/*
   * Copyright (C) 2015 Freie Universität Berlin
   *
   * This file is subject to the terms and conditions of the GNU Lesser
   * General Public License v2.1. See the file LICENSE in the top level
   * directory for more details.
   */
  
  /**
   * @ingroup     examples
   * @{
   *
   * @file
   * @brief       The cliend side of TinyDTLS (Simple echo)
   *
   * @author      Raul A. Fuentes Samaniego  <ra.fuentes.sam+RIOT@gmail.com>
   * @author      Olaf Bergmann <bergmann@tzi.org>
   * @author      Hauke Mehrtens <hauke@hauke-m.de>
   * @author      Oliver Hahm <oliver.hahm@inria.fr>
   * @}
   */
  
  #include <stdio.h>
  #include <inttypes.h>
  
  #include "net/gnrc.h"
  #include "net/gnrc/ipv6.h"
  #include "net/gnrc/udp.h"
  #include "net/gnrc/pktdump.h"
  #include "timex.h"
  #include "xtimer.h"
  
  #define ENABLE_DEBUG (0)
  #include "debug.h"
  
  /* TinyDTLS */
  #include "tinydtls.h"
  #include "dtls_debug.h"
  #include "dtls.h"
  #include "global.h"
  
  
  
  /* TODO: Remove the UNUSED_PARAM from TinyDTLS' stack? */
  #ifdef __GNUC__
  #define UNUSED_PARAM __attribute__((unused))
  #else
  #define UNUSED_PARAM
  #endif /* __GNUC__ */
  
  #ifdef DTLS_PSK
  
  #define PSK_DEFAULT_IDENTITY "Client_identity"
  #define PSK_DEFAULT_KEY      "secretPSK"
  #define PSK_OPTIONS          "i:k:"
  
  /* Max size for PSK lowered for embedded devices */
  #define PSK_ID_MAXLEN 32
  #define PSK_MAXLEN 32
  
  #endif /* DTLS_PSK */
  
  //#define DEFAULT_PORT 20220    /* DTLS default port  */
  #define DEFAULT_PORT 61618      /* First valid FEBx address  */
  
  #define CLIENT_PORT  DEFAULT_PORT + 1
  #define MAX_TIMES_TRY_TO_SEND 10
  
  static dtls_context_t *dtls_context = NULL;
  static char *client_payload;
  static size_t buflen = 0;
  
  static const unsigned char ecdsa_priv_key[] = {
      0x41, 0xC1, 0xCB, 0x6B, 0x51, 0x24, 0x7A, 0x14,
      0x43, 0x21, 0x43, 0x5B, 0x7A, 0x80, 0xE7, 0x14,
      0x89, 0x6A, 0x33, 0xBB, 0xAD, 0x72, 0x94, 0xCA,
      0x40, 0x14, 0x55, 0xA1, 0x94, 0xA9, 0x49, 0xFA
  };
  
  static const unsigned char ecdsa_pub_key_x[] = {
      0x36, 0xDF, 0xE2, 0xC6, 0xF9, 0xF2, 0xED, 0x29,
      0xDA, 0x0A, 0x9A, 0x8F, 0x62, 0x68, 0x4E, 0x91,
      0x63, 0x75, 0xBA, 0x10, 0x30, 0x0C, 0x28, 0xC5,
      0xE4, 0x7C, 0xFB, 0xF2, 0x5F, 0xA5, 0x8F, 0x52
  };
  
  static const unsigned char ecdsa_pub_key_y[] = {
      0x71, 0xA0, 0xD4, 0xFC, 0xDE, 0x1A, 0xB8, 0x78,
      0x5A, 0x3C, 0x78, 0x69, 0x35, 0xA7, 0xCF, 0xAB,
      0xE9, 0x3F, 0x98, 0x72, 0x09, 0xDA, 0xED, 0x0B,
      0x4F, 0xAB, 0xC3, 0x6F, 0xC7, 0x72, 0xF8, 0x29
  };
  
  
  /**
   * @brief This care about getting messages and continue with the DTLS flights.
   * This will handle all the packets arriving to the node.
   * Will determine if its from a new DTLS peer or a previous one.
   */
  static void dtls_handle_read(dtls_context_t *ctx, gnrc_pktsnip_t *pkt)
  {
  
      static session_t session;
  
      /*
       * NOTE: GNRC (Non-socket) issue: we need to modify the current
       * DTLS Context for the IPv6 src (and in a future the port src).
       */
  
      /* Taken from the tftp server example */
      char addr_str[IPV6_ADDR_MAX_STR_LEN];
      gnrc_pktsnip_t *tmp2;
  
      tmp2 = gnrc_pktsnip_search_type(pkt, GNRC_NETTYPE_IPV6);
      ipv6_hdr_t *hdr = (ipv6_hdr_t *)tmp2->data;
  
      ipv6_addr_to_str(addr_str, &hdr->src, sizeof(addr_str));
  
      /*
         *TODO: More testings with TinyDTLS is neccesary, but seem this is safe.
       */
      tmp2 = gnrc_pktsnip_search_type(pkt, GNRC_NETTYPE_UDP);
      udp_hdr_t *udp = (udp_hdr_t *)tmp2->data;
  
      session.size = sizeof(ipv6_addr_t) + sizeof(unsigned short);
      session.port = byteorder_ntohs(udp->src_port);
  
      DEBUG("DBG-Client: Msg received from \n\t Addr Src: %s"
            "\n\t Current Peer: %s \n", addr_str, (char *)dtls_get_app_data(ctx));
  
      ipv6_addr_from_str(&session.addr, addr_str);
  
      dtls_handle_message(ctx, &session, pkt->data, (unsigned int)pkt->size);
  
  }
  
  #ifdef DTLS_PSK
  static unsigned char psk_id[PSK_ID_MAXLEN] = PSK_DEFAULT_IDENTITY;
  static size_t psk_id_length = sizeof(PSK_DEFAULT_IDENTITY) - 1;
  static unsigned char psk_key[PSK_MAXLEN] = PSK_DEFAULT_KEY;
  static size_t psk_key_length = sizeof(PSK_DEFAULT_KEY) - 1;
  
  /**
   * This function is the "key store" for tinyDTLS. It is called to
   * retrieve a key for the given identity within this particular
   * session.
   */
  static int peer_get_psk_info(struct dtls_context_t *ctx UNUSED_PARAM,
                          const session_t *session UNUSED_PARAM,
                          dtls_credentials_type_t type,
                          const unsigned char *id, size_t id_len,
                          unsigned char *result, size_t result_length)
  {
  
      switch (type) {
          case DTLS_PSK_IDENTITY:
              /* Removed due probably in the motes is useless
                 if (id_len) {
                 dtls_debug("got psk_identity_hint: '%.*s'\n", id_len, id);
                 }
               */
  
              if (result_length < psk_id_length) {
                  dtls_warn("cannot set psk_identity -- buffer too small\n");
                  return dtls_alert_fatal_create(DTLS_ALERT_INTERNAL_ERROR);
              }
  
              memcpy(result, psk_id, psk_id_length);
              return psk_id_length;
          case DTLS_PSK_KEY:
              if (id_len != psk_id_length || memcmp(psk_id, id, id_len) != 0) {
                  dtls_warn("PSK for unknown id requested, exiting\n");
                  return dtls_alert_fatal_create(DTLS_ALERT_ILLEGAL_PARAMETER);
              }
              else if (result_length < psk_key_length) {
                  dtls_warn("cannot set psk -- buffer too small\n");
                  return dtls_alert_fatal_create(DTLS_ALERT_INTERNAL_ERROR);
              }
  
              memcpy(result, psk_key, psk_key_length);
              return psk_key_length;
          default:
              dtls_warn("unsupported request type: %d\n", type);
      }
  
      return dtls_alert_fatal_create(DTLS_ALERT_INTERNAL_ERROR);
  }
  #endif /* DTLS_PSK */
  
  
  #ifdef DTLS_ECC
  static int peer_get_ecdsa_key(struct dtls_context_t *ctx,
                const session_t *session,
                const dtls_ecdsa_key_t **result)
  {
      (void) ctx;
      (void) session;
  
      static const dtls_ecdsa_key_t ecdsa_key = {
          .curve = DTLS_ECDH_CURVE_SECP256R1,
          .priv_key = ecdsa_priv_key,
          .pub_key_x = ecdsa_pub_key_x,
          .pub_key_y = ecdsa_pub_key_y
      };
  
      *result = &ecdsa_key;
      return 0;
  }
  
  static int peer_verify_ecdsa_key(struct dtls_context_t *ctx,
                   const session_t *session,
                   const unsigned char *other_pub_x,
                   const unsigned char *other_pub_y,
                   size_t key_size)
  {
      (void) ctx;
      (void) session;
      (void) key_size;
      (void) other_pub_x;
      (void) other_pub_y;
      return 0;
  }
  #endif /* DTLS_ECC */
  
  /**
   * @brief This will try to transmit using only GNRC stack.
   * This is basically the original send function from gnrc/networking
   */
  static int gnrc_sending(char *addr_str, char *data, size_t data_len )
  {
      ipv6_addr_t addr;
      gnrc_pktsnip_t *payload, *udp, *ip;
  
      /* parse destination address */
      if (ipv6_addr_from_str(&addr, addr_str) == NULL) {
          puts("Error: unable to parse destination address");
          return -1;
      }
  
      /*  allocate payload */
      payload = gnrc_pktbuf_add(NULL, data, data_len, GNRC_NETTYPE_UNDEF);
  
      if (payload == NULL) {
          puts("Error: unable to copy data to packet buffer");
          return -1;
      }
  
      /* allocate UDP header */
      udp = gnrc_udp_hdr_build(payload, (uint16_t) CLIENT_PORT, (uint16_t) DEFAULT_PORT);
      if (udp == NULL) {
          puts("Error: unable to allocate UDP header");
          gnrc_pktbuf_release(payload);
          return -1;
      }
  
      /* allocate IPv6 header */
      ip = gnrc_ipv6_hdr_build(udp, NULL,  &addr);
      if (ip == NULL) {
          puts("Error: unable to allocate IPv6 header");
          gnrc_pktbuf_release(udp);
          return -1;
      }
  
      /*
       * WARNING: Too fast and the nodes dies in middle of retransmissions.
       *          This issue appears in the FIT-Lab (m3 motes).
       *          In native, is not required.
       */
      xtimer_usleep(500000);
  
      /* send packet */
      if (!gnrc_netapi_dispatch_send(GNRC_NETTYPE_UDP, GNRC_NETREG_DEMUX_CTX_ALL, ip)) {
          puts("Error: unable to locate UDP thread");
          gnrc_pktbuf_release(ip);
          return -1;
      }
  
      return 1;
  }
  
  /**
   * @brief This will print the data read from the Peer.
   * THIS AT THE END of the 6 flights (DTLS App Data).
   * Is here where we know that the connection has finished.
   * TODO: The connected variable could de modified here.
   */
  static int read_from_peer(struct dtls_context_t *ctx,
                 session_t *session, uint8 *data, size_t len)
  {
      /* Linux and Contiki version are exactly the same. */
      (void) session;
      (void) ctx;
      size_t i;
      printf("\n\n Echo received: ");
      for (i = 0; i < len; i++)
          printf("%c", data[i]);
      printf(" \n\n\n");
      return 0;
  }
  
  /**
   * @brief  Will try to transmit the next DTLS flight for a speicifc Peer.
   * NOTE:The global buff and buflen is used for be able to transmit the
   * Payload in segmented datagrams.
   */
  static void try_send(struct dtls_context_t *ctx, session_t *dst)
  {
  
      int res;
  
      res = dtls_write(ctx, dst, (uint8_t *)client_payload, buflen);
  
      if (res >= 0) {
          memmove(client_payload, client_payload + res, buflen - res);
          buflen -= res;
      }
      else {
          DEBUG("DBG-Client: dtls_write returned error!\n" );
      }
  }
  
  /**
   * @brief This SIGNAL function will prepare the next DTLS flight to send.
   */
  static int send_to_peer(struct dtls_context_t *ctx,
               session_t *session, uint8 *buf, size_t len)
  {
  
      (void) session;
      /*
       * For this testing with GNR we are to extract the peer's addresses and
       * making the connection from zero.
       */
      char *addr_str;
      addr_str = (char *)dtls_get_app_data(ctx);
  
  
      /* TODO: Confirm that indeed len size of data was sent, otherwise
       * return the correct number of bytes sent
       */
      gnrc_sending(addr_str, (char *)buf, len);
  
      return len;
  }
  
  
  
  /***
   *  This is a custom function for preparing the SIGNAL events and
   *  create a new DTLS context.
   */
  static void init_dtls(session_t *dst, char *addr_str)
  {
  
      static dtls_handler_t cb = {
          .write = send_to_peer,
          .read  = read_from_peer,
          .event = NULL,
  #ifdef DTLS_PSK
          .get_psk_info = peer_get_psk_info,
  #endif  /* DTLS_PSK */
  #ifdef DTLS_ECC
          .get_ecdsa_key = peer_get_ecdsa_key,
          .verify_ecdsa_key = peer_verify_ecdsa_key
  #endif  /* DTLS_ECC */
      };
  
  #ifdef DTLS_PSK
      puts("Client support PSK");
  #endif
  #ifdef DTLS_ECC
      puts("Client support ECC");
  #endif
  
      DEBUG("DBG-Client: Debug ON");
      /*
       *  The objective of ctx->App  is be able to retrieve
       *  enough information for restablishing a connection.
       *  This is to be used in the send_to_peer and (potentially) the
       *  read_from_peer, to continue the transmision with the next
       *  step of the DTLS flights.
       *  TODO: Take away the DEFAULT_PORT and CLIENT_PORT.
       */
      dst->size = sizeof(ipv6_addr_t) + sizeof(unsigned short);
      dst->port =  (unsigned short) DEFAULT_PORT;
  
      if (ipv6_addr_from_str(&dst->addr, addr_str) == NULL) {
          puts("ERROR: init_dtls was unable to load the IPv6 addresses!\n");
          dtls_context = NULL;
          return;
      }
  
      ipv6_addr_t addr_dbg;
      ipv6_addr_from_str(&addr_dbg, addr_str);
  
      /*akin to syslog: EMERG, ALERT, CRITC, NOTICE, INFO, DEBUG */
      dtls_set_log_level(DTLS_LOG_NOTICE);
  
      dtls_context = dtls_new_context(addr_str);
      if (dtls_context) {
          dtls_set_handler(dtls_context, &cb);
      }
  
      return;
  }
  
  /**
   * This is the "client" part of this program.
   * Will be called each time a message is transmitted.
   */
  static void client_send(char *addr_str, char *data, unsigned int delay)
  {
      int8_t iWatch;
      static session_t dst;
      static int connected = 0;
      msg_t msg;
  
     gnrc_netreg_entry_t entry = GNRC_NETREG_ENTRY_INIT_PID(CLIENT_PORT,
                                                             sched_active_pid);
      dtls_init();
  
      if (gnrc_netreg_register(GNRC_NETTYPE_UDP, &entry)) {
          puts("Unable to register ports");
          /*FIXME: Release memory?*/
          return;
      }
  
      if (strlen(data) > DTLS_MAX_BUF) {
          puts("Data too long ");
          return;
      }
  
      init_dtls(&dst, addr_str);
      if (!dtls_context) {
          dtls_emerg("cannot create context\n");
          puts("Client unable to load context!");
          return;
      }
  
      /* client_payload is global due to the SIGNAL function send_to_peer  */
      client_payload = data;
      buflen =  strlen(client_payload);
      iWatch = MAX_TIMES_TRY_TO_SEND;
  
      /*
       * dtls_connect is the one who begin all the process.
       * However, do it too fast, and the node will attend it before having a
       * valid IPv6 or even a route to the destiny (This could be verified as the
       * sequence number of the first DTLS Hello message will be greater than
       * zero).
       */
      //connected = dtls_connect(dtls_context, &dst) >= 0;
  
      /*
       * Until all the data is not sent we remains trying to connect to the
       * server. Plus a small watchdog.
       */
      while ((buflen > 0) && (iWatch > 0)) {
  
          /*
           * NOTE: I (rfuentess) personally think this should be until this point
           * instead before (that is why the previous  dtls_connect is by defualt
           * commented..
           */
          if (!connected) {
              connected = dtls_connect(dtls_context, &dst);
          }
          else if (connected < 0) {
              puts("Client DTLS was unable to establish a channel!\n");
              /*NOTE: Not sure what to do in this scenario (if can happens)*/
          }
          else {
              /*TODO: must happens always or only when connected?*/
              try_send(dtls_context, &dst);
          }
  
          /*
           * WARNING: The delay is KEY HERE!  Too fast, and we can kill the
           * DTLS state machine.  Another alternative is change to
           * blocking states (making the watchdog useless)
           *
           * msg_receive(&msg);
           */
  
          xtimer_usleep(delay);
  
          if (msg_try_receive(&msg) == 1) {
              dtls_handle_read(dtls_context, (gnrc_pktsnip_t *)(msg.content.ptr));
          }
  
          iWatch--;
      } /*END while*/
  
      dtls_free_context(dtls_context);
      /* unregister our UDP listener on this thread */
      gnrc_netreg_unregister(GNRC_NETTYPE_UDP, &entry);
      connected = 0; /*Probably this should be removed or global */
  
      /* Permanent or not permanent? */
      DEBUG("DTLS-Client: DTLS session finished\n");
  }
  
  int udp_client_cmd(int argc, char **argv)
  {
      uint32_t delay = 1000000;
  
      if (argc < 3) {
          printf("usage: %s <addr> <data> [<delay in us>]\n", argv[0]);
          return 1;
      }
      else if (argc > 3) {
          delay = atoi(argv[3]);
      }
      client_send(argv[1], argv[2],  delay);
  
  
      return 0;
  }