3 files changed, 83 insertions, 2 deletions

diff --git a/Compiler/Preprocessor.cs b/Compiler/Preprocessor.cs
new file mode 100644
index 0000000..01c14ab
--- /dev/null
+++ b/Compiler/Preprocessor.cs
@@ -0,0 +1,59 @@
+namespace Q1.Compiler;
+
+using System.Text.RegularExpressions;
+
+public static class Preprocessor
+{
+    private static readonly Dictionary<string, string> Defines = new();
+
+    public static string Process(string filePath)
+    {
+        List<string> lines = [];
+        ProcessFile(filePath, lines, []);
+        return string.Join(Environment.NewLine, lines);
+    }
+
+    private static void ProcessFile(string filePath, List<string> output, HashSet<string> includeGuard)
+    {
+        if (includeGuard.Contains(Path.GetFullPath(filePath)))
+            return; // prevent recursive includes
+        
+        includeGuard.Add(Path.GetFullPath(filePath));
+
+        foreach (string rawLine in File.ReadAllLines(filePath))
+        {
+            string line = rawLine.Trim();
+
+            if (line.StartsWith("#include"))
+            {
+                // simple format: #include "file"
+                Match match = Regex.Match(line, "#include\\s+\"([^\"]+)\"");
+                if (match.Success)
+                {
+                    string includePath = Path.Combine(Path.GetDirectoryName(filePath)!, match.Groups[1].Value);
+                    ProcessFile(includePath, output, includeGuard);
+                }
+                continue;
+            }
+            else if (line.StartsWith("#define"))
+            {
+                // simple format: #define NAME VALUE
+                Match match = Regex.Match(line, "#define\\s+(\\w+)\\s+(.*)");
+                if (match.Success)
+                    Defines[match.Groups[1].Value] = match.Groups[2].Value;
+                continue;
+            }
+            else if (line.StartsWith("#load"))
+            {
+                output.Add(line.Replace("#load", "#.include"));
+                continue;
+            }
+
+            // expand macros
+            foreach (KeyValuePair<string, string> kvp in Defines)
+                line = line.Replace(kvp.Key, kvp.Value);
+
+            output.Add(line);
+        }
+    }
+}
\ No newline at end of file
diff --git a/Compiler/Program.cs b/Compiler/Program.cs
index 3a277a1..09f7127 100644
--- a/Compiler/Program.cs
+++ b/Compiler/Program.cs
@@ -2,6 +2,7 @@
 
 using System.Text;
 using Antlr4.Runtime;
+using Antlr4.Runtime.Misc;
 using CommandLine;
 using visitors;
 using Parser = CommandLine.Parser;
@@ -26,7 +27,7 @@ public class Program
 
         try
         {
-            AntlrFileStream inputStream = new(options.InputFile);
+            ICharStream inputStream = new PreprocessingCharStream(options.InputFile);
             CGrammarLexer lexer = new(inputStream);
             lexer.RemoveErrorListeners();
 
@@ -48,4 +49,25 @@ public class Program
             Console.WriteLine($"{ex.Message}");
         }
     }
+}
+
+public class PreprocessingCharStream : ICharStream
+{
+    private readonly AntlrInputStream inner;
+
+    public PreprocessingCharStream(string filePath)
+    {
+        string preprocessed = Preprocessor.Process(filePath);
+        inner = new AntlrInputStream(preprocessed);
+    }
+
+    public int Index => inner.Index;
+    public int Size => inner.Size;
+    public string SourceName => inner.SourceName;
+    public void Consume() => inner.Consume();
+    public int LA(int i) => inner.LA(i);
+    public int Mark() => inner.Mark();
+    public void Release(int marker) => inner.Release(marker);
+    public void Seek(int index) => inner.Seek(index);
+    public string GetText(Interval interval) => inner.GetText(interval);
 }
\ No newline at end of file
diff --git a/Compiler/visitors/Main.cs b/Compiler/visitors/Main.cs
index cbd468f..3b32399 100644
--- a/Compiler/visitors/Main.cs
+++ b/Compiler/visitors/Main.cs
@@ -152,7 +152,7 @@ public partial class CCompilerVisitor : CGrammarBaseVisitor<object?>
                 .TrimEnd('\n')
                 .Trim();
 
-            this.Instruction("." + directive);
+            this.Instruction(directive);
         }
 
         return base.VisitErrorNode(node);