refactor: update build.go to use custom executable for building new exes

internal/custom_executable/build.go

@@ -3,52 +3,32 @@ package custom_executable
 import (
 	_ "embed"
 	"fmt"
-	"os"
 	"os/exec"
-	"path"
-	"strings"
 )
 
-//go:embed main.txt
 var content string
 
-func ReplaceAndBuild(content, outputPath, placeholder, randomString string) error {
-	// regex replace placeholder with random string
-	content = strings.ReplaceAll(content, placeholder, randomString)
-
-	// write content to file
-	file, err := os.Create("tmp.go")
-	if err != nil {
-		return fmt.Errorf("CodeCrafters Internal Error: failed to create tmp.go: %w", err)
+func ReplaceAndBuild(outputPath, randomString string) error {
+	// Our executable contains a placeholder for the random string
+	// The placeholder is <<<RANDOM>>>
+	// We will replace the placeholder with the random string
+	// The random string HAS to be the same length as the placeholder
+	if len(randomString) != 10 {
+		return fmt.Errorf("CodeCrafters Internal Error: randomString length must be 10")
 	}
-	defer file.Close()
-	file.WriteString(content)
 
-	// Run go build command
-	// ToDo: Remove log
-	goCmdFullPath := path.Join(os.Getenv("TESTER_DIR"), "go")
-	if goCmdFullPath == "go" {
-		return fmt.Errorf("CodeCrafters Internal Error: Couldn't find packaged go command.\nTESTER_DIR: %s", os.Getenv("TESTER_DIR"))
-	}
-	buildCmd := exec.Command(goCmdFullPath, "build", "-o", outputPath, "tmp.go")
+	command := fmt.Sprintf("echo -n \"%s\" | dd of=%s bs=1 seek=$((0x2070 + 4)) conv=notrunc", randomString, outputPath)
+	buildCmd := exec.Command("bash", "-c", command)
 	// buildCmd.Stdout = io.Discard
 	// buildCmd.Stderr = io.Discard
 	if err := buildCmd.Run(); err != nil {
-		return fmt.Errorf("CodeCrafters Internal Error: go build failed: %w", err)
-	}
-
-	err = os.Remove("tmp.go")
-	if err != nil {
-		return fmt.Errorf("CodeCrafters Internal Error: failed to remove tmp.go: %w", err)
+		return fmt.Errorf("CodeCrafters Internal Error: dd replace failed: %w", err)
 	}
 
 	return nil
 }
 
 func CreateExecutable(randomString, outputPath string) error {
-	// Define the file path, output path, and placeholder
-	placeholder := "PLACEHOLDER_RANDOM_STRING"
-
 	// Call the replaceAndBuild function
-	return ReplaceAndBuild(content, outputPath, placeholder, randomString)
+	return ReplaceAndBuild(outputPath, randomString)
 }