#define _XOPEN_SOURCE
#include <Xm/Scale.h>
#include <Xm/Xm.h>
#include <Xm/MwmUtil.h>
#include <X11/Shell.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>

void valueChanged (Widget, XtPointer, XtPointer);
void setBrightness (int);
int  getBrightness ();
int  getMaxBrightness ();

int main (int argc, char *argv[]) {
	XtAppContext application;
	Widget window = XtVaAppInitialize (
		&application, "Brightness",
		NULL, 0,
		&argc, argv,
		NULL,
		XmNtitle, "Brightness",
		NULL);
		
	int level   = getBrightness();
	int max     = getMaxBrightness();
	int percent =
		(float)(level) /
		(float)(max) * 100;
	
	Widget scale = XtVaCreateManagedWidget (
		"Brightness", xmScaleWidgetClass, window,
		XmNmaximum,   100,
		XmNminimum,   1,
		XmNvalue,     percent,
		NULL);
	XtAddCallback(scale, XmNvalueChangedCallback, valueChanged, NULL);
	
	XtVaSetValues(window, XmNmwmDecorations, MWM_DECOR_BORDER, NULL);
	XtVaSetValues(window, XmNmwmFunctions, MWM_FUNC_RESIZE, NULL);

	//XtVaSetValues(window, XtNheight, 400, NULL);
	//XtVaSetValues(window, XtNwidth, 400, NULL);
	
	XtRealizeWidget(window);
	XtAppMainLoop(application);
}

void valueChanged (Widget scale, XtPointer clientData, XtPointer callData) {
	(void)(scale);
	(void)(clientData);
	XmScaleCallbackStruct *event = (XmScaleCallbackStruct *)(callData);
	setBrightness(event->value);
}

void setBrightness (int level) {
	char command[32] = { 0 };
	snprintf(command, 32, "brightnessctl s %d%% -q", level);
	system(command);
}

int getBrightness () {
	FILE *stream = popen("brightnessctl g", "r");
	if (stream == NULL) {
		fprintf(stderr, "ERR could not get brightness\n");
		return 1;
	}
	int result = 1;
	fscanf(stream, "%d", &result);
	pclose(stream);
	return result;
}

int getMaxBrightness () {
	FILE *stream = popen("brightnessctl m", "r");
	if (stream == NULL) {
		fprintf(stderr, "ERR could not get brightness\n");
		return 1;
	}
	int result = 1;
	fscanf(stream, "%d", &result);
	pclose(stream);
	return result;
}