/* 
 * UCSD CSE123a
 * (from Byer's BU CS555 assignment)
 * Winter 2005
 *
 * A list that stored packets that have already been received
 * by the receiver.
 * 
 * Version 1.0
 */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include "srmp.h"

void sender_printList(srmp_send_ctrl_blk *info)
{
	pktbuf *curPacket;
	curPacket = info->sendQueue;
  	while(curPacket != NULL)
  	{
		printf("%d\n", curPacket->seqno);
		curPacket = curPacket->next;
	}

}


/* 
 *  Adds a packet in the send queue so that in the
 *  end the packets saved in the send queue are sorted
 *  by the sequence number.
 *
 *  Adjusts the last byte read (info->LBRead), which in fact happens to be
 *  one less than the seqno of the first packet.
 */
void
sender_add_packet(srmp_send_ctrl_blk  *info, unsigned short seqno, time_t currTime, char *data, int len)
{
  pktbuf *curPacket;
  
  curPacket = (pktbuf *)malloc(sizeof(pktbuf));
  
  curPacket->seqno = seqno;
  curPacket->len = len;
  curPacket->pktTime = currTime;
  curPacket->dupcount = info->dupcount;
  memcpy(curPacket->data, data, len);
  
  /* Find the slot where the packet fits */
  if (info->sendQueue == NULL)
    {
      /* First packet on the list */

      curPacket->next = NULL;
      info->sendQueue = curPacket;
    }
  else if (greater(info->sendQueue->seqno, seqno))
    {
      /* The packet which is added should become the first packet on the
	 list, i.e. be inserted before the current first packet on the list */

      curPacket->next = info->sendQueue;
      info->sendQueue = curPacket;
    }
  else
    {

      /* Walk across the list, find a place for the packet 
	 which would insert the packet between two packets:
	 - the packet previous to the added packet should have a smaller seqno
	 - the packet to the right of the added packet should either
	   be NULL or a packet with greater seqno */
      pktbuf *prev = info->sendQueue, *traverse = prev->next;

	if(prev->seqno == seqno)
    {
		free(curPacket);
		return;	
	}
      while ((traverse != NULL) && greater(seqno, traverse->seqno))
	{
	  prev = traverse;
	  traverse = traverse->next;
	}

      if (traverse == NULL)
	{
	  /* Appending to the end of the list */
	  prev->next = curPacket;
	  curPacket->next = NULL;
	}
      else
	{
	  if(traverse->seqno == seqno)
		{
			free(curPacket);
			return;
		}

	  /* Inserting into the middle of the list */
	  prev->next = curPacket;
	  curPacket->next = traverse;
	}

    }

}

void free_packet(pktbuf *pbuf)
{
  free(pbuf);
}

/*
 * Returns a packet whose sequence number equals to seqno.
 * If no such packet, returns NULL.
 *
 */
pktbuf *sender_get_packet(srmp_send_ctrl_blk *info, unsigned short seqno)
{
  pktbuf *traverse = info->sendQueue, *prev = NULL;

  while(traverse) {
      if (traverse->seqno == seqno) {
	  /*
	   * Unlink the node from the list 
	   *
	   */
	  if (prev == NULL) {
	      /* The first node on the list */
	      info->sendQueue = traverse->next;
	  }
	  else {
	    /* Some other node */
	    prev->next = traverse->next;
	  }
	  return traverse;
    }
    prev = traverse;
    traverse = traverse->next;
  }
  return NULL;
}


pktbuf *
clear_prev_packets(srmp_send_ctrl_blk *info, unsigned short seqno)
{
    pktbuf *traverse = info->sendQueue;

    while(traverse) {
	if (greater(seqno,traverse->seqno))
	    info->sendQueue = traverse->next;
	else
	    return traverse;
	traverse = traverse->next;
    }
    return NULL;
}

pktbuf *sender_copy_packet(srmp_send_ctrl_blk *info, unsigned short seqno)
{
    pktbuf *traverse = info->sendQueue;
    pktbuf *dest = (pktbuf *)malloc(sizeof(*traverse));

    while(traverse) {
        if (traverse->seqno == seqno) {
	    memcpy(dest,traverse,sizeof(*traverse));
	    return dest;
	}
	traverse = traverse->next;
  }
  return NULL;
}

int list_empty(srmp_send_ctrl_blk *info)
{
    pktbuf *traverse = info->sendQueue;
    if (traverse)
	return 0;
    else
	return 1;
}

pktbuf *get_head_item(srmp_send_ctrl_blk *info)
{
    return info->sendQueue;
}

int check_packet_time(srmp_send_ctrl_blk *info, long time)
{
  pktbuf *traverse = info->sendQueue;

  while(traverse) {
      if (difftime(time,traverse->pktTime) > 2.0) {
	  return traverse->seqno;
      }
      
      traverse = traverse->next;
  }
  return -1;
}