#include "..\Header\GeometryEngine.h"
#include "..\Header\MshFile.h"


/////////////////////////////////////////////////////////////////////////
// public constructor/destructor

GeometryEngine::GeometryEngine()
	: m_indexBuf(QOpenGLBuffer::IndexBuffer)
{
	initializeOpenGLFunctions();

	// Generate 2 VBOs
	m_arrayBuf.create();
	m_indexBuf.create();

	// Initializes cube geometry and transfers it to VBOs
	initCubeGeometry();
}

GeometryEngine::~GeometryEngine()
{
	m_arrayBuf.destroy();
	m_indexBuf.destroy();

	for (auto it : m_textures)
		delete it;
	m_textures.clear();
	m_textures.squeeze();
}


/////////////////////////////////////////////////////////////////////////
// private functions

void GeometryEngine::initCubeGeometry()
{

	try
	{
		MshFile file("..\\Release\\Msh\\cubeTex.msh");
		m_models = file.getModels();
		//TODO use models local, apply MVP directly to the vertex, save size and tex index info

		//TODO: handle the textures
	}
	catch (std::invalid_argument e)
	{
		//TODO: make a cool message box
		auto msg = e.what();
	}

	// Transfer vertex data to VBO 0
	m_arrayBuf.bind();
	m_arrayBuf.allocate(m_models->first()->segmList.front()->vertices.data(), m_models->first()->segmList.front()->vertices.size() * sizeof(VertexData));

	// Transfer index data to VBO 1
	m_indexBuf.bind();
	m_indexBuf.allocate(m_models->first()->segmList.front()->indices.data(), m_models->first()->segmList.front()->indices.size() * sizeof(GLuint));

	// load the texture
	initTexture();
}

void GeometryEngine::initTexture()
{
	// Load cube.png image
	QOpenGLTexture* new_texture = new QOpenGLTexture(QImage(":images/cube.png").mirrored());

	// Set nearest filtering mode for texture minification
	new_texture->setMinificationFilter(QOpenGLTexture::Nearest);

	// Set bilinear filtering mode for texture magnification
	new_texture->setMagnificationFilter(QOpenGLTexture::Linear);

	// Wrap texture coordinates by repeating
	// f.ex. texture coordinate (1.1, 1.2) is same as (0.1, 0.2)
	new_texture->setWrapMode(QOpenGLTexture::Repeat);

	m_textures.push_back(new_texture);
}


/////////////////////////////////////////////////////////////////////////
// public functions

void GeometryEngine::drawGeometry(QOpenGLShaderProgram *program)
{
	// Tell OpenGL which VBOs to use
	m_arrayBuf.bind();
	m_indexBuf.bind();
	m_textures.first()->bind();

	// Use texture unit 0 which contains cube.png
	program->setUniformValue("texture", 0);

	// Offset for position
	quintptr offset = 0;

	// Tell OpenGL programmable pipeline how to locate vertex position data
	int vertexLocation = program->attributeLocation("a_position");
	program->enableAttributeArray(vertexLocation);
	program->setAttributeBuffer(vertexLocation, GL_FLOAT, offset, 3, sizeof(VertexData));

	// Offset for texture coordinate
	offset += sizeof(QVector3D);

	// Tell OpenGL programmable pipeline how to locate vertex texture coordinate data
	int texcoordLocation = program->attributeLocation("a_texcoord");
	program->enableAttributeArray(texcoordLocation);
	program->setAttributeBuffer(texcoordLocation, GL_FLOAT, offset, 2, sizeof(VertexData));

	// Draw cube geometry using indices from VBO 1
	glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0);
}