/*
   Unix SMB/CIFS implementation.
   minimal iconv implementation
   Copyright (C) Andrew Tridgell 2001
   Copyright (C) Jelmer Vernooij 2002,2003

   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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

   From samba 3.0 beta and GNU libiconv-1.8
   It's bad but most of the time we can't use libc iconv service:
   - it doesn't round trip for most encoding
   - it doesn't know about Apple extension
*/

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif /* HAVE_CONFIG_H */

#include <arpa/inet.h>
#include <errno.h>
#include <stdlib.h>

#include <atalk/byteorder.h>
#include <atalk/logger.h>
#include <atalk/unicode.h>
#include <atalk/unicode.h>

/* Given a trailing UTF-8 byte, get the contribution from it to
 * the Unicode scalar value for a particular bit shift amount
 */
#define GETUCVAL(utf8_trailbyte,shift)  ((unsigned int) (( utf8_trailbyte & 0x3F) << shift))

/* Given a unicode scalar, get a trail UTF-8 byte for a particular bit shift amount */
#define GETUTF8TRAILBYTE(uc,shift)      ((char)( 0x80 | ((uc >> shift) & 0x3F) ) )



static size_t   utf8_pull(void *,char **, size_t *, char **, size_t *);
static size_t   utf8_push(void *,char **, size_t *, char **, size_t *);

struct charset_functions charset_utf8 =
{
	"UTF8",
	0x08000103,
	utf8_pull,
	utf8_push,
	CHARSET_VOLUME | CHARSET_MULTIBYTE | CHARSET_PRECOMPOSED,
	NULL,
	NULL, NULL
};

struct charset_functions charset_utf8_mac =
{
	"UTF8-MAC",
	0x08000103,
	utf8_pull,
	utf8_push,
	CHARSET_VOLUME | CHARSET_CLIENT | CHARSET_MULTIBYTE | CHARSET_DECOMPOSED,
	NULL,
	NULL, NULL
};

/* The Unicode Standard Version 6.2 – Core Specification          */
/* http://www.unicode.org/versions/Unicode6.2.0/ch03.pdf          */
/*                                                                */
/* Scalar Value               First    Second   Third    Fourth   */
/* 00000000 0xxxxxxx          0xxxxxxx                            */
/* 00000yyy yyxxxxxx          110yyyyy 10xxxxxx                   */
/* zzzzyyyy yyxxxxxx          1110zzzz 10yyyyyy 10xxxxxx          */
/* 000uuuuu zzzzyyyy yyxxxxxx 11110uuu 10uuzzzz 10yyyyyy 10xxxxxx */


/* ------------------- Convert from UTF-8 to UTF-16 -------------------*/

/* Code Points        First   Second  Third    Fourth  */
/* U+0000..U+007F      00..7F                          */
/* U+0080..U+07FF      C2..DF  80..BF                  */
/* U+0800..U+0FFF      E0      A0..BF  80..BF          */
/* U+1000..U+CFFF      E1..EC  80..BF  80..BF          */
/* U+D000..U+D7FF      ED      80..9F  80..BF          */
/* U+E000..U+FFFF      EE..EF  80..BF  80..BF          */
/* U+10000..U+3FFFF    F0      90..BF  80..BF  80..BF  */
/* U+40000..U+FFFFF    F1..F3  80..BF  80..BF  80..BF  */
/* U+100000..U+10FFFF  F4      80..8F  80..BF  80..BF  */

static size_t utf8_pull(void *cd _U_, char **inbuf, size_t *inbytesleft,
			 char **outbuf, size_t *outbytesleft)
{
	ucs2_t uc = 0;
	unsigned int codepoint;
	int len;

	while (*inbytesleft >= 1 && *outbytesleft >= 2) {
		unsigned char *c = (unsigned char *)*inbuf;
		len = 1;

		/* Arrange conditionals in the order of most frequent occurrence
		 * for users of Latin-based chars */
		if ((c[0] & 0x80) == 0) {                                /* 0xxx xxxx */ /* 1 byte  */
			uc = c[0];
		} else if ((c[0] & 0xe0) == 0xc0) {                             /* 110y yyyy */ /* 2 bytes */
			if (*inbytesleft < 2) goto inval;
			if (c[0] < 0xc2) goto ilseq;                                /* C2-DF */
			if ((c[1] & 0xc0) != 0x80) goto ilseq;                      /* 80-BF */
			uc = (ucs2_t) (((c[0] & 0x1f) << 6) | GETUCVAL(c[1],0)) ;
			len = 2;
		} else if ((c[0] & 0xf0) == 0xe0) {                                  /* 1110 zzzz */ /* 3 bytes */
			if (*inbytesleft < 3) goto inval;
			if (!((c[0] == 0xe0                && (c[1] & 0xe0) == 0xa0)  || /* E0    A0-BF*/
				  (0xe1 <= c[0] && c[0] <= 0xec && (c[1] & 0xc0) == 0x80) || /* E1-EC 80-BF */
				  (c[0] == 0xed                 && (c[1] & 0xe0) == 0x80) || /* ED    80-9F */
				  ((c[0] & 0xfe) == 0xee        && (c[1] & 0xc0) == 0x80)))  /* EE-EF 80-BF */
				goto ilseq;
			if ((c[2] & 0xc0) != 0x80) goto ilseq;                           /* 80-BF */
			uc = (ucs2_t) (((c[0] & 0x0f) << 12) | GETUCVAL(c[1],6) | GETUCVAL(c[2],0)) ;
			len = 3;
		} else if ((c[0] & 0xf8) == 0xf0) {                                         /* 1111 0uuu */ /* 4 bytes */
			if (*inbytesleft < 4) goto inval;
			if (*outbytesleft < 4) goto toobig;
			if (c[0] > 0xf4) goto ilseq;                                            /* happens for surrogate pairs only */
			if (!((c[0] == 0xf0                 && 0x90 <= c[1] && c[1] <= 0xbf) || /* F0    90-BF */
				  (0xf1 <= c[0] && c[0] <= 0xf3 && (c[1] & 0xc0) == 0x80) ||        /* F1-F3 80-BF */
				  (c[0] == 0xf4                 && (c[1] & 0xc0) == 0x80)))         /* F4    80-8F */
				goto ilseq;
			if ((c[2] & 0xc0) != 0x80) goto ilseq;                                  /* 80-BF */
			if ((c[3] & 0xc0) != 0x80) goto ilseq;                                  /* 80-BF */
			codepoint = ((c[0] & 0x07) << 18) | GETUCVAL(c[1],12) |
				GETUCVAL(c[2],6) |  GETUCVAL(c[3],0);
			SSVAL(*outbuf,0,(((codepoint - 0x10000) >> 10) + 0xD800)); /* hi  */
			SSVAL(*outbuf,2,(0xDC00 + (codepoint & 0x03FF)));          /* low */
			len = 4;
			(*inbuf)  += 4;
			(*inbytesleft)  -= 4;
			(*outbytesleft) -= 4;
			(*outbuf) += 4;
			continue;
		} else {
			goto ilseq;
		}

		SSVAL(*outbuf,0,uc);
		(*inbuf)  += len;
		(*inbytesleft)  -= len;
		(*outbytesleft) -= 2;
		(*outbuf) += 2;
	}

	if (*inbytesleft > 0) {
		goto toobig;
	}

	return 0;

toobig:
	LOG(log_debug, logtype_default, "short ucs-2 write");
	errno = E2BIG;
	return -1;

ilseq:
	LOG(log_debug, logtype_default, "malformed utf8 sequence");
	errno = EILSEQ;
	return -1;

inval:
	LOG(log_debug, logtype_default, "short utf8 char");
	errno = EINVAL;
	return -1;
}

/* --------------------- Convert from UTF-16 to UTF-8 -----------*/
static size_t utf8_push(void *cd _U_, char **inbuf, size_t *inbytesleft,
			 char **outbuf, size_t *outbytesleft)
{
	ucs2_t uc=0;
	ucs2_t hi, low;
	unsigned int codepoint;
	int olen, ilen;

	while (*inbytesleft >= 2 && *outbytesleft >= 1) {
		unsigned char *c = (unsigned char *)*outbuf;
		uc = SVAL((*inbuf),0);
		olen=1;
		ilen=2;

		/* Arrange conditionals in the order of most frequent occurrence for
		   users of Latin-based chars */
		if (uc < 0x80) {
			c[0] = uc;
		} else if (uc < 0x800) {
			if (*outbytesleft < 2) {
				LOG(log_debug, logtype_default, "short utf8 write");
				goto toobig;
			}
			c[1] = GETUTF8TRAILBYTE(uc, 0);
			c[0] = (char)(0xc0 | ((uc >> 6) & 0x1f));
			olen = 2;
		}
		else if ( uc >= 0x202a && uc <= 0x202e ) {
			/* ignore bidi hint characters */
			olen = 0;
		}
		/*
		 * A 2-byte uc value represents a stand-alone Unicode character if
		 *     0 <= uc < 0xd800 or 0xdfff < uc <= 0xffff.
		 * If  0xd800 <= uc <= 0xdfff, uc itself does not represent a Unicode character.
		 * Rather, it is just part of a surrogate pair.  A surrogate pair consists of
		 * a high surrogate in the range [0xd800 ... 0xdbff] and a low surrogate in the
		 * range [0xdc00 ... 0xdfff].  Together the pair maps to a single Unicode character
		 * whose scalar value is 64K or larger.  It is this scalar value that is transformed
		 * to UTF-8, not the individual surrogates.
		 *
		 * See www.unicode.org/faq/utf_bom.html for more info.
		 */

		else if ( 0xd800 <= uc && uc <= 0xdfff) {
			/* surrogate - needs 4 bytes from input and 4 bytes for output to UTF-8 */
			if (*outbytesleft < 4) {
				LOG(log_debug, logtype_default, "short utf8 write");
				goto toobig;
			}
			if (*inbytesleft < 4) {
				errno = EINVAL;
				return -1;
			}
			hi =  SVAL((*inbuf),0);
			low = SVAL((*inbuf),2);
			if ( 0xd800 <= hi && hi <= 0xdbff && 0xdc00 <= low && low <= 0xdfff) {
				codepoint = ((hi - 0xd800) << 10) + (low - 0xdc00) + 0x10000;
				c[3] = GETUTF8TRAILBYTE(codepoint, 0);
				c[2] = GETUTF8TRAILBYTE(codepoint, 6);
				c[1] = GETUTF8TRAILBYTE(codepoint, 12);
				c[0] = (char)(0xf0 | ((codepoint >> 18) & 0x07));
				ilen = olen = 4;
			} else { /* invalid values for surrogate */
				errno = EINVAL;
				return -1;
			}
		} else {
			if (*outbytesleft < 3) {
				LOG(log_debug, logtype_default, "short utf8 write");
				goto toobig;
			}
			c[2] = GETUTF8TRAILBYTE(uc, 0);
			c[1] = GETUTF8TRAILBYTE(uc, 6);
			c[0] = (char)(0xe0 | ((uc >> 12) & 0x0f));
			olen = 3;
		}

		(*inbytesleft)  -= ilen;
		(*outbytesleft) -= olen;
		(*inbuf)  += ilen;
		(*outbuf) += olen;
	}

	if (*inbytesleft == 1) {
		errno = EINVAL;
		return -1;
	}

	if (*inbytesleft > 1) {
		errno = E2BIG;
		return -1;
	}

	return 0;

toobig:
	errno = E2BIG;
	return -1;
}
