Added support for downloading assets (including auto-update)

- Added support for downloading assets (including auto-update)
- By default, auto-update is turned off. Enable it in settings.
- Default repository for app icons and names is [https://github.com/tverona1/QuestAppLauncher_assets]. This can be configured in config.json.

Assets/Scripts/DownloadHandlerFileWithProgress.cs

@@ -0,0 +1,112 @@
+using System;
+using System.IO;
+using UnityEngine;
+using UnityEngine.Networking;
+
+namespace QuestAppLauncher
+{
+    /// <summary>
+    /// File download handler class with callback for progress.
+    /// This is a download hanlder that can be assocaited with a UnityWebRequest.
+    /// Based on: DownloadHandlerFile.cs by Luke Holland
+    /// (https://gist.github.com/luke161/a251b01c00f58d65a252812be8dce670)
+    /// </summary>
+    public class DownloadHandlerFileWithProgress : DownloadHandlerScript
+    {
+        // Whether to remove file on error
+        public bool removeFileOnAbort = false;
+
+        // Total content length in bytes
+        private int contentLength;
+
+        // Bytes recieved so far
+        private int received;
+
+        // File stream to write to
+        private FileStream stream;
+
+        // Callback to incidate progress: Percentage, total content length and current received
+        private Action<float, int, int> downloadProgress;
+
+        // Whether we have successfully received all the data
+        private bool receivedAllData = false;
+
+        /// <summary>
+        /// Constructor for the file download handler. Instantiates base class in pre-allocated mode.
+        /// </summary>
+        /// <param name="localFilePath">Local path to save file to</param>
+        /// <param name="downloadProgress">Download progress indicator</param>
+        /// <param name="bufferSize">Buffer size</param>
+        /// <param name="fileShare">File sharing mode</param>
+        public DownloadHandlerFileWithProgress(string localFilePath, Action<float, int, int> downloadProgress = null,
+            int bufferSize = 32768, FileShare fileShare = FileShare.ReadWrite) : base(new byte[bufferSize])
+        {
+            string directory = Path.GetDirectoryName(localFilePath);
+            if (!Directory.Exists(directory))
+            {
+                Directory.CreateDirectory(directory);
+            }
+
+            this.downloadProgress = downloadProgress;
+            this.contentLength = -1;
+            this.received = 0;
+            this.stream = new FileStream(localFilePath, FileMode.OpenOrCreate, FileAccess.Write, fileShare, bufferSize);
+        }
+
+        protected override float GetProgress()
+        {
+            return contentLength <= 0 ? 0 : Mathf.Clamp01((float)this.received / (float)contentLength);
+        }
+
+        protected override void ReceiveContentLength(int contentLength)
+        {
+            this.contentLength = contentLength;
+        }
+
+        protected override bool ReceiveData(byte[] data, int dataLength)
+        {
+            if (data == null || data.Length == 0)
+            {
+                return false;
+            }
+
+            this.received += dataLength;
+            this.stream.Write(data, 0, dataLength);
+
+            if (null != this.downloadProgress)
+            {
+                this.downloadProgress(GetProgress(), this.contentLength, this.received);
+            }
+
+            return true;
+        }
+
+        protected override void CompleteContent()
+        {
+            this.receivedAllData = true;
+            CloseStream();
+        }
+
+        public new void Dispose()
+        {
+            CloseStream();
+            base.Dispose();
+        }
+
+        private void CloseStream()
+        {
+            string filePath = this.stream.Name;
+            if (this.stream != null)
+            {
+                this.stream.Dispose();
+                this.stream = null;
+            }
+
+            if (this.removeFileOnAbort && !this.receivedAllData && File.Exists(filePath))
+            {
+                // We have not successfully received all the content, so delete the file
+                File.Delete(filePath);
+            }
+        }
+    }
+}