package stty

import (
	"fmt"
	"os"
    "golang.org/x/sys/unix"
	"golang.org/x/term"
	"os/exec"
)

type stty struct {
}

func ValidateTtyFile(filepath string) error {
    file, err := os.Open(filepath)
	if err != nil {
		return err
	}
	defer file.Close()

	err = unix.Access(filepath, unix.W_OK)
	if err != nil {
		return err
	}

	if term.IsTerminal(int(file.Fd())) {
		return nil
	}
	return fmt.Errorf("File is not a tty.")
}

func Get() (*stty, error) {
	checkSttyCMD := exec.Command("stty", "--version")
	sttyOutput, err := checkSttyCMD.Output()
	if err != nil || len(sttyOutput) == 0 {
		return nil, fmt.Errorf("Stty is missing. Because: " + err.Error())
	}
	return &stty{}, nil
}

func (s *stty) SetBaudRate(portPath string, baudrate int) error {
	setBaudRateCMD := exec.Command("stty", "-F", portPath, fmt.Sprint(baudrate))
	_, err := setBaudRateCMD.Output()
	return err
}

func (s *stty) CheckBaudRate(portPath string) (baudrate int, err error) {
	checkBaudRateCMD := exec.Command("stty", "-F", portPath, "speed")
	sttyOutput, err := checkBaudRateCMD.Output()
	if err != nil {
		return 0, fmt.Errorf("Failed to invoke stty. Because: " + err.Error())
	}

	_, err = fmt.Sscan(string(sttyOutput), &baudrate)
	if err != nil {
		return 0, fmt.Errorf("Failed to read baudrate from stty output. Because:" + err.Error())
	}
	return baudrate, nil
}

func (s *stty) TestBaudRate(portPath string, baudrate int) (error) {
	err := s.SetBaudRate(portPath, baudrate)
	if err != nil {
		return fmt.Errorf("Failed to set baudrate using stty. Because: " + err.Error())
	}

	newBaudRate, err := s.CheckBaudRate(portPath)
	if err != nil {
		return fmt.Errorf("Failed to check baudrate using stty. Because: " + err.Error())
	}

	if newBaudRate == baudrate {
		return nil
	}
	return fmt.Errorf("Selected baudrate is not supported.") 
}