From 6f03e2203f7027cf62c9bd331f86f172bf83b012 Mon Sep 17 00:00:00 2001
From: Oliver Stene <me@oliste.no>
Date: Sun, 8 Feb 2026 19:35:03 +0100
Subject: [PATCH] diagnostic

---
 compiler/Compiler/Diagnostic.cs | 77 +++++++++++++++++++++++++++++++++
 compiler/Compiler/Program.cs    | 41 ++----------------
 compiler/Compiler/test.nub      | 32 ++++++++++++++
 3 files changed, 113 insertions(+), 37 deletions(-)
 create mode 100644 compiler/Compiler/test.nub

diff --git a/compiler/Compiler/Diagnostic.cs b/compiler/Compiler/Diagnostic.cs
index 5b976c6..5ed6891 100644
--- a/compiler/Compiler/Diagnostic.cs
+++ b/compiler/Compiler/Diagnostic.cs
@@ -74,4 +74,81 @@ public enum DiagnosticSeverity
 public sealed class CompileException(Diagnostic diagnostic) : Exception
 {
     public readonly Diagnostic Diagnostic = diagnostic;
+}
+
+public static class DiagnosticFormatter
+{
+    public static void Print(Diagnostic diagnostic, TextWriter writer)
+    {
+        var (label, color) = diagnostic.Severity switch
+        {
+            DiagnosticSeverity.Info => ("info", Ansi.Cyan),
+            DiagnosticSeverity.Warning => ("warning", Ansi.Yellow),
+            DiagnosticSeverity.Error => ("error", Ansi.Red),
+            _ => ("unknown", Ansi.Reset),
+        };
+
+        writer.Write(color);
+        writer.Write(label);
+        writer.Write(Ansi.Reset);
+        writer.Write(": ");
+        writer.WriteLine(diagnostic.Message);
+
+        if (diagnostic.File is null)
+            return;
+
+        var file = diagnostic.File;
+        var lineNumberWidth = diagnostic.File.Line.ToString().Length;
+
+        writer.WriteLine($" {new string(' ', lineNumberWidth)}{file.File}:{file.Line}:{file.Column}");
+        writer.WriteLine($"{new string(' ', lineNumberWidth)} | ");
+
+        var sourceLine = TryReadLine(file.File, file.Line);
+        if (sourceLine != null)
+        {
+            writer.Write($"{file.Line.ToString().PadLeft(lineNumberWidth)} | ");
+            writer.WriteLine(sourceLine);
+
+            writer.Write(new string(' ', lineNumberWidth));
+            writer.Write(" | ");
+            writer.Write(new string(' ', file.Column - 1));
+            writer.Write(color);
+            writer.Write(new string('^', Math.Max(1, file.Length)));
+            writer.WriteLine(Ansi.Reset);
+        }
+
+        writer.WriteLine($"{new string(' ', lineNumberWidth)} |");
+
+        if (!string.IsNullOrWhiteSpace(diagnostic.Help))
+        {
+            writer.WriteLine($"   = help: {diagnostic.Help}");
+        }
+    }
+
+    private static string? TryReadLine(string file, int line)
+    {
+        try
+        {
+            using var reader = new StreamReader(file);
+            for (var i = 1; i < line; i++)
+            {
+                if (reader.ReadLine() == null)
+                    return null;
+            }
+
+            return reader.ReadLine();
+        }
+        catch
+        {
+            return null;
+        }
+    }
+
+    private static class Ansi
+    {
+        public const string Reset = "\e[0m";
+        public const string Red = "\e[31m";
+        public const string Yellow = "\e[33m";
+        public const string Cyan = "\e[36m";
+    }
 }
\ No newline at end of file
diff --git a/compiler/Compiler/Program.cs b/compiler/Compiler/Program.cs
index a3781dd..c81f58e 100644
--- a/compiler/Compiler/Program.cs
+++ b/compiler/Compiler/Program.cs
@@ -1,45 +1,12 @@
 using Compiler;
 
-const string contents = """
-                        struct person {
-                            age: i32
-                            name: string
-                        }
+var file = File.ReadAllText("test.nub");
 
-                        func main(: i32 {
-                            let x: i32 = 23
-                            x = 24
-                            
-                            if true {
-                                x = 49
-                            } else {
-                                x = 3
-                            }
-                            
-                            let i: i32 = 0
-                            
-                            x = 1 + 2 * 34
-                            
-                            while i < 10 {
-                                i = i + 1
-                                x = i
-                            }
-                            
-                            let me: person = struct person { age = 21 name = "Oliver" }
-                            
-                            do_something(me.name)
-                            return x
-                        }
-
-                        func do_something(text: string): void {
-                        }
-                        """;
-
-var tokens = Tokenizer.Tokenize("test.nub", contents, out var tokenizerDiagnostics);
+var tokens = Tokenizer.Tokenize("test.nub", file, out var tokenizerDiagnostics);
 
 foreach (var diagnostic in tokenizerDiagnostics)
 {
-    Console.WriteLine(diagnostic.Message);
+    DiagnosticFormatter.Print(diagnostic, Console.Error);
 }
 
 if (tokenizerDiagnostics.Any(x => x.Severity == DiagnosticSeverity.Error))
@@ -51,7 +18,7 @@ var nodes = Parser.Parse("test.nub", tokens, out var parserDiagnostics);
 
 foreach (var diagnostic in parserDiagnostics)
 {
-    Console.WriteLine(diagnostic.Message);
+    DiagnosticFormatter.Print(diagnostic, Console.Error);
 }
 
 if (parserDiagnostics.Any(x => x.Severity == DiagnosticSeverity.Error))
diff --git a/compiler/Compiler/test.nub b/compiler/Compiler/test.nub
new file mode 100644
index 0000000..fa400d3
--- /dev/null
+++ b/compiler/Compiler/test.nub
@@ -0,0 +1,32 @@
+struct person {
+    age: i32
+    name: string
+}
+
+func main(): i32 {
+    let x: i32 = 23
+    x = 24
+    
+    if true {
+        x = 49
+    } else {
+        x = 3
+    }
+    
+    let i: i32 = 0
+    
+    x = 1 + 2 * 34
+    
+    while i < 10 {
+        i = i + 1
+        x = i
+    }
+    
+    let me: person = struct person { age = 21 name = "Oliver" }
+    
+    do_something(me.name)
+    return x
+}
+
+func do_something(text: string): void {
+}
\ No newline at end of file