/*
 This file is part of GNUnet.
 Copyright (C) 2010-2016, 2018 GNUnet e.V.

 GNUnet is free software: you can redistribute it and/or modify it
 under the terms of the GNU Affero General Public License as published
 by the Free Software Foundation, either version 3 of the License,
 or (at your option) any later version.

 GNUnet 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
 Affero General Public License for more details.

 You should have received a copy of the GNU Affero General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
/**
 * @file transport/gnunet-service-transport.c
 * @brief main for gnunet-service-transport
 * @author Christian Grothoff
 */
#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_statistics_service.h"
#include "gnunet_transport_service.h"
#include "gnunet_peerinfo_service.h"
#include "gnunet_ats_service.h"
#include "gnunet-service-transport.h"
#include "transport.h"


/**
 * How many messages can we have pending for a given client process
 * before we start to drop incoming messages?  We typically should
 * have only one client and so this would be the primary buffer for
 * messages, so the number should be chosen rather generously.
 *
 * The expectation here is that most of the time the queue is large
 * enough so that a drop is virtually never required.  Note that
 * this value must be about as large as 'TOTAL_MSGS' in the
 * 'test_transport_api_reliability.c', otherwise that testcase may
 * fail.
 */
#define MAX_PENDING (128 * 1024)


/**
 * What type of client is the `struct TransportClient` about?
 */
enum ClientType
{
  /**
   * We do not know yet (client is fresh).
   */
  CT_NONE = 0,

  /**
   * Is the CORE service, we need to forward traffic to it.
   */
  CT_CORE = 1,

  /**
   * It is a monitor, forward monitor data.
   */
  CT_MONITOR = 2,

  /**
   * It is a communicator, use for communication.
   */
  CT_COMMUNICATOR = 3
};


/**
 * Client connected to the transport service.
 */
struct TransportClient
{

  /**
   * Kept in a DLL.
   */
  struct TransportClient *next;

  /**
   * Kept in a DLL.
   */
  struct TransportClient *prev;

  /**
   * Handle to the client.
   */
  struct GNUNET_SERVICE_Client *client;

  /**
   * Message queue to the client.
   */
  struct GNUNET_MQ_Handle *mq;

  /**
   * What type of client is this?
   */
  enum ClientType type;

  union
  {

    /**
     * Peer identity to monitor the addresses of.
     * Zero to monitor all neighbours.  Valid if
     * @e type is #CT_MONITOR.
     */
    struct GNUNET_PeerIdentity monitor_peer;

    /**
     * If @e type is #CT_COMMUNICATOR, this communicator
     * supports communicating using these addresses.
     */
    const char *address_prefix;

  } details;

};


/**
 * Head of linked list of all clients to this service.
 */
static struct TransportClient *clients_head;

/**
 * Tail of linked list of all clients to this service.
 */
static struct TransportClient *clients_tail;

/**
 * Statistics handle.
 */
struct GNUNET_STATISTICS_Handle *GST_stats;

/**
 * Configuration handle.
 */
const struct GNUNET_CONFIGURATION_Handle *GST_cfg;

/**
 * Configuration handle.
 */
struct GNUNET_PeerIdentity GST_my_identity;

/**
 * Our private key.
 */
struct GNUNET_CRYPTO_EddsaPrivateKey *GST_my_private_key;


/**
 * Called whenever a client connects.  Allocates our
 * data structures associated with that client.
 *
 * @param cls closure, NULL
 * @param client identification of the client
 * @param mq message queue for the client
 * @return our `struct TransportClient`
 */
static void *
client_connect_cb (void *cls,
		   struct GNUNET_SERVICE_Client *client,
		   struct GNUNET_MQ_Handle *mq)
{
  struct TransportClient *tc;

  tc = GNUNET_new (struct TransportClient);
  tc->client = client;
  tc->mq = mq;
  GNUNET_CONTAINER_DLL_insert (clients_head,
                               clients_tail,
                               tc);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Client %p connected\n",
              tc);
  return tc;
}


/**
 * Called whenever a client is disconnected.  Frees our
 * resources associated with that client.
 *
 * @param cls closure, NULL
 * @param client identification of the client
 * @param app_ctx our `struct TransportClient`
 */
static void
client_disconnect_cb (void *cls,
		      struct GNUNET_SERVICE_Client *client,
		      void *app_ctx)
{
  struct TransportClient *tc = app_ctx;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Client %p disconnected, cleaning up.\n",
              tc);
  GNUNET_CONTAINER_DLL_remove (clients_head,
                               clients_tail,
                               tc);
  switch (tc->type)
  {
  case CT_NONE:
    break;
  case CT_CORE:
    break;
  case CT_MONITOR:
    break;
  case CT_COMMUNICATOR:
    break;
  }
  GNUNET_free (tc);
}


/**
 * Initialize a "CORE" client.  We got a start message from this
 * client, so add it to the list of clients for broadcasting of
 * inbound messages.
 *
 * @param cls the client
 * @param start the start message that was sent
 */
static void
handle_client_start (void *cls,
		     const struct StartMessage *start)
{
  struct TransportClient *tc = cls;
  const struct GNUNET_MessageHeader *hello;
  uint32_t options;

  options = ntohl (start->options);
  if ( (0 != (1 & options)) &&
       (0 !=
        memcmp (&start->self,
                &GST_my_identity,
                sizeof (struct GNUNET_PeerIdentity)) ) )
  {
    /* client thinks this is a different peer, reject */
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  if (CT_NONE != tc->type)
  {
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  tc->type = CT_CORE;
#if 0
  hello = GST_hello_get ();
  if (NULL != hello)
    unicast (tc,
             hello,
             GNUNET_NO);
#endif
  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Client sent us a HELLO.  Check the request.
 *
 * @param cls the client
 * @param message the HELLO message
 */
static int
check_client_hello (void *cls,
		    const struct GNUNET_MessageHeader *message)
{
  (void) cls;
  return GNUNET_OK; /* FIXME: check here? */
}


/**
 * Client sent us a HELLO.  Process the request.
 *
 * @param cls the client
 * @param message the HELLO message
 */
static void
handle_client_hello (void *cls,
		     const struct GNUNET_MessageHeader *message)
{
  struct TransportClient *tc = cls;

  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
	      "Received HELLO message\n");
  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Client asked for transmission to a peer.  Process the request.
 *
 * @param cls the client
 * @param obm the send message that was sent
 */
static int
check_client_send (void *cls,
		   const struct OutboundMessage *obm)
{
  uint16_t size;
  const struct GNUNET_MessageHeader *obmm;

  (void) cls;
  size = ntohs (obm->header.size) - sizeof (struct OutboundMessage);
  if (size < sizeof (struct GNUNET_MessageHeader))
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  obmm = (const struct GNUNET_MessageHeader *) &obm[1];
  if (size != ntohs (obmm->size))
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


/**
 * Client asked for transmission to a peer.  Process the request.
 *
 * @param cls the client
 * @param obm the send message that was sent
 */
static void
handle_client_send (void *cls,
		    const struct OutboundMessage *obm)
{
  struct TransportClient *tc = cls;
  const struct GNUNET_MessageHeader *obmm;

  obmm = (const struct GNUNET_MessageHeader *) &obm[1];
}


/**
 * Communicator started.  Test message is well-formed.
 *
 * @param cls the client
 * @param cam the send message that was sent
 */
static int
check_communicator_available (void *cls,
                              const struct GNUNET_TRANSPORT_CommunicatorAvailableMessage *cam)
{
  const char *addr;
  uint16_t size;

  (void) cls;
  size = ntohs (cam->header.size) - sizeof (*cam);
  if (0 == size)
    return GNUNET_OK; /* receive-only communicator */
  addr = (const char *) &cam[1];
  if ('\0' != addr[size-1])
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


/**
 * Communicator started.  Process the request.
 *
 * @param cls the client
 * @param cam the send message that was sent
 */
static void
handle_communicator_available (void *cls,
                               const struct GNUNET_TRANSPORT_CommunicatorAvailableMessage *cam)
{
  struct TransportClient *tc = cls;
  uint16_t size;

  if (CT_NONE != tc->type)
  {
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  tc->type = CT_COMMUNICATOR;
  size = ntohs (cam->header.size) - sizeof (*cam);
  if (0 == size)
    return GNUNET_OK; /* receive-only communicator */
  tc->details.address_prefix = GNUNET_strdup ((const char *) &cam[1]);
  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Address of our peer added.  Test message is well-formed.
 *
 * @param cls the client
 * @param aam the send message that was sent
 */
static int
check_add_address (void *cls,
                   const struct GNUNET_TRANSPORT_AddAddressMessage *aam)
{
  const char *addr;
  uint16_t size;

  (void) cls;
  size = ntohs (aam->header.size) - sizeof (*aam);
  if (0 == size)
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  addr = (const char *) &cam[1];
  if ('\0' != addr[size-1])
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


/**
 * Address of our peer added.  Process the request.
 *
 * @param cls the client
 * @param aam the send message that was sent
 */
static void
handle_add_address (void *cls,
                    const struct GNUNET_TRANSPORT_AddAddressMessage *aam)
{
  struct TransportClient *tc = cls;

  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Address of our peer deleted.  Process the request.
 *
 * @param cls the client
 * @param dam the send message that was sent
 */
static void
handle_del_address (void *cls,
                    const struct GNUNET_TRANSPORT_DelAddressMessage *dam)
{
  struct TransportClient *tc = cls;

  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Client asked for transmission to a peer.  Process the request.
 *
 * @param cls the client
 * @param obm the send message that was sent
 */
static int
check_incoming_msg (void *cls,
                    const struct GNUNET_TRANSPORT_IncomingMessage *im)
{
  uint16_t size;
  const struct GNUNET_MessageHeader *obmm;

  (void) cls;
  size = ntohs (im->header.size) - sizeof (*im);
  if (size < sizeof (struct GNUNET_MessageHeader))
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  obmm = (const struct GNUNET_MessageHeader *) &im[1];
  if (size != ntohs (obmm->size))
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


/**
 * Incoming meessage.  Process the request.
 *
 * @param cls the client
 * @param im the send message that was received
 */
static void
handle_incoming_msg (void *cls,
                     const struct GNUNET_TRANSPORT_IncomingMessage *im)
{
  struct TransportClient *tc = cls;

  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * New queue became available.  Check message.
 *
 * @param cls the client
 * @param aqm the send message that was sent
 */
static int
check_add_queue_message (void *cls,
                         const struct GNUNET_TRANSPORT_AddQueueMessage *aqm)
{
  const char *addr;
  uint16_t size;

  (void) cls;
  size = ntohs (aqm->header.size) - sizeof (*aqm);
  if (0 == size)
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  addr = (const char *) &aqm[1];
  if ('\0' != addr[size-1])
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


/**
 * New queue became available.  Process the request.
 *
 * @param cls the client
 * @param aqm the send message that was sent
 */
static void
handle_add_queue_message (void *cls,
                          const struct GNUNET_TRANSPORT_AddQueueMessage *aqm)
{
  struct TransportClient *tc = cls;

  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Queue to a peer went down.  Process the request.
 *
 * @param cls the client
 * @param dqm the send message that was sent
 */
static void
handle_del_queue_message (void *cls,
                          const struct GNUNET_TRANSPORT_DelQueueMessage *dqm)
{
  struct TransportClient *tc = cls;

  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Message was transmitted.  Process the request.
 *
 * @param cls the client
 * @param sma the send message that was sent
 */
static void
handle_send_message_ack (void *cls,
                         const struct GNUNET_TRANSPORT_SendMessageToAck *sma)
{
  struct TransportClient *tc = cls;

  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Function called when the service shuts down.  Unloads our plugins
 * and cancels pending validations.
 *
 * @param cls closure, unused
 */
static void
shutdown_task (void *cls)
{
  (void) cls;

  if (NULL != GST_stats)
  {
    GNUNET_STATISTICS_destroy (GST_stats,
                               GNUNET_NO);
    GST_stats = NULL;
  }
  if (NULL != GST_my_private_key)
  {
    GNUNET_free (GST_my_private_key);
    GST_my_private_key = NULL;
  }
}


/**
 * Initiate transport service.
 *
 * @param cls closure
 * @param c configuration to use
 * @param service the initialized service
 */
static void
run (void *cls,
     const struct GNUNET_CONFIGURATION_Handle *c,
     struct GNUNET_SERVICE_Handle *service)
{
  /* setup globals */
  GST_cfg = c;
  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_time (c,
                                           "transport",
                                           "HELLO_EXPIRATION",
                                           &hello_expiration))
  {
    hello_expiration = GNUNET_CONSTANTS_HELLO_ADDRESS_EXPIRATION;
  }
  GST_my_private_key = GNUNET_CRYPTO_eddsa_key_create_from_configuration (cfg);
  if (NULL == GST_my_private_key)
  {
    GNUNET_log(GNUNET_ERROR_TYPE_ERROR,
        _("Transport service is lacking key configuration settings. Exiting.\n"));
    GNUNET_SCHEDULER_shutdown ();
    return;
  }
  GNUNET_CRYPTO_eddsa_key_get_public (GST_my_private_key,
                                      &GST_my_identity.public_key);
  GNUNET_log(GNUNET_ERROR_TYPE_INFO,
             "My identity is `%s'\n",
             GNUNET_i2s_full (&GST_my_identity));

  GST_stats = GNUNET_STATISTICS_create ("transport",
                                        GST_cfg);
  GNUNET_SCHEDULER_add_shutdown (&shutdown_task,
				 NULL);
  /* start subsystems */
}


/**
 * Define "main" method using service macro.
 */
GNUNET_SERVICE_MAIN
("transport",
 GNUNET_SERVICE_OPTION_NONE,
 &run,
 &client_connect_cb,
 &client_disconnect_cb,
 NULL,
 /* communication with core */
 GNUNET_MQ_hd_fixed_size (client_start,
			  GNUNET_MESSAGE_TYPE_TRANSPORT_START,
			  struct StartMessage,
			  NULL),
 GNUNET_MQ_hd_var_size (client_hello,
			GNUNET_MESSAGE_TYPE_HELLO,
			struct GNUNET_MessageHeader,
			NULL),
 GNUNET_MQ_hd_var_size (client_send,
			GNUNET_MESSAGE_TYPE_TRANSPORT_SEND,
			struct OutboundMessage,
			NULL),
 /* communication with communicators */
 GNUNET_MQ_hd_var_size (communicator_available,
			GNUNET_MESSAGE_TYPE_TRANSPORT_NEW_COMMUNICATOR,
			struct GNUNET_TRANSPORT_CommunicatorAvailableMessage,
			NULL),
 GNUNET_MQ_hd_var_size (add_address,
			GNUNET_MESSAGE_TYPE_TRANSPORT_ADD_ADDRESS,
			struct GNUNET_TRANSPORT_AddAddressMessage,
			NULL),
 GNUNET_MQ_hd_fixed_size (del_address,
                          GNUNET_MESSAGE_TYPE_TRANSPORT_DEL_ADDRESS,
                          struct GNUNET_TRANSPORT_DelAddressMessage,
                          NULL),
 GNUNET_MQ_hd_var_size (incoming_msg,
			GNUNET_MESSAGE_TYPE_TRANSPORT_INCOMING_MSG,
			struct GNUNET_TRANSPORT_IncomingMessage,
			NULL),
 GNUNET_MQ_hd_var_size (add_queue_message,
			GNUNET_MESSAGE_TYPE_TRANSPORT_QUEUE_SETUP,
			struct GNUNET_TRANSPORT_AddQueueMessage,
			NULL),
 GNUNET_MQ_hd_fixed_size (del_queue_message,
                          GNUNET_MESSAGE_TYPE_TRANSPORT_QUEUE_TEARDOWN,
                          struct GNUNET_TRANSPORT_DelQueueMessage,
                          NULL),
 GNUNET_MQ_hd_fixed_size (send_message_ack,
                          GNUNET_MESSAGE_TYPE_TRANSPORT_SEND_MSG_ACK,
                          struct GNUNET_TRANSPORT_SendMessageToAck,
                          NULL),
 GNUNET_MQ_handler_end ());


/* end of file gnunet-service-transport.c */