package display

import (
	"os/exec"
	"regexp"
	"strings"
)


// Xset monitors/controls the display using xset
type Xset struct {}

// Suspend the display
func (Xset) Suspend() error {
	cmd := exec.Command("xset",
		"dpms",
		"force",
		"suspend",
	)
	return cmd.Run()
}

// IsOn determines if the display is on
func (Xset) IsOn() (bool, error) {
	cmd := exec.Command("xset", "q")
	outputBytes, err := cmd.CombinedOutput()
	if err != nil {
		return false, err
	}
	return determineIfDisplayIsOn(string(outputBytes)), nil
}

func determineIfDisplayIsOn(xsetOutput string) bool {
	if ! strings.Contains(xsetOutput, "Monitor") {
		// after booting xset q is missing this line
		// lacking better ideas assume display is on
		return true
	}

	re := regexp.MustCompile(`Monitor is (\w+)`)
	matches := re.FindStringSubmatch(xsetOutput)
	if len(matches) >= 2 {
		if matches[1] == "On" {
			return true
		}
	}
	return false
}