/*

    Character encoding transformation - basics

    Copyright (C) 2005 Olaf Klein, o.b.klein@gpsbabel.org

    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 USA
*/

#include "defs.h"
#include "cet.h"

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* ! ALL vec PARAMETERS HAVE TO BE A VALID POINTER TO A cet_cs_vec_t RECORD  ! */
 
/* =========================================================================== */
/* %%%            single character or value transmission                   %%% */
/* --------------------------------------------------------------------------- */

/* %%% cet_char_to_ucs4 %%%
 *
 * single character to UCS-4 code %%% 
 * return values: 0 if convertable character, otherwise 1
 */
 
int
cet_char_to_ucs4(const char src, const cet_cs_vec_t *vec, int *value)
{
	int trash, c;
	int *dest;

	c = ((unsigned char)src & 0xFF);
	dest = (value != NULL) ? value : &trash;
	
	*dest = c;
	c -= vec->ucs4_offset;

	if (c < 0) return CET_SUCCESS;
	else if ((c >= vec->ucs4_count) || (vec->ucs4_map[c] == -1)) return CET_ERROR;
	else 
	{
	    *dest = vec->ucs4_map[c];
	    return CET_SUCCESS;
	}
}

/* %%% cet_ucs4_to_utf8 %%%
 *
 * convert single UCS-4 value into UTF-8 sequence 
 *
 * return values: >= 0: length of produced UTF-8 sequence
 *                 < 0: -bytes more needed in target space
 */

int
cet_ucs4_to_utf8(char *dest, size_t dest_size, int value)
{
	int result;
	unsigned char trash[16];
	unsigned char *c;
	
	c = (dest != NULL) ? (unsigned char *) dest : trash;

	if ((value & 0xffffff80) == 0)			/* <= 7 bits */
	{
	    if (dest_size < 1) return (dest_size - 1);
	    *c++ = value;
	    result = 1;
	}
	else if ((value & 0xfffff800) == 0)		/* <= 11 bits */
	{
	    if (dest_size < 2) return (dest_size - 2);
	    *c++ = (0xc0 | (value >> 6));
	    *c++ = (0x80 | (value & 0x3f));
	    result = 2;

	}
	else if ((value & 0xffff0000) == 0)		/* <= 16 bits */
	{
	    if (dest_size < 3) return (dest_size - 3);
	    *c++ = (0xe0 |  (value >> 12));
	    *c++ = (0x80 | ((value >> 6) & 0x3f));
	    *c++ = (0x80 |  (value & 0x3f));
	    result = 3;
	}
	else if ((value & 0xffe00000) == 0)		/* <= 21 bits */
	{
	    if (dest_size < 4) return (dest_size - 4);
	    *c++ = (0xf0 |  (value >> 18));
	    *c++ = (0x80 | ((value >> 12) & 0x3f));
	    *c++ = (0x80 | ((value >> 6) & 0x3f));
	    *c++ = (0x80 |  (value & 0x3f));
	    result = 4;
	}
	else if ((value & 0xfc000000) == 0)		/* <= 26 bits */
	{
	    if (dest_size < 5) return (dest_size - 5);
	    *c++ = (0xf8 |  (value >> 24));
	    *c++ = (0x80 | ((value >> 18) & 0x3f));
	    *c++ = (0x80 | ((value >> 12) & 0x3f));
	    *c++ = (0x80 | ((value >> 6) & 0x3f));
	    *c++ = (0x80 |  (value & 0x3f));
	    result = 5;
	}
	else if ((value & 0x80000000) == 0)		/* <= 31 bits */
	{
	    if (dest_size < 6) return (dest_size - 6);
	    *c++ = (0xfc |  (value >> 30));
	    *c++ = (0x80 | ((value >> 24) & 0x3f));
	    *c++ = (0x80 | ((value >> 18) & 0x3f));
	    *c++ = (0x80 | ((value >> 12) & 0x3f));
	    *c++ = (0x80 | ((value >> 6) & 0x3f));
	    *c++ = (0x80 |  (value & 0x3f));
	    result = 6;
	}
	else
	{
	    return 0;				/* Value = -1 */
	}
	return result;
}

/* %%% cet_utf8_to_ucs4 %%% 
 *
 * decode single UTF-8 sequence into UCS-4 value
 *
 * return values: 0 if success, otherwise 1
 */
int
cet_utf8_to_ucs4(const char *str, int *bytes, int *value)
{
	unsigned char *cp = (unsigned char *)str;
	
	if (*cp < 0x80)
	{
	    if (bytes != NULL) *bytes = 1;
	    if (value != NULL) *value = *cp;
	    return CET_SUCCESS;
	}
	else
	{
	    unsigned char bits = 0xc0;
	    unsigned char mask = 0xe0;
	    int len = 0;
	    
	    for (len = 1; len <= 6; len++)			/* outer loop, test UTF-8 frame */
	    {	
		if ((*cp & mask) == bits)
		{
		    int i = len;
		    while (i-- > 0)
		    {
			cp++;
		        if ((*cp & 0xc0) != 0x80) break; 	/* invalid 	*/
			else if (i == 0)			/* all valid 	*/
			{
			    char *c = (char *)str;		/* found valid sequence, now storing value */
			    int res = *c++ & (mask ^ 0xFF);
			    i = len;
			    while (i-- > 0)			
				res = (res << 6) | (*c++ & 0x3f);
				
			    if (bytes != NULL) *bytes = len + 1;
			    if (value != NULL) *value = res;
			    return CET_SUCCESS;
			}
		    }		    
		}
		bits = (bits >> 1) | 0x80;
		mask = (mask >> 1) | 0x80;
	    }
	}
	if (bytes != NULL) *bytes = 1;
	if (value != NULL) *value = *cp;
	return CET_ERROR;						/* not valid */
}

/* %%% cet_ucs4_to_char %%%
 *
 * convert single UCS-4 value to original character from CS 
 *
 * return values: coverted character or "CET_NOT_CONVERTABLE_DEFAULT"
 *                if not possible
 */
short
cet_ucs4_to_char(const int value, const cet_cs_vec_t *vec)
{
	cet_ucs4_link_t *link;

	if ((link = (cet_ucs4_link_t *)vec->ucs4_link))
	{
	    int i = 0;
	    int j = vec->ucs4_links - 1;			/* validate ucs value against vec */
	    while (i <= j)
	    {
		int a = (i + j) >> 1;
		int x = link[a].value;
	    
		if (x < value) i = a + 1;
		else if (x > value) j = a - 1;
		else return link[a].origin;
	    }
	}

	if ((link = (cet_ucs4_link_t *)vec->ucs4_extra))	/* can be NULL */
	{
	    int i = 0;
	    int j = vec->ucs4_extras - 1;
	    while (i <= j)
	    {
		int a = (i + j) >> 1;
		int x = link[a].value;
		
		if (x < value) i = a + 1;
		else if (x > value) j = a - 1;
		else return link[a].origin;
	    }
	}

	if (value < vec->ucs4_offset + vec->ucs4_count)
	    return (char)value & 0xFF;
	else {
	    if (vec->fallback && (vec->fallback != vec))
		return cet_ucs4_to_char(value, vec->fallback);
	    else
		return CET_NOT_CONVERTABLE_DEFAULT;
	}
}

/* %%% cet_utf8_to_char %%%
 *
 * Convert single UTF-8 sequence directly into associated characted
 * by given character set.
 */
 
short
cet_utf8_to_char(const char *str, const cet_cs_vec_t *vec, /* out */ int *bytes, int *value)
{
	int b, v;
	
	cet_utf8_to_ucs4(str, &b, &v);			/* decode UTF-8 sequence */
	
	if (bytes != NULL) *bytes = b;
	if (value != NULL) *value = v;
	
	return cet_ucs4_to_char(v, vec);
}

/* =========================================================================== */
/* %%%                   full string transformation                        %%% */
/* =========================================================================== */

/* %%% cet_str_utf8_to_any %%%
 *
 * Converts a UTF-8 string to given character set 
 */
char *
cet_str_utf8_to_any(const char *src, const cet_cs_vec_t *vec)
{
	char *c = (char *)src;
	int len;
	char *res, *dest, *cend;

	if (c == NULL) return NULL;
	if (vec->ucs4_count == 0) return xstrdup(src); /* UTF-8 -> UTF-8 */
	
	len = strlen(c);
	res = dest = xmalloc(len + 1);	/* target will become smaller or equal length */
	
	cend = c + len;

	while (c < cend)
	{
	    int bytes;
	    *dest++ = cet_utf8_to_char(c, vec, &bytes, NULL);
	    c += bytes;
	}
	*dest = '\0';

	return res;
}


/* %%% cet_str_any_to_utf8 %%%
 *
 * Converts a string from given character set to UTF-8
 */
char *
cet_str_any_to_utf8(const char *src, const cet_cs_vec_t *vec)
{
	int len, value;
	char *result, *cin, *cout;
	char temp = CET_NOT_CONVERTABLE_DEFAULT;

	cin = (char *)src;
	if (cin == NULL) return NULL;
	if (vec->ucs4_count == 0) return xstrdup(src); /* UTF-8 -> UTF-8 */

	len = 0;
	while (*cin != '\0')		/* determine length of resulting UTF-8 string */
	{
	    if (CET_ERROR == cet_char_to_ucs4(*cin++, vec, &value))
		cet_char_to_ucs4(temp, vec, &value);
	    len += cet_ucs4_to_utf8(NULL, 6, value);
	}

	result = cout = xmalloc(len + 1);
	cin = (char *)src;

	while (*cin != '\0')		
	{
	    if (CET_ERROR == cet_char_to_ucs4(*cin++, vec, &value))
		cet_char_to_ucs4(temp, vec, &value);
	    cout += cet_ucs4_to_utf8(cout, 6, value);
	}
	*cout = '\0';			
	return result;
}

/* %%% cet_str_uni_to_utf8 %%%
 *
 * Converts an unicode string to UTF-8
 */
char *
cet_str_uni_to_utf8(const short *src, const int length)
{
	int i, len;
	unsigned short *cin;
	char *res, *cout;
	
	if (src == NULL) return NULL;
	
	len = 0;
	i = length;
	cin = (unsigned short *)src;

	while (i-- > 0)
	    len += cet_ucs4_to_utf8(NULL, 6, le_read16(cin++));
	
	res = cout = xmalloc(len + 1);
	cin = (unsigned short *)src;
	i = length;

	while (i-- > 0)
	    cout += cet_ucs4_to_utf8(cout, 6, le_read16(cin++));
	    
	*cout = '\0';

	return res;
}
