#include <WinSock2.h>
#include <WS2tcpip.h>
#include <stdlib.h>
#include <stdio.h>

constexpr unsigned int BUFSIZE = 512;
#pragma comment(lib, "ws2_32.lib")

// 소켓 함수 오류 출력 후 종료
void err_quit(char* msg)
{
	LPVOID lpMsgBuf;

	FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
		NULL, WSAGetLastError(), MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
		(LPTSTR)&lpMsgBuf, 0, NULL);

	MessageBox(NULL, (LPCTSTR)lpMsgBuf, (LPCWSTR)msg, MB_ICONERROR);

	LocalFree(lpMsgBuf);

	exit(-1);
}

// 소켓 함수 오류 출력
void err_display(char* msg)
{
	LPVOID lpMsgBuf;

	FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
		NULL, WSAGetLastError(), MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
		(LPTSTR)&lpMsgBuf, 0, NULL);

	printf("[%s] %ws", msg, (LPCTSTR)lpMsgBuf);

	LocalFree(lpMsgBuf);
}

int wmain(int argc, char* argv[])
{
	int retval;

	// 윈속 초기화
	WSADATA wsa;

	if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0)
	{
		return -1;
	}

	// socket()
	SOCKET listen_sock = socket(AF_INET, SOCK_STREAM, 0);

	if (listen_sock == INVALID_SOCKET)
	{
		err_quit("socket()");
	}

	// bind()
	SOCKADDR_IN serveraddr;
	ZeroMemory(&serveraddr, sizeof(serveraddr));
	serveraddr.sin_family = AF_INET;
	serveraddr.sin_port = htons(9000);
	serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);

	retval = bind(listen_sock, (SOCKADDR*)&serveraddr, sizeof(serveraddr));

	if (retval == SOCKET_ERROR)
	{
		err_quit("bind()");
	}

	// listen()
	retval = listen(listen_sock, SOMAXCONN);

	if (retval == SOCKET_ERROR)
	{
		err_quit("listen()");
	}

	while (true)
	{
		wprintf(L"Start!\n");

		// 데이터 통신에 사용할 변수
		SOCKADDR_IN clientaddr;
		int addrlen = sizeof(clientaddr);

		// accept()
		SOCKET client_sock = accept(listen_sock, (SOCKADDR*)&clientaddr, &addrlen);

		wprintf(L"accept!\n");

		if (client_sock == INVALID_SOCKET)
		{
			err_display("accept()");
			continue;
		}

		WCHAR addrBuf[BUFSIZE + 1];
		InetNtop(AF_INET, &clientaddr, (PWSTR)& addrBuf, BUFSIZE);

		wprintf(L"\n[TCP Server] Client Connect : IP = %s, Port = %d\n",
			addrBuf, ntohs(clientaddr.sin_port));


		// 클라이언트와 데이터 통신
		while (true)
		{
			char buf[BUFSIZE + 1];

			// 데이터 받기
			retval = recv(client_sock, buf, BUFSIZE, 0);

			if (retval == SOCKET_ERROR)
			{
				err_display("recv()");
				break;
			}
			else if (retval == 0)
			{
				break;
			}

			// 받은 데이터 출력
			buf[retval] = '\0';
			printf("%s", buf);
		}

		// closesocket()
		closesocket(client_sock);

		wprintf(L"\n[TCP Server] Client Disconnect : IP = %s, Port = %d\n",
			addrBuf, ntohs(clientaddr.sin_port));
	}

	// closesocket()
	closesocket(listen_sock);

	// 윈속 종료
	WSACleanup();

	return 0;
}