/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
/*
 * Copyright (C) 1999-2008 Novell, Inc. (www.novell.com)
 *
 * This library is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation.
 *
 * 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 Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library. If not, see <http://www.gnu.org/licenses/>.
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

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

#include "camel-memchunk.h"
#include "camel-trie.h"

#define d(x)

struct _trie_state {
	struct _trie_state *next;
	struct _trie_state *fail;
	struct _trie_match *match;
	guint final;
	gint id;
};

struct _trie_match {
	struct _trie_match *next;
	struct _trie_state *state;
	gunichar c;
};

/**
 * CamelTrie:
 *
 * A trie data structure.
 *
 * Since: 2.24
 **/
struct _CamelTrie {
	struct _trie_state root;
	GPtrArray *fail_states;
	gboolean icase;

	CamelMemChunk *match_chunks;
	CamelMemChunk *state_chunks;
};

static inline gunichar
trie_utf8_getc (const guchar **in,
                gsize inlen)
{
	register const guchar *inptr = *in;
	const guchar *inend = inptr + inlen;
	register guchar c, r;
	register gunichar u, m;

	if (inlen == 0)
		return 0;

	r = *inptr++;
	if (r < 0x80) {
		*in = inptr;
		u = r;
	} else if (r < 0xfe) { /* valid start char? */
		u = r;
		m = 0x7f80;	/* used to mask out the length bits */
		do {
			if (inptr >= inend)
				return 0;

			c = *inptr++;
			if ((c & 0xc0) != 0x80)
				goto error;

			u = (u << 6) | (c & 0x3f);
			r <<= 1;
			m <<= 5;
		} while (r & 0x40);

		*in = inptr;

		u &= ~m;
	} else {
	error:
		*in = (*in)+1;
		u = 0xfffe;
	}

	return u;
}

/**
 * camel_trie_new:
 * @icase: Case sensitivity for the #CamelTrie.
 *
 * Creates a new #CamelTrie. If @icase is %TRUE, then pattern matching
 * done by the CamelTrie will be case insensitive.
 *
 * Returns: The newly-created #CamelTrie.
 *
 * Since: 2.24
 **/
CamelTrie *
camel_trie_new (gboolean icase)
{
	CamelTrie *trie;

	trie = g_new (CamelTrie, 1);
	trie->root.next = NULL;
	trie->root.fail = NULL;
	trie->root.match = NULL;
	trie->root.final = 0;

	trie->fail_states = g_ptr_array_sized_new (8);
	trie->icase = icase;

	trie->match_chunks = camel_memchunk_new (8, sizeof (struct _trie_match));
	trie->state_chunks = camel_memchunk_new (8, sizeof (struct _trie_state));

	return trie;
}

/**
 * camel_trie_free:
 * @trie: The #CamelTrie to free.
 *
 * Frees the memory associated with the #CamelTrie @trie.
 *
 * Since: 2.24
 **/
void
camel_trie_free (CamelTrie *trie)
{
	g_ptr_array_free (trie->fail_states, TRUE);
	camel_memchunk_destroy (trie->match_chunks);
	camel_memchunk_destroy (trie->state_chunks);
	g_free (trie);
}

static struct _trie_match *
g (struct _trie_state *s,
   gunichar c)
{
	struct _trie_match *m = s->match;

	while (m && m->c != c)
		m = m->next;

	return m;
}

static struct _trie_state *
trie_insert (CamelTrie *trie,
             gint depth,
             struct _trie_state *q,
             gunichar c)
{
	struct _trie_match *m;

	m = camel_memchunk_alloc (trie->match_chunks);
	m->next = q->match;
	m->c = c;

	q->match = m;
	q = m->state = camel_memchunk_alloc (trie->state_chunks);
	q->match = NULL;
	q->fail = &trie->root;
	q->final = 0;
	q->id = -1;

	if (trie->fail_states->len < depth + 1) {
		guint size = trie->fail_states->len;

		size = MAX (size + 64, depth + 1);
		g_ptr_array_set_size (trie->fail_states, size);
	}

	q->next = trie->fail_states->pdata[depth];
	trie->fail_states->pdata[depth] = q;

	return q;
}

#if d(!)0
static void
dump_trie (struct _trie_state *s,
           gint depth)
{
	gchar *p = g_alloca ((depth * 2) + 1);
	struct _trie_match *m;

	memset (p, ' ', depth * 2);
	p[depth * 2] = '\0';

	fprintf (
		stderr, "%s[state] %p: final=%d; pattern-id=%d; fail=%p\n",
		p, s, s->final, s->id, s->fail);
	m = s->match;
	while (m) {
		fprintf (stderr, " %s'%c' -> %p\n", p, m->c, m->state);
		if (m->state)
			dump_trie (m->state, depth + 1);

		m = m->next;
	}
}
#endif

/*
 * final = empty set
 * FOR p = 1 TO #pat
 *   q = root
 *   FOR j = 1 TO m[p]
 *     IF g(q, pat[p][j]) == null
 *       insert(q, pat[p][j])
 *     ENDIF
 *     q = g(q, pat[p][j])
 *   ENDFOR
 *   final = union(final, q)
 * ENDFOR
*/

/**
 * camel_trie_add:
 * @trie: The #CamelTrie to add a pattern to.
 * @pattern: The pattern to add.
 * @pattern_id: The id to use for the pattern.
 *
 * Add a new pattern to the #CamelTrie @trie.
 *
 * Since: 2.24
 **/
void
camel_trie_add (CamelTrie *trie,
                const gchar *pattern,
                gint pattern_id)
{
	const guchar *inptr = (const guchar *) pattern;
	struct _trie_state *q, *q1, *r;
	struct _trie_match *m, *n;
	gint i, depth = 0;
	gunichar c;

	/* Step 1: add the pattern to the trie */

	q = &trie->root;

	while ((c = trie_utf8_getc (&inptr, -1))) {
		if (trie->icase)
			c = g_unichar_tolower (c);

		m = g (q, c);
		if (m == NULL) {
			q = trie_insert (trie, depth, q, c);
		} else {
			q = m->state;
		}

		depth++;
	}

	q->final = depth;
	q->id = pattern_id;

	/* Step 2: compute failure graph */

	for (i = 0; i < trie->fail_states->len; i++) {
		q = trie->fail_states->pdata[i];
		while (q) {
			m = q->match;
			while (m) {
				c = m->c;
				q1 = m->state;
				r = q->fail;
				while (r && (n = g (r, c)) == NULL)
					r = r->fail;

				if (r != NULL) {
					q1->fail = n->state;
					if (q1->fail->final > q1->final)
						q1->final = q1->fail->final;
				} else {
					if ((n = g (&trie->root, c)))
						q1->fail = n->state;
					else
						q1->fail = &trie->root;
				}

				m = m->next;
			}

			q = q->next;
		}
	}

	d (fprintf (stderr, "\nafter adding pattern '%s' to trie %p:\n", pattern, trie));
	d (dump_trie (&trie->root, 0));
}

/*
 * Aho-Corasick
 *
 * q = root
 * FOR i = 1 TO n
 *   WHILE q != fail AND g(q, text[i]) == fail
 *     q = h(q)
 *   ENDWHILE
 *   IF q == fail
 *     q = root
 *   ELSE
 *     q = g(q, text[i])
 *   ENDIF
 *   IF isElement(q, final)
 *     RETURN TRUE
 *   ENDIF
 * ENDFOR
 * RETURN FALSE
 */

/**
 * camel_trie_search:
 * @trie: The #CamelTrie to search in.
 * @buffer: The string to match against a pattern in @trie.
 * @buflen: The length of @buffer.
 * @matched_id: An integer address to store the matched pattern id in.
 *
 * Try to match the string @buffer with a pattern in @trie.
 *
 * Returns: The matched pattern, or %NULL if no pattern is matched.
 *
 * Since: 2.24
 **/
const gchar *
camel_trie_search (CamelTrie *trie,
                   const gchar *buffer,
                   gsize buflen,
                   gint *matched_id)
{
	const guchar *inptr, *inend, *prev, *pat;
	register gsize inlen = buflen;
	struct _trie_state *q;
	struct _trie_match *m = NULL; /* init to please gcc */
	gunichar c;

	inptr = (const guchar *) buffer;
	inend = inptr + buflen;

	q = &trie->root;
	pat = prev = inptr;
	while ((c = trie_utf8_getc (&inptr, inlen))) {
		inlen = (inend - inptr);

		if (c != 0xfffe) {
			if (trie->icase)
				c = g_unichar_tolower (c);

			while (q != NULL && (m = g (q, c)) == NULL)
				q = q->fail;

			if (q == &trie->root)
				pat = prev;

			if (q == NULL) {
				q = &trie->root;
				pat = inptr;
			} else if (m != NULL) {
				q = m->state;

				if (q->final) {
					if (matched_id)
						*matched_id = q->id;

					return (const gchar *) pat;
				}
			}
		}

		prev = inptr;
	}

	return NULL;
}