From 1e6e28cd575b1b854b9af7bfe4f1f1759da03903 Mon Sep 17 00:00:00 2001
From: Michael Bucari-Tovo <mbucari1@gmail.com>
Date: Sat, 18 Feb 2023 22:37:11 -0700
Subject: [PATCH] Start downloading asynchronously

---
 Source/AaxDecrypter/AudiobookDownloadBase.cs  |  2 ++
 Source/AaxDecrypter/NetworkFileStream.cs      | 21 ++++++-------------
 .../UnencryptedAudiobookDownloader.cs         |  3 +--
 3 files changed, 9 insertions(+), 17 deletions(-)

diff --git a/Source/AaxDecrypter/AudiobookDownloadBase.cs b/Source/AaxDecrypter/AudiobookDownloadBase.cs
index 43ceb5e0..ca730ca1 100644
--- a/Source/AaxDecrypter/AudiobookDownloadBase.cs
+++ b/Source/AaxDecrypter/AudiobookDownloadBase.cs
@@ -3,6 +3,7 @@ using Dinah.Core.Net.Http;
 using Dinah.Core.StepRunner;
 using FileManager;
 using System;
+using System.Diagnostics;
 using System.IO;
 using System.Threading.Tasks;
 
@@ -66,6 +67,7 @@ namespace AaxDecrypter
 
 		public async Task<bool> RunAsync()
 		{
+			await InputFileStream.BeginDownloadingAsync();
 			var progressTask = Task.Run(reportProgress);
 
 			AsyncSteps[$"Cleanup"] = CleanupAsync;
diff --git a/Source/AaxDecrypter/NetworkFileStream.cs b/Source/AaxDecrypter/NetworkFileStream.cs
index c7283ee8..ca89532b 100644
--- a/Source/AaxDecrypter/NetworkFileStream.cs
+++ b/Source/AaxDecrypter/NetworkFileStream.cs
@@ -136,10 +136,10 @@ namespace AaxDecrypter
 
 		/// <summary> Begins downloading <see cref="Uri"/> to <see cref="SaveFilePath"/> in a background thread. </summary>
 		/// <returns>The downloader <see cref="Task"/></returns>
-		private Task BeginDownloading()
+		public async Task BeginDownloadingAsync()
 		{
 			if (ContentLength != 0 && WritePosition == ContentLength)
-				return Task.CompletedTask;
+				return;
 
 			if (ContentLength != 0 && WritePosition > ContentLength)
 				throw new WebException($"Specified write position (0x{WritePosition:X10}) is larger than  {nameof(ContentLength)} (0x{ContentLength:X10}).");
@@ -149,7 +149,7 @@ namespace AaxDecrypter
 			foreach (var header in RequestHeaders)
 				request.Headers.Add(header.Key, header.Value);
 
-			var response = new HttpClient().Send(request, HttpCompletionOption.ResponseHeadersRead, _cancellationSource.Token);
+			var response = await new HttpClient().SendAsync(request, HttpCompletionOption.ResponseHeadersRead, _cancellationSource.Token);
 
 			if (response.StatusCode != HttpStatusCode.PartialContent)
 				throw new WebException($"Server at {Uri.Host} responded with unexpected status code: {response.StatusCode}.");
@@ -159,11 +159,11 @@ namespace AaxDecrypter
 			if (WritePosition == 0)
 				ContentLength = response.Content.Headers.ContentLength.GetValueOrDefault();
 
-			var networkStream = response.Content.ReadAsStream(_cancellationSource.Token);
+			var networkStream = await response.Content.ReadAsStreamAsync(_cancellationSource.Token);
 			_downloadedPiece = new EventWaitHandle(false, EventResetMode.AutoReset);
 
 			//Download the file in the background.
-			return Task.Run(() => DownloadFile(networkStream), _cancellationSource.Token);
+			_backgroundDownloadTask = Task.Run(() => DownloadFile(networkStream), _cancellationSource.Token);
 		}
 
 		/// <summary> Download <see cref="Uri"/> to <see cref="SaveFilePath"/>.</summary>
@@ -247,14 +247,7 @@ namespace AaxDecrypter
 		public override bool CanWrite => false;
 
 		[JsonIgnore]
-		public override long Length
-		{
-			get
-			{
-				_backgroundDownloadTask ??= BeginDownloading();
-				return ContentLength;
-			}
-		}
+		public override long Length => ContentLength;
 
 		[JsonIgnore]
 		public override long Position { get => _readFile.Position; set => Seek(value, SeekOrigin.Begin); }
@@ -274,8 +267,6 @@ namespace AaxDecrypter
 
 		public override int Read(byte[] buffer, int offset, int count)
 		{
-			_backgroundDownloadTask ??= BeginDownloading();
-
 			var toRead = Math.Min(count, Length - Position);
 			WaitToPosition(Position + toRead);
 			return IsCancelled ? 0 : _readFile.Read(buffer, offset, count);
diff --git a/Source/AaxDecrypter/UnencryptedAudiobookDownloader.cs b/Source/AaxDecrypter/UnencryptedAudiobookDownloader.cs
index ad9144ee..138c8ea0 100644
--- a/Source/AaxDecrypter/UnencryptedAudiobookDownloader.cs
+++ b/Source/AaxDecrypter/UnencryptedAudiobookDownloader.cs
@@ -26,8 +26,7 @@ namespace AaxDecrypter
 
 		protected override async Task<bool> Step_DownloadAndDecryptAudiobookAsync()
 		{
-			// MUST put InputFileStream.Length first, because it starts background downloader.
-			while (InputFileStream.Length > InputFilePosition && !InputFileStream.IsCancelled)
+			while (InputFilePosition < InputFileStream.Length && !InputFileStream.IsCancelled)
 				await Task.Delay(200);
 
 			if (IsCanceled)