/**
 * PANDA 3D SOFTWARE
 * Copyright (c) Carnegie Mellon University.  All rights reserved.
 *
 * All use of this software is subject to the terms of the revised BSD
 * license.  You should have received a copy of this license along
 * with this source code in a file named "LICENSE."
 *
 * @file switchNode.cxx
 * @author drose
 * @date 2002-07-31
 */

#include "pandabase.h"
#include "switchNode.h"
#include "cullTraverser.h"

TypeHandle SwitchNode::_type_handle;

/**
 *
 */
CycleData *SwitchNode::CData::
make_copy() const {
  return new CData(*this);
}

/**
 * Returns true if it is generally safe to combine this particular kind of
 * PandaNode with other kinds of PandaNodes of compatible type, adding
 * children or whatever.  For instance, an LODNode should not be combined with
 * any other PandaNode, because its set of children is meaningful.
 */
bool SwitchNode::
safe_to_combine() const {
  return false;
}

/**
 * Returns true if it is generally safe to combine the children of this
 * PandaNode with each other.  For instance, an LODNode's children should not
 * be combined with each other, because the set of children is meaningful.
 */
bool SwitchNode::
safe_to_combine_children() const {
  return false;
}

/**
 * Writes the contents of this object to the datagram for shipping out to a
 * Bam file.
 */
void SwitchNode::CData::
write_datagram(BamWriter *manager, Datagram &dg) const {
  dg.add_int32(_visible_child);
}

/**
 * This internal function is called by make_from_bam to read in all of the
 * relevant data from the BamFile for the new SwitchNode.
 */
void SwitchNode::CData::
fillin(DatagramIterator &scan, BamReader *manager) {
  _visible_child = scan.get_int32();
}

/**
 *
 */
SwitchNode::
SwitchNode(const SwitchNode &copy) :
  SelectiveChildNode(copy),
  _cycler(copy._cycler)
{
}

/**
 * Returns a newly-allocated Node that is a shallow copy of this one.  It will
 * be a different Node pointer, but its internal data may or may not be shared
 * with that of the original Node.
 */
PandaNode *SwitchNode::
make_copy() const {
  return new SwitchNode(*this);
}

/**
 * This function will be called during the cull traversal to perform any
 * additional operations that should be performed at cull time.  This may
 * include additional manipulation of render state or additional
 * visible/invisible decisions, or any other arbitrary operation.
 *
 * Note that this function will *not* be called unless set_cull_callback() is
 * called in the constructor of the derived class.  It is necessary to call
 * set_cull_callback() to indicated that we require cull_callback() to be
 * called.
 *
 * By the time this function is called, the node has already passed the
 * bounding-volume test for the viewing frustum, and the node's transform and
 * state have already been applied to the indicated CullTraverserData object.
 *
 * The return value is true if this node should be visible, or false if it
 * should be culled.
 */
bool SwitchNode::
cull_callback(CullTraverser *, CullTraverserData &) {
  select_child(get_visible_child());
  return true;
}

/**
 * Returns the index number of the first visible child of this node, or a
 * number >= get_num_children() if there are no visible children of this node.
 * This is called during the cull traversal, but only if
 * has_selective_visibility() has already returned true.  See
 * has_selective_visibility().
 */
int SwitchNode::
get_first_visible_child() const {
  return get_visible_child();
}

/**
 * Should be overridden by derived classes to return true if this kind of node
 * has the special property that just one of its children is visible at any
 * given time, and furthermore that the particular visible child can be
 * determined without reference to any external information (such as a
 * camera).  At present, only SequenceNodes and SwitchNodes fall into this
 * category.
 *
 * If this function returns true, get_visible_child() can be called to return
 * the index of the currently-visible child.
 */
bool SwitchNode::
has_single_child_visibility() const {
  return true;
}

/**
 * Returns the index of the child that should be visible.
 */
int SwitchNode::
get_visible_child() const {
  CDReader cdata(_cycler);
  return cdata->_visible_child;
}

/**
 * Tells the BamReader how to create objects of type SwitchNode.
 */
void SwitchNode::
register_with_read_factory() {
  BamReader::get_factory()->register_factory(get_class_type(), make_from_bam);
}

/**
 * Writes the contents of this object to the datagram for shipping out to a
 * Bam file.
 */
void SwitchNode::
write_datagram(BamWriter *manager, Datagram &dg) {
  SelectiveChildNode::write_datagram(manager, dg);
  manager->write_cdata(dg, _cycler);
}

/**
 * This function is called by the BamReader's factory when a new object of
 * type SwitchNode is encountered in the Bam file.  It should create the
 * SwitchNode and extract its information from the file.
 */
TypedWritable *SwitchNode::
make_from_bam(const FactoryParams &params) {
  SwitchNode *node = new SwitchNode("");
  DatagramIterator scan;
  BamReader *manager;

  parse_params(params, scan, manager);
  node->fillin(scan, manager);

  return node;
}

/**
 * This internal function is called by make_from_bam to read in all of the
 * relevant data from the BamFile for the new SwitchNode.
 */
void SwitchNode::
fillin(DatagramIterator &scan, BamReader *manager) {
  SelectiveChildNode::fillin(scan, manager);
  manager->read_cdata(scan, _cycler);
}