Add a handler for asserting against orders

MultiversalDiplomacy/Script/GameScriptHandler.cs

@@ -28,7 +28,7 @@ public class GameScriptHandler(World world, bool strict = false) : IScriptHandle
         // "---" submits the orders for validation to allow for assertions about it
         if (input == "---") {
             // TODO submit orders
-            // TODO return a new handler that handles asserts
+            return new ValidatedOrdersScriptHandler(World, Strict);
         }
 
         // A block of orders for a single power beginning with "{name}:"

MultiversalDiplomacy/Script/ValidatedOrdersScriptHandler.cs

@@ -0,0 +1,56 @@
+using System.Text.RegularExpressions;
+
+using MultiversalDiplomacy.Model;
+
+namespace MultiversalDiplomacy.Script;
+
+public class ValidatedOrdersScriptHandler(World world, bool strict = false) : IScriptHandler
+{
+    public string Prompt => "valid> ";
+
+    public World World { get; private set; } = world;
+
+    /// <summary>
+    /// Whether unsuccessful commands should terminate the script.
+    /// </summary>
+    public bool Strict { get; } = strict;
+
+    public IScriptHandler? HandleInput(string input)
+    {
+        var args = input.Split(' ', StringSplitOptions.RemoveEmptyEntries);
+        if (args.Length == 0)
+        {
+            return this;
+        }
+
+        var command = args[0];
+        switch (command)
+        {
+            case "assert" when args.Length == 1:
+                Console.WriteLine("Usage:");
+                break;
+
+            case "assert":
+                string assertion = input["assert ".Length..];
+                OrderRegex re = new(World);
+                Regex prov = new($"{re.Province} (.*)");
+                Match match = prov.Match(assertion);
+                if (!match.Success) {
+                    Console.WriteLine($"Could not parse province from {assertion}");
+                    return Strict ? null : this;
+                }
+                // TODO look up order once orders are validated and adjudicated
+                Console.WriteLine("Order lookup not implemented yet");
+                return null;
+
+            default:
+                // noop on comments that begin with #
+                if (command.StartsWith('#')) break;
+                Console.WriteLine($"Unrecognized command: {command}");
+                if (Strict) return null;
+                break;
+        }
+
+        return this;
+    }
+}