#define _XOPEN_SOURCE 700
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <X11/extensions/Xrandr.h>
#include <X11/extensions/XInput.h>

#define ACPID_SOCK_PATH "/var/run/acpid.socket"

/* once to go into tablet mode, twice to come out */
#define ACPI_ROTATE	"ibm/hotkey LEN0068:00 00000080 000060c0\n"

/* once on keydown, once on keyup */
#define ACPI_ROTATELOCK	"ibm/hotkey LEN0068:00 00000080 00006020\n"

/* from /usr/include/xorg/wacom-properties.h */
#define WACOM_PROP_ROTATION	"Wacom Rotation"
#define WACOM_DEV_STYLUS	"Wacom ISDv4 EC Pen stylus"
#define WACOM_DEV_ERASER	"Wacom ISDv4 EC Pen eraser"

#define TOUCH_PROP_MATRIX	"Coordinate Transformation Matrix"
#define TOUCH_DEV		"SYNAPTICS Synaptics Touch Digitizer V04"

#define GRAVITY_CUTOFF	(7.0)
#define DEV_PATH	"/sys/bus/iio/devices/iio:device%d"
#define SCALE_FILE	"in_accel_scale"
#define X_RAW_FILE	"in_accel_x_raw"
#define Y_RAW_FILE	"in_accel_y_raw"

int tabletmode = 0;
int rotatelock = 0;
enum rotation { NORMAL, INVERSE, LEFT, RIGHT };

static Display *dpy = NULL;

void rotatescreen(enum rotation r)
{
	Rotation xr[] = { RR_Rotate_0, RR_Rotate_180, RR_Rotate_90, RR_Rotate_270 };
	if (dpy == NULL) {
		dpy = XOpenDisplay(NULL);
	}
	static Window root = 0;
	if (root == 0) {
		root = RootWindow(dpy, DefaultScreen(dpy));
	}
	XRRScreenConfiguration *xsc = XRRGetScreenInfo(dpy, root);
	XRRSetScreenConfig(dpy, xsc, root, 0, xr[r], CurrentTime);
}

XDevice *findxdev(const char *device)
{
	int ndevs = 0;
	XDevice *dev = NULL;
	XDeviceInfo *devs = XListInputDevices(dpy, &ndevs);
	for (int i = 0; i < ndevs; i++) {
		if ((!strcmp(devs[i].name, device))) {
			dev = XOpenDevice(dpy, devs[i].id);
			break;
		}
	}
	XFreeDeviceList(devs);
	return dev;
}

void rotatetouch(enum rotation r)
{
	/*
	char *matrix[] = {
		"1 0 0 0 1 0 0 0 1",
		"-1 0 1 0 -1 1 0 0 1",
		"0 -1 1 1 0 0 0 0 1",
		"0 1 0 -1 0 1 0 0 1",
	};
	char cmd[256];
	sprintf(cmd, "xinput set-float-prop '%s' '%s' %s", TOUCH_DEVICE, TOUCH_PROP_MATRIX, matrix[r]);
	system(cmd);
	*/
	float matrix[][9] = {
		{ 1,  0, 0,  0,  1, 0, 0, 0, 1 },
		{ -1, 0, 1,  0, -1, 1, 0, 0, 1 },
		{ 0, -1, 1,  1,  0, 0, 0, 0, 1 },
		{ 0,  1, 0, -1,  0, 1, 0, 0, 1 },
	};
	Atom type = XInternAtom(dpy, "FLOAT", False);
	Atom prop = XInternAtom(dpy, TOUCH_PROP_MATRIX, False);
	if (!prop) {
		return;
	}

	XDevice *dev = findxdev(TOUCH_DEV);
	XChangeDeviceProperty(dpy, dev, prop, type, 32, PropModeReplace,
		(void*)matrix[r], 9);
}

void rotatewacompart(enum rotation r, XDevice *dev)
{
	unsigned char rotations[] = { 0, 3, 2, 1 };
	unsigned char *data;
	int format;
	unsigned long nitems, bytes_after;
	Atom type, prop;

	prop = XInternAtom(dpy, WACOM_PROP_ROTATION, True);
	if (!prop) {
		return;
	}

	XGetDeviceProperty(dpy, dev, prop, 0, 1000, False, AnyPropertyType, &type, &format, &nitems, &bytes_after, &data);
	if (nitems == 0 || format != 8) {
		return;
	}

	*data = rotations[r];
	XChangeDeviceProperty(dpy, dev, prop, type, format, PropModeReplace,
		data, nitems);
	XFlush(dpy);

	XFree(data);
}

void rotatewacom(enum rotation r)
{
	XDevice *stylus = NULL, *eraser = NULL;
	stylus = findxdev(WACOM_DEV_STYLUS);
	rotatewacompart(r, stylus);
	eraser = findxdev(WACOM_DEV_ERASER);
	rotatewacompart(r, eraser);
}

enum rotation setrotation(enum rotation r)
{
	static enum rotation prev = NORMAL;
	if (r == prev) {
		return r;
	}

	rotatescreen(r);
	/* Allow xinput to relocate devices */
	sleep(1);
	rotatetouch(r);
	rotatewacom(r);

	prev = r;
	return r;
}

int openacpi(const char *path)
{
	struct sockaddr_un sun = {0};
	int sock = socket(AF_UNIX, SOCK_STREAM, 0);
	if (sock == -1) {
		return -1;
	}

	sun.sun_family = AF_UNIX;
	strcpy(sun.sun_path, path ? path : ACPID_SOCK_PATH);
	if (connect(sock, (const struct sockaddr*)&sun, sizeof(sun)) == -1) {
		close(sock);
		return -1;
	}

	return sock;
}

void checkacpi(int acpi)
{
	static int nrotate = 0;
	static int nlock = 0;

	char buf[BUFSIZ];
	ssize_t n = read(acpi, buf, sizeof(buf));
	if (n <= 0) {
		return;
	}

	if (!strcmp(buf, ACPI_ROTATE)) {
		nrotate++;
		if (nrotate == 1) {
			tabletmode = 1;
			/* disable touchpad */
			/* disable trackpoint */
		} else if (nrotate == 3) {
			/* enable touchpad */
			/* enable trackpoint */
			setrotation(NORMAL);
			tabletmode = 0;
			nrotate = 0;
		}
	} else if (!strcmp(buf, ACPI_ROTATELOCK)) {
		nlock++;
		if (nlock == 2) {
			nlock = 0;
			rotatelock = ! rotatelock;
		}
	}
}

FILE *tryopen(const char *dir, const char *file)
{
	char *path = malloc(strlen(dir) + strlen(file) + 4);
	sprintf(path, "%s/%s", dir, file);
	FILE *dev = fopen(path, "r");
	free(path);
	return dev;
}

FILE *opendevfile(const char *file)
{
	static char devdir[sizeof(DEV_PATH) + 5] = { '\0' };
	FILE *dev = NULL;
	if (devdir[0] == '\0') {
		for (int i = 0; i < 255; i++) {
			sprintf(devdir, DEV_PATH, i);
			dev = tryopen(devdir, file);
			if (dev) {
				break;
			}
		}
	} else {
		dev = tryopen(devdir, file);
	}
	return dev;
}


double getgravity(double cutoff)
{
	FILE *scale = opendevfile(SCALE_FILE);

	if (scale == NULL) {
		return cutoff;
	}

	double scalefactor;
	fscanf(scale, "%lf", &scalefactor);
	fclose(scale);

	return cutoff / scalefactor;
}

double getraw(const char *file)
{
	double value = 0.0;
	FILE *raw = opendevfile(file);
	if (raw) {
		fscanf(raw, "%lg", &value);
		fclose(raw);
	}
	return value;
}

int main(void)
{
	double gravity = getgravity(GRAVITY_CUTOFF);

	int acpi = openacpi(NULL);
	if (acpi == -1) {
		tabletmode = 1;
		rotatelock = 0;
	}

	for (;;) {
		int nfds = acpi + 1;
		fd_set fds;
		FD_ZERO(&fds);
		struct timeval to = {0};
		to.tv_usec = 5000;
		int forever = 0;

		if (acpi != -1) {
			FD_SET(acpi, &fds);
			if (tabletmode == 0 || rotatelock == 1) {
				forever = 1;
			}
		}

		select(nfds, &fds, NULL, NULL, forever ? NULL : &to);

		if (acpi != -1 && FD_ISSET(acpi, &fds)) {
			checkacpi(acpi);
		}

		//if (tabletmode == 1 && rotatelock == 0) {
			double x = getraw(X_RAW_FILE);
			double y = getraw(Y_RAW_FILE);
			if (y <= -gravity) {
				setrotation(NORMAL);
			} else if (y >= gravity) {
				setrotation(INVERSE);
			} else if (x >= gravity) {
				setrotation(LEFT);
			} else if (x <= -gravity) {
				setrotation(RIGHT);
			}
		//}
	}

	return 1;
}