#include "..\Header\OglViewerWidget.h"

#include <QMouseEvent>
#include <math.h>
#include <iostream>

#define DEFAULT_Z_DISTANCE -5.0


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

OglViewerWidget::OglViewerWidget(QWidget *parent) :
	QOpenGLWidget(parent),
	m_dataEngine(0)
{
	setFocus();
	m_translation.setZ(DEFAULT_Z_DISTANCE);
}

OglViewerWidget::~OglViewerWidget()
{
	// Make sure the context is current when deleting the texture
	// and the buffers.
	makeCurrent();
	delete m_dataEngine;
	doneCurrent();
}


/////////////////////////////////////////////////////////////////////////
// protected functions

void OglViewerWidget::mousePressEvent(QMouseEvent *e)
{
	// Save mouse press position
	m_mouse.position = QVector2D(e->localPos());

	// Which button has been pressed?
	if (e->button() == Qt::LeftButton)
		m_mouse.left = true;
	else if (e->button() == Qt::RightButton)
		m_mouse.right = true;
}

void OglViewerWidget::mouseReleaseEvent(QMouseEvent *e)
{
	if (e->button() == Qt::LeftButton)
		m_mouse.left = false;
	else if (e->button() == Qt::RightButton)
		m_mouse.right = false;
}

void OglViewerWidget::mouseMoveEvent(QMouseEvent *e)
{
	if (m_mouse.left)
	{
		// get the difference between last press and now
		QVector2D diff = QVector2D(e->localPos()) - m_mouse.position;

		// update the new position
		m_mouse.position = QVector2D(e->localPos());

		// calculate the rotation axis and rotate
		m_rotation = QQuaternion::fromAxisAndAngle(QVector3D(diff.y(), diff.x(), 0.0).normalized(), diff.length() * 0.5) * m_rotation;

		// request an update
		update();
	}
	else if (m_mouse.right)
	{
		// get the difference between last press and now
		QVector2D diff = QVector2D(e->localPos()) - m_mouse.position;

		// update the new position
		m_mouse.position = QVector2D(e->localPos());

		// calculate the translation
		m_translation += {(float)(diff.x() * 0.01), (float)(diff.y() * -0.01), 0.0};

		// request an update
		update();
	}
}

void OglViewerWidget::wheelEvent(QWheelEvent *e)
{
	m_translation += {0.0, 0.0, (float)e->angleDelta().y() / 240};
	update();
}

void OglViewerWidget::keyPressEvent(QKeyEvent *e)
{
	if (e->key() == Qt::Key_Space)
	{
		m_rotation = QQuaternion();
		m_translation = { 0.0, 0.0, DEFAULT_Z_DISTANCE };
	}
	update();
}

void OglViewerWidget::initializeGL()
{
	initializeOpenGLFunctions();

	glClearColor(0, 0, 0, 1);

	initShaders();

	// Enable depth buffer
	glEnable(GL_DEPTH_TEST);

	// Enable back face culling
	glEnable(GL_CULL_FACE);

	m_dataEngine = new GeometryEngine;

}

void OglViewerWidget::resizeGL(int w, int h)
{
	// Calculate aspect ratio
	qreal aspect = qreal(w) / qreal(h ? h : 1);

	// Set near plane to 3.0, far plane to 7.0, field of view 45 degrees
	const qreal zNear = 0.1, zFar = 100.0, fov = 45.0;

	// Reset projection
	m_projection.setToIdentity();

	// Set perspective projection
	m_projection.perspective(fov, aspect, zNear, zFar);
}

void OglViewerWidget::paintGL()
{
	// Clear color and depth buffer
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	// Calculate model view transformation
	QMatrix4x4 view;
	view.translate(m_translation);
	view.rotate(m_rotation);

	// Set view-projection matrix
	m_program.setUniformValue("vp_matrix", m_projection * view);

	// Draw cube geometry
	m_dataEngine->drawGeometry(&m_program);
}


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

void OglViewerWidget::initShaders()
{
	// Compile vertex shader
	if (!m_program.addShaderFromSourceFile(QOpenGLShader::Vertex, ":/shaders/vshader.glsl"))
		close();

	// Compile fragment shader
	if (!m_program.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/shaders/fshader.glsl"))
		close();

	// Link shader pipeline
	if (!m_program.link())
		close();

	// Bind shader pipeline for use
	if (!m_program.bind())
		close();
}


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