/*
Copyright (C) 2017 Paweł Redman

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 3
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
*/

#include "shared.h"

#define HASH_MAX 4095

static size_t db_hash(uint32_t ipv4)
{
	// FIXME: Use an academically acclaimed hashing algorithm.
	return (((ipv4 >> 16) ^ ipv4) * 3137) & HASH_MAX;
}

db_entry *database[HASH_MAX + 1];
pthread_mutex_t database_mutex = PTHREAD_MUTEX_INITIALIZER;

// Returns a pointer to the relevant db_entry (newly created if didn't exist).
// This function locks the db_entry's mutex before returning.
// Returns NULL if calloc fails.
db_entry *db_find(uint32_t ipv4)
{
	size_t hash;
	db_entry *entry;

	hash = db_hash(ipv4);

	pthread_mutex_lock(&database_mutex);
	eli_for (entry, database[hash], ht_chain)
		if (entry->ipv4 == ipv4)
			break;

	if (!entry) {
		entry = calloc(1, sizeof(db_entry));
		if (!entry)
			goto out;
		entry->ipv4 = ipv4;
		pthread_mutex_init(&entry->mutex, NULL);
		eli_append(database + hash, entry, ht_chain);
	}

	pthread_mutex_lock(&entry->mutex);
out:
	pthread_mutex_unlock(&database_mutex);
	return entry;
}

static void destroy_entry(db_entry *entry)
{
	job_t *job, *next;

	for (job = entry->waiting_jobs; job; job = next) {
		next = job->waiting_list.next;
		job_destroy(job);
	}

	free(entry);
}

// Frees all entries and resets the database.
void db_destroy(void)
{
	size_t i;
	db_entry *entry, *next;

	pthread_mutex_lock(&database_mutex);

	for (i = 0; i < HASH_MAX; i++) {
		for (entry = database[i]; entry; entry = next) {
			next = entry->ht_chain.next;

			pthread_mutex_lock(&entry->mutex);
			free(entry->revdns.data);
			free(entry->whois.data);
			pthread_mutex_unlock(&entry->mutex);
			destroy_entry(entry);
		}

		database[i] = NULL;
	}

	pthread_mutex_unlock(&database_mutex);
}

void db_invalidate_cached_results(void)
{
	size_t i;
	db_entry *entry;

	pthread_mutex_lock(&database_mutex);

	for (i = 0; i < HASH_MAX; i++)
		eli_for(entry, database[i], ht_chain)
			entry->cached_result_valid = false;

	pthread_mutex_unlock(&database_mutex);
}