#include <stdio.h>
#include <stdlib.h>
#include "double_chained_functions.h"

messdaten* insertFirst (messdaten* firstelem, messdaten* newelement)
{
  if (firstelem != NULL)
    {
      newelement->next = firstelem;
      newelement->prev = firstelem->prev;
      firstelem->prev = newelement;
    }
  else
    {
      newelement->next = NULL;
      newelement->prev = newelement;
    }

  return (newelement);
}

messdaten* insertLast (messdaten* firstelem, messdaten* newelement)
{
  if (firstelem != NULL)
    {
      newelement->prev = firstelem->prev;
      firstelem->prev = newelement;
      newelement->prev->next = newelement;
      newelement->next = NULL;
    }

  else
    {
      firstelem = insertFirst (firstelem, newelement);
    }

  return (firstelem);
}

messdaten* insertPos (messdaten* firstelem, messdaten* newelement, int pos)
{
  int i = 0;
  messdaten* temp = firstelem;

  if (pos == 0)
    {
      firstelem = insertFirst (firstelem, newelement);
    }

  else
    {
      while (temp->next != NULL && i < (pos - 2))
	{
	  temp = temp->next;
	  i++;
	}

      if (temp->next != NULL)
	{
	  newelement->next = temp->next;
	  temp->next = newelement;
	  newelement->prev = temp->next->prev;
	  temp->next->prev = newelement;
	}
      else
	{
	  firstelem = insertLast (firstelem, newelement);
	  fprintf (stderr,"llfunct:insertPos->Warning Position is not existing. Element is added to the end of the list!!\n");
	}
    }

  return (firstelem);
}

messdaten* deleteFirst (messdaten* firstelem)
{
  messdaten* n = firstelem;

  firstelem = n->next;
  firstelem->prev = n->prev;
  free (n);

  return (firstelem);
}

messdaten* deleteLast (messdaten* firstelem)
{
  messdaten* temp = firstelem->prev;

  firstelem->prev = firstelem->prev->prev;
  free ((firstelem->prev->next));
  firstelem->prev->next = NULL;

  return (firstelem);
}

messdaten* deletePos (messdaten* firstelem, int pos)
{
  int i = 0;
  messdaten* temp = firstelem;
  messdaten* tempsec;

  while (i < (pos - 2))
    {
      temp = temp->next;
      i++;
    }

  tempsec = temp->next->next;
  tempsec->prev = temp;

  free (temp->next);
  temp->next = tempsec;

  return (firstelem);
}

messdaten* deleteAll (messdaten* firstelem)
{
  messdaten* temp;

  while (firstelem->next != NULL)
    {
      temp = firstelem;
      firstelem = temp->next;
      free (temp);
    }
  return (firstelem);
}