package dpms

import (
	"fmt"

	"github.com/jezek/xgb"
	xgbdpms "github.com/jezek/xgb/dpms"
	"github.com/jezek/xgb/xproto"

	"edge-infra.dev/pkg/sds/lib/xorg"
)

type NotPresentError struct {
	msg string
}

func (e *NotPresentError) Error() string {
	return e.msg
}

type DPMS interface {
	GetDPMSInfo() (*Info, error)
}

type dpms struct{}

func NewDPMS() DPMS {
	return &dpms{}
}

type Info struct {
	ScreenSaver *xproto.GetScreenSaverReply
	Timeouts    *xgbdpms.GetTimeoutsReply
	Info        *xgbdpms.InfoReply
	Capable     bool
}

func (d *dpms) GetDPMSInfo() (*Info, error) {
	dpmsInfo := Info{}
	dpmsPresent := true

	xgbConn, err := d.dpmsInit()
	if _, ok := err.(*NotPresentError); ok {
		dpmsPresent = false
	} else if err != nil {
		return nil, err
	}

	if err := addScreenSaver(xgbConn, &dpmsInfo); err != nil {
		return nil, err
	}

	if dpmsPresent {
		if err := addDPMSCapability(xgbConn, &dpmsInfo); err != nil {
			return nil, err
		}
	}

	if dpmsInfo.Capable {
		if err := addDPMSStates(xgbConn, &dpmsInfo); err != nil {
			return nil, err
		}
	}

	return &dpmsInfo, nil
}

func addScreenSaver(xgbConn *xgb.Conn, dpms *Info) error {
	screenSaver, err := xproto.GetScreenSaver(xgbConn).Reply()
	if err != nil {
		return err
	}
	dpms.ScreenSaver = screenSaver

	return nil
}

func addDPMSCapability(xgbConn *xgb.Conn, dpms *Info) error {
	capable, err := xgbdpms.Capable(xgbConn).Reply()
	if err != nil {
		return err
	} else if capable == nil {
		return fmt.Errorf("DPMS capability not found")
	}

	dpms.Capable = capable.Capable

	return nil
}

func addDPMSStates(xgbConn *xgb.Conn, dpms *Info) error {
	timeouts, err := xgbdpms.GetTimeouts(xgbConn).Reply()
	if err != nil {
		return err
	}

	info, err := xgbdpms.Info(xgbConn).Reply()
	if err != nil {
		return err
	}

	dpms.Timeouts = timeouts
	dpms.Info = info

	return nil
}

func (d *dpms) dpmsInit() (*xgb.Conn, error) {
	xgbConn, err := xorg.GetXGBConnection()
	if err != nil {
		return nil, err
	}

	reply, err := xproto.QueryExtension(xgbConn, 4, "DPMS").Reply()
	if err == nil && reply != nil && !reply.Present {
		return xgbConn, &NotPresentError{"DPMS Extension not found"}
	}

	if err := xgbdpms.Init(xgbConn); err != nil {
		return nil, err
	}

	return xgbConn, nil
}