s3270 package for Go, based on https://github.com/msalcantara/go3270

s3270.go

package s3270

import (
	"fmt"
	"log"
	"os/exec"
	"strings"
	"time"
)

const (
	Enter = "Enter"
	Tab   = "Tab"
	F1    = "PF(1)"
	F2    = "PF(2)"
	F3    = "PF(3)"
	F4    = "PF(4)"
	F5    = "PF(5)"
	F6    = "PF(6)"
	F7    = "PF(7)"
	F8    = "PF(8)"
	F9    = "PF(9)"
	F10   = "PF(10)"
	F11   = "PF(11)"
	F12   = "PF(12)"
)

var (
	ErrNoAddr           = fmt.Errorf("no Addr specified")
	ErrAlreadyConnected = fmt.Errorf("already connected")
)

func NewEmulator(addr, scriptPort string) Emulator {
	return Emulator{
		Addr:       addr,
		ScriptPort: scriptPort,
	}
}

type Emulator struct {
	Addr       string
	ScriptPort string
}

func (e *Emulator) Connect() error {
	if e.Addr == "" {
		return ErrNoAddr
	}

	if e.IsConnected() {
		return ErrAlreadyConnected
	}

	if e.ScriptPort == "" {
		e.ScriptPort = "5000"
	}

	e.connect()

	if !e.IsConnected() {
		e.exec("quit")

		log.Fatalf("error connecting to %s", e.Addr)
	}

	return nil
}

func (e *Emulator) Disconnect() error {
	if e.IsConnected() {
		return e.exec("quit")
	}

	time.Sleep(time.Second)

	return nil
}

func (e *Emulator) ConnectionState() (string, error) {
	return e.query("ConnectionState")
}

func (e *Emulator) IsConnected() bool {
	if s, err := e.ConnectionState(); err != nil || len(strings.TrimSpace(s)) == 0 {
		return false
	}

	return true
}

func (e *Emulator) FillString(x, y int, value string) error {
	if err := e.MoveCursor(x, y); err != nil {
		return fmt.Errorf("move cursor error: %v", err)
	}

	return e.SetString(value)
}

func (e *Emulator) SetString(value string) error {
	return e.exec(command("String(%s)", value))
}

func (e *Emulator) Press(key string) error {
	if !e.validaKeyboard(key) {
		return fmt.Errorf("invalid key %s", key)
	}

	return e.exec(key)
}

func (e *Emulator) Value(x, y, l int) (string, error) {
	return e.execOutput(command("Ascii(%d,%d,%d)", x, y, l))
}

func (e *Emulator) Cursor() (string, error) {
	return e.query("cursor")
}

func (e *Emulator) MoveCursor(x, y int) error {
	return e.exec(command("MoveCursor(%d,%d)", x, y))
}

func (e *Emulator) validaKeyboard(key string) bool {
	switch key {
	case Tab:
		return true
	case Enter:
		return true
	default:
		return false
	}
}

func (e *Emulator) query(keyword string) (string, error) {
	return e.execOutput(command("query(%s)", keyword))
}

func (e *Emulator) connect() {
	cmd := exec.Command("s3270", "-scriptport", e.ScriptPort, e.Addr)

	cmd.Start()

	go func() {
		if err := cmd.Wait(); err != nil {
			log.Fatalf("error to create an instance of 3270\n%v\n", err)
		}
	}()

	time.Sleep(4 * time.Second)
}

func (e *Emulator) exec(arg string) error {
	if err := exec.Command("x3270if", "-t", e.ScriptPort, arg).Run(); err != nil {
		return err
	}

	return nil
}

func (e *Emulator) execOutput(arg string) (string, error) {
	b, err := exec.Command("x3270if", "-t", e.ScriptPort, arg).Output()
	if err != nil {
		return "", err
	}

	return string(b), nil
}

func command(format string, a ...interface{}) string {
	return fmt.Sprintf(format, a...)
}