///////////////////////////////////////////////////////////////////////////
//
//		Realistic rain real-time simulation program
//
//		Pierre Rousseau
//
///////////////////////////////////////////////////////////////////////////
//
//		Particle systems handling
//
///////////////////////////////////////////////////////////////////////////

#ifndef __RAIN_CLOSE_DROPS_PARTICLES__
#define __RAIN_CLOSE_DROPS_PARTICLES__


#include "CommonRain.h"
#include "RainTextureFrameListener.h"
#include "RainManualHardwareBillboardMeshLoader.h"
#include "RainLight.h"






/** Class : CloseDropsParticles
  * defines a rain system, with cameras and shaders
  */
class CloseDropsParticles
{
private :
    SceneManager *mSceneMgr;
    RainLightManager *mRainLightMgr;
    SceneNode *mParticlesNode, *mParentCam, *mParentSyst;

    // wide angle camera used to render the drops
    Ogre::Camera *mCamera;
    RenderTexture *dropsTexture;
    MaterialPtr dropsTexturesMaterial;

    // simulation textures, containing particle positions
    unsigned int mActiveParticlesCount;
    RenderTexture *particlePosTexture, *particlePosTextureBackup;

    BillboardSet *bbSet1, *bbSet2; // billboardsets for ping-pong position textures


public :
    /** public variable : width of the particles */
    float mRainWidth;
    /** public variable : wheight of the particles (for streaks) */
    float mRainStreaksHeight;


    /** public functions */

    /** constructor, taking in parameters :
      *   - the SceneManager used in the scene
      *   - the SceneNode to which the particle system should be attached
      *   - the SceneNode to which the auxiliary camera (which we use to texture our drops) should be attached
      */
    CloseDropsParticles(SceneManager *sceneMgr, SceneNode *parentSyst, SceneNode *parentCam);

    /** Destructor */
    ~CloseDropsParticles();

    /** function wich creates the lights (streetlights and bindings to light the drops) */
    void createLights();

    /** function to retrieve a pointer to the rainLightManager associate with this CloseDropsParticles */
    RainLightManager *getLightManagerPtr();

    /** function which updates the lights, if they are animated */
    void updateLights();

    /** function which creates the position texture and it's backup. should be called when initiaiting the rendering of the first frame (through frame listener) */
    void definePosTextureAndBackup();

    /** control function, to check what the textures look like */
    void makeControlOverlay();

    /** function to update one of the two position RTT's ; if set to true, the primary texture will be updated */
    void updatePositionTexture(bool primary);

    /** function to update the different shader parameters used to update the particles positions, or render them */
    void updateFragmentProgramParameter(const String &name, float value);
    /** function to update the different shader parameters used to update the particles positions, or render them */
    void updateFragmentProgramParameter(const String &name, Ogre::Vector3 value);
    /** function to update the different shader parameters used to update the particles positions, or render them */
    void updateFragmentProgramParameter(const String &name, Ogre::Vector4 value);
    /** function to update the different shader parameters used to update the particles positions, or render them */

    /** function to update the different shader parameters used to update the particles positions, or render them */
    void updateShaderParameters(float tslf, float rainBbSide, float streaksHeight, int nbLights,
                                Vector3 viewPos, Vector3 viewDir, Vector3 fallVect, Vector3 boxMin, Vector3 boxMax, Vector3 lastMove, Vector3 randomMove, int useShader);


    /** function to update the different shader parameters used to update the particles positions, or render them */
    void updateTimeSinceLastFrame(float tslf);
    /** function to update the different shader parameters used to update the particles positions, or render them */
    void updateRainBilboardSideLength(float rainBbSide);
    /** function to update the different shader parameters used to update the particles positions, or render them */
    void updateStreaksHeight(float streaksHeight);
    /** function to update the different shader parameters used to update the particles positions, or render them */
    void updateLightCount(float nbLights);
    /** function to update the different shader parameters used to update the particles positions, or render them */
    void updateViewPos(Vector3 viewPos);
    /** function to update the different shader parameters used to update the particles positions, or render them */
    void updateViewDir(Vector3 viewDir);
    /** function to update the different shader parameters used to update the particles positions, or render them */
    void updateFallVector(Vector3 fallVect);
    /** function to update the different shader parameters used to update the particles positions, or render them */
    void updateBoxMin(Vector3 boxMin);
    /** function to update the different shader parameters used to update the particles positions, or render them */
    void updateBoxMax(Vector3 boxMax);
    /** function to update the different shader parameters used to update the particles positions, or render them */
    void updateLastMove(Vector3 lastMove);
    /** function to update the different shader parameters used to update the particles positions, or render them */
    void updateRandomMove(Vector3 randomMove);

    /** functions which hide the particle position billboards.
        billboards must be hidden when rendering the scene, and visible when updating the position texture */
    void hidePositionBillboards()
    {
        bbSet1->setVisible(false);
        bbSet2->setVisible(false);
    }
    /** functions which show the particle position billboards.
        billboards must be hidden when rendering the scene, and visible when updating the position texture */
    void showPositionBillboards()
    {
        bbSet1->setVisible(true);
        bbSet2->setVisible(true);
    }

private :

    /** this function defines the material used to texture the particles */
    void createMaterial(String name);

    /** creation of the auxiliary camera used to texture our particles */
    Camera* createDropsCamera();

    /** definition of the shader parameters used for the particles material */
    void GPUmaterial();
    
    /** function used to initialize the position texture */
    void initializeBillboardsPositionTexture();
    
    /** function which creates a simple quad mesh to use on our hardware billboards */
    MeshPtr createHardwareBillboardMesh(String materialName, String meshName=BILLBOARD_MESH_NAME);

    /** function to update a billboard mesh created as a manual resource, used to give it the appropriate texture coordinates */
    void modifyClonedHardwareBillboardMesh(MeshPtr &msh, int partNumber);

    /** function which initializes the vertex buffers and textures */
    void initParticles();
    
    /** function which defines the position renderTexture */
    void createBillboardsPositionRenderTexture(RenderTexture *PSPosTexture, Vector3 nodePos, BillboardSet *bbSet);

    /** function which defines the material used to update the particles position texture */
    void createBillboardsPositionTextureMaterial(String inputTextureName);
};




#endif // __RAIN_CLOSE_DROPS_PARTICLES__