package backlight

import (
	"fmt"
	"os"
	"path/filepath"
	"strconv"
	"strings"

	"git.trj.tw/golang/utils"
)

type Backlight struct {
	Directory string
}

const currentValueFile = "brightness"
const maxValueFile = "max_brightness"

func NewInstance(path string) (*Backlight, error) {
	bl := &Backlight{Directory: path}

	if !utils.CheckExists(path, true) {
		return nil, fmt.Errorf("backlight class directory check fail")
	}

	// check brightness and max_brightness file exists
	brightnessFile := filepath.Join(path, currentValueFile)
	maxBrightnessFile := filepath.Join(path, maxValueFile)

	if !utils.CheckExists(brightnessFile, false) {
		return nil, fmt.Errorf("brightness file check fail")
	}
	if !utils.CheckExists(maxBrightnessFile, false) {
		return nil, fmt.Errorf("max_brightness file check fail")
	}

	return bl, nil
}

func readBrightnessValue(file string) (val int, err error) {
	cnt, err := os.ReadFile(file)
	if err != nil {
		return 0, err
	}

	val, err = strconv.Atoi(strings.TrimSpace(string(cnt)))
	if err != nil {
		return 0, err
	}

	return
}

func (b *Backlight) GetCurrent() (val int, err error) {
	return readBrightnessValue(filepath.Join(b.Directory, currentValueFile))
}

func (b *Backlight) GetMax() (val int, err error) {
	return readBrightnessValue(filepath.Join(b.Directory, maxValueFile))
}

func (b *Backlight) SetValue(val int) (err error) {
	brightness := filepath.Join(b.Directory, "brightness")

	if err := os.WriteFile(brightness, []byte(fmt.Sprintf("%d", val)), 0644); err != nil {
		return err
	}

	return
}