/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
/*
 * Copyright (C) 2000 Helix Code, Inc.
 *
 * This program 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 the Gnome Library; see the file COPYING.LIB.  If not,
 * write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/* words.c: low-level indexing ops */

#include <ctype.h>
#include <errno.h>
#include <string.h>

#include <unicode.h>

#include "ibex_internal.h"

static signed char utf8_trans[] = {
	'A', 'A', 'A', 'A', 'A', 'A', -1, 'C', 'E', 'E', 'E', 'E', 'I', 'I',
	'I', 'I', -2, 'N', 'O', 'O', 'O', 'O', 'O', '*', 'O', 'U', 'U', 'U',
	'U', 'Y', -3, -4, 'a', 'a', 'a', 'a', 'a', 'a', -5, 'c', 'e', 'e',
	'e', 'e', 'i', 'i', 'i', 'i', -6, 'n', 'o', 'o', 'o', 'o', 'o', '/',
	'o', 'u', 'u', 'u', 'u', 'y', -7, 'y', 'A', 'a', 'A', 'a', 'A', 'a',
	'C', 'c', 'C', 'c', 'C', 'c', 'C', 'c', 'D', 'd', 'D', 'd', 'E', 'e',
	'E', 'e', 'E', 'e', 'E', 'e', 'E', 'e', 'G', 'g', 'G', 'g', 'G', 'g',
	'G', 'g', 'H', 'h', 'H', 'h', 'I', 'i', 'I', 'i', 'I', 'i', 'I', 'i',
	'I', 'i', -8, -9, 'J', 'j', 'K', 'k', 'k', 'L', 'l', 'L', 'l', 'L',
	'l', 'L', 'l', 'L', 'l', 'N', 'n', 'N', 'n', 'N', 'n', 'n', -10, -11,
	'O', 'o', 'O', 'o', 'O', 'o', -12, -13, 'R', 'r', 'R', 'r', 'R', 'r',
	'S', 'r', 'S', 's', 'S', 's', 'S', 's', 'T', 't', 'T', 't', 'T', 't',
	'U', 'u', 'U', 'u', 'U', 'u', 'U', 'u', 'U', 'u', 'U', 'u', 'W', 'w',
	'Y', 'y', 'Y', 'Z', 'z', 'Z', 'z', 'Z', 'z', 's'
};

static char *utf8_long_trans[] = {
	"AE", "TH", "TH", "ss", "ae", "th", "th", "IJ", "ij",
	"NG", "ng", "OE", "oe"
};

/* This is a bit weird. It takes pointers to the start and end (actually
 * just past the end) of a UTF-8-encoded word, and a buffer at least 1
 * byte longer than the length of the word. It copies the word into the
 * buffer in all lowercase without accents, and splits up ligatures.
 * (Since any ligature would be a multi-byte character in UTF-8, splitting
 * them into two US-ASCII characters won't overrun the buffer.)
 *
 * It is not safe to call this routine with bad UTF-8.
 */
static void
normalize_word (char *start, char *end, char *buf)
{
	unsigned char *s, *d;
	unicode_char_t uc;

	s = (unsigned char *)start;
	d = (unsigned char *)buf;
	while (s < (unsigned char *)end) {
		if (*s < 0x80) {
			/* US-ASCII character: copy unless it's
			 * an apostrophe.
			 */
			if (*s != '\'')
				*d++ = tolower (*s);
			s++;
		} else {
			char *next = unicode_get_utf8 (s, &uc);
			if (uc >= 0xc0 && uc < 0xc0 + sizeof (utf8_trans)) {
				signed char ch = utf8_trans[uc - 0xc0];
				if (ch > 0)
					*d++ = tolower (ch);
				else {
					*d++ = tolower (utf8_long_trans[-ch - 1][0]);
					*d++ = tolower (utf8_long_trans[-ch - 1][1]);
				}
				s = next;
			} else {
				while (s < (unsigned char *)next)
					*d++ = *s++;
			}
		}
	}
	*d = '\0';
}

enum { IBEX_ALPHA, IBEX_NONALPHA, IBEX_INVALID, IBEX_INCOMPLETE };

/* This incorporates parts of libunicode, because there's no way to
 * force libunicode to not read past a certain point.
 */
static int
utf8_category (char *sp, char **snp, char *send)
{
	unsigned char *p = (unsigned char *)sp, **np = (unsigned char **)snp;
	unsigned char *end = (unsigned char *)send;

	if (isascii (*p)) {
		*np = p + 1;
		if (isalpha (*p) || *p == '\'')
			return IBEX_ALPHA;
		return IBEX_NONALPHA;
	} else {
		unicode_char_t uc;
		int more;

		if ((*p & 0xe0) == 0xc0) {
			more = 1;
			uc = *p & 0x1f;
		} else if ((*p & 0xf0) == 0xe0) {
			more = 2;
			uc = *p & 0x0f;
		} else if ((*p & 0xf8) == 0xf0) {
			more = 3;
			uc = *p & 0x07;
		} else if ((*p & 0xfc) == 0xf8) {
			more = 4;
			uc = *p & 0x03;
		} else if ((*p & 0xfe) == 0xfc) {
			more = 5;
			uc = *p & 0x01;
		} else
			return IBEX_INVALID;

		if (p + more > end)
			return IBEX_INCOMPLETE;

		while (more--) {
			if ((*++p & 0xc0) != 0x80)
				return IBEX_INVALID;
			uc <<= 6;
			uc |= *p & 0x3f;
		}

		*np = p + 1;
		if (unicode_isalpha (uc))
			return IBEX_ALPHA;
		else
			return IBEX_NONALPHA;
	}
}

static ibex_file *
get_ibex_file (ibex *ib, char *name)
{
	ibex_file *ibf;

	ibf = g_tree_lookup (ib->files, name);
	if (!ibf) {
		ibf = g_malloc (sizeof (ibex_file));
		ibf->name = strdup (name);
		ibf->index = 0;
		g_tree_insert (ib->files, ibf->name, ibf);
		ib->dirty = TRUE;
	}
	return ibf;
}

static void
ref_word (ibex *ib, ibex_file *ibf, char *word)
{
	GPtrArray *refs;

	refs = g_hash_table_lookup (ib->words, word);
	if (!refs) {
		refs = g_ptr_array_new ();
		g_hash_table_insert (ib->words, g_strdup (word), refs);
		g_ptr_array_add (refs, ibf);
		ib->dirty = TRUE;
	} else if (g_ptr_array_index (refs, refs->len - 1) != ibf) {
		g_ptr_array_add (refs, ibf);
		ib->dirty = TRUE;
	}
}

/**
 * ibex_index_buffer: the lowest-level ibex indexing interface
 * @ib: an ibex
 * @name: the name of the file being indexed
 * @buffer: a buffer containing data from the file
 * @len: the length of @buffer
 * @unread: an output argument containing the number of unread bytes
 *
 * This routine indexes up to @len bytes from @buffer into @ib.
 * If @unread is NULL, the indexer assumes that the buffer ends on a
 * word boundary, and will index all the way to the end of the
 * buffer. If @unread is not NULL, and the buffer ends with an
 * alphabetic character, the indexer will assume that the buffer has
 * been cut off in the middle of a word, and return the number of
 * un-indexed bytes at the end of the buffer in *@unread. The caller
 * should then read in more data through whatever means it has
 * and pass in the unread bytes from the original buffer, followed
 * by the new data, on its next call.
 *
 * Return value: 0 on success, -1 on failure.
 **/
int
ibex_index_buffer (ibex *ib, char *name, char *buffer,
		   size_t len, size_t *unread)
{
	char *p, *q, *nq, *end, *word;
	ibex_file *ibf = get_ibex_file (ib, name);
	int wordsiz, cat;

	end = buffer + len;
	wordsiz = 20;
	word = g_malloc (wordsiz);

	p = buffer;
	while (p < end) {
		while (p < end) {
			cat = utf8_category (p, &q, end);
			if (cat != IBEX_NONALPHA)
				break;
			p = q;
		}
		if (p == end) {
			g_free (word);
			return 0;
		} else if (cat == IBEX_INVALID) {
			errno = EINVAL;
			g_free (word);
			return -1;
		} else if (cat == IBEX_INCOMPLETE)
			q = end;

		while (q < end) {
			cat = utf8_category (q, &nq, end);
			if (cat != IBEX_ALPHA)
				break;
			q = nq;
		}
		if (cat == IBEX_INVALID ||
		    (cat == IBEX_INCOMPLETE && !unread)) {
			errno = EINVAL;
			g_free (word);
			return -1;
		} else if (cat == IBEX_INCOMPLETE || (q == end && unread)) {
			*unread = end - p;
			g_free (word);
			return 0;
		}

		if (wordsiz < q - p + 1) {
			wordsiz = q - p + 1;
			word = g_realloc (word, wordsiz);
		}
		normalize_word (p, q, word);
		ref_word (ib, ibf, word);
		p = q;
	}

	if (unread)
		*unread = 0;
	g_free (word);
	return 0;
}