Add --pidfile support, and output error properly if XMPP_JID or XMPP_PASSWORD aren't set

RhinoReminds/Program.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.IO;
 using System.Threading.Tasks;
 using S22.Xmpp;
@@ -15,6 +16,7 @@ namespace RhinoReminds
 		public string Jid = null;
 
 		public string AvatarFilepath = string.Empty;
+		public string PidFile = null;
 
 		public string Password = null;
 	}
@@ -48,6 +50,7 @@ namespace RhinoReminds
 						Console.WriteLine($"    -f  --file    Specify where to save reminders (default: {settings.Filepath})");
 						Console.WriteLine("        --domain {domain}  Set the domain users are allowed to originate at. Defaults to any domain.");
 						Console.WriteLine("        --avatar  Update the XMPP account's avatar to the specified image. By default the avatar is not updated.");
+						Console.WriteLine("        --pidfile Save our process ID to the specified file, and delete it on exit");
 						Console.WriteLine();
 						Console.WriteLine("Environment Variables:");
 						Console.WriteLine("    XMPP_JID       The JID to login to");
@@ -67,18 +70,53 @@ namespace RhinoReminds
 					case "--avatar":
 						settings.AvatarFilepath = args[++i];
 						break;
+
+					case "--pidfile":
+						settings.PidFile = args[++i];
+						break;
 				}
 			}
 
 			settings.Jid = Environment.GetEnvironmentVariable("XMPP_JID");
 			settings.Password = Environment.GetEnvironmentVariable("XMPP_PASSWORD");
 
-			Run();
+			if (settings.Jid == null) {
+				Console.Error.WriteLine("Error: No JID specified to login with."); 
+				Console.Error.WriteLine("Do so with the XMPP_JID environment variable!");
+				return 15;
+			}
+			if (settings.Password == null) {
+				Console.Error.WriteLine("Error: No password specified to login with.");
+				Console.Error.WriteLine("Do so with the XMPP_PASSWORD environment variable!");
+				return 16;
+			}
 
+			if (settings.PidFile != null)
+				setupPidFile();
+
+			run();
+			// We shouldn't ever end up here, but just in case.....
+			cleanupPidFile();
 			return 0;
 		}
 
-		public static void Run()
+		private static void setupPidFile()
+		{
+			File.WriteAllText(settings.PidFile, Process.GetCurrentProcess().Id.ToString());
+			AppDomain.CurrentDomain.ProcessExit += (object sender, EventArgs e) => cleanupPidFile();
+			AppDomain.CurrentDomain.DomainUnload += (object sender, EventArgs e) => cleanupPidFile();
+		}
+
+		private static void cleanupPidFile() {
+			// Make sure we only do cleanup once
+			if (settings.PidFile == null)
+				return;
+
+			File.Delete(settings.PidFile);
+			settings.PidFile = null;
+		}
+
+		private static void run()
 		{
 			ClientListener client = new ClientListener(settings.Jid, settings.Password) {
 				ReminderFilePath = settings.Filepath
@@ -96,7 +134,16 @@ namespace RhinoReminds
 			}
 			// Connect to the server & start listening
 			// Make sure the program doesn't exit whilst we're connected
+			try
+			{
 				client.Start().Wait();
+			} catch (Exception) {
+				// Ensure we tidy up after ourselves by deleting the PID file
+				if (settings.PidFile != null)
+					cleanupPidFile();
+				// Re-throw the error
+				throw;
+			}
 		}
 	}
 }