/**
 * \file
 * string encoding conversions
 *
 * Author:
 *	Dick Porter (dick@ximian.com)
 *
 * (C) 2003 Ximian, Inc.
 */

#include <config.h>
#include <glib.h>
#include <string.h>

#include "strenc.h"

static const char trailingBytesForUTF8[256] = {
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
	1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
	2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 3,3,3,3,3,3,3,3,4,4,4,4,5,5,0,0
};

/**
 * mono_unicode_from_external:
 * \param in pointers to the buffer.
 * \param bytes number of bytes in the string.
 * Tries to turn a NULL-terminated string into UTF-16.
 *
 * First, see if it's valid UTF-8, in which case just turn it directly
 * into UTF-16.  Next, run through the colon-separated encodings in
 * \c MONO_EXTERNAL_ENCODINGS and do an \c iconv conversion on each,
 * returning the first successful conversion to UTF-16.  If no
 * conversion succeeds, return NULL.
 *
 * Callers must free the returned string if not NULL. \p bytes holds the number
 * of bytes in the returned string, not including the terminator.
 */
gunichar2 *
mono_unicode_from_external (const gchar *in, gsize *bytes)
{
	gchar *res=NULL;
	gchar **encodings;
	gchar *encoding_list;
	int i;
	glong lbytes;
	
	if(in==NULL) {
		return(NULL);
	}
	
	encoding_list=g_getenv ("MONO_EXTERNAL_ENCODINGS");
	if(encoding_list==NULL) {
		encoding_list = g_strdup("");
	}
	
	encodings=g_strsplit (encoding_list, ":", 0);
	g_free (encoding_list);
	for(i=0;encodings[i]!=NULL; i++) {
		/* "default_locale" is a special case encoding */
		if(!strcmp (encodings[i], "default_locale")) {
			gchar *utf8=g_locale_to_utf8 (in, -1, NULL, NULL, NULL);
			if(utf8!=NULL) {
				res=(gchar *) g_utf8_to_utf16 (utf8, -1, NULL, &lbytes, NULL);
				*bytes = (gsize) lbytes;
			}
			g_free (utf8);
		} else {
			/* Don't use UTF16 here. It returns the <FF FE> prepended to the string */
			res = g_convert (in, strlen (in), "UTF8", encodings[i], NULL, bytes, NULL);
			if (res != NULL) {
				gchar *ptr = res;
				res = (gchar *) g_utf8_to_utf16 (res, -1, NULL, &lbytes, NULL);
				*bytes = (gsize) lbytes;
				g_free (ptr);
			}
		}

		if(res!=NULL) {
			g_strfreev (encodings);
			*bytes *= 2;
			return((gunichar2 *)res);
		}
	}
	
	g_strfreev (encodings);
	
	if(g_utf8_validate (in, -1, NULL)) {
		glong items_written;
		gunichar2 *unires=g_utf8_to_utf16 (in, -1, NULL, &items_written, NULL);
		items_written *= 2;
		*bytes = items_written;
		return(unires);
	}

	return(NULL);
}

/**
 * mono_utf8_from_external:
 * \param in pointer to the string buffer.
 * Tries to turn a NULL-terminated string into UTF8.
 *
 * First, see if it's valid UTF-8, in which case there's nothing more
 * to be done.  Next, run through the colon-separated encodings in
 * \c MONO_EXTERNAL_ENCODINGS and do an \c iconv conversion on each,
 * returning the first successful conversion to UTF-8.  If no
 * conversion succeeds, return NULL.
 *
 * Callers must free the returned string if not NULL.
 *
 * This function is identical to \c mono_unicode_from_external, apart
 * from returning UTF-8 not UTF-16; it's handy in a few places to work
 * in UTF-8.
 */
gchar *mono_utf8_from_external (const gchar *in)
{
	gchar *res=NULL;
	gchar **encodings;
	gchar *encoding_list;
	int i;
	
	if(in==NULL) {
		return(NULL);
	}
	
	encoding_list=g_getenv ("MONO_EXTERNAL_ENCODINGS");
	if(encoding_list==NULL) {
		encoding_list = g_strdup("");
	}
	
	encodings=g_strsplit (encoding_list, ":", 0);
	g_free (encoding_list);
	for(i=0;encodings[i]!=NULL; i++) {
		
		/* "default_locale" is a special case encoding */
		if(!strcmp (encodings[i], "default_locale")) {
			res=g_locale_to_utf8 (in, -1, NULL, NULL, NULL);
			if(res!=NULL && !g_utf8_validate (res, -1, NULL)) {
				g_free (res);
				res=NULL;
			}
		} else {
			res=g_convert (in, -1, "UTF8", encodings[i], NULL,
				       NULL, NULL);
		}

		if(res!=NULL) {
			g_strfreev (encodings);
			return(res);
		}
	}
	
	g_strfreev (encodings);
	
	if(g_utf8_validate (in, -1, NULL)) {
		return(g_strdup (in));
	}

	return(NULL);
}

/**
 * mono_unicode_to_external:
 * \param uni a UTF-16 string to convert to an external representation.
 * Turns NULL-terminated UTF-16 into either UTF-8, or the first
 * working item in \c MONO_EXTERNAL_ENCODINGS if set.  If no conversions
 * work, then UTF-8 is returned.
 * Callers must free the returned string.
 */
gchar *mono_unicode_to_external (const gunichar2 *uni)
{
	gchar *utf8;
	gchar *encoding_list;
	
	/* Turn the unicode into utf8 to start with, because its
	 * easier to work with gchar * than gunichar2 *
	 */
	utf8=g_utf16_to_utf8 (uni, -1, NULL, NULL, NULL);
	g_assert (utf8!=NULL);
	
	encoding_list=g_getenv ("MONO_EXTERNAL_ENCODINGS");
	if(encoding_list==NULL) {
		/* Do UTF8 */
		return(utf8);
	} else {
		gchar *res, **encodings;
		int i;
		
		encodings=g_strsplit (encoding_list, ":", 0);
		g_free (encoding_list);
		for(i=0; encodings[i]!=NULL; i++) {
			if(!strcmp (encodings[i], "default_locale")) {
				res=g_locale_from_utf8 (utf8, -1, NULL, NULL,
							NULL);
			} else {
				res=g_convert (utf8, -1, encodings[i], "UTF8",
					       NULL, NULL, NULL);
			}

			if(res!=NULL) {
				g_free (utf8);
				g_strfreev (encodings);
				
				return(res);
			}
		}
	
		g_strfreev (encodings);
	}
	
	/* Nothing else worked, so just return the utf8 */
	return(utf8);
}

/**
 * mono_utf8_validate_and_len
 * \param source Pointer to putative UTF-8 encoded string.
 * Checks \p source for being valid UTF-8. \p utf is assumed to be
 * null-terminated.
 * \returns TRUE if \p source is valid.
 * \p oEnd will equal the null terminator at the end of the string if valid.
 * if not valid, it will equal the first charater of the invalid sequence.
 * \p oLength will equal the length to \p oEnd
 **/
gboolean
mono_utf8_validate_and_len (const gchar *source, glong* oLength, const gchar** oEnd)
{
	gboolean retVal = TRUE;
	gboolean lastRet = TRUE;
	guchar* ptr = (guchar*) source;
	guchar* srcPtr;
	guint length;
	guchar a;
	*oLength = 0;
	while (*ptr != 0) {
		length = trailingBytesForUTF8 [*ptr] + 1;
		srcPtr = (guchar*) ptr + length;
		switch (length) {
		default: retVal = FALSE;
		/* Everything else falls through when "TRUE"... */
		case 4: if ((a = (*--srcPtr)) < (guchar) 0x80 || a > (guchar) 0xBF) retVal = FALSE;
				if ((a == (guchar) 0xBF || a == (guchar) 0xBE) && *(srcPtr-1) == (guchar) 0xBF) {
				if (*(srcPtr-2) == (guchar) 0x8F || *(srcPtr-2) == (guchar) 0x9F ||
					*(srcPtr-2) == (guchar) 0xAF || *(srcPtr-2) == (guchar) 0xBF)
					retVal = FALSE;
				}
		case 3: if ((a = (*--srcPtr)) < (guchar) 0x80 || a > (guchar) 0xBF) retVal = FALSE;
		case 2: if ((a = (*--srcPtr)) < (guchar) 0x80 || a > (guchar) 0xBF) retVal = FALSE;

		switch (*ptr) {
		/* no fall-through in this inner switch */
		case 0xE0: if (a < (guchar) 0xA0) retVal = FALSE; break;
		case 0xED: if (a > (guchar) 0x9F) retVal = FALSE; break;
		case 0xEF: if (a == (guchar)0xB7 && (*(srcPtr+1) > (guchar) 0x8F && *(srcPtr+1) < 0xB0)) retVal = FALSE;
				   if (a == (guchar)0xBF && (*(srcPtr+1) == (guchar) 0xBE || *(srcPtr+1) == 0xBF)) retVal = FALSE; break;
		case 0xF0: if (a < (guchar) 0x90) retVal = FALSE; break;
		case 0xF4: if (a > (guchar) 0x8F) retVal = FALSE; break;
		default:   if (a < (guchar) 0x80) retVal = FALSE;
		}

		case 1: if (*ptr >= (guchar ) 0x80 && *ptr < (guchar) 0xC2) retVal = FALSE;
		}
		if (*ptr > (guchar) 0xF4)
			retVal = FALSE;
		//If the string is invalid, set the end to the invalid byte.
		if (!retVal && lastRet) {
			if (oEnd != NULL)
				*oEnd = (gchar*) ptr;
			lastRet = FALSE;
		}
		ptr += length;
		(*oLength)++;
	}
	if (retVal && oEnd != NULL)
		*oEnd = (gchar*) ptr;
	return retVal;
}


/**
 * mono_utf8_validate_and_len_with_bounds
 * \param source: Pointer to putative UTF-8 encoded string.
 * \param max_bytes: Max number of bytes that can be decoded.
 *
 * Checks \p source for being valid UTF-8. \p utf is assumed to be
 * null-terminated.
 *
 * This function returns FALSE if it needs to decode characters beyond \p max_bytes.
 *
 * \returns TRUE if \p source is valid.
 * \p oEnd will equal the null terminator at the end of the string if valid.
 * if not valid, it will equal the first charater of the invalid sequence.
 * \p oLength will equal the length to \p oEnd
 **/
gboolean
mono_utf8_validate_and_len_with_bounds (const gchar *source, glong max_bytes, glong* oLength, const gchar** oEnd)
{
	gboolean retVal = TRUE;
	gboolean lastRet = TRUE;
	guchar* ptr = (guchar*) source;
	guchar *end = ptr + max_bytes;
	guchar* srcPtr;
	guint length;
	guchar a;
	*oLength = 0;

	if (max_bytes < 1) {
		if (oEnd)
			*oEnd = (gchar*) ptr;
		return FALSE;
	}

	while (*ptr != 0) {
		length = trailingBytesForUTF8 [*ptr] + 1;
		srcPtr = (guchar*) ptr + length;
		
		/* since *ptr is not zero we must ensure that we can decode the current char + the byte after
		   srcPtr points to the first byte after the current char.*/
		if (srcPtr >= end) {
			retVal = FALSE;
			break;
		}
		switch (length) {
		default: retVal = FALSE;
		/* Everything else falls through when "TRUE"... */
		case 4: if ((a = (*--srcPtr)) < (guchar) 0x80 || a > (guchar) 0xBF) retVal = FALSE;
				if ((a == (guchar) 0xBF || a == (guchar) 0xBE) && *(srcPtr-1) == (guchar) 0xBF) {
				if (*(srcPtr-2) == (guchar) 0x8F || *(srcPtr-2) == (guchar) 0x9F ||
					*(srcPtr-2) == (guchar) 0xAF || *(srcPtr-2) == (guchar) 0xBF)
					retVal = FALSE;
				}
		case 3: if ((a = (*--srcPtr)) < (guchar) 0x80 || a > (guchar) 0xBF) retVal = FALSE;
		case 2: if ((a = (*--srcPtr)) < (guchar) 0x80 || a > (guchar) 0xBF) retVal = FALSE;

		switch (*ptr) {
		/* no fall-through in this inner switch */
		case 0xE0: if (a < (guchar) 0xA0) retVal = FALSE; break;
		case 0xED: if (a > (guchar) 0x9F) retVal = FALSE; break;
		case 0xEF: if (a == (guchar)0xB7 && (*(srcPtr+1) > (guchar) 0x8F && *(srcPtr+1) < 0xB0)) retVal = FALSE;
				   if (a == (guchar)0xBF && (*(srcPtr+1) == (guchar) 0xBE || *(srcPtr+1) == 0xBF)) retVal = FALSE; break;
		case 0xF0: if (a < (guchar) 0x90) retVal = FALSE; break;
		case 0xF4: if (a > (guchar) 0x8F) retVal = FALSE; break;
		default:   if (a < (guchar) 0x80) retVal = FALSE;
		}

		case 1: if (*ptr >= (guchar ) 0x80 && *ptr < (guchar) 0xC2) retVal = FALSE;
		}
		if (*ptr > (guchar) 0xF4)
			retVal = FALSE;
		//If the string is invalid, set the end to the invalid byte.
		if (!retVal && lastRet) {
			if (oEnd != NULL)
				*oEnd = (gchar*) ptr;
			lastRet = FALSE;
		}
		ptr += length;
		(*oLength)++;
	}
	if (retVal && oEnd != NULL)
		*oEnd = (gchar*) ptr;
	return retVal;
}