#include <Standard_NoSuchObject.hxx>
#include <Standard_NotImplemented.hxx>
#include <Standard_NoMoreObject.hxx>

// ------------
// constructor
// -----------

PCollection_HQueue::PCollection_HQueue() 
{
    TheLength = 0;
    TheFront  = new PCollection_QueueNode;
    TheBack   = TheFront;
}

// -----------------------------
// IsEmpty : is the queue empty ? 
// -----------------------------
Standard_Boolean PCollection_HQueue::IsEmpty() const {
    return TheLength == 0;
} 

// --------------------------------------
// Front : item at the front of the Queue 
// --------------------------------------
Item PCollection_HQueue::Front() const 
{
    if (TheFront->IsEmpty()) Standard_NoSuchObject::Raise();
    return TheFront->Value();
}

// --------------------------------------
// Clear : remove all items in the Queue 
// --------------------------------------
void PCollection_HQueue::Clear()
{   
   Handle(PCollection_QueueNode) temp; 
   while (TheLength != 0) {    
      temp = TheFront;
      TheFront = TheFront->Tail();
      if (TheLength == 1) TheBack = TheFront;
      temp.Delete();
      --TheLength;
   }  
}

// ------------------------------------
// Push : insert an item at the back
// ------------------------------------
void PCollection_HQueue::Push(const Item& T)
{   
    Handle(PCollection_QueueNode) L;
    L = new PCollection_QueueNode;
    if (TheLength == 0) 
     {
        L->ChangeForwardPointer(TheFront);
        TheBack = L;
        TheFront = TheBack;
     }
    else
     { 
        L->ChangeForwardPointer(TheBack->Tail()); 
        TheBack->ChangeForwardPointer(L);
        TheBack = L;
      };
    TheBack->SetValue(T);
    TheLength = TheLength + 1;          
  }

// ------------------------------------
// Pop : remove an item from the front
// ------------------------------------
void PCollection_HQueue::Pop()
{   
    if (TheFront->IsEmpty()) Standard_NoSuchObject::Raise();
    Handle(PCollection_QueueNode) temp = TheFront;
    TheFront = TheFront->Tail();
    temp.Delete();
    TheLength = TheLength - 1;
    if (TheLength == 0) TheBack = TheFront;
}

// ------------------------------------
// ChangeFront : replace the front by T
// ------------------------------------
void PCollection_HQueue::ChangeFront(const Item& T)
{   
    if (TheFront->IsEmpty()) Standard_NoSuchObject::Raise();
    TheFront->SetValue(T);       
}

// ------------------------------------
// ShallowCopy
// ------------------------------------
Handle(Standard_Persistent) PCollection_HQueue::ShallowCopy() const
{
  Handle(PCollection_HQueue) TheCopy;
  Handle(PCollection_QueueNode) TheList;

  TheCopy = new PCollection_HQueue;
  TheList = TheFront;


  for (Standard_Integer I = 1; I <= TheLength; I++){
    TheCopy->Push(TheList->Value());
    TheList = TheList->Tail();
  }

  return TheCopy;
  
}

// ------------------------------------
// ShallowDump
// ------------------------------------
void PCollection_HQueue::ShallowDump(Standard_OStream& S) const
{
  S << "begin class Queue "<< endl;
  S << "Length of Queue : "<< TheLength << endl;
  TheFront->ShallowDump(cout);
  S << "end of class Queue." << endl;
}



// -----------------------------
// Length : numbers of items 
// -----------------------------
Standard_Integer PCollection_HQueue::Length() const {
    return TheLength;
} 

// -----------------------------
// FFront : front of the queue  
// -----------------------------
Handle(PCollection_QueueNode) PCollection_HQueue::FFront() const {
    return TheFront;
} 

// -----------------------------
// FBack : the back of the queue  
// -----------------------------
Handle(PCollection_QueueNode) PCollection_HQueue::FBack() const {
    return TheBack;
} 

void PCollection_HQueue::Destroy()
{
#ifdef CSFDB
  Clear();
#endif
}