refactor: add flag parsing, improve code readability

src/main.go

@@ -1,82 +1,87 @@
 package main
 
 import (
+	"flag"
 	"fmt"
 	"log"
 	"net"
 	"os"
-	"strconv"
 	"strings"
 )
 
 func main() {
-	const BrotherPort int = 54921
-	BrotherIP := os.Args[1]
-	resolution := os.Args[2]
-	color := os.Args[3]
-
-	if net.ParseIP(BrotherIP) == nil {
-		fmt.Fprintf(os.Stderr, "Invalid IP address. Usage: %s <scanner ip>", os.Args[0])
-		os.Exit(0)
+	const brotherPort int = 54921
+
+	brotherIP := flag.String("a", "192.168.0.157", "IP address of the Brother scanner")
+	resolution := flag.Int("r", 300, "Resolution of the scan")
+	color := flag.String("c", "CGRAY", "Color mode of the scan")
+	adf := flag.Bool("m", false, "Enable scan of all pages from feeder")
+
+	flag.Parse()
+
+	if net.ParseIP(*brotherIP) == nil {
+		HandleError(fmt.Errorf("Invalid IP address: %s", *brotherIP))
 	}
 
 	log.Println("Valid IP address, opening socket...")
 
-	conn, err := net.Dial("tcp", fmt.Sprintf("%s:%d", BrotherIP, BrotherPort))
-	handleError(err)
+	socket, err := net.Dial("tcp", fmt.Sprintf("%s:%d", *brotherIP, brotherPort))
 
-	sendRequest(conn, resolution, color)
+	HandleError(err)
 
-	defer conn.Close()
-}
+	defer socket.Close()
 
-func sendRequest(conn net.Conn, _resolution string, _mode string) {
+	SendRequest(socket, *resolution, *color, *adf)
+}
 
-	reply := make([]byte, 128)
+func SendRequest(socket net.Conn, resolution int, _mode string, adf bool) {
 
-	resolution := checkResolution(_resolution)
-	mode, compression := checkMode(_mode)
+	mode, compression := GetCompressionMode(_mode)
 
 	log.Println("Reading scanner status...")
 
-	_, err := conn.Read(reply)
-	handleError(err)
+	status := ReadPacket(socket)[:7]
 
-	if "+OK 200" != string(reply[:7]) {
-		handleError(fmt.Errorf("Invalid reply from scanner: %s", reply))
+	if "+OK 200" != status {
+		HandleError(fmt.Errorf("Invalid reply from scanner: %s", status))
 	}
 
 	log.Println("Leasing options...")
 
-	resp := []byte(fmt.Sprintf("\x1bI\nR=%d,%d\nM=%s\n\x80", resolution, resolution, mode))
-	_, err = conn.Write(resp)
-	handleError(err)
+	request := []byte(fmt.Sprintf("\x1bI\nR=%d,%d\nM=%s\n\x80", resolution, resolution, mode))
+	SendPacket(socket, request)
 
-	_, err = conn.Read(reply)
-	handleError(err)
+	offer := ReadPacket(socket)
 
-	response := strings.Split(string(reply), ",")
+	if adf {
+		log.Println("Enabling automatic document feeder (ADF)")
+
+		request = []byte("\x1bD\nADF\n\x80")
+		SendPacket(socket, request)
+
+		ReadPacket(socket)
+	}
 
 	log.Println("Sending scan request...")
 
-	scanRequestFormat := "\x1bX\nR=%v,%v\nM=%s\nC=%s\nJ=MID\nB=50\nN=50\nA=0,0,%v,%v\n\x80"
+	offerOptions := strings.Split(offer, ",")
 
-	resp = []byte(fmt.Sprintf(scanRequestFormat, response[1], response[1], mode, compression, response[5], response[6]))
-	_, err = conn.Write(resp)
-	handleError(err)
+	requestFormat := "\x1bX\nR=%v,%v\nM=%s\nC=%s\nJ=MID\nB=50\nN=50\nA=0,0,%v,%v\n\x80"
+	request = []byte(fmt.Sprintf(requestFormat, offerOptions[1], offerOptions[1], mode, compression, offerOptions[5], offerOptions[6]))
+	SendPacket(socket, request)
+
+	log.Println("Scanning started...")
 }
 
-func checkResolution(_resolution string) int {
-	resolution, err := strconv.Atoi(_resolution)
+func HandleError(err error) {
 
-	if err != nil && resolution < 100 {
-		resolution = 300
+	if err != nil {
+		log.Fatal(err)
+		os.Exit(1)
 	}
-
-	return resolution
 }
 
-func checkMode(_mode string) (string, string) {
+func GetCompressionMode(_mode string) (string, string) {
 
 	if _mode == "GRAY64" {
 		return _mode, "NONE"
@@ -85,10 +90,16 @@ func checkMode(_mode string) (string, string) {
 	}
 }
 
-func handleError(err error) {
+func SendPacket(socket net.Conn, packet []byte) {
+	_, err := socket.Write(packet)
+	HandleError(err)
+}
 
-	if err != nil {
-		log.Fatal(err)
-		os.Exit(1)
-	}
+func ReadPacket(socket net.Conn) string {
+	reply := make([]byte, 128)
+
+	_, err := socket.Read(reply)
+	HandleError(err)
+
+	return string(reply)
 }