/****************************************************************************
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 Copyright (c) 2015-2016 Chukong Technologies Inc.
 Copyright (c) 2017-2018 Xiamen Yaji Software Co., Ltd.
 
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 of this software and associated documentation files (the "Software"), to deal
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 furnished to do so, subject to the following conditions:
 
 The above copyright notice and this permission notice shall be included in
 all copies or substantial portions of the Software.
 
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 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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#ifndef __CC_PU_PARTICLE_MESH_SURFACE_EMITTER_H__
#define __CC_PU_PARTICLE_MESH_SURFACE_EMITTER_H__

#include "extensions/Particle3D/PU/CCPUEmitter.h"

NS_CC_BEGIN

/** Definition of a Triangle
*/
class PUTriangle
{
public:
    /** The struct is used to return both the position and the normal
    */
    struct PositionAndNormal
    {
        Vec3 position;
        Vec3 normal;
    };

    /** Public attributes **/
    float squareSurface;
    Vec3 surfaceNormal;	// Normal of triangle v1-v2-v3
    Vec3 v1;				// Vertex v1
    Vec3 v2;				// Vertex v2
    Vec3 v3;				// Vertex v3
    Vec3 vn1;			// Normal of vertex v1
    Vec3 vn2;			// Normal of vertex v2
    Vec3 vn3;			// Normal of vertex v3
    Vec3 en1;			// Normal of edge v1-v2
    Vec3 en2;			// Normal of edge v2-v3
    Vec3 en3;			// Normal of edge v3-v1

    /** Constructor **/
    PUTriangle(){};

    /** Calculate the (square) surface of the triangle **/
    void calculateSquareSurface ();

    /** Calculate the surface normal of the triangle **/
    void calculateSurfaceNormal ();

    /** Calculate the edge normals of the 3 edges  **/
    void calculateEdgeNormals ();

    /** Determine a random position on this triangle **/
    const Vec3 getRandomTrianglePosition ();

    /** Determine a random position including its normal on a one of the edges **/
    const PositionAndNormal getRandomEdgePositionAndNormal ();

    /** Determine a random vertex including its normal of this triangle **/
    const PositionAndNormal getRandomVertexAndNormal ();
};

/** Comparer used for sorting vector in ascending order
*/
struct PUSortAscending
{
    bool operator() (const PUTriangle& a, const PUTriangle& b)
    {
        return a.squareSurface < b.squareSurface;
    }
};

/** Comparer used for sorting vector in descending order
*/
struct PUSortDescending
{
    bool operator() (const PUTriangle& a, const PUTriangle& b)
    {
        return a.squareSurface > b.squareSurface;
    }
};

/** Define a template class for a vector of triangles.
*/
typedef std::vector<PUTriangle> Triangles;

/** Class that constructs mesh information of a given mesh name
@remarks
*/
class MeshInfo
{
public:
    /** Defining several methods to emit particles on the mesh surface
    @remarks
        Sometimes the difference is not always visible, for example if the mesh contains triangles with more or
        less the same size. Only in case a mesh contains both small and large triangles the difference between
        the various distribution methods is more obvious.
    */
    enum MeshSurfaceDistribution
    { 
        MSD_HOMOGENEOUS,		// Distribute particles homogeneous (random) on the mesh surface
        MSD_HETEROGENEOUS_1,	// Distribute more particles on the smaller faces
        MSD_HETEROGENEOUS_2,	// Same as above, but now more particles are emitting from the larger faces
        MSD_VERTEX,				// Particles only emit from the vertices
        MSD_EDGE				// Particles emit random on the edges
    };

    /** Constructor **/
    MeshInfo (const std::string& meshName, 
        const MeshSurfaceDistribution distribution = MSD_HOMOGENEOUS,
        const Quaternion& orientation = Quaternion(),
        const Vec3& scale = Vec3::ZERO);

    /** Destructor **/
    ~MeshInfo ();

    /** Generate a random number. The high argument determines that numbers are 
        returned between [0..high] **/
    float getGaussianRandom (float high, float cutoff = 4);

    ///** Retrieve vertex info **/
    //void getMeshInformation(Ogre::MeshPtr mesh,
    //						const Vec3& position = Vec3::ZERO,
    //						const Quaternion& orient = Quaternion(),
    //						const Vec3& scale = Vec3::ONE);

    /** Get a triangle based on the index. */
    const PUTriangle& getTriangle (size_t triangleIndex);

    /** Get a random triangle (index) from the mesh. */
    size_t getRandomTriangleIndex();
    
    /** Get triangle number */
    size_t getTriangleCount() const { return _triangles.size(); }

    /** Returns both a random point on a given triangle and its normal vector.
        How the random point and the normal are determined depends on the distribution type.
    **/
    const PUTriangle::PositionAndNormal getRandomPositionAndNormal (const size_t triangleIndex);

protected:
    Triangles _triangles;
    MeshSurfaceDistribution mDistribution;
};

/** The MeshSurfaceEmitter is a ParticleEmitter that emits particles on the surface of a mesh.
@remarks
    There are several ways of emitting it on the surface, from the vertices, edges and faces of a mesh.
    It is also possible to define whether more particles emit on larger faces.
*/

class CC_EX_DLL PUMeshSurfaceEmitter : public PUEmitter
{
public:
    // Constants
    static const Vec3 DEFAULT_SCALE;
    static const MeshInfo::MeshSurfaceDistribution DEFAULT_DISTRIBUTION;

    static PUMeshSurfaceEmitter* create();

    /** Returns the mesh name.
    */
    const std::string& getMeshName() const;

    /** Sets the mesh name.
    */
    void setMeshName(const std::string& meshName, bool doBuild = true);

    /** Returns true if normals are used for the particle direction.
    */
    bool useNormals () const;

    /** Set indication whether normals are used for the particle direction.
    */
    void setUseNormals (bool useNormals);

    /** Returns the type op distribution.
    @remarks
        There are several ways to emit particles on the surface of a mesh. This attribute indicates
        the type of distribution on the surface.
    */
    MeshInfo::MeshSurfaceDistribution getDistribution() const;

    /** Set the type of particle distribution on the surface of a mesh.
    */
    void setDistribution(MeshInfo::MeshSurfaceDistribution distribution);

    /** Returns the scale of the mesh.
    */
    const Vec3& getScale () const;

    /** Set the scale of the mesh.
    @remarks
        This options makes it possible to scale the mesh independently from the particle system scale as a whole.
    */
    void setScale (const Vec3& scale);

    /** Build all the data needed to generate the particles.
    */
    void build();

    /** Build the data if the mesh name has been set.
    */
    virtual void prepare() override;

    /** Reverse it.
    */
    virtual void unPrepare() override;

    /** Determine a particle position on the mesh surface.
    */
    virtual void initParticlePosition(PUParticle3D* particle) override;

    /** See ParticleEmitter.
    */
    virtual unsigned short calculateRequestedParticles(float timeElapsed) override;

    /** Determine the particle direction.
    */
    virtual void initParticleDirection(PUParticle3D* particle) override;

    virtual PUMeshSurfaceEmitter* clone() override;
    virtual void copyAttributesTo (PUEmitter* emitter) override;

CC_CONSTRUCTOR_ACCESS:
    PUMeshSurfaceEmitter();
    virtual ~PUMeshSurfaceEmitter();

protected:
    std::string _meshName;
    Quaternion _orientation;
    Vec3 _scale;
    MeshInfo::MeshSurfaceDistribution _distribution;
    MeshInfo* _meshInfo;
    size_t _triangleIndex;
    bool _directionSet;
};

NS_CC_END

#endif