/*
 * Copyright 2013 (c) Anna Schumaker.
 */
#include <core/filter.h>
#include <core/string.h>

static GHashTable *filter_index = NULL;


GHashTable *__filter_copy(GHashTable *set)
{
	GHashTableIter iter;
	GHashTable *res;
	gpointer data;

	res = g_hash_table_new(g_direct_hash, g_direct_equal);
	g_hash_table_iter_init(&iter, set);

	while (g_hash_table_iter_next(&iter, &data, NULL))
		g_hash_table_add(res, data);

	return res;
}

void __filter_inline_intersect(GHashTable *lhs, GHashTable *rhs)
{
	GHashTableIter iter;
	gpointer data;

	g_hash_table_iter_init(&iter, rhs);
	while (g_hash_table_iter_next(&iter, &data, NULL)) {
		if (!g_hash_table_contains(lhs, data))
			g_hash_table_iter_remove(&iter);
	}
}


void filter_init()
{
	filter_index = g_hash_table_new_full(g_str_hash, g_str_equal, g_free,
			     (GDestroyNotify)g_hash_table_destroy);
}

void filter_deinit()
{
	g_hash_table_destroy(filter_index);
}

void filter_add(const gchar *text, void *data)
{
	const gchar *c = g_utf8_next_char(text);
	glong begin, end;
	GHashTable *set;
	gchar *substr;

	for (begin = 0, end = 1; end <= g_utf8_strlen(text, -1); end++) {
		substr = g_utf8_substring(text, begin, end);
		set    = g_hash_table_lookup(filter_index, substr);

		if (!set) {
			set = g_hash_table_new(g_direct_hash, g_direct_equal);
			g_hash_table_insert(filter_index, substr, set);
		}

		g_hash_table_add(set, data);

		if (g_unichar_isspace(g_utf8_get_char(c))) {
			c = g_utf8_next_char(c);
			begin = ++end;
		}

		c = g_utf8_next_char(c);
	}
}

void filter_remove(const gchar *text, void *data)
{
	const gchar *c = g_utf8_next_char(text);
	glong begin, end;
	GHashTable *set;
	gchar *substr;

	for (begin = 0, end = 1; end <= g_utf8_strlen(text, -1); end++) {
		substr = g_utf8_substring(text, begin, end);
		set    = g_hash_table_lookup(filter_index, substr);

		if (set)
			g_hash_table_remove(set, data);

		if (g_unichar_isspace(g_utf8_get_char(c))) {
			c = g_utf8_next_char(c);
			begin = ++end;
		}

		c = g_utf8_next_char(c);
	}
}

GHashTable *filter_search(const gchar *text)
{
	gchar *lower = string_lowercase(text);
	GHashTable *found, *res = NULL;
	glong begin, end;
	gchar *c, *substr;

	c = lower;

	for (begin = 0, end = 1; end <= g_utf8_strlen(lower, -1); end++) {
		c = g_utf8_next_char(c);
		if ((*c != '\0') && !g_unichar_isspace(g_utf8_get_char(c)))
			continue;

		substr = g_utf8_substring(lower, begin, end);
		found  = g_hash_table_lookup(filter_index, substr);
		g_free(substr);

		if (!found) {
			g_hash_table_destroy(res);
			res = NULL;
			break;
		}

		if (!res)
			res = __filter_copy(found);
		else
			__filter_inline_intersect(found, res);

		c = g_utf8_next_char(c);
		begin = ++end;
	}

	g_free(lower);
	return res;
}