/*
 * Copyright © 2023 Michael Smith <mikesmiffy128@gmail.com>
 * Copyright © 2022 Willian Henrique <wsimanbrazil@yahoo.com.br>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
 * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

#include <stdlib.h>
#ifdef _WIN32
#include <immintrin.h>
#endif

#include "bind.h"
#include "con_.h"
#include "hook.h"
#include "engineapi.h"
#include "errmsg.h"
#include "event.h"
#include "feature.h"
#include "gamedata.h"
#include "intdefs.h"
#include "mem.h"
#include "os.h"
#include "ppmagic.h"
#include "sst.h"
#include "vcall.h"
#include "x86.h"
#include "x86util.h"

FEATURE()
REQUIRE(bind)
REQUIRE(democustom)
REQUIRE_GAMEDATA(vtidx_GetDesktopResolution)
REQUIRE_GAMEDATA(vtidx_DispatchAllStoredGameMessages)

static bool lockdown = false;

#ifdef _WIN32

static void *gamewin, *inhookwin, *inhookthr;
static ulong inhooktid;

// UINT_PTR is a **stupid** typedef, but whatever.
static ssize __stdcall kproc(int code, UINT_PTR wp, ssize lp) {
	KBDLLHOOKSTRUCT *data = (KBDLLHOOKSTRUCT *)lp;
	if (lockdown && data->flags & LLKHF_INJECTED &&
			GetForegroundWindow() == gamewin) {
		return 1;
	}
	return CallNextHookEx(0, code, wp, lp);
}

static ssize __stdcall mproc(int code, UINT_PTR wp, ssize lp) {
	MSLLHOOKSTRUCT *data = (MSLLHOOKSTRUCT *)lp;
	if (lockdown && data->flags & LLMHF_INJECTED &&
			GetForegroundWindow() == gamewin) {
		return 1;
	}
	return CallNextHookEx(0, code, wp, lp);
}

// this is its own thread to meet the strict timing deadline, otherwise the
// hook gets silently removed. plus, we don't wanna incur latency anyway.
static ulong __stdcall inhookthrmain(void *param) {
	volatile u32 *sig = param;
	if (!SetWindowsHookExW(WH_KEYBOARD_LL, &kproc, 0, 0) ||
			!SetWindowsHookExW(WH_MOUSE_LL, &mproc, 0, 0)) {
		*sig = 2;
		return -1;
	}
	*sig = 1;
	MSG m; int ret;
	while ((ret = GetMessageW(&m, inhookwin, 0, 0)) > 0) DispatchMessage(&m);
	return ret;
}

static WNDPROC orig_wndproc;
static ssize __stdcall hook_wndproc(void *wnd, uint msg, UINT_PTR wp, ssize lp) {
	if (msg == WM_COPYDATA && lockdown) return DefWindowProcW(wnd, msg, wp, lp);
	return orig_wndproc(wnd, msg, wp, lp);
}

static bool win32_init(void) {
	gamewin = FindWindowW(L"Valve001", 0);
	// note: error messages here are a bit cryptic on purpose, but easy to find
	// in the code. in other words, we're hiding in plain sight :-)
	if (!gamewin) {
		errmsg_errorsys("failed to find window");
		return false;
	}
	orig_wndproc = (WNDPROC)SetWindowLongPtrW(gamewin, GWLP_WNDPROC,
			(ssize)hook_wndproc);
	if (!orig_wndproc) {
		errmsg_errorsys("failed to attach message handler");
	}
	return true;
}

static void win32_end(void) {
	// no error handling here because we'd crash either way. good luck!
	SetWindowLongW(gamewin, GWLP_WNDPROC, (ssize)orig_wndproc);
}

static void inhook_start(volatile u32 *sig) {
	inhookwin = CreateWindowW(L"sst-eventloop", L"sst-eventloop", WS_DISABLED,
			0, 0, 0, 0, HWND_MESSAGE, 0, 0, 0);
	inhookthr = CreateThread(0, 0, &inhookthrmain, (u32 *)sig, 0, &inhooktid);
}

static void inhook_check(void) {
	if (WaitForSingleObject(inhookthr, 0) == WAIT_OBJECT_0) {
		ulong status;
		GetExitCodeThread(inhookthr, &status);
		if (status) {
			// XXX: if this ever happens, it's a disaster! users might not
			// notice their run just dying all of a sudden. with any luck it
			// won't matter in practice but... this kind of sucks.
			con_warn("** sst: ERROR in message loop, abandoning RTA mode! **");
			// TODO(rta): stop demos, and stuff.
			lockdown = false;
		}
	}
}

static void inhook_stop(void) {
	PostThreadMessageW(inhooktid, WM_QUIT, 0, 0);
	if (WaitForSingleObject(inhookthr, INFINITE) == WAIT_FAILED) {
		errmsg_warnsys("couldn't wait for thread, status unknown");
		// XXX: now what!?
	}
	// assume WAIT_OBJECT_0
	ulong status;
	GetExitCodeThread(inhookthr, &status);
	if (status) {
		// not much else we can do now!
		con_warn("warning: RTA mode message loop had an error during shutdown");
	}
	CloseHandle(inhookthr);
}

#else

// TODO(linux): do some stuff, I guess...

#endif

bool ac_enable(void) {
	if (lockdown) return true;
#ifdef _WIN32
	// and now for some frivolously microoptimised spinlocking nonsense
	volatile u32 sig = 0; // paranoid volatile to ensure no loop misopt...
	inhook_start(&sig);
	register u32 x; // avoid double-reading the volatile
	// pausing in the middle here seems to produce shorter asm with gcc -O2 and
	// clang -O3 in godbolt (avoids unrolling of head which is unlikely to help)
	while (x = sig, _mm_pause(), !x);
	if (x == 2) { // else 1 for success
		con_warn("** sst: ERROR starting message loop, can't continue! **");
		CloseHandle(inhookthr);
		return false;
	}
#endif
	lockdown = true;
	return true;
}

HANDLE_EVENT(Tick, bool simulating) {
#ifdef _WIN32
	static uint fewticks = 0;
	// just check this every so often (roughly 0.1-0.3s depending on game)
	if (lockdown && !(++fewticks & 7)) inhook_check();
#endif
}

void ac_disable(void) {
	if (!lockdown) return;
#ifdef _WIN32
	inhook_stop();
#endif
	lockdown = false;
}

enum /* from InputEventType_t - terser names used here */ {
	BTNDOWN = 0, // data contains button code
	BTNUP, // "
	BTNDOUBLECLICK, // "
	ANALOGUEVALCHG, // data contains analogue code, data2 contains value
	SYSQUIT = 100,
	SYSCTRLHOTPLUG, // data contains controller ID
	SYSCTRLCOLDPLUG, // "
	// ranges for other things
	FIRSTVGUIEV = 1000,
	FIRSTAPPEV = 2000
};

struct inputevent {
	int type; // above enum
	int tick;
	int data, data2, data3;
};

DECL_VFUNC_DYN(void, GetDesktopResolution, int *, int *)
DECL_VFUNC_DYN(void, DispatchAllStoredGameMessages)

typedef void (*VCALLCONV DispatchInputEvent_func)(void *, struct inputevent *);
static DispatchInputEvent_func orig_DispatchInputEvent;
static void VCALLCONV hook_DispatchInputEvent(void *this,
		struct inputevent *ev) {
	// TODO(rta): do something here! (here's a quick reference/example)
	//switch (ev->type) {
	//	CASES(BTNDOWN, BTNUP, BTNDOUBLECLICK):
	//		const char *desc[] = {"DOWN", "UP", "DOUBLE"};
	//		const char *binding = bind_get(ev->data);
	//		if (!binding) binding = "[unbound]";
	//		con_msg("key %d %s => %s\n", ev->data, desc[ev->type - BTNDOWN],
	//					binding);
	//}
	orig_DispatchInputEvent(this, ev);
}

static bool find_DispatchInputEvent(void) {
#ifdef _WIN32
	// Crazy pointer-chasing path to get to DispatchInputEvent:
	// IGameUIFuncs interface
	// -> CGameUIFuncs::GetDesktopResolution vfunc
	//  -> IGame/CGame (first mov into ECX)
	//   -> CGame::DispatchAllStoredGameMessages vfunc
	//    -> DispatchInputEvent (first call instruction)
	void *gameuifuncs = factory_engine("VENGINE_GAMEUIFUNCS_VERSION005", 0);
	if (!gameuifuncs) {
		errmsg_errorx("couldn't get engine game UI interface");
		return false;
	}
	void *cgame;
	const uchar *insns = (const uchar*)VFUNC(gameuifuncs, GetDesktopResolution);
	for (const uchar *p = insns; p - insns < 16;) {
		if (p[0] == X86_MOVRMW && p[1] == X86_MODRM(0, 1, 5)) {
			void **indirect = mem_loadptr(p + 2);
			cgame = *indirect;
			goto ok;
		}
		NEXT_INSN(p, "CGame instance pointer");
	}
	errmsg_errorx("couldn't find pointer to CGame instance");
	return false;
ok:	insns = (const uchar *)VFUNC(cgame, DispatchAllStoredGameMessages);
	for (const uchar *p = insns; p - insns < 128;) {
		if (p[0] == X86_CALL) {
			orig_DispatchInputEvent = (DispatchInputEvent_func)(p + 5 +
					mem_loadoffset(p + 1));
			// Note: we could go further and dig HandleEngineKey from Key_Event,
			// but it seems like Key_Event isn't directly called from
			// DispatchInputEvent in L4D2 (or has a much different structure,
			// requiring another function call to lead to HandleEngineKey).
			return true;
		}
		NEXT_INSN(p, "DispatchInputEvent function");
	}
	errmsg_errorx("couldn't find DispatchInputEvent function");
#else
#warning TODO(linux): more find-y stuff
#endif
	return false;
}

INIT {
#if defined(_WIN32)
	if (!win32_init()) return false;
#elif defined(__linux__)
	// TODO(linux): call init things
#endif
	if (!find_DispatchInputEvent()) return false;
	orig_DispatchInputEvent = (DispatchInputEvent_func)hook_inline(
			(void *)orig_DispatchInputEvent, (void *)&hook_DispatchInputEvent);
	if (!orig_DispatchInputEvent) {
		errmsg_errorsys("couldn't hook DispatchInputEvent function");
		return false;
	}
	return true;
}

END {
#if defined(_WIN32)
	win32_end();
#elif defined(__linux__)
	// TODO(linux): call cleanup things
#endif
	ac_disable();
	unhook_inline((void *)orig_DispatchInputEvent);
}

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