/* build:
	gcc -O2 -Wall -W -Wno-unused-parameter -o set-backlight.o -c set-backlight.c
	gcc -o set-backlight set-backlight.o
*/

#define DSME_SET_DISPLAY_BRIGHTNESS 0x0289

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>

int main( int argc, char *argv[] ){
	int dsme_fd;
	unsigned level, is_n810 = 0;

	// get device model
	{
		FILE *fp;
		// code ported from advanced-backlight
		if((fp = fopen("/proc/component_version", "r")) != NULL){
			char version;
			fseek(fp, sizeof(char)*15, 0); // The important character is the 16th in the file
			fread(&version, sizeof(char), 1, fp);
			fclose(fp);
			if(version == '4') is_n810 = 1;
		}
	}

	// get brightness level argument
	if(argc != 2){
		fprintf(stderr, "Syntax: %s <brightness level 0-127>\n", argv[0]);
		return EXIT_FAILURE;
	}
	sscanf(argv[1], "%u", &level);
	if(level > 127) level = 127;
	if(level == 0 && !is_n810) level = 1;

	// open DSME socket
	struct sockaddr_un addr;
	dsme_fd = socket(PF_UNIX, SOCK_STREAM, 0);
	if(dsme_fd < 0){
		fprintf(stderr, "can't open dsme socket\n");
		return EXIT_FAILURE;
	}
	memset(&addr, 0, sizeof(addr));
	addr.sun_family = AF_UNIX;
	strcpy(addr.sun_path, "/tmp/dsmesock");
	if(connect(dsme_fd, (struct sockaddr *)&addr, sizeof(addr)) < 0){
		close(dsme_fd);
		fprintf(stderr, "can't connect to dsme socket\n");
		return EXIT_FAILURE;
	}

	// write brightness level to socket
	printf("setting brightness to %u\n", level);
	struct {
		unsigned len;
		unsigned type;
		unsigned arg;
	} message;
	message.len = sizeof(message);
	message.type = DSME_SET_DISPLAY_BRIGHTNESS;
	message.arg = ((unsigned)level * 2) + 1;
	send(dsme_fd, (void *)&message, sizeof(message), 0);

	// close DSME socket
	close(dsme_fd);

	return EXIT_SUCCESS;
}