#include <osg/Vec3>
#include <osg/Vec4>
#include <osg/Quat>
#include <osg/Matrix>
#include <osg/ShapeDrawable>
#include <osg/Geometry>
#include <osg/Geode>
#include <osg/Texture2D>

#include <osgDB/FileUtils>
#include <osgDB/ReadFile>

#include <osgUtil/Optimizer>

#include <osgViewer/Viewer>
#include <osgViewer/ViewerEventHandlers>

#include <iostream>

// for the grid data..
#include "../osghangglide/terrain_coords.h"

///////////////////////////////////////////////////////////////////
// vertex shader using just Vec4 coefficients
char vertexShaderSource_simple[] = 
    "uniform vec4 coeff; \n"
    "\n"
    "void main(void) \n"
    "{ \n"
    "\n"
    "    gl_TexCoord[0] = gl_Vertex; \n"
    "    vec4 vert = gl_Vertex; \n"
    "    vert.z = gl_Vertex.x*coeff[0] + gl_Vertex.x*gl_Vertex.x* coeff[1] + \n"
    "             gl_Vertex.y*coeff[2] + gl_Vertex.y*gl_Vertex.y* coeff[3]; \n"
    "    gl_Position = gl_ModelViewProjectionMatrix * vert;\n"
    "}\n";
  
  
//////////////////////////////////////////////////////////////////
// vertex shader using full Matrix4 coefficients
char vertexShaderSource_matrix[] = 
    "uniform vec4  origin; \n"
    "uniform mat4  coeffMatrix; \n"
    "\n"
    "void main(void) \n"
    "{ \n"
    "\n"
    "    gl_TexCoord[0] = gl_Vertex; \n"
    "    vec4 v = vec4(gl_Vertex.x, gl_Vertex.x*gl_Vertex.x, gl_Vertex.y, gl_Vertex.y*gl_Vertex.y ); \n"
    "    gl_Position = gl_ModelViewProjectionMatrix * (origin + coeffMatrix * v);\n"
    "}\n";

//////////////////////////////////////////////////////////////////
// vertex shader using texture read
char vertexShaderSource_texture[] = 
    "uniform sampler2D vertexTexture; \n"
    "\n"
    "void main(void) \n"
    "{ \n"
    "\n"
    "    gl_TexCoord[0] = gl_Vertex; \n"
    "    vec4 vert = gl_Vertex; \n"
    "    vert.z = texture2D( vertexTexture, gl_TexCoord[0].xy).x*0.0001; \n"
    "    gl_Position = gl_ModelViewProjectionMatrix * vert;\n"
    "}\n";


//////////////////////////////////////////////////////////////////
// fragment shader
//
char fragmentShaderSource[] = 
    "uniform sampler2D baseTexture; \n"
    "\n"
    "void main(void) \n"
    "{ \n"
    "    gl_FragColor = texture2D( baseTexture, gl_TexCoord[0].xy); \n"
    "}\n";



class UniformVarying : public osg::Uniform::Callback
{
    virtual void operator () (osg::Uniform* uniform, osg::NodeVisitor* nv)
    {
        const osg::FrameStamp* fs = nv->getFrameStamp();
        float value = sinf(fs->getSimulationTime());
        uniform->set(osg::Vec4(value,-value,-value,value));
    }
};

osg::Node* createModel(const std::string& shader, const std::string& textureFileName, const std::string& terrainFileName, bool dynamic, bool vbo)
{
    osg::Geode* geode = new osg::Geode;
    
    osg::Geometry* geom = new osg::Geometry;
    geode->addDrawable(geom);
    
    // dimensions for ~one million triangles :-)
    unsigned int num_x = 708;
    unsigned int num_y = 708;

    // set up state
    {
    
        osg::StateSet* stateset = geom->getOrCreateStateSet();

        osg::Program* program = new osg::Program;
        stateset->setAttribute(program);

        if (shader=="simple")
        {
            osg::Shader* vertex_shader = new osg::Shader(osg::Shader::VERTEX, vertexShaderSource_simple);
            program->addShader(vertex_shader);

            osg::Uniform* coeff = new osg::Uniform("coeff",osg::Vec4(1.0,-1.0f,-1.0f,1.0f));
            
            stateset->addUniform(coeff);

            if (dynamic)
            {
                coeff->setUpdateCallback(new UniformVarying);
                coeff->setDataVariance(osg::Object::DYNAMIC);
                stateset->setDataVariance(osg::Object::DYNAMIC);
            }
            
        }
        else if (shader=="matrix")
        {
            osg::Shader* vertex_shader = new osg::Shader(osg::Shader::VERTEX, vertexShaderSource_matrix);
            program->addShader(vertex_shader);

            osg::Uniform* origin = new osg::Uniform("origin",osg::Vec4(0.0f,0.0f,0.0f,1.0f));
            stateset->addUniform(origin);

            osg::Uniform* coeffMatrix = new osg::Uniform("coeffMatrix",
                osg::Matrix(1.0f,0.0f,1.0f,0.0f,
                            0.0f,0.0f,-1.0f,0.0f,
                            0.0f,1.0f,-1.0f,0.0f,
                            0.0f,0.0f,1.0f,0.0f));

            stateset->addUniform(coeffMatrix);
        }
        else if (shader=="texture")
        {
            osg::Shader* vertex_shader = new osg::Shader(osg::Shader::VERTEX, vertexShaderSource_texture);
            program->addShader(vertex_shader);

            osg::Image* image = 0;

            if (terrainFileName.empty())
            {
                image = new osg::Image;
                unsigned int tx = 38;
                unsigned int ty = 39;
                image->allocateImage(tx,ty,1,GL_LUMINANCE,GL_FLOAT,1);
                for(unsigned int r=0;r<ty;++r)
                {
                    for(unsigned int c=0;c<tx;++c)
                    {
                        *((float*)image->data(c,r)) = vertex[r+c*39][2]*0.1;
                    }
                }

                num_x = tx;
                num_y = tx;
            }
            else
            {
                image = osgDB::readImageFile(terrainFileName);

                num_x = image->s();
                num_y = image->t();
            }

            osg::Texture2D* vertexTexture = new osg::Texture2D(image);


            vertexTexture->setFilter(osg::Texture::MIN_FILTER,osg::Texture::NEAREST);
            vertexTexture->setFilter(osg::Texture::MAG_FILTER,osg::Texture::NEAREST);
            vertexTexture->setInternalFormat(GL_LUMINANCE_FLOAT32_ATI);
            stateset->setTextureAttributeAndModes(1,vertexTexture);

            osg::Uniform* vertexTextureSampler = new osg::Uniform("vertexTexture",1);
            stateset->addUniform(vertexTextureSampler);

        }

        osg::Shader* fragment_shader = new osg::Shader(osg::Shader::FRAGMENT, fragmentShaderSource);
        program->addShader(fragment_shader);

        osg::Texture2D* texture = new osg::Texture2D(osgDB::readImageFile(textureFileName));
        stateset->setTextureAttributeAndModes(0,texture);

        osg::Uniform* baseTextureSampler = new osg::Uniform("baseTexture",0);
        stateset->addUniform(baseTextureSampler);

    }


    // set up geometry data.

    osg::Vec3Array* vertices = new osg::Vec3Array( num_x * num_y );
    
    float dx = 1.0f/(float)(num_x-1);
    float dy = 1.0f/(float)(num_y-1);
    osg::Vec3 row(0.0f,0.0f,0.0);
    
    unsigned int vert_no = 0;
    unsigned int iy;
    for(iy=0; iy<num_y; ++iy)
    {
        osg::Vec3 column = row;
        for(unsigned int ix=0;ix<num_x;++ix)
        {
            (*vertices)[vert_no++] = column;
            column.x() += dx;
        }        
        row.y() += dy;
    }

    geom->setVertexArray(vertices);

    osg::VertexBufferObject* vbObject = new osg::VertexBufferObject;
    vertices->setVertexBufferObject(vbObject);
    
    osg::ElementBufferObject* ebo = new osg::ElementBufferObject;

    for(iy=0; iy<num_y-1; ++iy)
    {
        unsigned int element_no = 0;
        osg::DrawElementsUInt* elements = new osg::DrawElementsUInt(GL_TRIANGLE_STRIP, num_x*2);
        unsigned int index = iy * num_x;
        for(unsigned int ix = 0; ix<num_x; ++ix)
        {
            (*elements)[element_no++] = index + num_x;
            (*elements)[element_no++] = index++;
        }
        geom->addPrimitiveSet(elements); 
        
        if (ebo) elements->setElementBufferObject(ebo);   
    }
    
    geom->setUseVertexBufferObjects(vbo);

    return geode;
}

int main(int argc, char *argv[])
{
    // use an ArgumentParser object to manage the program arguments.
    osg::ArgumentParser arguments(&argc,argv);

    // set up the usage document, in case we need to print out how to use this program.
    arguments.getApplicationUsage()->setDescription(arguments.getApplicationName()+" is the example which demonstrate support for ARB_vertex_program.");
    arguments.getApplicationUsage()->setCommandLineUsage(arguments.getApplicationName()+" [options] filename ...");
    arguments.getApplicationUsage()->addCommandLineOption("-h or --help","Display this information");
   
    // construct the viewer.
    osgViewer::Viewer viewer;

    // add the stats handler
    viewer.addEventHandler(new osgViewer::StatsHandler);

    std::string shader("simple");
    while(arguments.read("-s",shader)) {}
    
    std::string textureFileName("Images/lz.rgb");
    while(arguments.read("-t",textureFileName)) {}

    std::string terrainFileName("");
    while(arguments.read("-d",terrainFileName)) {}

    bool dynamic = true;
    while(arguments.read("--static")) { dynamic = false; }

    bool vbo = false;
    while(arguments.read("--vbo")) { vbo = true; }

    // if user request help write it out to cout.
    if (arguments.read("-h") || arguments.read("--help"))
    {
        arguments.getApplicationUsage()->write(std::cout);
        return 1;
    }
    
    // load the nodes from the commandline arguments.
    osg::Node* model = createModel(shader,textureFileName,terrainFileName, dynamic, vbo);
    if (!model)
    {
        return 1;
    }
    
    viewer.setSceneData(model);

    return viewer.run();
}
