/**
 * @file
 * SLIP Interface
 *
 */

/*
 * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * This file is built upon the file: src/arch/rtxc/netif/sioslip.c
 *
 * Author: Magnus Ivarsson <magnus.ivarsson(at)volvo.com>
 *         Simon Goldschmidt
 */


/**
 * @defgroup slipif SLIP
 * @ingroup netifs
 *
 * This is an arch independent SLIP netif. The specific serial hooks must be
 * provided by another file. They are sio_open, sio_read/sio_tryread and sio_send
 *
 * Usage: This netif can be used in three ways:
 *        1. For NO_SYS==0, an RX thread can be used which blocks on sio_read()
 *           until data is received.
 *        2. In your main loop, call slipif_poll() to check for new RX bytes,
 *           completed packets are fed into netif->input().
 *        3. Call slipif_received_byte[s]() from your serial RX ISR and
 *           slipif_process_rxqueue() from your main loop. ISR level decodes
 *           packets and puts completed packets on a queue which is fed into
 *           the stack from the main loop (needs SYS_LIGHTWEIGHT_PROT for
 *           pbuf_alloc to work on ISR level!).
 *
 */

#include "slipif.h"
#include "lwip/opt.h"

#include "lwip/def.h"
#include "lwip/pbuf.h"
#include "lwip/stats.h"
#include "lwip/snmp.h"
#include "lwip/sys.h"

#define SLIP_END     0xC0 /* 0300: start and end of every packet */
#define SLIP_ESC     0xDB /* 0333: escape start (one byte escaped data follows) */
#define SLIP_ESC_END 0xDC /* 0334: following escape: original byte is 0xC0 (END) */
#define SLIP_ESC_ESC 0xDD /* 0335: following escape: original byte is 0xDB (ESC) */

/** Maximum packet size that is received by this netif */
#ifndef SLIP_MAX_SIZE
#define SLIP_MAX_SIZE 1500
#endif

#ifndef SLIP_CHUNK_SIZE
#define SLIP_CHUNK_SIZE 120
#endif

enum slipif_recv_state {
  SLIP_RECV_NORMAL,
  SLIP_RECV_ESCAPE
};



static void 
slipif_send_chunk(uint8_t c, int fd, uint8_t *chunk, size_t *current_index, size_t chunksize, int flush){
    if (*current_index >= chunksize) {
      write(0,"stra", 5);
        //chunk is already full, send it and reset
        write(fd, chunk, chunksize);
        *current_index = 0;
    }
    // add byte to chunk, (can not be full, we checked)
    if (*current_index < chunksize) {
        chunk[*current_index] = c;
        (*current_index)++;
    }
    // if either chunk is full or we shall flush, send it
    if ((*current_index >= chunksize) || ( flush != 0)) {
      write(0,"full", 5);
       write(fd, chunk, *current_index);
        *current_index = 0;
    }
}


/**
 * Send a pbuf doing the necessary SLIP encapsulation
 *
 * Uses the serial layer's sio_send()
 *
 * @param netif the lwip network interface structure for this slipif
 * @param p the pbuf chain packet to send
 * @return always returns ERR_OK since the serial layer does not provide return values
 */
static err_t
slipif_output(struct netif *netif, struct pbuf *p)
{
  struct slipif_priv *priv;
  struct pbuf *q;
  u16_t i;
  u8_t c;

  uint8_t chunk[SLIP_CHUNK_SIZE];
  size_t current_index = 0;

  LWIP_ASSERT("netif != NULL", (netif != NULL));
  LWIP_ASSERT("netif->state != NULL", (netif->state != NULL));
  LWIP_ASSERT("p != NULL", (p != NULL));

  LWIP_DEBUGF(SLIP_DEBUG, ("slipif_output: sending %"U16_F" bytes\n", p->tot_len));
  priv = (struct slipif_priv *)netif->state;

  /* Send pbuf out on the serial I/O device. */
  /* Start with packet delimiter. */
  slipif_send_chunk(SLIP_END, priv->fd, chunk, &current_index, sizeof(chunk), 0);

  for (q = p; q != NULL; q = q->next) {
    for (i = 0; i < q->len; i++) {
      c = ((u8_t *)q->payload)[i];
      switch (c) {
        case SLIP_END:
          /* need to escape this byte (0xC0 -> 0xDB, 0xDC) */
          slipif_send_chunk(SLIP_ESC, priv->fd, chunk, &current_index, sizeof(chunk), 0);
          slipif_send_chunk(SLIP_ESC_END, priv->fd, chunk, &current_index, sizeof(chunk), 0);
          break;
        case SLIP_ESC:
          /* need to escape this byte (0xDB -> 0xDB, 0xDD) */
          slipif_send_chunk(SLIP_ESC, priv->fd, chunk, &current_index, sizeof(chunk), 0);
          slipif_send_chunk(SLIP_ESC_ESC, priv->fd, chunk, &current_index, sizeof(chunk), 0);
          break;
        default:
          /* normal byte - no need for escaping */
          slipif_send_chunk(c, priv->fd, chunk, &current_index, sizeof(chunk), 0);
          break;
      }
    }
  }
  /* End with packet delimiter, flush the chunk */
  slipif_send_chunk(SLIP_END, priv->fd, chunk, &current_index, sizeof(chunk), 1);
  return ERR_OK;
}

#if LWIP_IPV4
/**
 * Send a pbuf doing the necessary SLIP encapsulation
 *
 * Uses the serial layer's sio_send()
 *
 * @param netif the lwip network interface structure for this slipif
 * @param p the pbuf chain packet to send
 * @param ipaddr the ip address to send the packet to (not used for slipif)
 * @return always returns ERR_OK since the serial layer does not provide return values
 */
static err_t
slipif_output_v4(struct netif *netif, struct pbuf *p, const ip4_addr_t *ipaddr)
{
  LWIP_UNUSED_ARG(ipaddr);
  return slipif_output(netif, p);
}
#endif /* LWIP_IPV4 */

#if LWIP_IPV6
/**
 * Send a pbuf doing the necessary SLIP encapsulation
 *
 * Uses the serial layer's sio_send()
 *
 * @param netif the lwip network interface structure for this slipif
 * @param p the pbuf chain packet to send
 * @param ipaddr the ip address to send the packet to (not used for slipif)
 * @return always returns ERR_OK since the serial layer does not provide return values
 */
static err_t
slipif_output_v6(struct netif *netif, struct pbuf *p, const ip6_addr_t *ipaddr)
{
  LWIP_UNUSED_ARG(ipaddr);
  return slipif_output(netif, p);
}
#endif /* LWIP_IPV6 */

/**
 * Handle the incoming SLIP stream character by character
 *
 * @param netif the lwip network interface structure for this slipif
 * @param c received character (multiple calls to this function will
 *        return a complete packet, NULL is returned before - used for polling)
 * @return The IP packet when SLIP_END is received
 */
static struct pbuf *
slipif_rxbyte(struct netif *netif, u8_t c)
{
  struct slipif_priv *priv;
  struct pbuf *t;

  LWIP_ASSERT("netif != NULL", (netif != NULL));
  LWIP_ASSERT("netif->state != NULL", (netif->state != NULL));

  priv = (struct slipif_priv *)netif->state;

  switch (priv->state) {
    case SLIP_RECV_NORMAL:
      switch (c) {
        case SLIP_END:
          if (priv->recved > 0) {
            /* Received whole packet. */
            /* Trim the pbuf to the size of the received packet. */
            pbuf_realloc(priv->q, priv->recved);

            LINK_STATS_INC(link.recv);

            LWIP_DEBUGF(SLIP_DEBUG, ("slipif: Got packet (%"U16_F" bytes)\n", priv->recved));
            t = priv->q;
            priv->p = priv->q = NULL;
            priv->i = priv->recved = 0;
            return t;
          }
          return NULL;
        case SLIP_ESC:
          priv->state = SLIP_RECV_ESCAPE;
          return NULL;
        default:
          break;
      } /* end switch (c) */
      break;
    case SLIP_RECV_ESCAPE:
      /* un-escape END or ESC bytes, leave other bytes
         (although that would be a protocol error) */
      switch (c) {
        case SLIP_ESC_END:
          c = SLIP_END;
          break;
        case SLIP_ESC_ESC:
          c = SLIP_ESC;
          break;
        default:
          break;
      }
      priv->state = SLIP_RECV_NORMAL;
      break;
    default:
      break;
  } /* end switch (priv->state) */

  /* byte received, packet not yet completely received */
  if (priv->p == NULL) {
    /* allocate a new pbuf */
    LWIP_DEBUGF(SLIP_DEBUG, ("slipif_input: alloc\n"));
    priv->p = pbuf_alloc(PBUF_LINK, (PBUF_POOL_BUFSIZE - PBUF_LINK_HLEN - PBUF_LINK_ENCAPSULATION_HLEN), PBUF_POOL);

    if (priv->p == NULL) {
      LINK_STATS_INC(link.drop);
      LWIP_DEBUGF(SLIP_DEBUG, ("slipif_input: no new pbuf! (DROP)\n"));
      /* don't process any further since we got no pbuf to receive to */
      return NULL;
    }

    if (priv->q != NULL) {
      /* 'chain' the pbuf to the existing chain */
      pbuf_cat(priv->q, priv->p);
    } else {
      /* p is the first pbuf in the chain */
      priv->q = priv->p;
    }
  }

  /* this automatically drops bytes if > SLIP_MAX_SIZE */
  if ((priv->p != NULL) && (priv->recved <= SLIP_MAX_SIZE)) {
    ((u8_t *)priv->p->payload)[priv->i] = c;
    priv->recved++;
    priv->i++;
    if (priv->i >= priv->p->len) {
      /* on to the next pbuf */
      priv->i = 0;
      if (priv->p->next != NULL && priv->p->next->len > 0) {
        /* p is a chain, on to the next in the chain */
        priv->p = priv->p->next;
      } else {
        /* p is a single pbuf, set it to NULL so next time a new
         * pbuf is allocated */
        priv->p = NULL;
      }
    }
  }
  return NULL;
}

/** Like slipif_rxbyte, but passes completed packets to netif->input
 *
 * @param netif The lwip network interface structure for this slipif
 * @param c received character
 */
static void
slipif_rxbyte_input(struct netif *netif, u8_t c)
{
  struct pbuf *p;
  p = slipif_rxbyte(netif, c);
  if (p != NULL) {
    if (netif->input(p, netif) != ERR_OK) {
      pbuf_free(p);
    }
  }
}


/**
 * @ingroup slipif
 * SLIP netif initialization
 *
 * Call the arch specific sio_open and remember
 * the opened device in the state field of the netif.
 *
 * @param netif the lwip network interface structure for this slipif
 * @return ERR_OK if serial line could be opened,
 *         ERR_MEM if no memory could be allocated,
 *         ERR_IF is serial line couldn't be opened
 *
 * @note If netif->state is interpreted as an u8_t serial port number.
 *
 */
err_t
slipif_init(struct netif *netif)
{
  struct slipif_priv *priv;

  LWIP_ASSERT("slipif needs an input callback", netif->input != NULL);

  LWIP_DEBUGF(SLIP_DEBUG, ("slipif_init: netif->num=%"U16_F"\n", (u16_t)sio_num));


  netif->name[0] = 's';
  netif->name[1] = 'l';
#if LWIP_IPV4
  netif->output = slipif_output_v4;
#endif /* LWIP_IPV4 */
#if LWIP_IPV6
  netif->output_ip6 = slipif_output_v6;
#endif /* LWIP_IPV6 */
  netif->mtu = SLIP_MAX_SIZE;

  /* private data needs to be allocated by user and passed via state (see netif_add()) */
  priv = netif->state;
  /* Initialize private data */
  priv->p = NULL;
  priv->q = NULL;
  priv->state = SLIP_RECV_NORMAL;
  priv->i = 0;
  priv->recved = 0;
  
  LWIP_ASSERT("slipif private data fd needs to be initialized before calling netif_add()", priv->fd != 0);

  

  /* initialize the snmp variables and counters inside the struct netif */
  MIB2_INIT_NETIF(netif, snmp_ifType_slip, SLIP_SIO_SPEED(priv->sd));

  return ERR_OK;
}

/**
 * @ingroup slipif
 * Polls the serial device and feeds the IP layer with incoming packets.
 *
 * @param netif The lwip network interface structure for this slipif
 */
void
slipif_poll(struct netif *netif)
{
  struct slipif_priv *priv;

  LWIP_ASSERT("netif != NULL", (netif != NULL));
  LWIP_ASSERT("netif->state != NULL", (netif->state != NULL));

  priv = (struct slipif_priv *)netif->state;

  uint8_t chunk[SLIP_CHUNK_SIZE];
  int read_bytes = read(priv->fd, chunk, sizeof(chunk));

  for (int i = 0; i < read_bytes; i++){
    slipif_rxbyte_input(netif, chunk[i]);
  }
}