#define _GNU_SOURCE

#include <dlfcn.h>
#include <libgen.h>
#include <linux/limits.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <unistd.h>

#define DLSYM_GOT_260B	0x0804adb0
#define DLOPEN_GOT_260B 0x0804b830

//from sdk
#define	RF_DEPTHHACK	0x000008		// for view weapon Z crunching
#define	RF_NOSHADOW	0x000010		// don't add stencil shadows
#define CG_R_ADDREFENTITYTOSCENE 60

typedef int syscall_t(int command, ...);
typedef void dllEntry_t(syscall_t *);

syscall_t  *orig_syscall = NULL;
dllEntry_t *orig_dllEntry = NULL;
void *cgameLibHandle = NULL;

// do t3h depthhack
int our_syscall(int command, ...) {
	int arg[10];
	va_list args;
	va_start(args, command);
	int count = 0;
	for (; count < 10; count++)
		arg[count] = va_arg(args, int);
	va_end(args);

	if( command == CG_R_ADDREFENTITYTOSCENE ){
		// arg[0] passes pointer to a refEntity_t, just change renderfx at right offset (which is 4)
		//refEnt->renderfx |= RF_DEPTHHACK | RF_NOSHADOW;
		*(int *)(arg[0]+4) |= RF_DEPTHHACK | RF_NOSHADOW;
	}

	return orig_syscall(command, arg[0], arg[1], arg[2], arg[3], arg[4], arg[5], arg[6], arg[7], arg[8], arg[9]);
}

void cg_dllEntry(syscall_t *syscallptr) {
	orig_syscall = syscallptr;
	orig_dllEntry(our_syscall);
}

// detour dllEntry so we can intercept cgame's syscall
void *our_dlsym(void *handle, const char *symbol) {
	void *result = dlsym(handle, symbol);

	// Hook dllEntry	
	if (!strcmp(symbol, "dllEntry") && handle ==  cgameLibHandle ) {
		orig_dllEntry = result;
		return cg_dllEntry;
	}

	return result;
}

// get the libhandle to cgame
void *our_dlopen(const char *filename, int flag) {
	void *result = dlopen(filename, flag);

	if (result && filename)
		if (strstr(filename, "cgame.mp.i386.so"))			
			cgameLibHandle = result;
}

//this is the dll initat0r
void __attribute__ ((constructor)) hookInit() {
	char exeFilename[PATH_MAX];
	memset(exeFilename, 0, sizeof(exeFilename));

	if (readlink("/proc/self/exe", exeFilename, sizeof(exeFilename)) <= 0) {
		printf("Can't find et.x86\n");
		exit(1);
	}

	// Find et.x86
	if (!strcmp(basename(exeFilename), "et.x86")) {
		// hook dlsym() and dlopen() through GOT
		*(void **)DLSYM_GOT_260B = our_dlsym;
		*(void **)DLOPEN_GOT_260B = our_dlopen;
	}
}