1 files changed, 88 insertions, 16 deletions

diff --git a/main.go b/main.go
index 101e8d7..b4fa941 100644
--- a/main.go
+++ b/main.go
@@ -7,9 +7,88 @@ import (
 	"strings"
 )
 
+type ProgramState struct {
+	Labels map[string]uint
+	Defs   map[string]any
+}
+
+func parseFile(input_file_name string, input []byte) ([]byte, error) {
+	lines := strings.Split(string(input), "\n")
+
+	state := ProgramState{
+		Labels: make(map[string]uint),
+		Defs:   make(map[string]any),
+	}
+
+	label_line_number := uint(0)
+	for line_nb, line := range lines {
+		is_label_defined := strings.Contains(line, ":")
+
+		if is_label_defined {
+			parts := strings.Split(line, ":")
+			for _, label := range parts[:len(parts)-1] {
+				label = strings.ToUpper(label)
+				if _, ok := state.Labels[label]; ok {
+					fmt.Fprintf(
+						os.Stderr,
+						"File %s, line %d:\nLabel %s is already defined",
+						input_file_name,
+						line_nb,
+						label,
+					)
+					os.Exit(1)
+				}
+				state.Labels[label] = label_line_number
+			}
+
+			line = parts[len(parts)-1]
+		}
+
+		line = strings.TrimSpace(line)
+
+		next_instruction, err := Instructions.Parse(nil, line)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"File %s, line %d (1st pass):\n%w",
+				input_file_name,
+				line_nb,
+				err,
+			)
+		}
+
+		// TODO: Handle the case of program bigger than MBC (or maybe do it directly in the parameters)
+		label_line_number += uint(len(next_instruction))
+	}
+
+	result := []byte{}
+	for line_nb, line := range lines {
+		is_label_defined := strings.Contains(line, ":")
+
+		if is_label_defined {
+			parts := strings.Split(line, ":")
+
+			line = parts[len(parts)-1]
+		}
+
+		next_instruction, err := Instructions.Parse(&state, line)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"File %s, line %d (2nd pass): %w",
+				input_file_name,
+				line_nb,
+				err,
+			)
+		}
+
+		result = append(result, next_instruction...)
+	}
+
+	return result, nil
+}
+
 func main() {
 	if len(os.Args) != 3 {
-		fmt.Fprintf(os.Stderr, "Usage: gbasm [input_file] [output_file]")
+		fmt.Fprintf(os.Stderr, "Usage: gbasm [input_file] [output_file]\n")
 		os.Exit(1)
 	}
 
@@ -18,38 +97,31 @@ func main() {
 
 	input_file, err := os.Open(input_file_name)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "Error while opening input file: %s", err.Error())
+		fmt.Fprintf(os.Stderr, "Error while opening input file: %s\n", err.Error())
 		os.Exit(1)
 	}
 
 	input, err := io.ReadAll(input_file)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "Error while reading input file: %s", err.Error())
+		fmt.Fprintf(os.Stderr, "Error while reading input file: %s\n", err.Error())
 		os.Exit(1)
 	}
 
-	lines := strings.Split(string(input), "\n")
-
-	result := []byte{}
-	for _, line := range lines {
-		next_instruction, err := Instructions.Parse(line)
-		if err != nil {
-			fmt.Fprintf(os.Stderr, "%s", err.Error())
-			os.Exit(1)
-		}
-
-		result = append(result, next_instruction...)
+	result, err := parseFile(input_file_name, input)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %s\n", err.Error())
+		os.Exit(1)
 	}
 
 	output_file, err := os.Create(output_file_name)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "Error while opening output file: %s", err.Error())
+		fmt.Fprintf(os.Stderr, "Error while opening output file: %s\n", err.Error())
 		os.Exit(1)
 	}
 
 	_, err = output_file.Write(result)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "Error while writing to output file: %s", err.Error())
+		fmt.Fprintf(os.Stderr, "Error while writing to output file: %s\n", err.Error())
 		os.Exit(1)
 	}
 }