Add an option to execute JavaScript files from the CLI

JSS/CommandLineOptions.cs

@@ -0,0 +1,19 @@
+using CommandLine;
+
+namespace JSS.CLI;
+
+internal interface IExecutionOptions
+{
+    [Option('s', "script", HelpText = "Path to a JavaScript file to execute.")]
+    public string? Script { get; }
+}
+
+internal sealed class CommandLineOptions : IExecutionOptions
+{
+    public CommandLineOptions(string? script)
+    {
+        Script = script;
+    }
+
+    public string? Script { get; }
+}

JSS/FileExecutor.cs

@@ -0,0 +1,35 @@
+using JSS.Lib;
+using JSS.Lib.Execution;
+
+namespace JSS.CLI;
+
+internal sealed class FileExecutor
+{
+    public FileExecutor(VM globalVm, string filePath)
+    {
+        _vm = globalVm;
+        _filePath = filePath;
+    }
+
+    public void ExecuteFile()
+    {
+        try
+        {
+            var fileContent = File.ReadAllText(_filePath);
+            var parser = new Parser(fileContent);
+            var script = parser.Parse(_vm);
+            var result = script.ScriptEvaluation();
+            Print.PrintCompletion(result);
+        }
+        catch (Exception e)
+        {
+            Print.PrintException(e);
+        }
+
+        Console.WriteLine("Press any key to exit.");
+        Console.ReadKey();
+    }
+
+    private readonly VM _vm;
+    private readonly string _filePath;
+}

JSS/JSS.CLI.csproj

@@ -7,6 +7,10 @@
     <Nullable>enable</Nullable>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="CommandLineParser" Version="2.9.1" />
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\JSS.Lib\JSS.Lib.csproj" />
   </ItemGroup>

JSS/Program.cs

@@ -1,30 +1,25 @@
-using JSS.Lib;
+using CommandLine;
 using JSS.CLI;
 using JSS.Lib.Execution;
 
 var completion = Realm.InitializeHostDefinedRealm(out VM globalVm);
 if (completion.IsAbruptCompletion())
 {
     Print.PrintCompletion(completion);
+    return;
 }
 
-while (true)
-{
-    Console.Write("> ");
-
-    try
+Parser.Default.ParseArguments<CommandLineOptions>(args)
+    .WithParsed(options =>
     {
-        var input = Console.ReadLine() ?? "";
-        var parser = new Parser(input);
-        var script = parser.Parse(globalVm);
-        var result = script.ScriptEvaluation();
-        Print.PrintCompletion(result);
-    }
-    catch (Exception e)
-    {
-        Print.PrintException(e);
-    }
-
-    // NOTE: We need this empty write line to prevent the background color from spilling over
-    Console.WriteLine();
-}
+        if (!string.IsNullOrEmpty(options.Script))
+        {
+            var fileExecutor = new FileExecutor(globalVm, options.Script);
+            fileExecutor.ExecuteFile();
+        }
+        else
+        {
+            var repl = new Repl(globalVm);
+            repl.ExecuteRepl();
+        }
+    });

JSS/Repl.cs

@@ -0,0 +1,42 @@
+using JSS.Lib;
+using JSS.Lib.Execution;
+
+namespace JSS.CLI;
+
+internal sealed class Repl
+{
+    public Repl(VM globalVm)
+    {
+        _vm = globalVm;
+    }
+
+    public void ExecuteRepl()
+    {
+        while (true)
+        {
+            Console.Write("> ");
+            EvaluateLine();
+        }
+    }
+
+    private void EvaluateLine()
+    {
+        try
+        {
+            var input = Console.ReadLine() ?? "";
+            var parser = new Parser(input);
+            var script = parser.Parse(_vm);
+            var result = script.ScriptEvaluation();
+            Print.PrintCompletion(result);
+        }
+        catch (Exception e)
+        {
+            Print.PrintException(e);
+        }
+
+        // NOTE: We need this empty write line to prevent the background color from spilling over
+        Console.WriteLine();
+    }
+
+    private readonly VM _vm;
+}