Add CancelDownload method to provider interface

Instead of just calling Thread.Abort which is messy and doesn't let
providers clean up (for instance podcasts continue to download on a
separate thread), add a CancelDownload method to the IRadioProvider
interface which is called when a download is cancelled.

If the provider doesn't return from the main provider thread within 10
seconds, fall back to using Thread.Abort and set the download to Errored
so that the hung / blocked stack trace can be reported.

This resolves #154.

Classes/DownloadHandler.cs

@@ -1,6 +1,6 @@
 /* 
  * This file is part of Radio Downloader.
- * Copyright © 2007-2013 by the authors - see the AUTHORS file for details.
+ * Copyright © 2007-2014 by the authors - see the AUTHORS file for details.
  * 
  * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General
  * Public License as published by the Free Software Foundation, either version 3 of the License, or (at your
@@ -40,6 +40,9 @@ internal class DownloadHandler : Database
         private Thread downloadThread;
         private object downloadThreadLock = new object();
 
+        private bool cancelled;
+        private bool cancelResponse;
+
         public DownloadHandler(int epid)
         {
             using (SQLiteCommand command = new SQLiteCommand("select pr.progid, pluginid, pr.image as progimg, ep.duration, ep.image as epimg, pr.extid as progextid, ep.extid as epextid from episodes as ep, programmes as pr where ep.epid=@epid and ep.progid=pr.progid", FetchDbConn()))
@@ -125,13 +128,34 @@ public void Start()
             }
         }
 
-        public void Cancel()
+        public bool Cancel()
         {
             lock (this.downloadThreadLock)
             {
-                if (this.downloadThread != null && this.downloadThread.IsAlive)
+                lock (this.pluginInstanceLock)
                 {
+                    this.cancelled = true;
+
+                    if (this.downloadThread == null || !this.downloadThread.IsAlive)
+                    {
+                        return true;
+                    }
+
+                    this.pluginInstance.CancelDownload();
+
+                    for (int wait = 0; wait < 20; wait++)
+                    {
+                        Thread.Sleep(500);
+
+                        if (this.cancelResponse)
+                        {
+                            return true;
+                        }
+                    }
+
+                    // No timely response to request, kill the thread
                     this.downloadThread.Abort();
+                    return false;
                 }
             }
         }
@@ -198,11 +222,6 @@ private void DownloadProgThread()
 
                 fileExtension = this.pluginInstance.DownloadProgramme(this.progExtId, this.episodeExtId, this.providerProgInfo, this.providerEpisodeInfo, finalName);
             }
-            catch (ThreadAbortException)
-            {
-                // The download has been cancelled
-                return;
-            }
             catch (DownloadException downloadExp)
             {
                 if (downloadExp.ErrorType == ErrorType.UnknownError)
@@ -222,6 +241,11 @@ private void DownloadProgThread()
                 return;
             }
 
+            if (this.cancelled)
+            {
+                this.cancelResponse = true;
+            }
+
             finalName += "." + fileExtension;
 
             lock (Database.DbUpdateLock)

Classes/DownloadManager.cs

@@ -1,6 +1,6 @@
 /* 
  * This file is part of Radio Downloader.
- * Copyright © 2007-2012 by the authors - see the AUTHORS file for details.
+ * Copyright © 2007-2014 by the authors - see the AUTHORS file for details.
  * 
  * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General
  * Public License as published by the Free Software Foundation, either version 3 of the License, or (at your
@@ -59,27 +59,22 @@ public static void AddDownloads(int[] epids)
             StartNextDownload();
         }
 
-        public static void CancelDownload(int epid)
+        public static bool CancelDownload(int epid)
         {
-            bool cancelled = false;
-
             lock (downloads)
             {
-                if (downloads.ContainsKey(epid))
+                if (!downloads[epid].Cancel())
                 {
-                    downloads[epid].Cancel();
-                    cancelled = true;
-
-                    downloads.Remove(epid);
-                    startedDownloads.Remove(epid);
+                    return false;
                 }
-            }
 
-            if (cancelled)
-            {
-                UpdateTotalProgress();
-                StartNextDownload();
+                downloads.Remove(epid);
+                startedDownloads.Remove(epid);
             }
+
+            UpdateTotalProgress();
+            StartNextDownload();
+            return true;
         }
 
         private static void ResumeDownloadsAsync()

Classes/Model/Download.cs

@@ -850,7 +850,10 @@ private static void RemoveAsync(int epid, bool auto)
         {
             if (!auto)
             {
-                DownloadManager.CancelDownload(epid);
+                if (!DownloadManager.CancelDownload(epid))
+                {
+                    return;
+                }
             }
 
             lock (Database.DbUpdateLock)

Interfaces/IRadioProvider.cs

@@ -1,6 +1,6 @@
 /* 
  * This file is part of Radio Downloader.
- * Copyright © 2007-2012 by the authors - see the AUTHORS file for details.
+ * Copyright © 2007-2014 by the authors - see the AUTHORS file for details.
  * 
  * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General
  * Public License as published by the Free Software Foundation, either version 3 of the License, or (at your
@@ -89,6 +89,11 @@ public interface IRadioProvider
         /// <exception cref="DownloadException">Thrown when an expected error is encountered whilst downloading.</exception>
         /// <returns>The file extension of a successful download.</returns>
         string DownloadProgramme(string progExtId, string episodeExtId, ProgrammeInfo progInfo, EpisodeInfo epInfo, string finalName);
+
+        /// <summary>
+        /// Cancel the episode download currently in progress.
+        /// </summary>
+        void CancelDownload();
     }
 
     /// <summary>

Providers/PodcastProvider/Classes/DownloadWrapper.cs

@@ -1,6 +1,6 @@
 /* 
  * This file is part of the Podcast Provider for Radio Downloader.
- * Copyright © 2007-2013 by the authors - see the AUTHORS file for details.
+ * Copyright © 2007-2014 by the authors - see the AUTHORS file for details.
  * 
  * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General
  * Public License as published by the Free Software Foundation, either version 3 of the License, or (at your
@@ -27,9 +27,6 @@ internal class DownloadWrapper
 
         private Uri downloadUrl;
         private string destPath;
-        private bool downloadComplete;
-
-        private Exception downloadError;
 
         public DownloadWrapper(Uri downloadUrl, string destPath)
         {
@@ -41,15 +38,11 @@ public DownloadWrapper(Uri downloadUrl, string destPath)
 
         public event DownloadProgressEventHandler DownloadProgress;
 
-        public bool Complete
-        {
-            get { return this.downloadComplete; }
-        }
+        public bool Complete { get; private set; }
 
-        public Exception Error
-        {
-            get { return this.downloadError; }
-        }
+        public Exception Error { get; private set; }
+
+        public bool Cancelled { get; private set; }
 
         public void Download()
         {
@@ -63,6 +56,12 @@ public void Download()
             this.downloadClient.DownloadFileAsync(this.downloadUrl, this.destPath);
         }
 
+        public void Cancel()
+        {
+            this.Cancelled = true;
+            this.downloadClient.CancelAsync();
+        }
+
         private void DownloadClient_DownloadProgressChanged(object sender, System.Net.DownloadProgressChangedEventArgs e)
         {
             if (this.DownloadProgress != null)
@@ -73,18 +72,21 @@ private void DownloadClient_DownloadProgressChanged(object sender, System.Net.Do
 
         private void DownloadClient_DownloadFileCompleted(object sender, System.ComponentModel.AsyncCompletedEventArgs e)
         {
-            if (!e.Cancelled)
+            if (e.Cancelled && !this.Cancelled)
             {
-                SystemEvents.PowerModeChanged -= this.PowerModeChange;
+                // Cancelled before retry
+                return;
+            }
 
-                if (e.Error != null)
-                {
-                    this.downloadError = e.Error;
-                }
-                else
-                {
-                    this.downloadComplete = true;
-                }
+            SystemEvents.PowerModeChanged -= this.PowerModeChange;
+
+            if (e.Error != null)
+            {
+                this.Error = e.Error;
+            }
+            else if (!this.Cancelled)
+            {
+                this.Complete = true;
             }
         }
 

Providers/PodcastProvider/Classes/PodcastProvider.cs

@@ -393,6 +393,11 @@ public string DownloadProgramme(string progExtId, string episodeExtId, Programme
                 while ((!this.doDownload.Complete) && this.doDownload.Error == null)
                 {
                     Thread.Sleep(500);
+
+                    if (this.doDownload.Cancelled)
+                    {
+                        return null;
+                    }
                 }
 
                 if (this.doDownload.Error != null)
@@ -433,6 +438,11 @@ public string DownloadProgramme(string progExtId, string episodeExtId, Programme
             return extension;
         }
 
+        public void CancelDownload()
+        {
+            this.doDownload.Cancel();
+        }
+
         internal void RaiseFindNewException(Exception exception)
         {
             if (this.FindNewException != null)