/*
 * This file is part of the PCEPlib, a PCEP protocol library.
 *
 * Copyright (C) 2020 Volta Networks https://voltanet.io/
 *
 * 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; 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 * Author : Brady Johnson <brady@voltanet.io>
 *
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <pthread.h>
#include <stdbool.h>
#include <stdio.h>

#include "pcep_session_logic.h"
#include "pcep_session_logic_internals.h"
#include "pcep_timers.h"
#include "pcep_utils_logging.h"
#include "pcep_utils_memory.h"

/* global var needed for callback handlers */
extern pcep_session_logic_handle *session_logic_handle_;

/* internal util function to create session_event's */
static pcep_session_event *create_session_event(pcep_session *session)
{
	pcep_session_event *event =
		pceplib_malloc(PCEPLIB_INFRA, sizeof(pcep_session_event));
	event->session = session;
	event->expired_timer_id = TIMER_ID_NOT_SET;
	event->received_msg_list = NULL;
	event->socket_closed = false;

	return event;
}


/* A function pointer to this function is passed to pcep_socket_comm
 * for each pcep_session creation, so it will be called whenever
 * messages are ready to be read. This function will be called
 * by the socket_comm thread.
 * This function will decode the read PCEP message and give it
 * to the session_logic_loop so it can be handled by the session_logic
 * state machine. */
int session_logic_msg_ready_handler(void *data, int socket_fd)
{
	if (data == NULL) {
		pcep_log(LOG_WARNING,
			 "%s: Cannot handle msg_ready with NULL data",
			 __func__);
		return -1;
	}

	if (session_logic_handle_->active == false) {
		pcep_log(
			LOG_WARNING,
			"%s: Received a message ready notification while the session logic is not active",
			__func__);
		return -1;
	}

	pcep_session *session = (pcep_session *)data;

	pthread_mutex_lock(&(session_logic_handle_->session_logic_mutex));
	session_logic_handle_->session_logic_condition = true;

	/* This event will ultimately be handled by handle_socket_comm_event()
	 * in pcep_session_logic_states.c */
	pcep_session_event *rcvd_msg_event = create_session_event(session);

	int msg_length = 0;
	double_linked_list *msg_list = pcep_msg_read(socket_fd);

	if (msg_list == NULL) {
		/* The socket was closed, or there was a socket read error */
		pcep_log(LOG_INFO,
			 "%s: PCEP connection closed for session [%d]",
			 __func__, session->session_id);
		dll_destroy(msg_list);
		rcvd_msg_event->socket_closed = true;
		socket_comm_session_teardown(session->socket_comm_session);
		pcep_session_cancel_timers(session);
		session->socket_comm_session = NULL;
		session->session_state = SESSION_STATE_INITIALIZED;
		enqueue_event(session, PCE_CLOSED_SOCKET, NULL);
	} else if (msg_list->num_entries == 0) {
		/* Invalid message received */
		increment_unknown_message(session);
		dll_destroy_with_data(msg_list);
	} else {
		/* Just logging the first of potentially several messages
		 * received */
		struct pcep_message *msg =
			((struct pcep_message *)msg_list->head->data);
		pcep_log(
			LOG_INFO,
			"%s: [%ld-%ld] session_logic_msg_ready_handler received message of type [%d] len [%d] on session [%d]",
			__func__, time(NULL), pthread_self(),
			msg->msg_header->type, msg->encoded_message_length,
			session->session_id);

		rcvd_msg_event->received_msg_list = msg_list;
		msg_length = msg->encoded_message_length;
	}

	queue_enqueue(session_logic_handle_->session_event_queue,
		      rcvd_msg_event);
	pthread_cond_signal(&(session_logic_handle_->session_logic_cond_var));
	pthread_mutex_unlock(&(session_logic_handle_->session_logic_mutex));

	return msg_length;
}


/* A function pointer to this function was passed to pcep_socket_comm,
 * so it will be called when a message is sent. This is useful since
 * message sending is asynchronous, and there are times that actions
 * need to be performed only after a message has been sent. */
void session_logic_message_sent_handler(void *data, int socket_fd)
{
	(void)socket_fd;

	if (data == NULL) {
		pcep_log(LOG_WARNING,
			 "%s: Cannot handle msg_sent with NULL data", __func__);
		return;
	}

	pcep_session *session = (pcep_session *)data;
	if (session->destroy_session_after_write == true) {
		/* Do not call destroy until all of the queued messages are
		 * written */
		if (session->socket_comm_session != NULL
		    && session->socket_comm_session->message_queue->num_entries
			       == 0) {
			destroy_pcep_session(session);
		}
	} else {
		/* Reset the keep alive timer for every message sent on
		 * the session, only if the session is not destroyed */
		if (session->timer_id_keep_alive == TIMER_ID_NOT_SET) {
			pcep_log(
				LOG_INFO,
				"%s: [%ld-%ld] pcep_session_logic set keep alive timer [%d secs] for session [%d]",
				__func__, time(NULL), pthread_self(),
				session->pcc_config
					.keep_alive_pce_negotiated_timer_seconds,
				session->session_id);
			session->timer_id_keep_alive = create_timer(
				session->pcc_config
					.keep_alive_pce_negotiated_timer_seconds,
				session);
		} else {
			pcep_log(
				LOG_INFO,
				"%s: [%ld-%ld] pcep_session_logic reset keep alive timer [%d secs] for session [%d]",
				__func__, time(NULL), pthread_self(),
				session->pcc_config
					.keep_alive_pce_negotiated_timer_seconds,
				session->session_id);
			reset_timer(session->timer_id_keep_alive);
		}
	}
}


/* A function pointer to this function was passed to pcep_socket_comm,
 * so it will be called whenever the socket is closed. this function
 * will be called by the socket_comm thread. */
void session_logic_conn_except_notifier(void *data, int socket_fd)
{
	if (data == NULL) {
		pcep_log(LOG_WARNING,
			 "%s: Cannot handle conn_except with NULL data",
			 __func__);
		return;
	}

	if (session_logic_handle_->active == false) {
		pcep_log(
			LOG_WARNING,
			"%s: Received a connection exception notification while the session logic is not active",
			__func__);
		return;
	}

	pcep_session *session = (pcep_session *)data;
	pcep_log(
		LOG_INFO,
		"%s: [%ld-%ld] pcep_session_logic session_logic_conn_except_notifier socket closed [%d], session [%d]",
		__func__, time(NULL), pthread_self(), socket_fd,
		session->session_id);

	pthread_mutex_lock(&(session_logic_handle_->session_logic_mutex));
	pcep_session_event *socket_event = create_session_event(session);
	socket_event->socket_closed = true;
	queue_enqueue(session_logic_handle_->session_event_queue, socket_event);
	session_logic_handle_->session_logic_condition = true;

	pthread_cond_signal(&(session_logic_handle_->session_logic_cond_var));
	pthread_mutex_unlock(&(session_logic_handle_->session_logic_mutex));
}


/*
 * this method is the timer expire handler, and will only
 * pass the event to the session_logic loop and notify it
 * that there is a timer available. this function will be
 * called by the timers thread.
 */
void session_logic_timer_expire_handler(void *data, int timer_id)
{
	if (data == NULL) {
		pcep_log(LOG_WARNING, "%s: Cannot handle timer with NULL data",
			 __func__);
		return;
	}

	if (session_logic_handle_->active == false) {
		pcep_log(
			LOG_WARNING,
			"%s: Received a timer expiration while the session logic is not active",
			__func__);
		return;
	}

	pcep_log(LOG_INFO, "%s: [%ld-%ld] timer expired handler timer_id [%d]",
		 __func__, time(NULL), pthread_self(), timer_id);
	pcep_session_event *expired_timer_event =
		create_session_event((pcep_session *)data);
	expired_timer_event->expired_timer_id = timer_id;

	pthread_mutex_lock(&(session_logic_handle_->session_logic_mutex));
	session_logic_handle_->session_logic_condition = true;
	queue_enqueue(session_logic_handle_->session_event_queue,
		      expired_timer_event);

	pthread_cond_signal(&(session_logic_handle_->session_logic_cond_var));
	pthread_mutex_unlock(&(session_logic_handle_->session_logic_mutex));
}


/*
 * session_logic event loop
 * this function is called upon thread creation from pcep_session_logic.c
 */
void *session_logic_loop(void *data)
{
	if (data == NULL) {
		pcep_log(LOG_WARNING,
			 "%s: Cannot start session_logic_loop with NULL data",
			 __func__);

		return NULL;
	}

	pcep_log(LOG_NOTICE, "%s: [%ld-%ld] Starting session_logic_loop thread",
		 __func__, time(NULL), pthread_self());

	pcep_session_logic_handle *session_logic_handle =
		(pcep_session_logic_handle *)data;

	while (session_logic_handle->active) {
		/* Mutex locking for session_logic_loop condition variable */
		pthread_mutex_lock(
			&(session_logic_handle->session_logic_mutex));

		/* this internal loop helps avoid spurious interrupts */
		while (!session_logic_handle->session_logic_condition) {
			pthread_cond_wait(
				&(session_logic_handle->session_logic_cond_var),
				&(session_logic_handle->session_logic_mutex));
		}

		pcep_session_event *event = queue_dequeue(
			session_logic_handle->session_event_queue);
		while (event != NULL) {
			if (event->session == NULL) {
				pcep_log(
					LOG_INFO,
					"%s: [%ld-%ld] Invalid session_logic_loop event [%s] with NULL session",
					__func__, time(NULL), pthread_self(),
					(event->expired_timer_id
					 != TIMER_ID_NOT_SET)
						? "timer"
						: "message");
				pceplib_free(PCEPLIB_INFRA, event);
				event = queue_dequeue(
					session_logic_handle
						->session_event_queue);
				continue;
			}

			/* Check if the session still exists, and synchronize
			 * possible session destroy */
			pcep_log(
				LOG_DEBUG,
				"%s: session_logic_loop checking session_list sessionPtr %p",
				__func__, event->session);
			pthread_mutex_lock(
				&(session_logic_handle->session_list_mutex));
			if (ordered_list_find(
				    session_logic_handle->session_list,
				    event->session)
			    == NULL) {
				pcep_log(
					LOG_INFO,
					"%s: [%ld-%ld] In-flight event [%s] for destroyed session being discarded",
					__func__, time(NULL), pthread_self(),
					(event->expired_timer_id
					 != TIMER_ID_NOT_SET)
						? "timer"
						: "message");
				pceplib_free(PCEPLIB_INFRA, event);
				event = queue_dequeue(
					session_logic_handle
						->session_event_queue);
				pthread_mutex_unlock(
					&(session_logic_handle
						  ->session_list_mutex));
				continue;
			}

			if (event->expired_timer_id != TIMER_ID_NOT_SET) {
				handle_timer_event(event);
			}

			if (event->received_msg_list != NULL) {
				handle_socket_comm_event(event);
			}

			pceplib_free(PCEPLIB_INFRA, event);
			event = queue_dequeue(
				session_logic_handle->session_event_queue);

			pthread_mutex_unlock(
				&(session_logic_handle->session_list_mutex));
		}

		session_logic_handle->session_logic_condition = false;
		pthread_mutex_unlock(
			&(session_logic_handle->session_logic_mutex));
	}

	pcep_log(LOG_NOTICE, "%s: [%ld-%ld] Finished session_logic_loop thread",
		 __func__, time(NULL), pthread_self());

	return NULL;
}