// SPDX-FileCopyrightText: Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
// SPDX-License-Identifier: BSD-3-Clause
#include "vtkPriorityQueue.h"
#include "vtkObjectFactory.h"

VTK_ABI_NAMESPACE_BEGIN
vtkStandardNewMacro(vtkPriorityQueue);

// Instantiate priority queue with default size and extension size of 1000.
vtkPriorityQueue::vtkPriorityQueue()
{
  this->Size = 0;
  this->Extend = 1000;
  this->Array = nullptr;
  this->MaxId = -1;
  this->ItemLocation = vtkIdTypeArray::New();
}

// Allocate priority queue with specified size and amount to extend
// queue (if reallocation required).
void vtkPriorityQueue::Allocate(vtkIdType sz, vtkIdType ext)
{
  this->ItemLocation->Allocate(sz, ext);
  this->Size = (sz > 0 ? sz : 1);
  delete[] this->Array;
  this->Array = new vtkPriorityQueue::Item[sz];
  this->Extend = (ext > 0 ? ext : 1);
  this->MaxId = -1;
}

// Destructor for the vtkPriorityQueue class
vtkPriorityQueue::~vtkPriorityQueue()
{
  this->ItemLocation->Delete();
  delete[] this->Array;
}

// Insert id with priority specified.
void vtkPriorityQueue::Insert(double priority, vtkIdType id)
{
  vtkIdType i, idx;
  vtkPriorityQueue::Item temp;

  // check and make sure item hasn't been inserted before
  if (id <= this->ItemLocation->GetMaxId() && this->ItemLocation->GetValue(id) != -1)
  {
    return;
  }

  // start by placing new entry at bottom of tree
  if (++this->MaxId >= this->Size)
  {
    this->Resize(this->MaxId + 1);
  }
  this->Array[this->MaxId].priority = priority;
  this->Array[this->MaxId].id = id;

  vtkIdType oldMaxId = this->ItemLocation->GetMaxId();
  this->ItemLocation->InsertValue(id, this->MaxId); // this does allocation
  for (i = oldMaxId + 1; i < id; i++)
  {
    // initialize previously unused elements
    this->ItemLocation->SetValue(i, -1);
  }

  // now begin percolating towards top of tree
  for (i = this->MaxId;
       i > 0 && this->Array[i].priority < this->Array[(idx = (i - 1) / 2)].priority; i = idx)
  {
    temp = this->Array[i];

    this->ItemLocation->SetValue(temp.id, idx);
    this->Array[i] = this->Array[idx];

    this->ItemLocation->SetValue(this->Array[idx].id, i);
    this->Array[idx] = temp;
  }
}

// Simplified call for easier wrapping for Tcl.
vtkIdType vtkPriorityQueue::Pop(vtkIdType location)
{
  double priority;
  return this->Pop(location, priority);
}

// Removes item at specified location from tree; then reorders and
// balances tree. The location == 0 is the root of the tree.
vtkIdType vtkPriorityQueue::Pop(vtkIdType location, double& priority)
{
  vtkIdType idx;
  vtkPriorityQueue::Item temp;

  if (this->MaxId < 0)
  {
    return -1;
  }

  vtkIdType id = this->Array[location].id;
  priority = this->Array[location].priority;

  // move the last item to the location specified and push into the tree
  this->Array[location].id = this->Array[this->MaxId].id;
  this->Array[location].priority = this->Array[this->MaxId].priority;

  this->ItemLocation->SetValue(this->Array[location].id, location);
  this->ItemLocation->SetValue(id, -1);

  if (--this->MaxId <= 0)
  {
    return id;
  }

  // percolate down the tree from the specified location
  vtkIdType lastNodeToCheck = (this->MaxId - 1) / 2;
  for (vtkIdType j = 0, i = location; i <= lastNodeToCheck; i = j)
  {
    idx = 2 * i + 1;

    if (this->Array[idx].priority < this->Array[idx + 1].priority || idx == this->MaxId)
    {
      j = idx;
    }
    else
    {
      j = idx + 1;
    }

    if (this->Array[i].priority > this->Array[j].priority)
    {
      temp = this->Array[i];

      this->ItemLocation->SetValue(temp.id, j);
      this->Array[i] = this->Array[j];

      this->ItemLocation->SetValue(this->Array[j].id, i);
      this->Array[j] = temp;
    }
    else
    {
      break;
    }
  }

  // percolate up the tree from the specified location
  for (vtkIdType i = location; i > 0; i = idx)
  {
    idx = (i - 1) / 2;

    if (this->Array[i].priority < this->Array[idx].priority)
    {
      temp = this->Array[i];

      this->ItemLocation->SetValue(temp.id, idx);
      this->Array[i] = this->Array[idx];

      this->ItemLocation->SetValue(this->Array[idx].id, i);
      this->Array[idx] = temp;
    }
    else
    {
      break;
    }
  }

  return id;
}

// Protected method reallocates queue.
vtkPriorityQueue::Item* vtkPriorityQueue::Resize(vtkIdType sz)
{
  vtkPriorityQueue::Item* newArray;
  vtkIdType newSize;

  if (sz >= this->Size)
  {
    newSize = this->Size + sz;
  }
  else
  {
    newSize = sz;
  }

  if (newSize <= 0)
  {
    newSize = 1;
  }

  newArray = new vtkPriorityQueue::Item[newSize];

  if (this->Array)
  {
    memcpy(
      newArray, this->Array, (sz < this->Size ? sz : this->Size) * sizeof(vtkPriorityQueue::Item));
    delete[] this->Array;
  }

  this->Size = newSize;
  this->Array = newArray;

  return this->Array;
}

// Reset all of the entries in the queue so they don not have a priority
void vtkPriorityQueue::Reset()
{
  this->MaxId = -1;
  this->ItemLocation->Reset();
}

void vtkPriorityQueue::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os, indent);

  os << indent << "Number Of Entries: " << this->MaxId + 1 << "\n";
  os << indent << "Size: " << this->Size << "\n";
  os << indent << "Extend size: " << this->Extend << "\n";
}
VTK_ABI_NAMESPACE_END
