[smuxi: 139/179] Engine-MessageBuffer: handle missing action correctly

[Mirco M. M. Bauer <mmmbauer src gnome org>]

commit d6d474e2b829c4227bc6e90ece66a6f67e1a3a5e
Author: Mirco Bauer <meebey meebey net>
Date:   Tue May 2 18:16:24 2017 +0800

    Engine-MessageBuffer: handle missing action correctly
    
    If smuxi-message-buffer was called without an action it is failing with an ugly
    exception:
    
        $ smuxi-message-buffer
        2017-05-02 18:17:39,529 [Main] FATAL Smuxi.Engine.MainClass - System.InvalidOperationException: 
Sequence contains no elements
          at System.Linq.Enumerable.First[TSource] (System.Collections.Generic.IEnumerable`1[T] source) 
[0x0006c] in <63992662b765477a898ef49cdcc99ee2>:0
          at Smuxi.Engine.MainClass.Main (System.String[] args) [0x000df] in 
/tmp/buildd/smuxi-1.0.6/src/Engine-MessageBuffer/Main.cs:76
    
    Instead of that unhandled exception check if the action is missing and if so
    show the general command line usage help output.

 src/Engine-MessageBuffer/Main.cs |   28 +++++++++++++++++++---------
 1 files changed, 19 insertions(+), 9 deletions(-)
---
diff --git a/src/Engine-MessageBuffer/Main.cs b/src/Engine-MessageBuffer/Main.cs
index 32e31f8..8237542 100644
--- a/src/Engine-MessageBuffer/Main.cs
+++ b/src/Engine-MessageBuffer/Main.cs
@@ -54,14 +54,7 @@ namespace Smuxi.Engine
             };
             parser.Add("h|help", _("Show this help"),
                 val => {
-                    Console.WriteLine(_("Usage: smuxi-message-buffer [options] action action-options"));
-                    Console.WriteLine();
-                    Console.WriteLine(_("Actions:"));
-                    Console.WriteLine("  cat");
-                    Console.WriteLine("  convert/copy/cp");
-                    Console.WriteLine();
-                    Console.WriteLine(_("Options:"));
-                    parser.WriteOptionDescriptions(Console.Out);
+                    ShowUsage(parser);
                     Environment.Exit(0);
                 }
             );
@@ -73,7 +66,12 @@ namespace Smuxi.Engine
                     repo.Threshold = log4net.Core.Level.Debug;
                 }
 
-                var action = args.Skip(mainArgs.Count()).First();
+                var action = args.Skip(mainArgs.Count()).FirstOrDefault();
+                if (String.IsNullOrEmpty(action)) {
+                    ShowUsage(parser);
+                    Environment.Exit(1);
+                }
+
                 var actionArgs = args.Skip(mainArgs.Count() + 1);
                 switch (action.ToLower()) {
                     case "cat":
@@ -101,6 +99,18 @@ namespace Smuxi.Engine
             }
         }
 
+        static void ShowUsage(OptionSet mainOptions)
+        {
+            Console.WriteLine(_("Usage: smuxi-message-buffer [options] action action-options"));
+            Console.WriteLine();
+            Console.WriteLine(_("Actions:"));
+            Console.WriteLine("  cat");
+            Console.WriteLine("  convert/copy/cp");
+            Console.WriteLine();
+            Console.WriteLine(_("Options:"));
+            mainOptions.WriteOptionDescriptions(Console.Out);
+        }
+
         static void CatAction(string action, IEnumerable<string> args)
         {
             var dbFormat = "";