/*
 * Copyright (C) 2018 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 <string>

#include <ignition/math/OrientedBox.hh>
#include <ignition/math/Pose3.hh>

#include "gazebo/common/Events.hh"
#include "gazebo/common/UpdateInfo.hh"

#include "gazebo/physics/Entity.hh"
#include "gazebo/physics/World.hh"

#include "gazebo/transport/Node.hh"

#include "ContainPlugin.hh"

namespace gazebo
{
  namespace physics
  {
    typedef boost::weak_ptr<physics::Entity> EntityWeakPtr;
  }

  /// \brief Private data class for the ContainPlugin class
  class ContainPluginPrivate
  {
    /// \brief Connection to world update.
    public: event::ConnectionPtr updateConnection;

    /// \brief Pointer to the world.
    public: physics::WorldPtr world;

    /// \brief Scoped name of the entity we're checking.
    public: std::string entityName;

    /// \brief Pointer to the entity we're checking.
    public: physics::EntityWeakPtr entity;

    /// \brief Box representing the volume to check.
    public: ignition::math::OrientedBoxd box;

    /// \brief Gazebo transport node for communication.
    public: transport::NodePtr gzNode;

    /// \brief pointer to an entity whose pose the geometry will track
    public: physics::EntityWeakPtr containerEntity;

    /// \brief scoped name of entity to track
    public: std::string containerEntityName;

    /// \brief Publisher which publishes contain / doesn't contain messages.
    public: transport::PublisherPtr containGzPub;

    /// \brief Subscriber to enable messages.
    public: transport::SubscriberPtr enableGzSub;

    /// \brief Namespace for the topics:
    /// /<ns>/contain
    /// /<ns>/enable
    public: std::string ns;

    /// \brief 1 if contains, 0 if doesn't contain, -1 if unset
    public: int contain = -1;
  };
}

using namespace gazebo;

GZ_REGISTER_WORLD_PLUGIN(ContainPlugin)

/////////////////////////////////////////////////
ContainPlugin::ContainPlugin() : WorldPlugin(),
    dataPtr(new ContainPluginPrivate)
{
}

/////////////////////////////////////////////////
void ContainPlugin::Load(physics::WorldPtr _world, sdf::ElementPtr _sdf)
{
  // Entity name
  if (!_sdf->HasElement("entity"))
  {
    gzerr << "Missing required parameter <entity>, plugin will not be "
          << "initialized." << std::endl;
    return;
  }
  this->dataPtr->entityName = _sdf->Get<std::string>("entity");

  // Namespace
  if (!_sdf->HasElement("namespace"))
  {
    gzerr << "Missing required parameter <namespace>, plugin will not be "
          << "initialized." << std::endl;
    return;
  }
  this->dataPtr->ns = _sdf->Get<std::string>("namespace");

  // Pose
  if (!_sdf->HasElement("pose"))
  {
    gzerr << "Missing required parameter <pose>, plugin will not be "
          << "initialized." << std::endl;
    return;
  }
  auto pose = _sdf->Get<ignition::math::Pose3d>("pose");
  sdf::ParamPtr frameParam = _sdf->GetElement("pose")->GetAttribute("frame");
  if (frameParam)
  {
    this->dataPtr->containerEntityName = frameParam->GetAsString();
  }

  // Geometry
  if (!_sdf->HasElement("geometry"))
  {
    gzerr << "Missing required parameter <geometry>, plugin will not be "
          << "initialized." << std::endl;
    return;
  }
  auto geometryElem = _sdf->GetElement("geometry");

  // Only box for now
  if (!geometryElem->HasElement("box"))
  {
    gzerr << "Missing required parameter <box>, plugin will not be "
          << "initialized." << std::endl;
    return;
  }
  auto boxElem = geometryElem->GetElement("box");

  if (!boxElem->HasElement("size"))
  {
    gzerr << "Missing required parameter <size>, plugin will not be "
          << "initialized." << std::endl;
    return;
  }
  auto size = boxElem->Get<ignition::math::Vector3d>("size");

  this->dataPtr->box = ignition::math::OrientedBoxd(size, pose);

  this->dataPtr->world = _world;

  // Start/stop
  this->dataPtr->gzNode = transport::NodePtr(new transport::Node());
  this->dataPtr->gzNode->Init();
  this->dataPtr->enableGzSub = this->dataPtr->gzNode->Subscribe("/" +
      this->dataPtr->ns + "/enable", &ContainPlugin::Enable, this);

  auto enabled = true;
  if (_sdf->HasElement("enabled"))
    enabled = _sdf->Get<bool>("enabled");

  if (enabled)
  {
    boost::shared_ptr<msgs::Int> msg(new msgs::Int());
    msg->set_data(1);
    this->Enable(msg);
  }
}

//////////////////////////////////////////////////
void ContainPlugin::Enable(ConstIntPtr &_msg)
{
  auto enable = _msg->data() == 1;

  // Already started
  if (enable && this->dataPtr->updateConnection)
  {
    gzwarn << "Contain plugin is already enabled." << std::endl;
    return;
  }

  // Already stopped
  if (!enable && !this->dataPtr->updateConnection)
  {
    gzwarn << "Contain plugin is already disabled." << std::endl;
    return;
  }

  // Start
  if (enable)
  {
    // Start update
    this->dataPtr->updateConnection = event::Events::ConnectWorldUpdateBegin(
        std::bind(&ContainPlugin::OnUpdate, this, std::placeholders::_1));

    this->dataPtr->containGzPub = this->dataPtr->gzNode->Advertise<msgs::Int>(
        "/" + this->dataPtr->ns + "/contain");

    gzmsg << "Started contain plugin [" << this->dataPtr->ns << "]"
          << std::endl;
    return;
  }

  // Stop
  {
    this->dataPtr->updateConnection.reset();
    this->dataPtr->containGzPub.reset();
    this->dataPtr->contain = -1;

    gzmsg << "Stopped contain plugin [" << this->dataPtr->ns << "]"
          << std::endl;
    return;
  }
}

/////////////////////////////////////////////////
void ContainPlugin::OnUpdate(const common::UpdateInfo &/*_info*/)
{
  // Only get the entity once
  physics::EntityPtr entity = this->dataPtr->entity.lock();
  if (!entity)
  {
    this->dataPtr->entity = this->dataPtr->world->GetEntity(
        this->dataPtr->entityName);
    entity = this->dataPtr->entity.lock();
    if (!entity)
    {
      // Could not find entity being tested
      this->PublishContains(false);
      return;
    }
  }

  ignition::math::Vector3d entityInWorldFrame =
    entity->GetWorldPose().Ign().Pos();

  ignition::math::Vector3d entityInBoxFrame;
  if (!this->dataPtr->containerEntityName.empty())
  {
    physics::EntityPtr referenceEntity = this->dataPtr->containerEntity.lock();
    // box is in a potentially moving reference frame
    if (!referenceEntity)
    {
      this->dataPtr->containerEntity = this->dataPtr->world->GetEntity(
        this->dataPtr->containerEntityName);
      referenceEntity = this->dataPtr->containerEntity.lock();
      if (!referenceEntity)
      {
        // Could not find reference entity
        this->PublishContains(false);
        return;
      }
    }

    auto worldToBox = referenceEntity->GetWorldPose().Ign();
    auto boxToWorld = worldToBox.Inverse();
    // Transform the entity vector from world frame to the frame the box is in
    entityInBoxFrame = (boxToWorld.Rot() * entityInWorldFrame)
      + boxToWorld.Pos();
  }
  else
  {
    // box frame is world frame
    entityInBoxFrame = entityInWorldFrame;
  }

  this->PublishContains(this->dataPtr->box.Contains(entityInBoxFrame));
}

//////////////////////////////////////////////////
void ContainPlugin::PublishContains(const bool _contains)
{
  int containNow = _contains ? 1 : 0;
  if (containNow != this->dataPtr->contain)
  {
    this->dataPtr->contain = containNow;

    msgs::Int msg;
    msg.set_data(this->dataPtr->contain);
    this->dataPtr->containGzPub->Publish(msg);
  }
}