Add a repl script handling framework

MultiversalDiplomacy/CommandLine/ReplOptions.cs

@@ -1,12 +1,84 @@
 using CommandLine;
 
+using MultiversalDiplomacy.Script;
+
 namespace MultiversalDiplomacy.CommandLine;
 
 [Verb("repl", HelpText = "Begin an interactive 5dplomacy session.")]
 public class ReplOptions
 {
+    [Option('i', "input", HelpText = "Begin the repl session by executing the commands in this file.")]
+    public string? InputFile { get; set; }
+
+    [Option('o', "output", HelpText = "Echo the repl session to this file. Specify a directory to autogenerate a filename.")]
+    public string? OutputFile { get; set; }
+
     public static void Execute(ReplOptions args)
     {
-        throw new NotImplementedException();
+        IEnumerable<string>? inputFileLines = null;
+        if (args.InputFile is not null) {
+            var fullPath = Path.GetFullPath(args.InputFile);
+            inputFileLines = File.ReadAllLines(fullPath);
+            Console.WriteLine($"Reading from {fullPath}");
+        }
+
+        // Create a writer to the output file, if specified.
+        StreamWriter? outputWriter = null;
+        if (args.OutputFile is not null)
+        {
+            string fullPath = Path.GetFullPath(args.OutputFile);
+            string outputPath = Directory.Exists(fullPath)
+                ? Path.Combine(fullPath, $"{DateTime.UtcNow:yyyyMMddHHmmss}.log")
+                : fullPath;
+            Console.WriteLine($"Echoing to {outputPath}");
+            outputWriter = File.CreateText(outputPath);
+        }
+
+        IEnumerable<string?> GetInputs()
+        {
+            foreach (string line in inputFileLines ?? [])
+            {
+                var trimmed = line.Trim();
+                // File inputs weren't echoed to the terminal so they need to be echoed here
+                Console.WriteLine($"{trimmed}");
+                yield return trimmed;
+            }
+
+            string? input;
+            do
+            {
+                input = Console.ReadLine();
+                yield return input;
+            }
+            while (input is not null);
+            // The last null is returned because an EOF means we should quit the repl.
+        }
+
+        IScriptHandler? handler = new ReplScriptHandler();
+
+        Console.Write(handler.Prompt);
+        foreach (string? nextInput in GetInputs())
+        {
+            // Handle quitting directly.
+            if (nextInput is null || nextInput == "quit" || nextInput == "exit")
+            {
+                break;
+            }
+            string input = nextInput.Trim();
+            outputWriter?.WriteLine(input);
+            outputWriter?.Flush();
+
+            // Delegate all other command parsing to the handler.
+            handler = handler.HandleInput(input);
+
+            // Quit if the handler ends processing, otherwise prompt for the next command.
+            if (handler is null)
+            {
+                break;
+            }
+            Console.Write(handler.Prompt);
+        }
+
+        Console.WriteLine("exiting");
     }
 }

MultiversalDiplomacy/Script/IScriptHandler.cs

@@ -0,0 +1,21 @@
+namespace MultiversalDiplomacy.Script;
+
+/// <summary>
+/// A handler that interprets and executes 5dp script commands. Script handlers may create additional script handlers
+/// and delegate handling to them, allowing a sort of recursive parsing of script commands.
+/// </summary>
+public interface IScriptHandler
+{
+    /// <summary>
+    /// When used interactively, the prompt that should be displayed.
+    /// </summary>
+    public string Prompt { get; }
+
+    /// <summary>
+    /// Process a line of input.
+    /// </summary>
+    /// <returns>
+    /// The handler that should handle the next line of input, or null if script handling should end.
+    /// </returns>
+    public IScriptHandler? HandleInput(string input);
+}

MultiversalDiplomacy/Script/ReplScriptHandler.cs

@@ -0,0 +1,16 @@
+namespace MultiversalDiplomacy.Script;
+
+/// <summary>
+/// A script handler for the interactive repl.
+/// </summary>
+public class ReplScriptHandler : IScriptHandler
+{
+    public string Prompt => "5dp> ";
+
+    public IScriptHandler? HandleInput(string input)
+    {
+        Console.WriteLine($"[{input}]");
+
+        return this;
+    }
+}