/*
 *  XMail by Davide Libenzi ( Intranet and Internet mail server )
 *  Copyright (C) 1999,..,2004  Davide Libenzi
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *  Davide Libenzi <davidel@xmailserver.org>
 *
 */

#include "SysInclude.h"
#include "SysDep.h"
#include "SvrDefines.h"
#include "ShBlocks.h"
#include "ResLocks.h"
#include "StrUtils.h"
#include "BuffSock.h"
#include "SList.h"
#include "MailConfig.h"
#include "MessQueue.h"
#include "MailSvr.h"
#include "MiscUtils.h"
#include "SvrUtils.h"
#include "DNS.h"
#include "DNSCache.h"

#define DNS_CACHE_DIRCTORY      "dnscache"
#define DNS_MX_CACHE_DIRCTORY   "mx"
#define DNS_NS_CACHE_DIRCTORY   "ns"
#define DNS_CACHE_LINE_MAX      2048

static int CDNS_CleanupPath(char const *pszCachePath);
static char *CDNS_GetCacheFilePath(char const *pszDomain, char const *pszSubDir,
				   char *pszFilePath);
static int CDNS_MxLoad(char const *pszDomain, char *&pszMXDomains);
static int CDNS_MxSave(char const *pszDomain, char const *pszMXDomains, SYS_UINT32 TTL);

static int iNumCacheDirs = DNS_HASH_NUM_DIRS;

static int CDNS_CleanupPath(char const *pszCachePath)
{

	return (0);

}

int CDNS_Initialize(int iCacheDirCount)
{

	while (!IsPrimeNumber(iCacheDirCount))
		++iCacheDirCount;

	iNumCacheDirs = iCacheDirCount;

///////////////////////////////////////////////////////////////////////////////
//  Setup cache subdirectories
///////////////////////////////////////////////////////////////////////////////
	char szCacheBasePath[SYS_MAX_PATH] = "";

	CfgGetRootPath(szCacheBasePath, sizeof(szCacheBasePath));

	StrNCat(szCacheBasePath, DNS_CACHE_DIRCTORY, sizeof(szCacheBasePath));
	AppendSlash(szCacheBasePath);

	for (int ii = 0; ii < iNumCacheDirs; ii++) {
///////////////////////////////////////////////////////////////////////////////
//  Setup MX cache subdirectories
///////////////////////////////////////////////////////////////////////////////
		char szCachePath[SYS_MAX_PATH] = "";

		sprintf(szCachePath, "%s%s" SYS_SLASH_STR "%d",
			szCacheBasePath, DNS_MX_CACHE_DIRCTORY, ii);

		if (SysExistDir(szCachePath)) {

			if (CDNS_CleanupPath(szCachePath) < 0)
				return (ErrGetErrorCode());

		} else {

			if (SysMakeDir(szCachePath) < 0)
				return (ErrGetErrorCode());

		}

///////////////////////////////////////////////////////////////////////////////
//  Setup NS cache subdirectories
///////////////////////////////////////////////////////////////////////////////

	}

	return (0);

}

static char *CDNS_GetCacheFilePath(char const *pszDomain, char const *pszSubDir,
				   char *pszFilePath)
{

	char szRootPath[SYS_MAX_PATH] = "";

	CfgGetRootPath(szRootPath, sizeof(szRootPath));

///////////////////////////////////////////////////////////////////////////////
//  Calculate domain string hash
///////////////////////////////////////////////////////////////////////////////
	char *pszLwrDomain = SysStrDup(pszDomain);

	if (pszLwrDomain == NULL)
		return (NULL);

	StrLower(pszLwrDomain);

	SYS_UINT32 uStringHash = MscHashString(pszLwrDomain, strlen(pszLwrDomain));

///////////////////////////////////////////////////////////////////////////////
//  Build cache file path
///////////////////////////////////////////////////////////////////////////////
	SysSNPrintf(pszFilePath, SYS_MAX_PATH - 1,
		    "%s%s" SYS_SLASH_STR "%s" SYS_SLASH_STR "%u" SYS_SLASH_STR "%s", szRootPath,
		    DNS_CACHE_DIRCTORY, pszSubDir, (unsigned int) (uStringHash % iNumCacheDirs),
		    pszLwrDomain);

	SysFree(pszLwrDomain);

	return (pszFilePath);

}

static int CDNS_MxLoad(char const *pszDomain, char *&pszMXDomains)
{
///////////////////////////////////////////////////////////////////////////////
//  Build cached file path
///////////////////////////////////////////////////////////////////////////////
	char szFilePath[SYS_MAX_PATH] = "";

	if (CDNS_GetCacheFilePath(pszDomain, DNS_MX_CACHE_DIRCTORY, szFilePath) == NULL)
		return (ErrGetErrorCode());

///////////////////////////////////////////////////////////////////////////////
//  Try to get file infos
///////////////////////////////////////////////////////////////////////////////
	SYS_FILE_INFO FI;

	if (SysGetFileInfo(szFilePath, FI) < 0)
		return (ErrGetErrorCode());

	char szResLock[SYS_MAX_PATH] = "";
	RLCK_HANDLE hResLock = RLckLockSH(CfgGetBasedPath(szFilePath, szResLock,
							  sizeof(szResLock)));

	if (hResLock == INVALID_RLCK_HANDLE)
		return (ErrGetErrorCode());

	FILE *pCacheFile = fopen(szFilePath, "rt");

	if (pCacheFile == NULL) {
		RLckUnlockSH(hResLock);

		ErrSetErrorCode(ERR_FILE_OPEN);
		return (ERR_FILE_OPEN);
	}
///////////////////////////////////////////////////////////////////////////////
//  Read TTL line ( 1st ) and check if it's time expired
///////////////////////////////////////////////////////////////////////////////
	char szCacheLine[DNS_CACHE_LINE_MAX] = "";

	if (MscFGets(szCacheLine, sizeof(szCacheLine) - 1, pCacheFile) == NULL) {
		fclose(pCacheFile);
		RLckUnlockSH(hResLock);

		ErrSetErrorCode(ERR_DNS_CACHE_FILE_FMT);
		return (ERR_DNS_CACHE_FILE_FMT);
	}

	unsigned long ulCurTime = (unsigned long) time(NULL);
	unsigned long ulTTL = (unsigned long) atol(szCacheLine);

	if (ulCurTime > ((unsigned long) FI.tMod + ulTTL)) {
		fclose(pCacheFile);
		RLckUnlockSH(hResLock);

		ErrSetErrorCode(ERR_DNS_CACHE_FILE_EXPIRED);
		return (ERR_DNS_CACHE_FILE_EXPIRED);
	}
///////////////////////////////////////////////////////////////////////////////
//  Read MX domains line ( 2nd )
///////////////////////////////////////////////////////////////////////////////
	if (MscFGets(szCacheLine, sizeof(szCacheLine) - 1, pCacheFile) == NULL) {
		fclose(pCacheFile);
		RLckUnlockSH(hResLock);

		ErrSetErrorCode(ERR_DNS_CACHE_FILE_FMT);
		return (ERR_DNS_CACHE_FILE_FMT);
	}

	if ((pszMXDomains = SysStrDup(szCacheLine)) == NULL) {
		ErrorPush();
		fclose(pCacheFile);
		RLckUnlockSH(hResLock);
		return (ErrorPop());
	}

	fclose(pCacheFile);

	RLckUnlockSH(hResLock);

	return (0);

}

static int CDNS_MxSave(char const *pszDomain, char const *pszMXDomains, SYS_UINT32 TTL)
{
///////////////////////////////////////////////////////////////////////////////
//  Build cached file path
///////////////////////////////////////////////////////////////////////////////
	char szFilePath[SYS_MAX_PATH] = "";

	if (CDNS_GetCacheFilePath(pszDomain, DNS_MX_CACHE_DIRCTORY, szFilePath) == NULL)
		return (ErrGetErrorCode());

	char szResLock[SYS_MAX_PATH] = "";
	RLCK_HANDLE hResLock = RLckLockEX(CfgGetBasedPath(szFilePath, szResLock,
							  sizeof(szResLock)));

	if (hResLock == INVALID_RLCK_HANDLE)
		return (ErrGetErrorCode());

	FILE *pCacheFile = fopen(szFilePath, "wt");

	if (pCacheFile == NULL) {
		RLckUnlockEX(hResLock);

		ErrSetErrorCode(ERR_FILE_CREATE, szFilePath);
		return (ERR_FILE_CREATE);
	}
///////////////////////////////////////////////////////////////////////////////
//  1st line ( TTL )
///////////////////////////////////////////////////////////////////////////////
	fprintf(pCacheFile, "%lu\n", (unsigned long) TTL);

///////////////////////////////////////////////////////////////////////////////
//  2nd line ( MX domains )
///////////////////////////////////////////////////////////////////////////////
	fprintf(pCacheFile, "%s\n", pszMXDomains);

	fclose(pCacheFile);

	RLckUnlockEX(hResLock);

	return (0);

}

int CDNS_GetDomainMX(char const *pszDomain, char *&pszMXDomains, char const *pszSmartDNS)
{
///////////////////////////////////////////////////////////////////////////////
//  Try to get the cached copy
///////////////////////////////////////////////////////////////////////////////
	if (CDNS_MxLoad(pszDomain, pszMXDomains) == 0)
		return (0);

///////////////////////////////////////////////////////////////////////////////
//  If the list of smart DNS hosts is NULL, do a full DNS query
///////////////////////////////////////////////////////////////////////////////
	SYS_UINT32 TTL = 0;

	if (pszSmartDNS == NULL) {
		char szCName[MAX_HOST_NAME] = "";
		int iResult = DNS_GetDomainMX(pszDomain, pszMXDomains,
					      szCName, &TTL);

		if (iResult < 0) {
			if (iResult != ERR_DNS_IS_CNAME)
				return (ErrGetErrorCode());

			if (DNS_GetDomainMX(szCName, pszMXDomains, NULL, &TTL) < 0)
				return (ErrGetErrorCode());
		}

		return (CDNS_MxSave(pszDomain, pszMXDomains, TTL));
	}

///////////////////////////////////////////////////////////////////////////////
//  Parse the list of smart DNS hosts
///////////////////////////////////////////////////////////////////////////////
	char **ppszTokens = StrTokenize(pszSmartDNS, ",:");

	if (ppszTokens == NULL)
		return (ErrGetErrorCode());

	int iTokensCount = StrStringsCount(ppszTokens);

	if (iTokensCount < 2) {
		StrFreeStrings(ppszTokens);

		ErrSetErrorCode(ERR_BAD_SMARTDNSHOST_SYNTAX);
		return (ERR_BAD_SMARTDNSHOST_SYNTAX);
	}
///////////////////////////////////////////////////////////////////////////////
//  Walk through the list of smart DNS hosts to find a DNS response
///////////////////////////////////////////////////////////////////////////////
	for (int ii = 0; ii < (iTokensCount - 1); ii += 2) {
		int iQuerySockType =
		    (stricmp(ppszTokens[ii + 1], "tcp") == 0) ? DNS_QUERY_TCP : DNS_QUERY_UDP;

		if (DNS_GetDomainMXDirect(ppszTokens[ii], pszDomain, iQuerySockType,
					  pszMXDomains, &TTL) == 0) {
			StrFreeStrings(ppszTokens);

			return (CDNS_MxSave(pszDomain, pszMXDomains, TTL));
		}
	}

	StrFreeStrings(ppszTokens);

	return (ErrGetErrorCode());

}