Use FileMonitor to synchronize Mailer bot (#1108) (v2)

Move SessionFileMonitor into a generic FileMonitor class
Use FileMonintor for both SessionCache and the Mailer bot
Allows multiple MCC instances to share the same database files

(Add files missing in the previous commit)

MinecraftClient/FileMonitor.cs

@@ -1,27 +1,32 @@
 using System;
+using System.Collections.Generic;
 using System.IO;
+using System.Text;
 using System.Threading;
 
-namespace MinecraftClient.Protocol.Session
+namespace MinecraftClient
 {
     /// <summary>
-    /// Monitor session file changes on disk
+    /// Monitor file changes on disk
     /// </summary>
-    class SessionFileMonitor
+    public class FileMonitor : IDisposable
     {
-        private FileSystemWatcher monitor;
-        private Thread polling;
+        private FileSystemWatcher monitor = null;
+        private Thread polling = null;
 
         /// <summary>
-        /// Create a new SessionFileMonitor and start monitoring
+        /// Create a new FileMonitor and start monitoring
         /// </summary>
         /// <param name="folder">Folder to monitor</param>
         /// <param name="filename">Filename inside folder</param>
         /// <param name="handler">Callback for file changes</param>
-        public SessionFileMonitor(string folder, string filename, FileSystemEventHandler handler)
+        public FileMonitor(string folder, string filename, FileSystemEventHandler handler)
         {
             if (Settings.DebugMessages)
-                ConsoleIO.WriteLineFormatted("§8Initializing disk session cache using FileSystemWatcher");
+            {
+                string callerClass = new System.Diagnostics.StackFrame(1).GetMethod().DeclaringType.Name;
+                ConsoleIO.WriteLineFormatted(String.Format("§8[{0}] Initializing FileSystemWatcher for file: {1}", callerClass, Path.Combine(folder, filename)));
+            }
 
             try
             {
@@ -36,13 +41,29 @@ namespace MinecraftClient.Protocol.Session
             catch
             {
                 if (Settings.DebugMessages)
-                    ConsoleIO.WriteLineFormatted("§8Failed to initialize FileSystemWatcher, retrying using Polling");
+                {
+                    string callerClass = new System.Diagnostics.StackFrame(1).GetMethod().DeclaringType.Name;
+                    ConsoleIO.WriteLineFormatted(String.Format("§8[{0}] Failed to initialize FileSystemWatcher, retrying using Polling", callerClass));
+                }
 
+                monitor = null;
                 polling = new Thread(() => PollingThread(folder, filename, handler));
+                polling.Name = String.Format("{0} Polling thread: {1}", this.GetType().Name, Path.Combine(folder, filename));
                 polling.Start();
             }
         }
 
+        /// <summary>
+        /// Stop monitoring and dispose the inner resources
+        /// </summary>
+        public void Dispose()
+        {
+            if (monitor != null)
+                monitor.Dispose();
+            if (polling != null)
+                polling.Abort();
+        }
+
         /// <summary>
         /// Fallback polling thread for use when operating system does not support FileSystemWatcher
         /// </summary>
@@ -51,7 +72,7 @@ namespace MinecraftClient.Protocol.Session
         /// <param name="handler">Callback when file changes</param>
         private void PollingThread(string folder, string filename, FileSystemEventHandler handler)
         {
-            string filePath = String.Concat(folder, Path.DirectorySeparatorChar, filename);
+            string filePath = Path.Combine(folder, filename);
             DateTime lastWrite = GetLastWrite(filePath);
             while (true)
             {
@@ -79,5 +100,62 @@ namespace MinecraftClient.Protocol.Session
             }
             else return DateTime.MinValue;
         }
+
+        /// <summary>
+        /// Opens a text file, reads all lines of the file, and then closes the file. Retry several times if the file is in use
+        /// </summary>
+        /// <param name="filePath">The file to open for reading</param>
+        /// <param name="maxTries">Maximum read attempts</param>
+        /// <param name="encoding">Encoding (default is UTF8)</param>
+        /// <exception cref="System.IO.IOException">Thrown when failing to read the file despite multiple retries</exception>
+        /// <returns>All lines</returns>
+        public static string[] ReadAllLinesWithRetries(string filePath, int maxTries = 3, Encoding encoding = null)
+        {
+            int attempt = 0;
+            if (encoding == null)
+                encoding = Encoding.UTF8;
+            while (true)
+            {
+                try
+                {
+                    return File.ReadAllLines(filePath, encoding);
+                }
+                catch (IOException)
+                {
+                    attempt++;
+                    if (attempt < maxTries)
+                        Thread.Sleep(new Random().Next(50, 100) * attempt); // Back-off like CSMA/CD
+                    else throw;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Creates a new file, writes a collection of strings to the file, and then closes the file.
+        /// </summary>
+        /// <param name="filePath">The file to open for writing</param>
+        /// <param name="lines">The lines to write to the file</param>
+        /// <param name="maxTries">Maximum read attempts</param>
+        /// <param name="encoding">Encoding (default is UTF8)</param>
+        public static void WriteAllLinesWithRetries(string filePath, IEnumerable<string> lines, int maxTries = 3, Encoding encoding = null)
+        {
+            int attempt = 0;
+            if (encoding == null)
+                encoding = Encoding.UTF8;
+            while (true)
+            {
+                try
+                {
+                    File.WriteAllLines(filePath, lines, encoding);
+                }
+                catch (IOException)
+                {
+                    attempt++;
+                    if (attempt < maxTries)
+                        Thread.Sleep(new Random().Next(50, 100) * attempt); // Back-off like CSMA/CD
+                    else throw;
+                }
+            }
+        }
     }
 }