Update file handling logic

src/modules/espresso/Espresso.Shell/Program.cs

@@ -5,6 +5,7 @@ using System;
 using System.CommandLine;
 using System.CommandLine.Invocation;
 using System.IO;
+using System.Runtime.InteropServices;
 using System.Threading;
 
 namespace Espresso.Shell
@@ -14,6 +15,9 @@ namespace Espresso.Shell
         private static Mutex mutex = null;
         private const string appName = "Espresso";
 
+        const int ERROR_SHARING_VIOLATION = 32;
+        const int ERROR_LOCK_VIOLATION = 33;
+
         static int Main(string[] args)
         {
             bool instantiated;
@@ -106,6 +110,10 @@ namespace Espresso.Shell
                         Filter = Path.GetFileName(config)
                     };
                     watcher.Changed += new FileSystemEventHandler(HandleEspressoConfigChange);
+
+                    // Initially the file might not be updated, so we need to start processing
+                    // settings right away.
+                    ProcessSettings(config);
                 }
                 catch (Exception ex)
                 {
@@ -151,12 +159,28 @@ namespace Espresso.Shell
         }
 
         private static void HandleEspressoConfigChange(object sender, FileSystemEventArgs e)
+        {
+            ProcessSettings(e.FullPath);
+        }
+
+        private static void ProcessSettings(string fullPath)
         {
             Console.WriteLine("Detected a file change. Reacting...");
             try
             {
-                var settings = JsonConvert.DeserializeObject<EspressoSettingsModel>(File.ReadAllText(e.FullPath));
+                EspressoSettingsModel settings = null;
 
+                var fileStream = GetSettingsFile(fullPath, 10);
+                if (fileStream != null)
+                {
+                    using (fileStream)
+                    {
+                        using StreamReader reader = new StreamReader(fileStream);
+                        settings = JsonConvert.DeserializeObject<EspressoSettingsModel>(reader.ReadToEnd());
+                    }
+
+                    if (settings != null)
+                    {
                         // If the settings were successfully processed, we need to set the right mode of operation.
                         // INDEFINITE = 0
                         // TIMED = 1
@@ -203,12 +227,47 @@ namespace Espresso.Shell
                                 }
                         }
                     }
+                    else
+                    {
+                        Console.WriteLine("Settings are null.");
+                    }
+                }
+                else
+                {
+                    Console.WriteLine("Could not get handle on file.");
+                }
+            }
             catch (Exception ex)
             {
                 ForceExit($"There was a problem reading the configuration file.\n{ex.Message}", 1);
             }
         }
 
+        private static FileStream GetSettingsFile(string path, int retries)
+        {
+            for (int i = 0; i < retries; i++)
+            {
+                FileStream fileStream = null;
+                try
+                {
+                    fileStream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.None);
+                    return fileStream;
+                }
+                catch (IOException ex)
+                {
+                    var errorCode = Marshal.GetHRForException(ex) & ((1 << 16) - 1);
+                    if (errorCode == ERROR_SHARING_VIOLATION || errorCode == ERROR_LOCK_VIOLATION)
+                    {
+                        Console.WriteLine("There was another process using the file, so couldn't pick the settings up.");
+                    }
+
+                    Thread.Sleep(50);
+                }
+            }
+
+            return null;
+        }
+
         private static void ResetNormalPowerState()
         {
             bool success = APIHelper.SetNormalKeepAwake();