#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <error.h>
#include <errno.h>
#include <limits.h>
#include <unistd.h>
#include <string.h>
#include "linux/input.h"

#define INPUT_DEV_NODE "/dev/input/by-path/platform-ffc04000.i2c-event"
#define SYSFS_DEVICE_DIR "/sys/devices/platform/soc/ffc04000.i2c/i2c-0/0-0053/"

#define EV_CODE_X (0)
#define EV_CODE_Y (1)
#define EV_CODE_Z (2)

#define LOOP_COUNT (100)

void write_sysfs_cntl_file(const char *dir_name, const char *file_name,
		const char *write_str) {

	char path[PATH_MAX];
	int path_length;
	int file_fd;
	int result;

	// create the path to the file we need to open
	path_length = snprintf(path, PATH_MAX, "%s/%s",	dir_name, file_name);
	if(path_length < 0)
		error(1, 0, "path output error");
	if(path_length >= PATH_MAX)
		error(1, 0, "path length overflow");

	// open the file
	file_fd = open(path, O_WRONLY | O_SYNC);
	if(file_fd < 0)
		error(1, errno, "could not open file '%s'", path);
	
	// write the string to the file
	result = write(file_fd, write_str, strlen(write_str));
	if(result < 0)
		error(1, errno, "writing to '%s'", path);
	if((size_t)(result) != strlen(write_str))
		error(1, errno, "buffer underflow writing '%s'", path);

	// close the file
	result = close(file_fd);
	if(result < 0)
		error(1, errno, "could not close file '%s'", path);
}

int main(void) {
	int event_dev_fd;
	const char *input_dev_node = INPUT_DEV_NODE;
	int result;
	struct input_event the_event;

	// enable adxl
	write_sysfs_cntl_file(SYSFS_DEVICE_DIR, "disable", "0");

	// set the sample rate to maximum
	write_sysfs_cntl_file(SYSFS_DEVICE_DIR, "rate", "15");

	// do not auto sleep
	write_sysfs_cntl_file(SYSFS_DEVICE_DIR, "autosleep", "0");
	
	// open the event device node
	event_dev_fd = open(input_dev_node, O_RDONLY | O_SYNC);
	if(event_dev_fd < 0)
		error(1, errno, "could not open file '%s'", input_dev_node);
	
	printf("Please tap the DE10 Nano board.\n");
	
	while(1) {
		// read the next event
		result = read(event_dev_fd, &the_event, 
				sizeof(struct input_event));
		if(result < 0)
			error(1, errno, "reading %d from '%s'", 
					sizeof(struct input_event),
					input_dev_node);
		if(result != sizeof(struct input_event))
			error(1, 0, "did not read %d bytes from '%s'", 
					sizeof(struct input_event),
					input_dev_node);
	
		if((the_event.type == EV_KEY) && (the_event.code == BTN_TOUCH))
			break;
	}
	
	printf("Tap detected.\n");

	// close the device node
	result = close(event_dev_fd);
	if(result < 0)
		error(1, errno, "could not close file '%s'", input_dev_node);

	// disable adxl
	write_sysfs_cntl_file(SYSFS_DEVICE_DIR, "disable", "1");
}