/*
 * Copyright 2005 - 2016 Zarafa and its licensors
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
#include <memory>
#include <cstring>
#include <cstdlib>
#include "rtf.h"

static const unsigned int crctable[256] = {
  0x00000000, 0x77073096, 0xee0e612c, 0x990951ba,
  0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
  0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
  0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
  0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
  0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
  0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,
  0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
  0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
  0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
  0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940,
  0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
  0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116,
  0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
  0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
  0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
  0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a,
  0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
  0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818,
  0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
  0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
  0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
  0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c,
  0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
  0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
  0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
  0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
  0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
  0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086,
  0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
  0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4,
  0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
  0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
  0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
  0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
  0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
  0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe,
  0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
  0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
  0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
  0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252,
  0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
  0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60,
  0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
  0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
  0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
  0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04,
  0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
  0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a,
  0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
  0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
  0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
  0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e,
  0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
  0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
  0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
  0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
  0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
  0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0,
  0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
  0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6,
  0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
  0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
  0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d,
};

static unsigned int crc32(const char *data, unsigned int len)
{
	unsigned int crc = 0;
	const char *p = data;

	while(len--) {
		crc = (crc >> 8) ^ crctable[(crc ^ *p++) & 0xff];
	}

	return crc;
}

// Based on jtnef (TNEFUtils.java)
static const char lpPrebuf[] =
	"{\\rtf1\\ansi\\mac\\deff0\\deftab720{\\fonttbl;}"
	"{\\f0\\fnil \\froman \\fswiss \\fmodern \\fscript "
	"\\fdecor MS Sans SerifSymbolArialTimes New RomanCourier"
	"{\\colortbl\\red0\\green0\\blue0\n\r\\par "
	"\\pard\\plain\\f0\\fs20\\b\\i\\u\\tab\\tx";

struct RTFHeader {
	unsigned int ulCompressedSize;
	unsigned int ulUncompressedSize;
	unsigned int ulMagic;
	unsigned int ulChecksum;
};

unsigned int rtf_get_uncompressed_length(char *lpData, unsigned int ulSize)
{
	// Check if we have a full header
	if(ulSize < sizeof(RTFHeader)) 
		return 0;
	
	// Return the size
	return ((RTFHeader *)lpData)->ulUncompressedSize;
}

// FIXME bad data can buffer overflow when ulUncompressedSize is incorrect
// lpDest should be pre-allocated to the uncompressed size
unsigned int rtf_decompress(char *lpDest, char *lpSrc, unsigned int ulBufSize)
{
	auto lpHeader = reinterpret_cast<struct RTFHeader *>(lpSrc);
	auto lpStart = lpSrc;
	unsigned int ulFlags = 0;
	unsigned int ulFlagNr = 0;
	unsigned char c1 = 0;
	unsigned char c2 = 0;
	unsigned int ulOffset = 0;
	unsigned int ulSize = 0;
	const unsigned int prebufSize = strlen(lpPrebuf);

	// Check if we have a full header
	if(ulBufSize < sizeof(RTFHeader)) 
		return 1;
	
	lpSrc += sizeof(struct RTFHeader);
	
	if(lpHeader->ulMagic == 0x414c454d) {
		// Uncompressed RTF
		memcpy(lpDest, lpSrc, ulBufSize - sizeof(RTFHeader));
		return 0;
	} else if (lpHeader->ulMagic != 0x75465a4c) {
		return 1;
	}
	// Allocate a buffer to decompress into (uncompressed size plus prebuffered data)
	std::unique_ptr<char[]> lpBuffer(new char[lpHeader->ulUncompressedSize+prebufSize]);
	memcpy(lpBuffer.get(), lpPrebuf, prebufSize);

	// Start writing just after the prebuffered data
	char *lpWrite = lpBuffer.get() + prebufSize;

	while (lpWrite < lpBuffer.get() + lpHeader->ulUncompressedSize + prebufSize) {
		// Get next bit from flags
		ulFlags = ulFlagNr++ % 8 == 0 ? *lpSrc++ : ulFlags >> 1;

		if (lpSrc >= lpStart + ulBufSize)
			// Reached the end of the input buffer somehow. We currently return OK
			// and the decoded data up to now.
			break;
		if (!(ulFlags & 1)) {
			*lpWrite++ = *lpSrc++;
			if (lpSrc >= lpStart + ulBufSize)
				break;
			continue;
		}
		if (lpSrc + 2 >= lpStart + ulBufSize)
			break;
		// Reference to existing data
		c1 = *lpSrc++;
		c2 = *lpSrc++;

		// Offset is first 12 bits
		ulOffset = (((unsigned int)c1) << 4) | (c2 >> 4);
		// Size is last 4 bits, plus 2 (0 and 1 are impossible, because 1 would be a literal (ie ulFlags & 1 == 0)
		ulSize = (c2 & 0xf) + 2;

		// We now have offset and size within our current 4k window. If the offset is after the
		// write pointer, then go back one window. (due to wrapping buffer)
		ulOffset = ((lpWrite - lpBuffer.get()) / 4096) * 4096 + ulOffset;
		if (ulOffset > (unsigned int)(lpWrite - lpBuffer.get()))
			ulOffset -= 4096;
		while (ulSize && lpWrite < &lpBuffer[lpHeader->ulUncompressedSize+prebufSize] && ulOffset < lpHeader->ulUncompressedSize + prebufSize) {
			*lpWrite++ = lpBuffer[ulOffset++];
			--ulSize;
		}
	}
	// Copy back the data without the prebuffer
	memcpy(lpDest, &lpBuffer[prebufSize], lpHeader->ulUncompressedSize);
	return 0;
}

// Find pattern in buffer, and return the longest match found.
static void strmatch(const char *lpszBuffer, unsigned int cbBuffer,
    const char *lpszPattern, unsigned int cbPattern, const char **lppszMatch,
    unsigned int *lpcbMatch)
{
	const char		*lpszBufCur = lpszBuffer;
	const char		*lpszPatCur = NULL;
	unsigned int	ulCount = 0;
	const char		*lpszMatch = NULL;
	unsigned int cbMatch = 0;

	while (cbMatch < cbPattern && lpszBufCur + cbMatch < lpszBuffer + cbBuffer)
	{
		lpszPatCur = lpszPattern;
		ulCount = 0;
		while (true)
		{
			if (lpszPatCur == lpszPattern + cbPattern ||
				lpszBufCur == lpszBuffer + cbBuffer ||
				((*lpszPatCur != *lpszBufCur || *lpszPatCur == '\n' || *lpszPatCur == '\r') && ulCount) > 0)
			{
				if (ulCount > cbMatch)
				{
					cbMatch = ulCount;
					lpszMatch = lpszBufCur - ulCount;
				}
				break;
			} 
			else if (*lpszPatCur == *lpszBufCur && *lpszPatCur != '\n' && *lpszPatCur != '\r')
			{
				++lpszBufCur;
				++lpszPatCur;
				++ulCount;
			}
			else
				++lpszBufCur;
		}
	}

	*lppszMatch = lpszMatch;
	*lpcbMatch = cbMatch;
}

// Compressed lpSrc of size ulBufSize into a new buffer, and returns it in lppDest.
unsigned int rtf_compress(char **lppDest, unsigned int *lpulDestSize, char *lpSrc, unsigned int ulBufSize) {
	/* The following CRC start value was deduced by experiment to create correct CRC values.
	 * The RTFLIB32.LIB file in MAPI seems to use a standard crc32 function to create its header
 	 * checksums, the question was, what is the start value for the crc register, and what
	 * data should be fed to it. 
	 * I found out that basically all the *compressed* data is sent
	 * through the crc checksum, excluding headers and stuff like that. The actual start value
	 * is zero, contrary to what POSIX states (POSIX starts with 0xffffffff) and the return value is NOT
	 * a bitwise NOT of the crc value that is calculated from the crc32 table.
	 * This gives us outlook-compatible RTF streams. (Man, I'm such a l33t h4xx0r)
	 */
	unsigned int ulRetVal = 0;
	unsigned int ulDestBufSize = ulBufSize+1024;
	unsigned int ulCursor = 0;
	unsigned int ulOutCursor = 0;
	unsigned int ulFlagCursor = 0;
	unsigned int ulFlagNr = 0;
	RTFHeader *lpHeader = NULL;
	
	const char *lpMatch = NULL;
	unsigned int cbMatch = 0;
	const unsigned int cbPrebuf = strlen(lpPrebuf);
	auto lpDest = static_cast<char *>(malloc(ulDestBufSize));
	if(lpDest == NULL)
		return 1;

	std::unique_ptr<char[]> lpTmp(new char[ulBufSize+cbPrebuf]);
	memcpy(lpTmp.get(), lpPrebuf, cbPrebuf);
	memcpy(lpTmp.get() + cbPrebuf, lpSrc, ulBufSize);
	lpSrc = &lpTmp[cbPrebuf];
	ulOutCursor = sizeof(RTFHeader);

	while(ulCursor <= ulBufSize) {
		if(ulFlagNr == 0) {
			lpDest[ulOutCursor] = 0;
			ulFlagCursor = ulOutCursor;
			++ulOutCursor;
			if(ulOutCursor >= ulDestBufSize) {
				ulDestBufSize += 1024;
				auto lpRealloc = static_cast<char *>(realloc(lpDest, ulDestBufSize)); // this shouldn't happen very often, so 1k is fine
				if (!lpRealloc) {
					ulRetVal = 1;
					goto exit;
				}
				lpDest = lpRealloc;
			}
			ulFlagNr = 8;
		}

		if(ulBufSize == ulCursor) {
			/* YAY
			 *
			 * Another strange thing; the stream should be capped off at the end with a reference to the two-byte area
			 * just in front of the current buffer position ... When this is removed, windows refuses to decode the data .. 
			 * Also, I can't actually see these two bytes in the decoded data ....
			 * (yes, offset is 12 bits)
			 */
			int offset = (strlen(lpPrebuf) + ulBufSize) & 0x0fff;

			lpDest[ulOutCursor++] = offset >> 4;

			if(ulOutCursor >= ulDestBufSize) {
				ulDestBufSize += 1024;
				auto lpRealloc = static_cast<char *>(realloc(lpDest, ulDestBufSize)); // this shouldn't happen very often, so 1k is fine
				if (!lpRealloc) {
					ulRetVal = 1;
					goto exit;
				}
				lpDest = lpRealloc;
			}

			lpDest[ulOutCursor++] = (offset << 4) & 0xf0;

			if(ulOutCursor >= ulDestBufSize) {
				ulDestBufSize += 1024;
				auto lpRealloc = static_cast<char *>(realloc(lpDest, ulDestBufSize)); // this shouldn't happen very often, so 1k is fine
				if (!lpRealloc) {
					ulRetVal = 1;
					goto exit;
				}
				lpDest = lpRealloc;
			}

			lpDest[ulFlagCursor] |= 1 << (8 - ulFlagNr);
			break;
		}
		
		// lpSrc == lpTmp + cbPrebuf
		char *lpSearchStart = ulCursor + cbPrebuf >= 4096 ? &lpTmp[ulCursor + cbPrebuf - 4095] : &lpTmp[0];
		strmatch(
			lpSearchStart,
			&lpSrc[ulCursor] - lpSearchStart,
			&lpSrc[ulCursor],
			ulBufSize - ulCursor >= 17 ? 17 : ulBufSize - ulCursor,
			&lpMatch,
			&cbMatch
		);
		
		if (lpMatch != NULL && cbMatch >= 3) {
			// Offset is defined as the offset in the current or previous 4k page. When offset
			// is bigger than the write position in the current page, the previous page is
			// targeted.
			char *lpCurPage = lpSrc - cbPrebuf + ((ulCursor + cbPrebuf) / 4096) * 4096;
			unsigned int offset = lpMatch - lpCurPage;

			offset &= 0x0fff;
			
			lpDest[ulOutCursor++] = offset >> 4;

			if(ulOutCursor >= ulDestBufSize) {
				ulDestBufSize += 1024;
				auto lpRealloc = static_cast<char *>(realloc(lpDest, ulDestBufSize)); // this shouldn't happen very often, so 1k is fine
				if (!lpRealloc) {
					ulRetVal = 1;
					goto exit;
				}
				lpDest = lpRealloc;
			}

			lpDest[ulOutCursor++] = ((offset << 4) & 0xf0) | ((cbMatch - 2) & 0x0f);

			if(ulOutCursor >= ulDestBufSize) {
				ulDestBufSize += 1024;
				auto lpRealloc = static_cast<char *>(realloc(lpDest, ulDestBufSize)); // this shouldn't happen very often, so 1k is fine
				if (!lpRealloc) {
					ulRetVal = 1;
					goto exit;
				}
				lpDest = lpRealloc;
			}
			
			ulCursor += cbMatch;
			lpDest[ulFlagCursor] |= 1 << (8 - ulFlagNr);
		} else {
			lpDest[ulOutCursor++] = lpSrc[ulCursor++];

			if(ulOutCursor >= ulDestBufSize) {
				ulDestBufSize += 1024;
				auto lpRealloc = static_cast<char *>(realloc(lpDest, ulDestBufSize)); // this shouldn't happen very often, so 1k is fine
				if (!lpRealloc) {
					ulRetVal = 1;
					goto exit;
				}
				lpDest = lpRealloc;
			}
		}
		--ulFlagNr;
	}

	lpHeader = (RTFHeader *)lpDest;

	lpHeader->ulCompressedSize = ulOutCursor - sizeof(unsigned int);
	lpHeader->ulUncompressedSize = ulBufSize;
	lpHeader->ulMagic = 0x75465a4c;
	lpHeader->ulChecksum = crc32((char *)&lpDest[sizeof(RTFHeader)], ulOutCursor - sizeof(RTFHeader));

	*lppDest = lpDest;
	*lpulDestSize = ulOutCursor;

	lpDest = NULL;

exit:
	free(lpDest);
	return ulRetVal;
}
