#include "Render_Utils.h"

#include <algorithm>

#include "glew.h"
#include "freeglut.h"


void Core::RenderContext::initFromOBJ(obj::Model& model)
{
    vertexArray = 0;
    vertexBuffer = 0;
    vertexIndexBuffer = 0;
    unsigned int vertexDataBufferSize = sizeof(float) * model.vertex.size();
    unsigned int vertexNormalBufferSize = sizeof(float) * model.normal.size();
    unsigned int vertexTexBufferSize = sizeof(float) * model.texCoord.size();

    size = model.faces["default"].size();
    unsigned int vertexElementBufferSize = sizeof(unsigned short) * size;


    glGenVertexArrays(1, &vertexArray);
    glBindVertexArray(vertexArray);


    glGenBuffers(1, &vertexIndexBuffer);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vertexIndexBuffer);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, vertexElementBufferSize, &model.faces["default"][0], GL_STATIC_DRAW);

    glGenBuffers(1, &vertexBuffer);
    glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);

    glEnableVertexAttribArray(0);
    glEnableVertexAttribArray(1);
    glEnableVertexAttribArray(2);
    
    glBufferData(GL_ARRAY_BUFFER, vertexDataBufferSize + vertexNormalBufferSize + vertexTexBufferSize, NULL, GL_STATIC_DRAW);

    glBufferSubData(GL_ARRAY_BUFFER, 0, vertexDataBufferSize, &model.vertex[0]);

    glBufferSubData(GL_ARRAY_BUFFER, vertexDataBufferSize, vertexNormalBufferSize, &model.normal[0]);

    glBufferSubData(GL_ARRAY_BUFFER, vertexDataBufferSize + vertexNormalBufferSize, vertexTexBufferSize, &model.texCoord[0]);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)(0));
    glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, 0, (void*)(vertexDataBufferSize));
    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, (void*)(vertexNormalBufferSize + vertexDataBufferSize));
}

void Core::DrawVertexArray(const float * vertexArray, int numVertices, int elementSize )
{
	glVertexAttribPointer(0, elementSize, GL_FLOAT, false, 0, vertexArray);
	glEnableVertexAttribArray(0);

	glDrawArrays(GL_TRIANGLES, 0, numVertices);
}

void Core::DrawVertexArrayIndexed( const float * vertexArray, const int * indexArray, int numIndexes, int elementSize )
{
	glVertexAttribPointer(0, elementSize, GL_FLOAT, false, 0, vertexArray);
	glEnableVertexAttribArray(0);

	glDrawElements(GL_TRIANGLES, numIndexes, GL_UNSIGNED_INT, indexArray);
}


//void Core::DrawVertexArray( const VertexData & data )
//{
//	int numAttribs = std::min(VertexData::MAX_ATTRIBS, data.NumActiveAttribs);
//	for(int i = 0; i < numAttribs; i++)
//	{
//		glVertexAttribPointer(i, data.Attribs[i].Size, GL_FLOAT, false, 0, data.Attribs[i].Pointer);
//		glEnableVertexAttribArray(i);
//	}
//	glDrawArrays(GL_TRIANGLES, 0, data.NumVertices);
//}

void Core::DrawContext(Core::RenderContext& context)
{

	glBindVertexArray(context.vertexArray);
	glDrawElements(
		GL_TRIANGLES,      // mode
		context.size,    // count
		GL_UNSIGNED_SHORT,   // type
		(void*)0           // element array buffer offset
	);
	glBindVertexArray(0);
}