//************************************************************
//
//              STringList.C
//
//************************************************************
//
//      Copyright (C) 1996
//
//              J. Fritz Barnes
//              Graduate Student
//              Computer Science Department
//              University of California
//              Davis, CA  95616
//
//
//      Permission is granted to use at your own risk and
//      distribute this software in source and binary forms
//      provided the above copyright notice and this paragraph
//      are preserved on all copies.  This software is provided
//      "as is" with no express or implied warranty.
//
//************************************************************

#include "STringList.h"
#include <assert.h>

/* ============================================================

	STringList - Constructors/Destructors
	
   ============================================================ */

STringList :: STringList( void )
{
   headtail = new STringListElem;
   headtail->elemValue = "End of List Sentinel";

   headtail->next = headtail->prev = headtail;

   length = 0;
}

STringList :: STringList( const STring& s )
{
   headtail = new STringListElem;
   headtail->elemValue = "End of List Sentinel";
   headtail->next = headtail->prev = headtail;
   length = 0;

   Append( s );
}

STringList :: STringList( const STringList& sl )
{
   headtail = new STringListElem;
   headtail->elemValue = "End of List Sentinel";
   headtail->next = headtail->prev = headtail;
   length = 0;

   STringListElem* ptr = sl.headtail->next;

   while ( ptr != sl.headtail ) {
      Append( ptr->elemValue );
      ptr = ptr->next;
   }
}

STringList::~STringList( void )
{
   STringListElem* ptr = headtail->next;

   while ( ptr != headtail ) {
      STringListElem* delPtr = ptr;
      ptr = ptr->next;
      delete delPtr;
   }

   delete headtail;
}

/* ============================================================

	STringList - AssignMent Operator
	
   ============================================================ */

STringList& STringList::operator = ( const STringList& sl )
{
   // First Delete the old list
   STringListElem* ptr = headtail->next;

   while ( ptr != headtail ) {
      STringListElem* delPtr = ptr;
      ptr = ptr->next;
      delete delPtr;
   }

   // Set at initial state
   length = 0;
   headtail->next = headtail->prev = headtail;

   // Next copy elements from sl
   ptr = sl.headtail->next;

   while ( ptr != sl.headtail ) {
      Append( ptr->elemValue );
      ptr = ptr->next;
   }

   return *this;
}

/* ============================================================

	STringList - Element Access Functions
	
   ============================================================ */

const STring& STringList::operator [] ( int index ) const
{
   return Find_Element( index )->elemValue;
}

int STringList::Get_Length( void )
{
   return length;
}

/* ============================================================

	STringList - Element Insertion & appending
	
   ============================================================ */

void STringList::Append( const STring& s )
{
   STringListElem* newPtr = new STringListElem;
   newPtr->elemValue = s;

   newPtr->next = headtail;
   newPtr->prev = headtail->prev;
   headtail->prev->next = newPtr;
   headtail->prev = newPtr;
   length++;
}

void STringList::Append( const STringList& sl )
{
   STringListElem* ptr = sl.headtail->next;

   while ( ptr != sl.headtail ) {
      Append( ptr->elemValue );
      ptr = ptr->next;
   }
}

void STringList::Insert( const int i, const STring& s )
{
   STringListElem* ptr = Find_Element( i );

   STringListElem* newPtr = new STringListElem;
   newPtr->elemValue = s;

   newPtr->next = ptr;
   newPtr->prev = ptr->prev;
   ptr->prev->next = newPtr;
   ptr->prev = newPtr;
   length++;
}

/* ============================================================

	STringList - Element Replacement and Removal
	
   ============================================================ */

void STringList::Replace( const int i, const STring& s )
{
   STringListElem* ptr = Find_Element( i );

   ptr->elemValue = s;
}

void STringList::Remove( const int i )
{
   STringListElem* ptr = Find_Element( i );
   ptr->prev->next = ptr->next;
   ptr->next->prev = ptr->prev;
   delete ptr;
   length--;
}

/* ============================================================

	STringList - Find_Element helper function, this lets us
		     locate the ith element
	
   ============================================================ */

STringListElem* STringList::Find_Element( int index )
{
   // Validate index
   assert( index >= 0 && index < length );

   // Use for loop to find the item desired
   STringListElem* ptr = headtail->next;
   for( int i=0; i<index; i++) {
      ptr = ptr->next;
   }
   return ptr;
}

const STringListElem* STringList::Find_Element( int index ) const 
{
   // Validate index
   assert( index >= 0 && index < length );

   STringListElem* ptr = headtail->next;
   for( int i=0; i<index; i++) {
      ptr = ptr->next;
   }
   return ptr;
}

/* ============================================================

	STringList - Output operator
	
   ============================================================ */

ostream& operator << ( ostream& os, const STringList& sl )
{
   STringListElem* ptr = sl.headtail->next;
   while ( ptr != sl.headtail ) {
      os << ptr->elemValue << endl;
      ptr = ptr->next;
   }

   return os;
}