// Gerardo Marx 24/09/2026
// gpio command tool
// eg. ./gpio 17 out 1
//	   ./gpio 17 in 
//	   ./gpio 17 blink 500(ms)


#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

// prototype functions
int gpio_export(const char *gpio);
int gpio_direction(const char *gpio, const char *direction); // this function
int gpio_write(const char *gpio, const char *value); // write function
int gpio_read(const char *gpio); //read function
int gpio_unexport(const char *gpio);

int main(int argc, char *argv[]){
	int fd;
	const char *pin;
	const char *dir;
	const char *val = NULL;
	
	// checking that at least gpio and direction is passed
	if(argc<3){
		printf("Usage:\n");
		printf(" %s <gpio> in\n", argv[0]);
		printf(" %s <gpio> out <value>\n", argv[0]);
		return 1;
	}
	
    pin = argv[1]; // get gpio number from argument
	dir = argv[2]; // get gpio direction from arguments
	
	//const char *val = argv[3];
	// checking the gpio direction
	if(strcmp(dir, "out") == 0) {
			if(argc<4){
			printf("Error: GPIO out option requires a value.\n");
			printf("Usage: %s <gpio> out <0|1>\n", argv[0]);
			return 1;
			}
			val = argv[3];
			}

	gpio_export(pin); 
	gpio_direction(pin, dir);
	gpio_write(pin, val);
	gpio_unexport(pin);
	
}

// comple functions
//
// gpio_export
int gpio_export(const char *gpio){
	int fd;
	fd = open("/sys/class/gpio/chip0/export", O_WRONLY);
	if(fd<0){
		perror("Error opening the GPIO path during export");
		return -1;
	}
	write(fd,gpio,strlen(gpio));
	close(fd);
	return 0;
}

// gpio direction

int gpio_direction(const char *gpio, const char *direction){
	// pin direction - convert into functions
	int fd;
	char path[64];
	snprintf(path, sizeof(path),
			"/sys/class/gpio/chip0/gpio%s/direction", gpio);
	fd = open(path, O_WRONLY); //gpio number
	if(fd<0)
	{
		perror("Error opening the GPIO path");
		return -1;
	}
	write(fd,direction,strlen(direction));
	close(fd);
	return 0;
}


int gpio_write(const char *gpio, const char *value){
	int fd;
	char path[64];
	snprintf(path, sizeof(path),
			"/sys/class/gpio/chip0/gpio%s/value", gpio);
	fd = open(path, O_WRONLY);
	if(fd<0){
		perror("Error opening the GPIO path during write");
		return -1;
	}
	if(write(fd,value, strlen(value)) < 0) {
		perror("write");
		close(fd);
		return -1;
	}
	//write(fd, value, strlen(value));
	close(fd);
	return 0;
}

// gpio read
int gpio_read(const char *gpio); //read function




// unexport
int gpio_unexport(const char *gpio){
	int fd;
	fd = open("/sys/class/gpio/chip0/unexport", O_WRONLY);
	if(fd<0)
	{
		perror("Error opening the GPIO path during unexport");
		return -1;
	}
	if(write(fd,gpio, strlen(gpio)) < 0) {
		perror("unexport");
		close(fd);
		return -1;
	}
	close(fd);
	return 0;
}