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if (string.IsNullOrWhiteSpace(fileName))
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{
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_logger.LogWarning("No file name provided and no default file name configured");
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return BadRequest(new { error = "File name is required" });
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}
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_logger.LogInformation("Using default file name from settings: {FileName}", fileName);
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}
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// Get the file storage path (relative to solution folder)
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var fileStoragePath = _fileStorageSettings.Path;
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// If path is not absolute, make it relative to the solution root
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if (!Path.IsPathRooted(fileStoragePath))
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{
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var solutionRoot = Directory.GetCurrentDirectory();
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// Go up from api folder to solution root if needed
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if (solutionRoot.EndsWith("api", StringComparison.OrdinalIgnoreCase))
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{
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solutionRoot = Directory.GetParent(solutionRoot)?.FullName ?? solutionRoot;
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}
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fileStoragePath = Path.Combine(solutionRoot, fileStoragePath);
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}
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// Sanitize fileName to prevent directory traversal attacks
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var sanitizedFileName = Path.GetFileName(fileName);
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var filePath = Path.Combine(fileStoragePath, sanitizedFileName);
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// Verify file exists
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if (!System.IO.File.Exists(filePath))
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{
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_logger.LogWarning("File not found: {FilePath}", filePath);
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return NotFound(new { error = "File not found" });
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}
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var fileInfo = new FileInfo(filePath);
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var fileLength = fileInfo.Length;
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// Determine content type
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if (!_contentTypeProvider.TryGetContentType(filePath, out var contentType))
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{
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contentType = "application/octet-stream";
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}
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// Send email notification asynchronously (fire and forget with error handling)
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// This is done before streaming to ensure notification is sent for both full and range downloads
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var userIp = HttpContext.Connection.RemoteIpAddress?.ToString();
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_ = Task.Run(async () =>
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{
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try
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{
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await _emailSender.SendFileDownloadNotificationAsync(sanitizedFileName, userIp, CancellationToken.None);
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}
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catch (Exception ex)
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{
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_logger.LogError(ex, "Failed to send file download notification for {FileName}", sanitizedFileName);
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}
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});
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// Check if this is a range request
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var rangeHeader = Request.Headers[HeaderNames.Range].ToString();
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if (!string.IsNullOrEmpty(rangeHeader))
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{
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return await HandleRangeRequest(filePath, fileLength, contentType, rangeHeader, sanitizedFileName);
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}
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// Full file download
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_logger.LogInformation("Starting full file download: {FileName} ({FileSize} bytes)", sanitizedFileName, fileLength);
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var stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read, BufferSize, useAsync: true);
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Response.Headers.Append(HeaderNames.AcceptRanges, "bytes");
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Response.Headers.Append(HeaderNames.ContentLength, fileLength.ToString());
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return File(stream, contentType, sanitizedFileName, enableRangeProcessing: true);
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}
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catch (Exception ex)
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{
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_logger.LogError(ex, "Error downloading file: {FileName}", fileName);
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return StatusCode(StatusCodes.Status500InternalServerError, new { error = "An error occurred while downloading the file" });
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}
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}
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/// <summary>
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/// Handles HTTP range requests for partial content downloads and resume support.
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/// </summary>
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private async Task<IActionResult> HandleRangeRequest(
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string filePath,
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long fileLength,
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string contentType,
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string rangeHeader,
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string fileName)
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{
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try
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{
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// Parse range header (format: "bytes=start-end")
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var range = rangeHeader.Replace("bytes=", "").Split('-');
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long startByte = 0;
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long endByte = fileLength - 1;
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if (!string.IsNullOrEmpty(range[0]))
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{
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startByte = long.Parse(range[0]);
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}
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if (range.Length > 1 && !string.IsNullOrEmpty(range[1]))
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{
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endByte = long.Parse(range[1]);
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}
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// Validate range
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if (startByte > endByte || startByte >= fileLength)
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{
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_logger.LogWarning("Invalid range request: {Range} for file size {FileLength}", rangeHeader, fileLength);
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return StatusCode(StatusCodes.Status416RangeNotSatisfiable);
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}
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// Adjust end byte if it exceeds file length
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if (endByte >= fileLength)
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{
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endByte = fileLength - 1;
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}
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var contentLength = endByte - startByte + 1;
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_logger.LogInformation(
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"Range request for {FileName}: bytes {Start}-{End}/{Total} ({ContentLength} bytes)",
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fileName, startByte, endByte, fileLength, contentLength);
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// Open file stream and seek to start position
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var stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read, BufferSize, useAsync: true);
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stream.Seek(startByte, SeekOrigin.Begin);
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// Set response headers for partial content
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Response.StatusCode = StatusCodes.Status206PartialContent;
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Response.Headers.Append(HeaderNames.AcceptRanges, "bytes");
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Response.Headers.Append(HeaderNames.ContentRange, $"bytes {startByte}-{endByte}/{fileLength}");
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Response.Headers.Append(HeaderNames.ContentLength, contentLength.ToString());
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Response.ContentType = contentType;
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// Stream the requested range
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await StreamRangeAsync(stream, Response.Body, contentLength);
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await stream.DisposeAsync();
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return new EmptyResult();
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}
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catch (Exception ex)
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{
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_logger.LogError(ex, "Error processing range request for file: {FileName}", fileName);
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return StatusCode(StatusCodes.Status500InternalServerError);
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}
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}
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/// <summary>
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/// Efficiently streams a specific byte range from source to destination.
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/// </summary>
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private static async Task StreamRangeAsync(Stream source, Stream destination, long bytesToRead)
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{
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var buffer = new byte[BufferSize];
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long totalBytesRead = 0;
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while (totalBytesRead < bytesToRead)
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{
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var bytesToReadThisIteration = (int)Math.Min(BufferSize, bytesToRead - totalBytesRead);
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var bytesRead = await source.ReadAsync(buffer.AsMemory(0, bytesToReadThisIteration));
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if (bytesRead == 0)
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{
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break; // End of stream
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}
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await destination.WriteAsync(buffer.AsMemory(0, bytesRead));
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totalBytesRead += bytesRead;
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}
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await destination.FlushAsync();
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}
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}
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}
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