/* MDB Tools - A library for reading MS Access database files
 * Copyright (C) 2000 Brian Bruns
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include <errno.h>
#include "mdbtools.h"

#ifndef MIN
#define MIN(a,b) (a>b ? b : a)
#endif

static size_t decompress_unicode(const char *src, size_t slen, char *dst, size_t dlen) {
	unsigned int compress=1;
	size_t tlen = 0;
	while (slen > 0 && tlen < dlen) {
		if (*src == 0) {
			compress = (compress) ? 0 : 1;
			src++;
			slen--;
		} else if (compress) {
			dst[tlen++] = *src++;
			dst[tlen++] = 0;
			slen--;
		} else if (slen >= 2){
			dst[tlen++] = *src++;
			dst[tlen++] = *src++;
			slen-=2;
		} else { // Odd # of bytes
			break;
		}
	}
	return tlen;
}

#if HAVE_ICONV
static size_t decompressed2ascii_with_iconv(MdbHandle *mdb, const char *in_ptr, size_t len_in, char *dest, size_t dlen) {
	char *out_ptr = dest;
	size_t len_out = dlen - 1;

	while (1) {
		iconv(mdb->iconv_in, (ICONV_CONST char **)&in_ptr, &len_in, &out_ptr, &len_out);
		/* 
		 * Have seen database with odd number of bytes in UCS-2, shouldn't happen but protect against it
		 */
		if (!IS_JET3(mdb) && len_in<=1) {
			//fprintf(stderr, "Detected invalid number of UCS-2 bytes\n");
			break;
		}
		if ((!len_in) || (errno == E2BIG)) break;
		/* Don't bail if impossible conversion is encountered */
		in_ptr += (IS_JET3(mdb)) ? 1 : 2;
		len_in -= (IS_JET3(mdb)) ? 1 : 2;
		*out_ptr++ = '?';
		len_out--;
	}
	dlen -= len_out + 1;
	dest[dlen] = '\0';
	return dlen;
}
#else
static size_t decompressed2ascii_without_iconv(MdbHandle *mdb, const char *in_ptr, size_t len_in, char *dest, size_t dlen) {
	if (IS_JET3(mdb)) {
		int count = 0;
		snprintf(dest, dlen, "%.*s%n", (int)len_in, in_ptr, &count);
		return count;
	}
	/* rough UCS-2LE to ISO-8859-1 conversion */
	/* wcstombs would be better; see libxls implementation for 
	 * a multi-platform solution */
	unsigned int i;
	for (i=0; 2*i+1<len_in && i<dlen-1; i++)
		dest[i] = (in_ptr[2*i+1] == 0) ? in_ptr[2*i] : '?';
	dest[i] = '\0';
	return i;
}
#endif

/*
 * This function is used in reading text data from an MDB table.
 * 'dest' will receive a converted, null-terminated string.
 * dlen is the available size of the destination buffer.
 * Returns the length of the converted string, not including the terminator.
 */
int
mdb_unicode2ascii(MdbHandle *mdb, const char *src, size_t slen, char *dest, size_t dlen)
{
	char *tmp = NULL;
	size_t len_in;
	const char *in_ptr = NULL;

	if ((!src) || (!dest) || (!dlen))
		return 0;

	/* Uncompress 'Unicode Compressed' string into tmp */
	if (!IS_JET3(mdb) && (slen>=2)
			&& ((src[0]&0xff)==0xff) && ((src[1]&0xff)==0xfe)) {
		tmp = (char *)g_malloc(slen*2);
		len_in = decompress_unicode(src + 2, slen - 2, tmp, slen * 2);
		in_ptr = tmp;
	} else {
		len_in = slen;
		in_ptr = src;
	}

#if HAVE_ICONV
	dlen = decompressed2ascii_with_iconv(mdb, in_ptr, len_in, dest, dlen);
#else
	dlen = decompressed2ascii_without_iconv(mdb, in_ptr, len_in, dest, dlen);
#endif

	if (tmp) g_free(tmp);
	return dlen;
}

/*
 * This function is used in writing text data to an MDB table.
 * If slen is 0, strlen will be used to calculate src's length.
 */
int
mdb_ascii2unicode(MdbHandle *mdb, const char *src, size_t slen, char *dest, size_t dlen)
{
        size_t len_in, len_out;
        const char *in_ptr = NULL;
        char *out_ptr = NULL;

	if ((!src) || (!dest) || (!dlen))
		return 0;

        in_ptr = src;
        out_ptr = dest;
        len_in = (slen) ? slen : strlen(in_ptr);
        len_out = dlen;

#ifdef HAVE_ICONV
	iconv(mdb->iconv_out, (ICONV_CONST char **)&in_ptr, &len_in, &out_ptr, &len_out);
	//printf("len_in %d len_out %d\n", len_in, len_out);
	dlen -= len_out;
#else
	if (IS_JET3(mdb)) {
		dlen = MIN(len_in, len_out);
		strncpy(out_ptr, in_ptr, dlen);
	} else {
		unsigned int i;
		slen = MIN(len_in, len_out/2);
		dlen = slen*2;
		for (i=0; i<slen; i++) {
			out_ptr[i*2] = in_ptr[i];
			out_ptr[i*2+1] = 0;
		}
	}
#endif

	/* Unicode Compression */
	if(!IS_JET3(mdb) && (dlen>4)) {
		unsigned char *tmp = g_malloc(dlen);
		unsigned int tptr = 0, dptr = 0;
		int comp = 1;

		tmp[tptr++] = 0xff;
		tmp[tptr++] = 0xfe;
		while((dptr < dlen) && (tptr < dlen)) {
			if (((dest[dptr+1]==0) && (comp==0))
			 || ((dest[dptr+1]!=0) && (comp==1))) {
				/* switch encoding mode */
				tmp[tptr++] = 0;
				comp = (comp) ? 0 : 1;
			} else if (dest[dptr]==0) {
				/* this string cannot be compressed */
				tptr = dlen;
			} else if (comp==1) {
				/* encode compressed character */
				tmp[tptr++] = dest[dptr];
				dptr += 2;
			} else if (tptr+1 < dlen) {
				/* encode uncompressed character */
				tmp[tptr++] = dest[dptr];
				tmp[tptr++] = dest[dptr+1];
				dptr += 2;
			} else {
				/* could not encode uncompressed character
				 * into single byte */
				tptr = dlen;
			}
		}
		if (tptr < dlen) {
			memcpy(dest, tmp, tptr);
			dlen = tptr;
		}
		g_free(tmp);
	}

	return dlen;
}

const char*
mdb_target_charset(MdbHandle *mdb)
{
#ifdef HAVE_ICONV
	const char *iconv_code = getenv("MDBICONV");
	if (!iconv_code)
		iconv_code = "UTF-8";
	return iconv_code;
#else
	if (!IS_JET3(mdb))
		return "ISO-8859-1";
	return NULL; // same as input: unknown
#endif
}

void mdb_iconv_init(MdbHandle *mdb)
{
	const char *iconv_code;

	/* check environment variable */
	if (!(iconv_code=getenv("MDBICONV"))) {
		iconv_code="UTF-8";
	}

#ifdef HAVE_ICONV
	if (!IS_JET3(mdb)) {
		mdb->iconv_out = iconv_open("UCS-2LE", iconv_code);
		mdb->iconv_in = iconv_open(iconv_code, "UCS-2LE");
	} else {
		/* According to Microsoft Knowledge Base pages 289525 and */
		/* 202427, code page info is not contained in the database */
		const char *jet3_iconv_code;

		/* check environment variable */
		if (!(jet3_iconv_code=getenv("MDB_JET3_CHARSET"))) {
			jet3_iconv_code="CP1252";
		}

		mdb->iconv_out = iconv_open(jet3_iconv_code, iconv_code);
		mdb->iconv_in = iconv_open(iconv_code, jet3_iconv_code);
	}
#endif
}
void mdb_iconv_close(MdbHandle *mdb)
{
#ifdef HAVE_ICONV
    if (mdb->iconv_out != (iconv_t)-1) iconv_close(mdb->iconv_out);
    if (mdb->iconv_in != (iconv_t)-1) iconv_close(mdb->iconv_in);
#endif
}