// SPDX-License-Identifier: ISC
// SPDX-FileCopyrightText: 2024 Matthew Wozniak <me@woz.blue>

#define NO_EXTERNS
#include "api.h"
#undef NO_EXTERNS
#include "os.h"
#include "log.h"
#include "sst/x86.h"

struct engserver *engserver = NULL;
struct engclient *engclient = NULL;
struct engineapi *engineapi = NULL;
struct enginetools *enginetools = NULL;
struct demoplayer *demoplayer = NULL;
struct videomode **videomode = NULL;
struct movieinfo *movieinfo = NULL;
void (*cbuf_addtext)(char *) = NULL;

// TODO: should this be split up?

bool api_init(void) {
	void *engine_dll = os_dlhandle("engine");
	createinterface_func engine_factory =
		(createinterface_func)os_dlsym(engine_dll, "CreateInterface");
	if (!engine_factory) bail("couldn't get engine factory");
	engserver = engine_factory(VENGINE_SERVER_INTERFACE_VERSION, NULL);
	if (!engserver) bail("couldn't get IVEngineServer from engine");
	engclient = engine_factory(VENGINE_CLIENT_INTERFACE_VERSION, NULL);
	if (!engclient) bail("couldn't get IVEngineClient from engine");
	engineapi = engine_factory(VENGINE_LAUNCHER_INTERFACE_VERSION, NULL);
	if (!engineapi) bail("couldn't get IEngineAPI from engine");
	enginetools = engine_factory(VENGINE_TOOL_INTERFACE_VERSION, NULL);
	if (!engineapi) bail("couldn't get IEngineTools from engine");

	// find cbuf_addtext
	const u8 *instr = (const u8 *)engserver->vt->server_command;
	// ServerCommand() calls a few small functions before Cbuf_AddText but they
	// get inlined. look for 'push esi' and then a call.
	for (const u8 *p = instr; p - instr < 64;) {
		if (*p == X86_PUSHESI && *++p == X86_CALL) {
			// jump is relative to after the instruction
			cbuf_addtext = (void (*)(char *))(p + 5 + *(i32 *)(p + 1));
		}
		int l = x86_len(p);
		if (l == -1)
			bail("invalid instruction looking for cbuf_addtext");
		p += l;
	}
	if (!cbuf_addtext) bail("couldn't find cbuf_addtext");

	// find demoplayer
	instr = (const u8 *)engclient->vt->is_playing_demo;
	// CEngineClient::IsPlayingDemo is a wrapper around a demoplayer call
	// The first thing it does should be load a ptr to demoplayer into ECX
	if (instr[0] != X86_MOVRMW || instr[1] != X86_MODRM(0, 1, 5))
		bail("couldn't get demoplayer");
	demoplayer = **(struct demoplayer ***)(instr + 2);
	debug("demoplayer = %p", (void *)demoplayer);

	// find videomode
	// CEngineAPI::SetEngineWindow calls videomode->SetGameWindow after
	// detaching the current window with another vcall. Look for the second one.
	// This, like the demoplayer, is a pointer. Mind the double dereference.
	instr = (const u8 *)engineapi->vt->set_engine_window;
	int mov_ecx_counter = 0;
	for (const u8 *p = instr; p - instr < 64;) {
		if (p[0] == X86_MOVRMW && p[1] == X86_MODRM(0, 1, 5)
				&& ++mov_ecx_counter == 2) {
			videomode = *(struct videomode ***)(p + 2);
			break;
		}
		int l = x86_len(p);
		if (l == -1)
			bail("invalid instruction looking for videomode");
		p += l;
	}
	debug("videomode = %p", (void *)videomode);
	
	return true;
}

// vi: sw=4 ts=4 noet tw=80 cc=80