/*
 * SPDX-FileName:terrain_stg.cxx -- data structures and routines for managing terrain scenery.
 * SPDX-FileCopyrightText: 1997  Curtis L. Olson  - http://www.flightgear.org/~curt
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

#include <config.h>

#include <stdio.h>
#include <string.h>

#include <osg/Camera>
#include <osg/Transform>
#include <osg/MatrixTransform>
#include <osg/PositionAttitudeTransform>
#include <osg/CameraView>
#include <osg/LOD>
#include <osgTerrain/TerrainTile>

#include <osgViewer/Viewer>

#include <simgear/constants.h>
#include <simgear/sg_inlines.h>
#include <simgear/debug/logstream.hxx>
#include <simgear/scene/tgdb/userdata.hxx>
#include <simgear/scene/tgdb/VPBTechnique.hxx>
#include <simgear/scene/material/matlib.hxx>
#include <simgear/scene/material/mat.hxx>
#include <simgear/scene/util/SGNodeMasks.hxx>
#include <simgear/scene/util/OsgMath.hxx>
#include <simgear/scene/util/SGSceneUserData.hxx>
#include <simgear/scene/model/CheckSceneryVisitor.hxx>
#include <simgear/scene/sky/sky.hxx>

#include <simgear/bvh/BVHNode.hxx>
#include <simgear/bvh/BVHLineSegmentVisitor.hxx>
#include <simgear/bvh/BVHTerrainTile.hxx>
#include <simgear/structure/commands.hxx>

#include <Viewer/renderer.hxx>
#include <Main/fg_props.hxx>
#include <GUI/MouseCursor.hxx>

#include "terrain_stg.hxx"

using namespace flightgear;
using namespace simgear;

class FGGroundPickCallback : public SGPickCallback {
public:
  FGGroundPickCallback() : SGPickCallback(PriorityScenery)
  { }

  virtual bool buttonPressed( int button,
                              const osgGA::GUIEventAdapter&,
                              const Info& info )
  {
    // only on left mouse button
    if (button != 0)
      return false;

    SGGeod geod = SGGeod::fromCart(info.wgs84);
    SG_LOG( SG_TERRAIN, SG_INFO, "Got ground pick at " << geod );

    SGPropertyNode *c = fgGetNode("/sim/input/click", true);
    c->setDoubleValue("longitude-deg", geod.getLongitudeDeg());
    c->setDoubleValue("latitude-deg", geod.getLatitudeDeg());
    c->setDoubleValue("elevation-m", geod.getElevationM());
    c->setDoubleValue("elevation-ft", geod.getElevationFt());
    fgSetBool("/sim/signals/click", 1);

    return true;
  }
};

class FGSceneryIntersect : public osg::NodeVisitor {
public:
    FGSceneryIntersect(const SGLineSegmentd& lineSegment,
                       const osg::Node* skipNode) :
        osg::NodeVisitor(osg::NodeVisitor::TRAVERSE_ACTIVE_CHILDREN),
        _lineSegment(lineSegment),
        _skipNode(skipNode),
        _material(0),
        _haveHit(false)
    { }

    bool getHaveHit() const
    { return _haveHit; }
    const SGLineSegmentd& getLineSegment() const
    { return _lineSegment; }
    const simgear::BVHMaterial* getMaterial() const
    { return _material; }

    virtual void apply(osg::Node& node)
    {
        if (&node == _skipNode)
            return;
        if (!testBoundingSphere(node.getBound()))
            return;

        addBoundingVolume(node);
    }

    virtual void apply(osg::Group& group)
    {
        if (&group == _skipNode)
            return;
        if (!testBoundingSphere(group.getBound()))
            return;

        traverse(group);
        addBoundingVolume(group);

        if (_haveHit && dynamic_cast<osgTerrain::TerrainTile*>(&group) && ! _material) {
            // In the case of TerrainTiles, we do not have material information within the mesh itself.
            // So instead it must be retrieved from the raster.
            osgTerrain::TerrainTile* tile = dynamic_cast<osgTerrain::TerrainTile*>(&group);
            simgear::VPBTechnique* technique = tile ? dynamic_cast<simgear::VPBTechnique*>(tile->getTerrainTechnique()) : 0;
            _material = technique ? technique->getMaterial(toOsg(_lineSegment.getEnd())) : 0;
        }
    }

    virtual void apply(osg::Transform& transform)
    { handleTransform(transform); }
    virtual void apply(osg::Camera& camera)
    {
        if (camera.getRenderOrder() != osg::Camera::NESTED_RENDER)
            return;
        handleTransform(camera);
    }
    virtual void apply(osg::CameraView& transform)
    { handleTransform(transform); }
    virtual void apply(osg::MatrixTransform& transform)
    { handleTransform(transform); }
    virtual void apply(osg::PositionAttitudeTransform& transform)
    { handleTransform(transform); }

private:
    void handleTransform(osg::Transform& transform)
    {
        if (&transform == _skipNode)
            return;
        // Hmm, may be this needs to be refined somehow ...
        if (transform.getReferenceFrame() != osg::Transform::RELATIVE_RF)
            return;

        if (!testBoundingSphere(transform.getBound()))
            return;

        osg::Matrix inverseMatrix;
        if (!transform.computeWorldToLocalMatrix(inverseMatrix, this))
            return;
        osg::Matrix matrix;
        if (!transform.computeLocalToWorldMatrix(matrix, this))
            return;

        SGLineSegmentd lineSegment = _lineSegment;
        bool haveHit = _haveHit;
        const simgear::BVHMaterial* material = _material;

        _haveHit = false;
        _lineSegment = lineSegment.transform(SGMatrixd(inverseMatrix.ptr()));

        addBoundingVolume(transform);
        traverse(transform);

        if (_haveHit) {
            _lineSegment = _lineSegment.transform(SGMatrixd(matrix.ptr()));
        } else {
            _lineSegment = lineSegment;
            _material = material;
            _haveHit = haveHit;
        }
    }

    simgear::BVHNode* getNodeBoundingVolume(osg::Node& node)
    {
        SGSceneUserData* userData = SGSceneUserData::getSceneUserData(&node);
        if (!userData)
            return 0;
        return userData->getBVHNode();
    }
    void addBoundingVolume(osg::Node& node)
    {
        simgear::BVHNode* bvNode = getNodeBoundingVolume(node);
        if (!bvNode)
            return;

        // Find ground intersection on the bvh nodes
        simgear::BVHLineSegmentVisitor lineSegmentVisitor(_lineSegment,
                                                          0/*startTime*/);
        bvNode->accept(lineSegmentVisitor);
        if (!lineSegmentVisitor.empty()) {
            _lineSegment = lineSegmentVisitor.getLineSegment();
            _material = lineSegmentVisitor.getMaterial();
            _haveHit = true;
        }
    }

    bool testBoundingSphere(const osg::BoundingSphere& bound) const
    {
        if (!bound.valid())
            return false;

        SGSphered sphere(toVec3d(toSG(bound._center)), bound._radius);
        return intersects(_lineSegment, sphere);
    }

    SGLineSegmentd _lineSegment;
    const osg::Node* _skipNode;

    const simgear::BVHMaterial* _material;
    bool _haveHit;
};

////////////////////////////////////////////////////////////////////////////

// Terrain Management system
FGStgTerrain::FGStgTerrain() :
    _tilemgr()
{
    _inited  = false;
}

FGStgTerrain::~FGStgTerrain()
{
    SG_LOG(SG_TERRAIN, SG_INFO, "FGStgTerrain::dtor");
}


// Initialize the Scenery Management system
void FGStgTerrain::init( osg::Group* terrain ) {
    // Already set up.
    if (_inited)
        return;

    SG_LOG(SG_TERRAIN, SG_INFO, "FGStgTerrain::init - init tilemgr");

    // remember the scene terrain branch on scenegraph
    terrain_branch = terrain;

    // initialize the tile manager
    _tilemgr.init();

    // Toggle the setup flag.
    _inited = true;
}

void FGStgTerrain::reinit()
{
    SG_LOG(SG_TERRAIN, SG_INFO, "FGStgTerrain::reinit - reinit tilemgr");

    _tilemgr.reinit();
}

void FGStgTerrain::shutdown()
{
    SG_LOG(SG_TERRAIN, SG_INFO, "FGStgTerrain::shutdown - shutdown tilemgr");

    _tilemgr.shutdown();

    terrain_branch = NULL;

    // Toggle the setup flag.
    _inited = false;
}


void FGStgTerrain::update(double dt)
{
    _tilemgr.update(dt);
}

void FGStgTerrain::bind()
{
    SG_LOG(SG_TERRAIN, SG_INFO, "FGStgTerrain::bind - noop");
}

void FGStgTerrain::unbind()
{
    SG_LOG(SG_TERRAIN, SG_INFO, "FGStgTerrain::unbind - noop");
}

bool
FGStgTerrain::get_cart_elevation_m(const SGVec3d& pos, double max_altoff,
                                   double& alt,
                                   const simgear::BVHMaterial** material,
                                   const osg::Node* butNotFrom)
{
  bool ok;

  SGGeod geod = SGGeod::fromCart(pos);
  if (!geod.isValid())
      return false;

  geod.setElevationM(geod.getElevationM() + max_altoff);

  ok = get_elevation_m(geod, alt, material, butNotFrom);

  return ok;
}

bool
FGStgTerrain::get_elevation_m(const SGGeod& geod, double& alt,
                              const simgear::BVHMaterial** material,
                              const osg::Node* butNotFrom)
{
    if (!geod.isValid())
        return false;

    SGVec3d start = SGVec3d::fromGeod(geod);

    SGGeod geodEnd = geod;
    geodEnd.setElevationM(SGMiscd::min(geod.getElevationM() - 10, -10000));
    SGVec3d end = SGVec3d::fromGeod(geodEnd);

    FGSceneryIntersect intersectVisitor(SGLineSegmentd(start, end), butNotFrom);
    intersectVisitor.setTraversalMask(SG_NODEMASK_TERRAIN_BIT);
    terrain_branch->accept(intersectVisitor);

    if (!intersectVisitor.getHaveHit())
        return false;

    geodEnd = SGGeod::fromCart(intersectVisitor.getLineSegment().getEnd());
    alt = geodEnd.getElevationM();
    if (material) {
        *material = intersectVisitor.getMaterial();
  }

  return true;
}

bool
FGStgTerrain::get_cart_ground_intersection(const SGVec3d& pos, const SGVec3d& dir,
                                           SGVec3d& nearestHit,
                                           const osg::Node* butNotFrom)
{
  // We assume that starting positions in the center of the earth are invalid
  if ( norm1(pos) < 1 )
    return false;

  // Make really sure the direction is normalized, is really cheap compared to
  // computation of ground intersection.
  SGVec3d start = pos;
  SGVec3d end = start + 1e5*normalize(dir); // FIXME visibility ???

  FGSceneryIntersect intersectVisitor(SGLineSegmentd(start, end), butNotFrom);
  intersectVisitor.setTraversalMask(SG_NODEMASK_TERRAIN_BIT);
  terrain_branch->accept(intersectVisitor);

  if (!intersectVisitor.getHaveHit())
      return false;

  nearestHit = intersectVisitor.getLineSegment().getEnd();
  return true;
}

bool FGStgTerrain::scenery_available(const SGGeod& position, double range_m)
{
  if( schedule_scenery(position, range_m, 0.0) )
  {
    double elev = 0.0;

    bool got_elev = get_elevation_m(SGGeod::fromGeodM(position, SG_MAX_ELEVATION_M), elev, 0, 0);

    if (!got_elev) {
        SG_LOG(SG_TERRAIN, SG_DEBUG, "FGStgTerrain::scenery_available - false" );
        return false;
    }

    SGVec3f p = SGVec3f::fromGeod(SGGeod::fromGeodM(position, elev));
    osg::FrameStamp* framestamp
            = globals->get_renderer()->getFrameStamp();

    FGScenery* pSceneryManager = globals->get_scenery();
    simgear::CheckSceneryVisitor csnv(pSceneryManager->getPager(), toOsg(p), range_m, framestamp);
    // currently the PagedLODs will not be loaded by the DatabasePager
    // while the splashscreen is there, so CheckSceneryVisitor force-loads
    // missing objects in the main thread
    terrain_branch->accept(csnv);
    if(!csnv.isLoaded()) {
        SG_LOG(SG_TERRAIN, SG_DEBUG, "FGScenery::scenery_available: waiting on CheckSceneryVisitor");
        return false;
    }

    SG_LOG(SG_TERRAIN, SG_DEBUG, "FGStgTerrain::scenery_available - true" );
    return true;
  } else {
    SG_LOG(SG_TERRAIN, SG_DEBUG, "FGScenery::scenery_available: waiting on tile manager");
  }
  SG_LOG(SG_TERRAIN, SG_DEBUG, "FGStgTerrain::scenery_available - false" );
  return false;
}

bool FGStgTerrain::schedule_scenery(const SGGeod& position, double range_m, double duration)
{
    SG_LOG(SG_TERRAIN, SG_BULK, "FGStgTerrain::schedule_scenery");

    return _tilemgr.schedule_scenery( position, range_m, duration );
}

void FGStgTerrain::materialLibChanged()
{
    _tilemgr.materialLibChanged();
}
