From aedc605445a45cbbe5cc7e4d0c6f582412a83c62 Mon Sep 17 00:00:00 2001
From: Mattias Hansson <mattias@techserio.com>
Date: Wed, 5 Nov 2025 19:14:26 +0100
Subject: [PATCH] Added goto

---
 internal/commands/goto.go | 106 ++++++++++++++++++++++++++++++++++++++
 main.go                   |   1 +
 2 files changed, 107 insertions(+)
 create mode 100644 internal/commands/goto.go

diff --git a/internal/commands/goto.go b/internal/commands/goto.go
new file mode 100644
index 0000000..78d277f
--- /dev/null
+++ b/internal/commands/goto.go
@@ -0,0 +1,106 @@
+package commands
+
+import (
+	"fmt"
+	"strings"
+
+	"c65gm/internal/compiler"
+	"c65gm/internal/preproc"
+	"c65gm/internal/utils"
+)
+
+// GotoCommand handles GOTO statements
+// Syntax: GOTO <target>
+// Where target is:
+//   - Label name (naked identifier)
+//   - Word variable (indirect jump via jmp (var))
+//   - Expression/address (numeric constant or expression)
+//
+// Note: Byte variable jumps not supported - use inline asm for zero-page jumps
+type GotoCommand struct {
+	targetName string
+	targetKind compiler.VarKind
+	address    uint16
+	isVar      bool
+	isLabel    bool // true if neither var nor expression
+}
+
+func (c *GotoCommand) WillHandle(line preproc.Line) bool {
+	params, err := utils.ParseParams(line.Text)
+	if err != nil || len(params) == 0 {
+		return false
+	}
+	return strings.ToUpper(params[0]) == "GOTO"
+}
+
+func (c *GotoCommand) Interpret(line preproc.Line, ctx *compiler.CompilerContext) error {
+	// Clear state
+	c.targetName = ""
+	c.address = 0
+	c.isVar = false
+	c.isLabel = false
+
+	params, err := utils.ParseParams(line.Text)
+	if err != nil {
+		return err
+	}
+
+	if len(params) != 2 {
+		return fmt.Errorf("GOTO: expected 2 parameters, got %d", len(params))
+	}
+
+	targetParam := params[1]
+	scope := ctx.CurrentScope()
+
+	constLookup := func(name string) (int64, bool) {
+		sym := ctx.SymbolTable.Lookup(name, scope)
+		if sym != nil && sym.IsConst() {
+			return int64(sym.Value), true
+		}
+		return 0, false
+	}
+
+	// Try ParseOperandParam - handles variables, constants, expressions
+	varName, varKind, value, isVar, err := compiler.ParseOperandParam(
+		targetParam, ctx.SymbolTable, scope, constLookup)
+
+	if err != nil {
+		// Not a variable or expression -> treat as label
+		c.targetName = targetParam
+		c.isLabel = true
+		return nil
+	}
+
+	// It's either a variable or expression/constant
+	if isVar {
+		// It's a variable
+		if varKind == compiler.KindByte {
+			return fmt.Errorf("GOTO: cannot jump to byte variable %q (use inline assembler for zero-page jumps)", targetParam)
+		}
+		c.targetName = varName
+		c.targetKind = varKind
+		c.isVar = true
+		return nil
+	}
+
+	// It's an expression/constant
+	c.address = value
+	c.isVar = false
+	c.isLabel = false
+	return nil
+}
+
+func (c *GotoCommand) Generate(_ *compiler.CompilerContext) ([]string, error) {
+	if c.isVar {
+		// Indirect jump through word variable
+		return []string{fmt.Sprintf("\tjmp (%s)", c.targetName)}, nil
+	}
+
+	if c.isLabel {
+		// Jump to label
+		return []string{fmt.Sprintf("\tjmp %s", c.targetName)}, nil
+	}
+
+	// Jump to computed address
+	return []string{fmt.Sprintf("\tjmp $%04x", c.address)}, nil
+}
diff --git a/main.go b/main.go
index 2ba9f15..0280c6f 100644
--- a/main.go
+++ b/main.go
@@ -95,6 +95,7 @@ func registerCommands(comp *compiler.Compiler) {
 	comp.Registry().Register(&commands.FendCommand{})
 	comp.Registry().Register(&commands.IncrCommand{})
 	comp.Registry().Register(&commands.DecrCommand{})
+	comp.Registry().Register(&commands.GotoCommand{})
 
 }