/*******************************************************************************
 *
 * Copyright (c) 2011, 2012, 2013, 2014, 2015 Olaf Bergmann (TZI) and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Eclipse Distribution License v. 1.0 which accompanies this distribution.
 *
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at 
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *    Olaf Bergmann  - initial API and implementation
 *    Hauke Mehrtens - memory optimization, ECC integration
 *
 *******************************************************************************/

/**
 * @file peer.h
 * @brief information about peers in a DTLS session
 */

#ifndef _DTLS_PEER_H_
#define _DTLS_PEER_H_

#include <sys/types.h>

#include "tinydtls.h"
#include "global.h"
#include "session.h"

#include "state.h"
#include "crypto.h"

#ifndef DTLS_PEERS_NOHASH
#include "uthash.h"
#endif /* DTLS_PEERS_NOHASH */

typedef enum { DTLS_CLIENT=0, DTLS_SERVER } dtls_peer_type;

/** 
 * Holds security parameters, local state and the transport address
 * for each peer. */
typedef struct dtls_peer_t {
#ifdef DTLS_PEERS_NOHASH
  struct dtls_peer_t *next;
#else /* DTLS_PEERS_NOHASH */
  UT_hash_handle hh;
#endif /* DTLS_PEERS_NOHASH */

  session_t session;	     /**< peer address and local interface */

  dtls_peer_type role;       /**< denotes if this host is DTLS_CLIENT or DTLS_SERVER */
  dtls_state_t state;        /**< DTLS engine state */
  int16_t optional_handshake_message; /**< optional next handshake message, DTLS_HT_NO_OPTIONAL_MESSAGE, if no optional message is expected. */

  dtls_security_parameters_t *security_params[2];
  dtls_handshake_parameters_t *handshake_params;
} dtls_peer_t;

/**
 * Holds ClientHello's sequence numbers for the stateless address verification. */
typedef struct dtls_ephemeral_peer_t {
  session_t *session;         /**< peer address and local interface */
  uint64_t rseq;             /**< ClientHello record sequence number */
  uint16_t mseq;             /**< ClientHello handshake message sequence number */
} dtls_ephemeral_peer_t;

static inline dtls_security_parameters_t *dtls_security_params_epoch(dtls_peer_t *peer, uint16_t epoch)
{
  if (peer->security_params[0] && peer->security_params[0]->epoch == epoch) {
    return peer->security_params[0];
  } else if (peer->security_params[1] && peer->security_params[1]->epoch == epoch) {
    return peer->security_params[1];
  } else {
    return NULL;
  }
}

/**
 * Get security parameter for read epoch.
 *
 * @param peer    The remote party where the packet is received from.
 * @param epoch   The read epoch the packet is received in.
 * @return The security parameter for the remote party and read epoch. @c NULL if not available.
 */
static inline dtls_security_parameters_t *dtls_security_params_read_epoch(dtls_peer_t *peer, uint16_t epoch)
{
  if (peer->handshake_params) {
    if (peer->handshake_params->hs_state.read_epoch == epoch) {
    	return dtls_security_params_epoch(peer, epoch);
    }
  } else if (peer->security_params[0] && peer->security_params[0]->epoch == epoch) {
    return peer->security_params[0];
  }
  return NULL;
}

static inline dtls_security_parameters_t *dtls_security_params(dtls_peer_t *peer)
{
  return peer->security_params[0];
}

static inline dtls_security_parameters_t *dtls_security_params_next(dtls_peer_t *peer)
{
  if (peer->security_params[1])
    dtls_security_free(peer->security_params[1]);

  peer->security_params[1] = dtls_security_new();
  if (!peer->security_params[1]) {
    return NULL;
  }
  peer->security_params[1]->epoch = peer->security_params[0]->epoch + 1;
  return peer->security_params[1];
}

static inline void dtls_security_params_free_other(dtls_peer_t *peer)
{
  dtls_security_parameters_t * security0 = peer->security_params[0];
  dtls_security_parameters_t * security1 = peer->security_params[1];

  if (!security0 || !security1 || security0->epoch < security1->epoch)
    return;

  dtls_security_free(security1);
  peer->security_params[1] = NULL;
}

static inline void dtls_security_params_switch(dtls_peer_t *peer)
{
  dtls_security_parameters_t * security = peer->security_params[1];

  peer->security_params[1] = peer->security_params[0];
  peer->security_params[0] = security;
}

void peer_init(void);

/**
 * Creates a new peer for given @p session. The current configuration
 * is initialized with the cipher suite TLS_NULL_WITH_NULL_NULL (i.e.
 * no security at all). This function returns a pointer to the new
 * peer or NULL on error. The caller is responsible for releasing the
 * storage allocated for this peer using dtls_free_peer().
 *
 * @param session  The remote peer's address and local interface index.
 * @return A pointer to a newly created and initialized peer object
 * or NULL on error.
 */
dtls_peer_t *dtls_new_peer(const session_t *session);

/** Releases the storage allocated to @p peer. */
void dtls_free_peer(dtls_peer_t *peer);

/** Returns the current state of @p peer. */
static inline dtls_state_t dtls_peer_state(const dtls_peer_t *peer) {
  return peer->state;
}

/**
 * Checks if given @p peer is connected. This function returns
 * @c 1 if connected, or @c 0 otherwise.
 */
static inline int dtls_peer_is_connected(const dtls_peer_t *peer) {
  return peer->state == DTLS_STATE_CONNECTED;
}

#endif /* _DTLS_PEER_H_ */