/*
 * Copyright (C) 2012 Open Source Robotics Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
*/

#include "gazebo/common/Exception.hh"
#include "gazebo/common/Assert.hh"

#include "gazebo/physics/bullet/bullet_inc.h"
#include "gazebo/physics/bullet/BulletTypes.hh"
#include "gazebo/physics/bullet/BulletLink.hh"
#include "gazebo/physics/bullet/BulletMotionState.hh"
#include "gazebo/physics/bullet/BulletCollision.hh"
#include "gazebo/physics/bullet/BulletHeightmapShape.hh"

using namespace gazebo;
using namespace physics;

//////////////////////////////////////////////////
BulletHeightmapShape::BulletHeightmapShape(CollisionPtr _parent)
    : HeightmapShape(_parent)
{
  // Bullet need the height values flipped in the y direction
  this->flipY = true;
}

//////////////////////////////////////////////////
BulletHeightmapShape::~BulletHeightmapShape()
{
}

//////////////////////////////////////////////////
void BulletHeightmapShape::Init()
{
  HeightmapShape::Init();

  float maxHeight = this->GetMaxHeight();
  float minHeight = this->GetMinHeight();

  // This will force the Z-axis to be up
  int upIndex = 2;
  btVector3 localScaling(this->scale.X(), this->scale.Y(), 1.0);

  this->heightFieldShape  = new btHeightfieldTerrainShape(
      this->vertSize,     // # of heights along width
      this->vertSize,     // # of height along height
      &this->heights[0],  // The heights
      1,                  // Height scaling
      minHeight,          // Min height
      maxHeight,          // Max height
      upIndex,            // Up axis
      PHY_FLOAT,
      false);             // Flip quad edges

  this->heightFieldShape->setLocalScaling(localScaling);

  // This is suppose to match up with Ogre rendering a bit better.
  this->heightFieldShape->setUseZigzagSubdivision(true);

  // Get a pointer to the parent collision
  BulletCollisionPtr bParent;
  bParent = boost::dynamic_pointer_cast<BulletCollision>(this->collisionParent);

  GZ_ASSERT(bParent != nullptr,
      "Bullet collision parent of a heightmap is null");

  bParent->SetCollisionShape(this->heightFieldShape, false);

  BulletLinkPtr bLink = boost::dynamic_pointer_cast<BulletLink>(
      bParent->GetParent());

  GZ_ASSERT(bLink != nullptr, "Bullet heightmap does not have a link.");

  BulletMotionStatePtr motionState = bLink->motionState;

  GZ_ASSERT(motionState != nullptr, "Invalid motion state for heightmap.");

  btTransform tr;
  tr.setIdentity();
  // change the relative transform of the height field so that the minimum
  // height is at the same z coordinate. Bullet shifts the height map such
  // that its center is the AABB center.
  tr.setOrigin(btVector3(0, 0, (maxHeight - minHeight) * 0.5 + minHeight));

  // TODO FIXME this doesn't work. Some sort of fixed relative transform has
  // to be set, but MotionState::SetWorldTransform() doesn't even consider
  // the parameter input, so this does virtually nothing...
  // Set the transform for the heightmap.
  motionState->setWorldTransform(tr);
}
