port from perforce

intromat/Intromat/ViewModels/CodePreviewViewModel.cs

@@ -0,0 +1,64 @@
+using System.Linq;
+using System.Reactive.Linq;
+using System.Text;
+using Intromat.Model.Compiler;
+using Intromat.Model.Compiler.Error;
+using ReactiveUI;
+
+namespace Intromat.ViewModels
+{
+    public class CodePreviewViewModel : ReactiveObject
+    {
+        private readonly ObservableAsPropertyHelper<string> _compiledCode;
+
+        private IStatement? _code;
+
+        private string? _compilerError;
+
+        public CodePreviewViewModel()
+        {
+            this.WhenAnyValue(vm => vm.Code).Where(c => c != null)
+                .Select(Compile)
+                .ToProperty(this, vm => vm.CompiledCode, out _compiledCode);
+        }
+
+        public IStatement? Code
+        {
+            get => _code;
+            set => this.RaiseAndSetIfChanged(ref _code, value);
+        }
+
+        public string? CompilerError
+        {
+            get => _compilerError;
+            set => this.RaiseAndSetIfChanged(ref _compilerError, value);
+        }
+
+        public string CompiledCode => _compiledCode.Value;
+
+        private string Compile(IStatement? c)
+        {
+            if (c == null)
+            {
+                CompilerError = "No code provided";
+                return string.Empty;
+            }
+
+            CompilerError = string.Empty;
+            CompilerContext ctx = new();
+            var sb = new StringBuilder();
+            try
+            {
+                c.CompileHeader(ctx, sb);
+                c.Compile(ctx, sb);
+                return sb.ToString();
+            }
+            catch (CompilerException e)
+            {
+                string trace = string.Join("\n", ctx.VariablesScopesStack.Select(s => s.Identifier));
+                CompilerError = e.Message + "\nProblem is near:\n" + trace;
+                return string.Empty;
+            }
+        }
+    }
+}