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

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

OglViewerWidget::OglViewerWidget(QWidget *parent) :
	QOpenGLWidget(parent),
	geometries(0),
	texture(0)
{
	setFocus();
}

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

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();
	}
}

void OglViewerWidget::keyPressEvent(QKeyEvent *e)
{
	if (e->key() == Qt::Key_Space)
		m_rotation = QQuaternion();

	update();
}

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

	glClearColor(0, 0, 0, 1);

	initShaders();
	initTextures();

	// Enable depth buffer
	glEnable(GL_DEPTH_TEST);

	// Enable back face culling
	glEnable(GL_CULL_FACE);

	geometries = new GeometryEngine;

}

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

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

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

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

void OglViewerWidget::initTextures()
{
	// Load cube.png image
	texture = new QOpenGLTexture(QImage(":images/cube.png").mirrored());

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

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

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

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 = 3.0, zFar = 7.0, 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);

	texture->bind();

	// Calculate model view transformation
	QMatrix4x4 matrix;
	matrix.translate(0.0, 0.0, -5.0);
	matrix.rotate(m_rotation);

	// Set modelview-projection matrix
	program.setUniformValue("mvp_matrix", m_projection * matrix);

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

	// Draw cube geometry
	geometries->drawCubeGeometry(&program);
}