#include "dat.h"
#include "fn.h"

#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <unistd.h>
#include <xcb/xcb.h>
#include <xkbcommon/xkbcommon.h>
#include <xkbcommon/xkbcommon-x11.h>
#include <xcb-imdkit/imdkit.h>
#include <xcb-imdkit/encoding.h>

u32int keymaplookup(struct xkb_state*, uint8_t, u16int);
char *ximcompound(const char*, size_t, size_t*);

typedef struct Ic Ic;
struct Ic
{
	Ic		*next;
	xcb_im_input_context_t	*xic;
	xcb_im_client_t	*client;
	int		engaged;
	u32int		style;
	int		cap;
	int		encoding;
	int		prestarted;
	int		nprerune;
	xcb_window_t	clientwin;
	xcb_window_t	focuswin;
	xcb_point_t	spot;
	int		hasspot;
	Caret		caret;
};

typedef struct Clientenc Clientenc;
struct Clientenc
{
	Clientenc	*next;
	xcb_im_client_t	*client;
	int		encoding;
};

enum
{
	Ecompound,
	Eutf8,
};

static xcb_connection_t *conn;
static xcb_im_t *xim;
static struct xkb_state *kstate;
static xcb_window_t rootwin;
static int opened;
static Ic *ics;
static Ic *preowner;
static Ic passthrough;
static Clientenc *clientenc;
static Channel *replyc;
static int wakefd[2] = {-1, -1};

static char *encs[] = {"COMPOUND_TEXT", "UTF8_STRING"};
static u32int styles[] = {
	XCB_IM_PreeditPosition | XCB_IM_StatusNothing,
	XCB_IM_PreeditCallbacks | XCB_IM_StatusNothing,
	XCB_IM_PreeditNothing | XCB_IM_StatusNothing,
};
static int stylecaps[] = {0, Cclientpreedit, 0};

static int
stylecap(u32int style, int *cap)
{
	int i;

	for(i = 0; i < nelem(styles); i++)
		if(styles[i] == style){
			*cap = stylecaps[i];
			return 1;
		}
	*cap = 0;
	return 0;
}

static int
wakeinit(void)
{
	int fd[2];
	int flags, i;

	if(wakefd[0] >= 0)
		return 0;
	if(pipe(fd) < 0)
		return -1;
	for(i = 0; i < nelem(fd); i++){
		flags = fcntl(fd[i], F_GETFL);
		if(flags < 0 || fcntl(fd[i], F_SETFL,
		   flags | O_NONBLOCK) < 0)
			goto fail;
		flags = fcntl(fd[i], F_GETFD);
		if(flags < 0 || fcntl(fd[i], F_SETFD,
		   flags | FD_CLOEXEC) < 0)
			goto fail;
	}
	wakefd[0] = fd[0];
	wakefd[1] = fd[1];
	return 0;
fail:
	close(fd[0]);
	close(fd[1]);
	return -1;
}

/* imthread only leaves a wake token; XIM ownership stays on the XIM thread. */
void
ximownernotify(void)
{
	uchar token;
	int n;

	if(wakefd[1] < 0)
		return;
	token = 0;
	do
		n = write(wakefd[1], &token, 1);
	while(n < 0 && errno == EINTR);
	/* EAGAIN means a pending byte will already wake the XIM poll loop. */
}

static int
wakedrain(void)
{
	uchar buf[32];
	int n, total;

	total = 0;
	for(;;){
		n = read(wakefd[0], buf, sizeof buf);
		if(n > 0){
			total += n;
			continue;
		}
		if(n < 0 && errno == EINTR)
			continue;
		break;
	}
	return total;
}

static int
getencoding(xcb_im_client_t *client)
{
	Clientenc *p;

	for(p = clientenc; p != nil; p = p->next)
		if(p->client == client)
			return p->encoding;
	return Ecompound;
}

static int
setencoding(xcb_im_client_t *client, int encoding)
{
	Clientenc *p;

	if(client == nil)
		return -1;
	for(p = clientenc; p != nil; p = p->next)
		if(p->client == client){
			p->encoding = encoding;
			return 0;
		}
	p = calloc(1, sizeof *p);
	if(p == nil)
		return -1;
	p->client = client;
	p->encoding = encoding;
	p->next = clientenc;
	clientenc = p;
	return 0;
}

static void
clearencoding(xcb_im_client_t *client)
{
	Clientenc *p, **link;

	for(link = &clientenc; (p = *link) != nil; link = &p->next)
		if(p->client == client){
			*link = p->next;
			free(p);
			return;
		}
}

static void
clearencodings(void)
{
	Clientenc *next, *p;

	for(p = clientenc; p != nil; p = next){
		next = p->next;
		free(p);
	}
	clientenc = nil;
}

static void
ximlog(char *msg)
{
	fprint(2, "strans: xim: %s\n", msg);
}

static int
kinit(void)
{
	struct xkb_context *context;
	struct xkb_keymap *keymap;
	struct xkb_state *state;
	int32_t device;
	int ok;

	context = nil;
	keymap = nil;
	state = nil;
	ok = -1;
	context = xkb_context_new(XKB_CONTEXT_NO_FLAGS);
	if(context == nil || !xkb_x11_setup_xkb_extension(conn,
	   XKB_X11_MIN_MAJOR_XKB_VERSION, XKB_X11_MIN_MINOR_XKB_VERSION,
	   XKB_X11_SETUP_XKB_EXTENSION_NO_FLAGS, nil, nil, nil, nil))
		goto out;
	device = xkb_x11_get_core_keyboard_device_id(conn);
	if(device < 0)
		goto out;
	keymap = xkb_x11_keymap_new_from_device(context, conn, device,
		XKB_KEYMAP_COMPILE_NO_FLAGS);
	if(keymap == nil)
		goto out;
	state = xkb_state_new(keymap);
	if(state == nil)
		goto out;
	xkb_state_unref(kstate);
	kstate = state;
	state = nil;
	ok = 0;
out:
	xkb_state_unref(state);
	xkb_keymap_unref(keymap);
	xkb_context_unref(context);
	return ok;
}

static u32int
kget(uint8_t kc, u16int state)
{
	return keymaplookup(kstate, kc, state);
}

static xcb_screen_t*
getscreen(int scr)
{
	xcb_screen_iterator_t iter;
	const xcb_setup_t *setup;

	setup = xcb_get_setup(conn);
	if(setup == nil)
		return nil;
	iter = xcb_setup_roots_iterator(setup);
	for(; iter.rem; scr--, xcb_screen_next(&iter))
		if(scr == 0)
			return iter.data;
	return nil;
}

static void
readattrs(Ic *state)
{
	const xcb_im_preedit_attr_t *attr;
	xcb_window_t clientwin, focuswin;
	xcb_point_t spot;
	int hasspot;

	clientwin = xcb_im_input_context_get_client_window(state->xic);
	focuswin = xcb_im_input_context_get_focus_window(state->xic);
	spot = state->spot;
	hasspot = 0;
	if(state->style == (XCB_IM_PreeditPosition | XCB_IM_StatusNothing) &&
	   (xcb_im_input_context_get_preedit_attr_mask(state->xic) &
	    XCB_XIM_XNSpotLocation_MASK)){
		attr = xcb_im_input_context_get_preedit_attr(state->xic);
		if(attr != nil){
			spot = attr->spot_location;
			hasspot = 1;
		}
	}
	state->clientwin = clientwin;
	state->focuswin = focuswin;
	state->spot = spot;
	state->hasspot = hasspot;
}

static int
translate(xcb_window_t win, int x, int y, Caret *caret)
{
	xcb_translate_coordinates_cookie_t cookie;
	xcb_translate_coordinates_reply_t *reply;

	if(win == XCB_NONE)
		return 0;
	cookie = xcb_translate_coordinates(conn, win, rootwin, x, y);
	reply = xcb_translate_coordinates_reply(conn, cookie, nil);
	if(reply == nil || !reply->same_screen){
		free(reply);
		return 0;
	}
	caret->valid = 1;
	caret->x = reply->dst_x;
	caret->y = reply->dst_y;
	caret->h = 0;
	free(reply);
	return 1;
}

static int
placebottom(Ic *state, xcb_window_t win)
{
	xcb_get_geometry_cookie_t gcookie;
	xcb_get_geometry_reply_t *geometry;
	int height;

	if(win == XCB_NONE)
		return 0;
	gcookie = xcb_get_geometry(conn, win);
	geometry = xcb_get_geometry_reply(conn, gcookie, nil);
	if(geometry == nil)
		return 0;
	height = geometry->height;
	free(geometry);
	if(!translate(win, 0, 0, &state->caret))
		return 0;
	state->caret.y += height;
	return 1;
}

static void
place(Ic *state)
{
	xcb_window_t win[2];
	int i, nwin;

	memset(&state->caret, 0, sizeof state->caret);
	win[0] = state->focuswin;
	nwin = 1;
	if(state->clientwin != state->focuswin)
		win[nwin++] = state->clientwin;
	if(state->hasspot && translate(state->focuswin,
	   state->spot.x, state->spot.y, &state->caret))
		return;
	for(i = 0; i < nwin; i++)
		if(placebottom(state, win[i]))
			return;
}

static void
refreshplace(Ic *state)
{
	readattrs(state);
	place(state);
}

static void
commit(Ic *state, char *s, int nbyte)
{
	char *wire;
	size_t nwire;

	if(nbyte == 0)
		return;
	wire = s;
	nwire = nbyte;
	if(state->encoding == Ecompound){
		wire = ximcompound(s, nbyte, &nwire);
		if(wire == nil)
			return;
	}
	xcb_im_commit_string(xim, state->xic, XCB_XIM_LOOKUP_CHARS,
		wire, (u32int)nwire, 0);
	if(wire != s)
		free(wire);
}

static void
clearpreedit(Ic *state)
{
	xcb_im_preedit_draw_fr_t frame;

	if(state == nil || !state->prestarted)
		return;
	memset(&frame, 0, sizeof frame);
	frame.chg_length = state->nprerune;
	frame.status = 1;
	xcb_im_preedit_draw_callback(xim, state->xic, &frame);
	xcb_im_preedit_done_callback(xim, state->xic);
	state->prestarted = 0;
	state->nprerune = 0;
	if(preowner == state)
		preowner = nil;
	xcb_flush(conn);
}

static void
updatepreedit(Ic *state, Str *pre)
{
	xcb_im_preedit_draw_fr_t frame;
	u32int feedback[Maxrunes];
	char utf[Maxutf], *wire;
	size_t nwire;
	int i, nbyte;

	if(!(state->style & XCB_IM_PreeditCallbacks))
		return;
	if(pre->n == 0){
		clearpreedit(state);
		return;
	}
	nbyte = stoutf(pre, utf, sizeof utf);
	wire = utf;
	nwire = nbyte;
	if(state->encoding == Ecompound){
		wire = ximcompound(utf, nbyte, &nwire);
		if(wire == nil)
			return;
	}
	for(i = 0; i < pre->n; i++)
		feedback[i] = XCB_XIM_UNDERLINE;
	if(!state->prestarted){
		xcb_im_preedit_start_callback(xim, state->xic);
		state->prestarted = 1;
	}
	memset(&frame, 0, sizeof frame);
	frame.caret = pre->n;
	frame.chg_length = state->nprerune;
	frame.length_of_preedit_string = (u16int)nwire;
	frame.preedit_string = (uchar*)wire;
	frame.feedback_array.size = pre->n;
	frame.feedback_array.items = feedback;
	xcb_im_preedit_draw_callback(xim, state->xic, &frame);
	state->nprerune = pre->n;
	preowner = state;
	if(wire != utf)
		free(wire);
}

static int
meaningful(u32int key)
{
	return key != 0 && (key < Kmodfirst || key > Kmodlast);
}

static void
sendrequest(Ic *state, int op, u32int key, u32int mod, Keyres *res)
{
	Keyreq kr;

	memset(&kr, 0, sizeof kr);
	kr.owner = state;
	kr.cap = state->cap;
	kr.op = op;
	kr.ks = key;
	kr.mod = mod & Mmask;
	kr.caret = state->caret;
	kr.reply = replyc;
	chansend(keyc, &kr);
	chanrecv(replyc, res);
}

static void
checkpreowner(void)
{
	Keyres res;

	if(preowner == nil)
		return;
	sendrequest(preowner, Keycap, 0, 0, &res);
	if(!res.eaten)
		clearpreedit(preowner);
}

static void
checkownerwake(void)
{
	if(wakedrain() > 0)
		checkpreowner();
}

static void
keypress(Ic *state, u32int key, u32int mod, Keyres *res)
{
	if(meaningful(key)){
		if(preowner != nil && preowner != state)
			clearpreedit(preowner);
		state->engaged = 1;
	}
	sendrequest(state, Keypress, key, mod, res);
}

static void
release(Ic *state)
{
	Keyres res;

	if(state == nil)
		return;
	clearpreedit(state);
	if(!state->engaged)
		return;
	sendrequest(state, Keyrelease, 0, 0, &res);
	state->engaged = 0;
}

static void
resetic(Ic *state, xcb_im_reset_ic_reply_fr_t *reply)
{
	Keyres pending, res;
	char utf[Maxutf], *wire;
	size_t nwire;
	int nbyte;

	if(state == nil)
		return;
	sclear(&pending.preedit);
	if(!state->engaged){
		clearpreedit(state);
		return;
	}
	sendrequest(state, Keycap, 0, 0, &pending);
	sendrequest(state, Keyreset, 0, 0, &res);
	clearpreedit(state);
	if(reply == nil || !pending.eaten || pending.preedit.n == 0)
		return;
	nbyte = stoutf(&pending.preedit, utf, sizeof utf);
	if(state->encoding == Ecompound)
		wire = ximcompound(utf, nbyte, &nwire);
	else{
		nwire = nbyte;
		wire = malloc(nwire);
		if(wire != nil)
			memmove(wire, utf, nwire);
	}
	if(wire == nil)
		return;
	reply->committed_string = (uchar*)wire;
	reply->byte_length_of_committed_string = nwire;
}

static void
kpress(Ic *state, xcb_key_press_event_t *ev)
{
	Keyres res;
	char buf[Maxutf];
	u32int key, rune;
	int n, wasvalid;

	key = kget(ev->detail, ev->state);
	rune = xkb_keysym_to_utf32(key);
	if(rune >= ' ' && rune != 0x7f)
		key = rune;
	else if(key >= 0xff00 && key <= 0xffff)
		key = Kspec + (key - 0xff00);
	else
		key = rune;
	if(meaningful(key)){
		wasvalid = state->caret.valid;
		refreshplace(state);
		if(state->engaged && wasvalid && !state->caret.valid)
			sendrequest(state, Keycaret, 0, 0, &res);
	}
	keypress(state, key, ev->state, &res);
	n = stoutf(&res.commit, buf, sizeof buf);
	commit(state, buf, n);
	updatepreedit(state, &res.preedit);
	if(!res.eaten)
		xcb_im_forward_event(xim, state->xic, ev);
	xcb_flush(conn);
}

static void
icunlink(Ic *state)
{
	Ic **p;

	for(p = &ics; *p != nil; p = &(*p)->next)
		if(*p == state){
			*p = state->next;
			return;
		}
}

static void
icfree(void *p)
{
	Ic *state;

	state = p;
	/* The owner remains valid until imthread acknowledges its release. */
	release(state);
	icunlink(state);
	free(state);
}

static void
setstyle(Ic *state, u32int style)
{
	int cap;

	if(!stylecap(style, &cap))
		style = XCB_IM_PreeditNothing | XCB_IM_StatusNothing;
	state->style = style;
	state->cap = cap;
}

static void
icinstall(xcb_im_client_t *client, xcb_im_input_context_t *ic, Ic *state)
{
	if(state == nil){
		ximlog("out of memory; passing input context through");
		xcb_im_input_context_set_data(ic, &passthrough, nil);
		return;
	}
	state->xic = ic;
	state->client = client;
	state->encoding = getencoding(client);
	setstyle(state, xcb_im_input_context_get_input_style(ic));
	refreshplace(state);
	state->next = ics;
	ics = state;
	xcb_im_input_context_set_data(ic, state, icfree);
}

static void
iccreate(xcb_im_client_t *client, xcb_im_input_context_t *ic)
{
	if(ic == nil || xcb_im_input_context_get_data(ic) != nil)
		return;
	icinstall(client, ic, calloc(1, sizeof(Ic)));
}

static void
callback(xcb_im_t *im, xcb_im_client_t *client, xcb_im_input_context_t *ic,
	const xcb_im_packet_header_fr_t *hdr, void *frame, void *arg, void *user)
{
	xcb_key_press_event_t *ev;
	Ic *state;

	USED(im);
	USED(frame);
	USED(user);
	if(hdr->major_opcode == XCB_XIM_ENCODING_NEGOTIATION){
		if(arg != nil && setencoding(client,
		   *(u16int*)arg == 1 ? Eutf8 : Ecompound) < 0)
			die("xim: cannot remember client encoding");
		return;
	}
	if(hdr->major_opcode == XCB_XIM_DISCONNECT ||
	   hdr->major_opcode == XCB_XIM_CLOSE){
		for(state = ics; state != nil; state = state->next)
			if(state->client == client)
				release(state);
		clearencoding(client);
		return;
	}

	if(hdr->major_opcode == XCB_XIM_CREATE_IC){
		iccreate(client, ic);
		return;
	}
	if(ic == nil)
		return;
	state = xcb_im_input_context_get_data(ic);
	if(state == nil)
		return;
	if(state == &passthrough){
		if(hdr->major_opcode == XCB_XIM_FORWARD_EVENT){
			ev = arg;
			if(ev != nil)
				xcb_im_forward_event(xim, ic, ev);
		}
		return;
	}
	switch(hdr->major_opcode){
	case XCB_XIM_FORWARD_EVENT:
		ev = arg;
		if(ev != nil && (ev->response_type & ~0x80) == XCB_KEY_PRESS)
			kpress(state, ev);
		break;
	case XCB_XIM_SET_IC_VALUES:
	case XCB_XIM_SET_IC_FOCUS:
		refreshplace(state);
		if(state->engaged){
			Keyres res;

			sendrequest(state, Keycaret, 0, 0, &res);
		}
		break;
	case XCB_XIM_DESTROY_IC:
	case XCB_XIM_UNSET_IC_FOCUS:
		release(state);
		break;
	case XCB_XIM_RESET_IC:
		resetic(state, arg);
		break;
	}
}

static void
ximclose(void)
{
	Ic *state, *next;

	for(state = ics; state != nil; state = state->next)
		release(state);
	if(xim != nil){
		if(opened)
			xcb_im_close_im(xim);
		xcb_im_destroy(xim);
		xim = nil;
	}
	opened = 0;
	preowner = nil;
	clearencodings();
	for(state = ics; state != nil; state = next){
		next = state->next;
		free(state);
	}
	ics = nil;
	rootwin = XCB_NONE;
	xkb_state_unref(kstate);
	kstate = nil;
	if(conn != nil){
		xcb_disconnect(conn);
		conn = nil;
	}
	if(replyc != nil){
		chanfree(replyc);
		replyc = nil;
	}
}

static int
ximinit(void)
{
	xcb_screen_t *screen;
	xcb_window_t win;
	xcb_im_styles_t st;
	xcb_im_encodings_t enc;
	int scr;

	replyc = chancreate(sizeof(Keyres), 0);
	if(replyc == nil){
		ximlog("cannot create reply channel");
		return -1;
	}
	if(wakeinit() < 0){
		ximlog("cannot create owner wake pipe");
		return -1;
	}
	st.nStyles = nelem(styles);
	st.styles = styles;
	enc.nEncodings = nelem(encs);
	enc.encodings = encs;
	xcb_compound_text_init();
	conn = xcb_connect(nil, &scr);
	if(conn == nil || xcb_connection_has_error(conn)){
		ximlog("cannot connect to X server");
		return -1;
	}
	screen = getscreen(scr);
	if(screen == nil){
		ximlog("cannot find X screen");
		return -1;
	}
	rootwin = screen->root;
	if(kinit() < 0){
		ximlog("cannot read keyboard mapping");
		return -1;
	}
	win = xcb_generate_id(conn);
	xcb_create_window(conn, XCB_COPY_FROM_PARENT, win, screen->root,
		0, 0, 1, 1, 0, XCB_WINDOW_CLASS_INPUT_OUTPUT,
		screen->root_visual, 0, nil);
	xim = xcb_im_create(conn, scr, win, "strans",
		XCB_IM_ALL_LOCALES, &st, nil, nil, &enc,
		XCB_EVENT_MASK_KEY_PRESS, callback, nil);
	if(xim == nil){
		ximlog("cannot create XIM server");
		return -1;
	}
	if(!xcb_im_open_im(xim)){
		ximlog("cannot claim XIM selection");
		return -1;
	}
	opened = 1;
	return 0;
}

void
ximthread(void *arg)
{
	struct pollfd pfd[2];
	xcb_generic_event_t *ev;
	uint8_t type;
	int fd, n;

	USED(arg);
	threadsetname("xim");
	if(ximinit() < 0){
		ximclose();
		die("xim: initialization failed");
	}
	fd = xcb_get_file_descriptor(conn);
	pfd[0].fd = fd;
	pfd[0].events = POLLIN;
	pfd[1].fd = wakefd[0];
	pfd[1].events = POLLIN;
	for(;;){
		pfd[0].revents = pfd[1].revents = 0;
		n = poll(pfd, nelem(pfd), -1);
		if(n < 0){
			if(errno == EINTR)
				continue;
			break;
		}
		if(pfd[1].revents & POLLIN)
			checkownerwake();
		if(pfd[0].revents)
			while((ev = xcb_poll_for_event(conn)) != nil){
				type = ev->response_type & ~0x80;
				if(type == XCB_MAPPING_NOTIFY){
					if(kinit() < 0)
						ximlog("cannot refresh keyboard mapping");
				}else
					xcb_im_filter_event(xim, ev);
				free(ev);
				/* Ownership changes outrank the next queued X event. */
				checkownerwake();
			}
		if(pfd[0].revents & (POLLERR|POLLHUP|POLLNVAL))
			break;
	}
	n = xcb_connection_has_error(conn);
	ximclose();
	if(n)
		die("xim: X server disconnected");
	die("xim: frontend stopped");
}