/* IPXWrapper - Common functions
 * Copyright (C) 2011-2024 Daniel Collins <solemnwarning@solemnwarning.net>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
*/

#include <windows.h>
#include <iphlpapi.h>

#include "common.h"
#include "config.h"

enum ipx_log_level min_log_level = LOG_INFO;

/* Must be kept in sync with DLL_INDICES in mkstubs.pl! */
static const char *dll_names[] = {
	"ipxwrapper.dll",
	"wsock32.dll",
	"mswsock.dll",
	"dpwsockx.dll",
	"ws2_32.dll",
	"wpcap.dll",
	"ipxconfig.exe",
	NULL
};

static HANDLE dll_handles[] = {NULL, NULL, NULL, NULL, NULL, NULL, NULL};

/* Convert a windows error number to an error message */
const char *w32_error(DWORD errnum) {
	static char buf[1024] = {'\0'};
	
	FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, NULL, errnum, 0, buf, 1023, NULL);
	buf[strcspn(buf, "\r\n")] = '\0';
	return buf;	
}

HKEY reg_open_main(bool readwrite)
{
	return reg_open_subkey(HKEY_CURRENT_USER, "Software\\IPXWrapper", readwrite);
}

HKEY reg_open_subkey(HKEY parent, const char *path, bool readwrite)
{
	if(parent == NULL)
	{
		return NULL;
	}
	
	HKEY key;
	int err;
	
	if(readwrite)
	{
		err = RegCreateKeyEx(parent, path, 0, NULL, 0, KEY_READ | KEY_WRITE, NULL, &key, NULL);
	}
	else{
		err = RegOpenKeyEx(parent, path, 0, KEY_READ, &key);
	}
	
	if(err != ERROR_SUCCESS)
	{
		if(err != ERROR_FILE_NOT_FOUND)
		{
			log_printf(LOG_ERROR, "Could not open registry: %s", w32_error(err));
		}
		
		return NULL;
	}
	
	return key;
}

void reg_close(HKEY key)
{
	if(key != NULL)
	{
		RegCloseKey(key);
	}
}

/* Check if a value exists.
 * Returns true on success, false on failure.
*/
bool reg_check_value(HKEY key, const char *name)
{
	if(key != NULL && RegQueryValueEx(key, name, NULL, NULL, NULL, NULL) == ERROR_SUCCESS)
	{
		return true;
	}
	
	return false;
}

bool reg_get_bin(HKEY key, const char *name, void *buf, size_t size, const void *default_value)
{
	if(key != NULL)
	{
		DWORD bs = size;
		int err = RegQueryValueEx(key, name, NULL, NULL, (BYTE*)buf, &bs);
		
		if(err == ERROR_SUCCESS)
		{
			if(bs == size)
			{
				return true;
			}
			else{
				log_printf(LOG_WARNING, "Registry value with incorrect size: %s", name);
			}
		}
		else if(err != ERROR_FILE_NOT_FOUND)
		{
			log_printf(LOG_ERROR, "Error reading registry value: %s", w32_error(err));
		}
	}
	
	if(default_value)
	{
		memcpy(buf, default_value, size);
	}
	
	return false;
}

bool reg_set_bin(HKEY key, const char *name, void *buf, size_t size)
{
	if(key != NULL)
	{
		int err = RegSetValueEx(key, name, 0, REG_BINARY, (BYTE*)buf, size);
		
		if(err == ERROR_SUCCESS)
		{
			return true;
		}
		else{
			log_printf(LOG_ERROR, "Error writing registry value: %s", w32_error(err));
		}
	}
	
	return false;
}

DWORD reg_get_dword(HKEY key, const char *name, DWORD default_value)
{
	DWORD buf;
	reg_get_bin(key, name, &buf, sizeof(buf), &default_value);
	
	return buf;
}

bool reg_set_dword(HKEY key, const char *name, DWORD value)
{
	if(key != NULL)
	{
		int err = RegSetValueEx(key, name, 0, REG_DWORD, (BYTE*)&value, sizeof(value));
		
		if(err == ERROR_SUCCESS)
		{
			return true;
		}
		else{
			log_printf(LOG_ERROR, "Error writing registry value: %s", w32_error(err));
		}
	}
	
	return false;
}

/* Read a 32-bit network address from the registry.
 * Returns default_value upon failure.
*/
addr32_t reg_get_addr32(HKEY key, const char *name, addr32_t default_value)
{
	unsigned char buf[4], default_buf[4];
	
	addr32_out(default_buf, default_value);
	reg_get_bin(key, name, buf, 4, default_buf);
	
	return addr32_in(buf);
}

/* Store a 32-bit network address in the registry.
 * Returns true on success, false on failure.
*/
bool reg_set_addr32(HKEY key, const char *name, addr32_t value)
{
	unsigned char buf[4];
	addr32_out(buf, value);
	
	return reg_set_bin(key, name, buf, sizeof(buf));
}

/* Read a 48-bit network address from the registry.
 * Returns default_value upon failure.
*/
addr48_t reg_get_addr48(HKEY key, const char *name, addr48_t default_value)
{
	unsigned char buf[6], default_buf[6];
	
	addr48_out(default_buf, default_value);
	reg_get_bin(key, name, buf, 6, default_buf);
	
	return addr48_in(buf);
}

/* Store a 48-bit network address in the registry.
 * Returns true on success, false on failure.
*/
bool reg_set_addr48(HKEY key, const char *name, addr48_t value)
{
	unsigned char buf[6];
	addr48_out(buf, value);
	
	return reg_set_bin(key, name, buf, sizeof(buf));
}

/* Read a string value from the registry.
 *
 * Returns the value or default_value in a newly allocated buffer. The caller
 * is responsible for freeing it.
*/
char *reg_get_string(HKEY key, const char *name, const char *default_value)
{
	if(key != NULL)
	{
		DWORD value_type;
		DWORD value_size = 0;
		
		LSTATUS reg_err = RegQueryValueEx(key, name, NULL, &value_type, NULL, &value_size);
		if(reg_err == ERROR_SUCCESS || reg_err == ERROR_MORE_DATA)
		{
			if(value_type == REG_SZ)
			{
				size_t buffer_size = value_size + 1; /* Extra space for nul terminator. */
				char *buffer = malloc(buffer_size);
				
				if(buffer != NULL)
				{
					reg_err = RegQueryValueEx(key, name, NULL, &value_type, (BYTE*)(buffer), &value_size);
					if(reg_err == ERROR_SUCCESS)
					{
						if(value_type == REG_SZ)
						{
							buffer[value_size] = '\0';
							return buffer;
						}
						else{
							log_printf(LOG_ERROR, "Expected REG_SZ value, got type %u", (unsigned)(value_type));
						}
					}
					else if(reg_err != ERROR_FILE_NOT_FOUND)
					{
						log_printf(LOG_ERROR, "Error reading registry: %s", w32_error(reg_err));
					}
					
					free(buffer);
				}
				else{
					log_printf(LOG_ERROR, "Memory alloation failed");
				}
			}
			else{
				log_printf(LOG_ERROR, "Expected REG_SZ value, got type %u", (unsigned)(value_type));
			}
		}
		else if(reg_err != ERROR_FILE_NOT_FOUND)
		{
			log_printf(LOG_ERROR, "Error reading registry: %s", w32_error(reg_err));
		}
	}
	
	char *default_copy = strdup(default_value);
	if(default_copy == NULL)
	{
		log_printf(LOG_ERROR, "Memory alloation failed");
		abort();
	}
	
	return default_copy;
}

/* Store a string value in the registry.
 * Returns true on success, false on failure.
*/
bool reg_set_string(HKEY key, const char *name, const char *value)
{
	if(key != NULL)
	{
		int err = RegSetValueEx(key, name, 0, REG_SZ, (BYTE*)(value), strlen(value));
		
		if(err == ERROR_SUCCESS)
		{
			return true;
		}
		else{
			log_printf(LOG_ERROR, "Error writing registry value: %s", w32_error(err));
		}
	}
	
	return false;
}

void load_dll(unsigned int dllnum, bool direct) {
	char path[512];
	const char *dll;
	
	if(dllnum && dllnum != 5) {
		GetSystemDirectory(path, sizeof(path));
		
		if(strlen(path) + strlen(dll_names[dllnum]) + 2 > sizeof(path))
		{
			if(!direct)
			{
				log_printf(LOG_ERROR, "Path buffer too small, cannot load %s", dll_names[dllnum]);
			}
			
			abort();
		}
		
		strcat(path, "\\");
		strcat(path, dll_names[dllnum]);
		
		dll = path;
	}
	else{
		dll = dll_names[dllnum];
	}
	
	dll_handles[dllnum] = LoadLibrary(dll);
	if(!dll_handles[dllnum])
	{
		if(!direct)
		{
			log_printf(LOG_ERROR, "Error loading %s: %s", dll, w32_error(GetLastError()));
		}
		
		abort();
	}
}

void unload_dlls(void) {
	int i;
	
	for(i = 0; dll_names[i]; i++) {
		if(dll_handles[i]) {
			DWORD flt_id;
			HANDLE flt_thread = CreateThread(NULL, 0, &FreeLibrary, dll_handles[i], 0, &flt_id);
			if(flt_thread == NULL)
			{
				log_printf(LOG_ERROR, "FreeLibrary thread creation failed (%s) - %s will not be unloaded!\n", w32_error(GetLastError()), dll_names[i]);
			}
			else{
				/* Detatch thread. */
				CloseHandle(flt_thread);
			}
			
			dll_handles[i] = NULL;
		}
	}
}

void __stdcall *find_sym(unsigned int dllnum, const char *symbol) {
	if(!dll_handles[dllnum]) {
		load_dll(dllnum, false);
	}
	
	void *ptr = GetProcAddress(dll_handles[dllnum], symbol);
	if(!ptr) {
		log_printf(LOG_ERROR, "Missing symbol in %s: %s", dll_names[dllnum], symbol);
		abort();
	}
	
	return ptr;
}

void __stdcall *find_sym_direct(unsigned int dllnum, const char *symbol) {
	if(!dll_handles[dllnum]) {
		load_dll(dllnum, true);
	}
	
	void *ptr = GetProcAddress(dll_handles[dllnum], symbol);
	if(!ptr)
	{
		abort();
	}
	
	return ptr;
}

void __stdcall log_call(unsigned int entry, const char *symbol, unsigned int target)
{
	log_printf(LOG_CALL, "%s:%s -> %s", dll_names[entry], symbol, dll_names[target]);
}

wchar_t *get_module_path(HMODULE module)
{
	size_t size   = 256;
	wchar_t *path = NULL;
	
	do {
		free(path);
		
		size *= 2;
		
		if(!(path = (wchar_t*)(malloc(sizeof(wchar_t) * size))))
		{
			SetLastError(ERROR_NOT_ENOUGH_MEMORY);
			return NULL;
		}
	} while(GetModuleFileNameW(module, path, size) == size);
	
	return path;
}

wchar_t *get_module_relative_path(HMODULE module, const wchar_t *relative_path)
{
	wchar_t *module_path = get_module_path(module);
	if(module_path == NULL)
	{
		return NULL;
	}
	
	wchar_t *module_path_last_slash = wcsrchr(module_path, '\\');
	
	size_t module_path_base_len = module_path_last_slash != NULL
		? (module_path_last_slash - module_path) + 1
		: 0;
	
	wchar_t *path = malloc((module_path_base_len + wcslen(relative_path) + 1) * sizeof(wchar_t));
	if(path == NULL)
	{
		free(module_path);
		SetLastError(ERROR_NOT_ENOUGH_MEMORY);
		return NULL;
	}
	
	memcpy(path, module_path, (module_path_base_len * sizeof(wchar_t)));
	wcscpy((path + module_path_base_len), relative_path);
	
	free(module_path);
	
	return path;
}

void init_critical_section(CRITICAL_SECTION *critical_section)
{
	/* > If the function succeeds, the return value is nonzero.  If the
	 * > function fails, the return value is zero. To get extended error
	 * > information, call GetLastError().  For Windows Me/98/95:  This
	 * > function has no return value. If the function fails, it will
	 * > raise an exception.
	 *
	 * - https://www.tenouk.com/crstufunction3.html
	 *
	 * The above goes against what the documentation (MSDN '98) says, but
	 * in testing, it returns FALSE on Windows 98 and GetLastError() yields
	 * nonsensical error codes, so its probably right and we ignore the
	 * result when running on pre-Windows 2000 systems.
	*/

	if(!InitializeCriticalSectionAndSpinCount(critical_section, 0x80000000) && windows_at_least_2000())
	{
		log_printf(LOG_ERROR, "Failed to initialise critical section: %s", w32_error(GetLastError()));
		abort();
	}
}

bool windows_at_least_2000()
{
	static int result = 0;
	int result_view = __atomic_load_n(&result, __ATOMIC_SEQ_CST);

	if(result_view == 0)
	{
		OSVERSIONINFO osver;
		osver.dwOSVersionInfoSize = sizeof(osver);
		GetVersionEx(&osver);
		
		if(osver.dwMajorVersion >= 5)
		{
			__atomic_store_n(&result, 1, __ATOMIC_SEQ_CST);
			return true;
		}
		else{
			__atomic_store_n(&result, -1, __ATOMIC_SEQ_CST);
			return false;
		}
	}

	return result_view > 0;
}