/*
 * Copyright (C) 2007 Tobias Brunner
 * Hochschule fuer Technik Rapperswil
 *
 * 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 2 of the License, or (at your
 * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
 *
 * 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.
 */

#include "mediation_manager.h"

#include <daemon.h>
#include <threading/mutex.h>
#include <utils/linked_list.h>
#include <processing/jobs/mediation_job.h>

typedef struct peer_t peer_t;

/**
 * An entry in the linked list.
 */
struct peer_t {
	/** id of the peer */
	identification_t *id;

	/** sa id of the peer, NULL if offline */
	ike_sa_id_t *ike_sa_id;

	/** list of peer ids that reuested this peer */
	linked_list_t *requested_by;
};

/**
 * Implementation of peer_t.destroy.
 */
static void peer_destroy(peer_t *this)
{
	DESTROY_IF(this->id);
	DESTROY_IF(this->ike_sa_id);
	this->requested_by->destroy_offset(this->requested_by,
									   offsetof(identification_t, destroy));
	free(this);
}

/**
 * Creates a new entry for the list.
 */
static peer_t *peer_create(identification_t *id, ike_sa_id_t* ike_sa_id)
{
	peer_t *this = malloc_thing(peer_t);

	/* clone everything */
	this->id = id->clone(id);
	this->ike_sa_id = ike_sa_id ? ike_sa_id->clone(ike_sa_id) : NULL;
	this->requested_by = linked_list_create();

	return this;
}

typedef struct private_mediation_manager_t private_mediation_manager_t;

/**
 * Additional private members of mediation_manager_t.
 */
struct private_mediation_manager_t {
	/**
	 * Public interface of mediation_manager_t.
	 */
	 mediation_manager_t public;

	 /**
	  * Lock for exclusivly accessing the manager.
	  */
	 mutex_t *mutex;

	 /**
	  * Linked list with state entries.
	  */
	 linked_list_t *peers;
};

/**
 * Registers a peer's ID at another peer, if it is not yet registered
 */
static void register_peer(peer_t *peer, identification_t *peer_id)
{
	iterator_t *iterator;
	identification_t *current;

	iterator = peer->requested_by->create_iterator(peer->requested_by, TRUE);
	while (iterator->iterate(iterator, (void**)&current))
	{
		if (peer_id->equals(peer_id, current))
		{
			iterator->destroy(iterator);
			return;
		}
	}
	iterator->destroy(iterator);

	peer->requested_by->insert_last(peer->requested_by,
									peer_id->clone(peer_id));
}

/**
 * Get a peer_t object by a peer's id
 */
static status_t get_peer_by_id(private_mediation_manager_t *this,
							   identification_t *id, peer_t **peer)
{
	iterator_t *iterator;
	peer_t *current;
	status_t status = NOT_FOUND;

	iterator = this->peers->create_iterator(this->peers, TRUE);
	while (iterator->iterate(iterator, (void**)&current))
	{
		if (id->equals(id, current->id))
		{
			if (peer)
			{
				*peer = current;
			}
			status = SUCCESS;
			break;
		}
	}
	iterator->destroy(iterator);

	return status;
}

/**
 * Check if a given peer is registered at other peers. If so, remove it there
 * and then remove peers completely that are not online and have no registered
 * peers.
 */
static void unregister_peer(private_mediation_manager_t *this,
							identification_t *peer_id)
{
	iterator_t *iterator, *iterator_r;
	peer_t *peer;
	identification_t *registered;

	iterator = this->peers->create_iterator(this->peers, TRUE);
	while (iterator->iterate(iterator, (void**)&peer))
	{
		iterator_r = peer->requested_by->create_iterator(peer->requested_by,
														 TRUE);
		while (iterator_r->iterate(iterator_r, (void**)&registered))
		{
			if (peer_id->equals(peer_id, registered))
			{
				iterator_r->remove(iterator_r);
				registered->destroy(registered);
				break;
			}
		}
		iterator_r->destroy(iterator_r);

		if (!peer->ike_sa_id && !peer->requested_by->get_count(peer->requested_by))
		{
			iterator->remove(iterator);
			peer_destroy(peer);
			break;
		}
	}
	iterator->destroy(iterator);
}

/**
 * Implementation of mediation_manager_t.remove
 */
static void remove_sa(private_mediation_manager_t *this, ike_sa_id_t *ike_sa_id)
{
	iterator_t *iterator;
	peer_t *peer;

	this->mutex->lock(this->mutex);

	iterator = this->peers->create_iterator(this->peers, TRUE);
	while (iterator->iterate(iterator, (void**)&peer))
	{
		if (ike_sa_id->equals(ike_sa_id, peer->ike_sa_id))
		{
			iterator->remove(iterator);

			unregister_peer(this, peer->id);

			peer_destroy(peer);
			break;
		}
	}
	iterator->destroy(iterator);

	this->mutex->unlock(this->mutex);
}

/**
 * Implementation of mediation_manager_t.update_sa_id
 */
static void update_sa_id(private_mediation_manager_t *this, identification_t *peer_id, ike_sa_id_t *ike_sa_id)
{
	iterator_t *iterator;
	peer_t *peer;
	bool found = FALSE;

	this->mutex->lock(this->mutex);

	iterator = this->peers->create_iterator(this->peers, TRUE);
	while (iterator->iterate(iterator, (void**)&peer))
	{
		if (peer_id->equals(peer_id, peer->id))
		{
			DESTROY_IF(peer->ike_sa_id);
			found = TRUE;
			break;
		}
	}
	iterator->destroy(iterator);

	if (!found)
	{
		DBG2(DBG_IKE, "adding peer '%Y'", peer_id);
		peer = peer_create(peer_id, NULL);
		this->peers->insert_last(this->peers, peer);
	}

	DBG2(DBG_IKE, "changing registered IKE_SA ID of peer '%Y'", peer_id);
	peer->ike_sa_id = ike_sa_id ? ike_sa_id->clone(ike_sa_id) : NULL;

	/* send callbacks to registered peers */
	identification_t *requester;
	while(peer->requested_by->remove_last(peer->requested_by,
										  (void**)&requester) == SUCCESS)
	{
		job_t *job = (job_t*)mediation_callback_job_create(requester, peer_id);
		lib->processor->queue_job(lib->processor, job);
		requester->destroy(requester);
	}

	this->mutex->unlock(this->mutex);
}

/**
 * Implementation of mediation_manager_t.check.
 */
static ike_sa_id_t *check(private_mediation_manager_t *this,
			identification_t *peer_id)
{
	peer_t *peer;
	ike_sa_id_t *ike_sa_id;

	this->mutex->lock(this->mutex);

	if (get_peer_by_id(this, peer_id, &peer) != SUCCESS)
	{
		this->mutex->unlock(this->mutex);
		return NULL;
	}

	ike_sa_id = peer->ike_sa_id;

	this->mutex->unlock(this->mutex);

	return ike_sa_id;
}

/**
 * Implementation of mediation_manager_t.check_and_register.
 */
static ike_sa_id_t *check_and_register(private_mediation_manager_t *this,
			identification_t *peer_id, identification_t *requester)
{
	peer_t *peer;
	ike_sa_id_t *ike_sa_id;

	this->mutex->lock(this->mutex);

	if (get_peer_by_id(this, peer_id, &peer) != SUCCESS)
	{
		DBG2(DBG_IKE, "adding peer %Y", peer_id);
		peer = peer_create(peer_id, NULL);
		this->peers->insert_last(this->peers, peer);
	}

	if (!peer->ike_sa_id)
	{
		/* the peer is not online */
		DBG2(DBG_IKE, "requested peer '%Y' is offline, registering peer '%Y'",
			 peer_id, requester);
		register_peer(peer, requester);
		this->mutex->unlock(this->mutex);
		return NULL;
	}

	ike_sa_id = peer->ike_sa_id;

	this->mutex->unlock(this->mutex);

	return ike_sa_id;
}

/**
 * Implementation of mediation_manager_t.destroy.
 */
static void destroy(private_mediation_manager_t *this)
{
	this->mutex->lock(this->mutex);

	this->peers->destroy_function(this->peers, (void*)peer_destroy);

	this->mutex->unlock(this->mutex);
	this->mutex->destroy(this->mutex);
	free(this);
}

/*
 * Described in header.
 */
mediation_manager_t *mediation_manager_create()
{
	private_mediation_manager_t *this = malloc_thing(private_mediation_manager_t);

	this->public.destroy = (void(*)(mediation_manager_t*))destroy;
	this->public.remove = (void(*)(mediation_manager_t*,ike_sa_id_t*))remove_sa;
	this->public.update_sa_id = (void(*)(mediation_manager_t*,identification_t*,ike_sa_id_t*))update_sa_id;
	this->public.check = (ike_sa_id_t*(*)(mediation_manager_t*,identification_t*))check;
	this->public.check_and_register = (ike_sa_id_t*(*)(mediation_manager_t*,identification_t*,identification_t*))check_and_register;

	this->peers = linked_list_create();
	this->mutex = mutex_create(MUTEX_TYPE_DEFAULT);

	return (mediation_manager_t*)this;
}