/*
 * Copyright (c) 2024-2026 Jakob Kaivo <jkk@ung.org>
 *
 * *VERY* loosely based on  https://gitlab.freedesktop.org/hadess/iio-sensor-proxy/-/raw/master/src/monitor-sensor.c
 *
 */

#define _XOPEN_SOURCE 700

#include <errno.h>
#include <fcntl.h>
#include <glob.h>
#include <libgen.h>
#include <limits.h>
#include <locale.h>
#include <math.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>

#ifndef O_SEARCH
#define O_SEARCH 0
#endif

#define DEFAULT_OUTPUT		"eDP-1"

#define SWAY_MAGIC		"i3-ipc"
#define SWAY_RUN_COMMAND	0

#define RADIANS_TO_DEGREES	(180.0/M_PI)
#define THRESHOLD		(35)

typedef enum {
	NORMAL = 0,
	RIGHT  = 1,
	INVERT = 2,
	LEFT   = 3,
} orientation;

static char *angles[] = { "0", "90", "180", "270" };

static void rotate(int sway_socket, const char *out, orientation angle)
{
	char buf[128];
	uint32_t msg_type = SWAY_RUN_COMMAND;
	uint32_t msg_length = snprintf(buf, sizeof(buf), "output %s transform %s", out, angles[angle]);
	write(sway_socket, SWAY_MAGIC, strlen(SWAY_MAGIC));
	write(sway_socket, &msg_length, sizeof(msg_length));
	write(sway_socket, &msg_type, sizeof(msg_type));
	write(sway_socket, buf, msg_length);

	/* read and discard the response */
	/* it will mostly be: [ { "success": true } ] */ 
	read(sway_socket, buf, strlen(SWAY_MAGIC));
	read(sway_socket, &msg_length, sizeof(msg_length));
	read(sway_socket, &msg_type, sizeof(msg_type));
	while (msg_length != 0) {
		size_t toread = msg_length > sizeof(buf) ? sizeof(buf) : msg_length;
		ssize_t nread = read(sway_socket, buf, toread);
		msg_length -= nread;
	}
}

static int find_accel(char *devno)
{
	if (devno) {
		char path[PATH_MAX] = "";
		snprintf(path, sizeof(path), "/sys/bus/iio/devices/iio:device%s", devno);
		return open(path, O_DIRECTORY | O_SEARCH);
	}

	int dirfd = -1;

	glob_t gl = { 0 };
	glob("/sys/bus/iio/devices/iio:device*/in_accel_x_raw", 0, NULL, &gl);

	if (gl.gl_pathc == 1) {
		dirfd = open(dirname(gl.gl_pathv[0]), O_DIRECTORY | O_SEARCH);
		if (dirfd == -1) {
			perror("opening device directory");
			exit(1);
		}
	} else if (gl.gl_pathc == 0) {
		fprintf(stderr, "no IIO accelerometers found\n");
		exit(1);
	} else {
		fprintf(stderr, "multiple IIO accelerometers found:\n");
		for (size_t i = 0; i < gl.gl_pathc; i++) {
			fprintf(stderr, "%s\n", basename(dirname(gl.gl_pathv[i])));
		}
		/* TODO: implement this */
		fprintf(stderr, "select one with -a <device#>\n");
		exit(1);
	}

	globfree(&gl);

	return dirfd;
}

static double read_val(int dirfd, const char *path)
{
	int fd = openat(dirfd, path, O_RDONLY);
	char buf[32] = {0};
	read(fd, buf, sizeof(buf));
	double ret = 0;
	sscanf(buf, "%lg", &ret);
	close(fd);
	return ret;
}

int open_swaysock(void)
{
	char *swaysock = getenv("SWAYSOCK");
	if (swaysock == NULL) {
		fprintf(stderr, "SWAYSOCK not set\n");
		exit(1);
	}

	int sway_socket = socket(AF_UNIX, SOCK_STREAM, 0);
	if (sway_socket == -1) {
		perror("socket()");
		exit(1);
	}

	struct sockaddr_un sun = {
		.sun_family = AF_UNIX,
	};
	/* This is it - the one time it's appropriate to use str*n*cpy */
	strncpy(sun.sun_path, swaysock, sizeof(sun.sun_path));

	if (connect(sway_socket, (struct sockaddr *)&sun, sizeof(sun)) == -1) {
		perror("connect()");
		exit(1);
	}

	return sway_socket;
}

int main(int argc, char *argv[])
{
	char *output = DEFAULT_OUTPUT;
	char *accel = NULL;

	setlocale(LC_ALL, "");

	int c;
	while ((c = getopt(argc, argv, "a:o:l:n:r:u:i:")) != -1) {
		switch (c) {
		case 'a':
			accel = optarg;
			break;

		case 'o':
			output = optarg;
			break;

		case 'n':
			angles[NORMAL] = optarg;
			break;

		case 'r':
			angles[RIGHT] = optarg;
			break;

		case 'i':
			angles[INVERT] = optarg;
			break;

		case 'l':
			angles[LEFT] = optarg;
			break;

		default:
			return 1;
		}
	}

	int devdir = find_accel(accel);
	int sway_socket = open_swaysock();

	for (;;) {
		double x_raw = read_val(devdir, "in_accel_x_raw");
		double y_raw = read_val(devdir, "in_accel_y_raw");
		double z_raw = read_val(devdir, "in_accel_z_raw");
		double scale = read_val(devdir, "scale");

		int x = (int)(x_raw * scale);
		int y = (int)(y_raw * scale);
		int z = (int)(z_raw * scale);

		int portrait = round(atan2(x, sqrt(x * y + z * z)) * RADIANS_TO_DEGREES);
		int landscape = round(atan2(y, sqrt(x * x + z * z)) * RADIANS_TO_DEGREES);

		if (abs(portrait) > THRESHOLD) {
			rotate(sway_socket, output, portrait < 0 ? LEFT : RIGHT);
		} else if (abs(landscape) > THRESHOLD) {
			rotate(sway_socket, output, landscape < 0 ? INVERT : NORMAL);
		}

		sleep(1);
	}
}