/***************************************************************************
 *   Copyright 2010 Stefan Majewsky <majewsky@gmx.net>                     *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU Library General Public License          *
 *   version 2 as published by the Free Software Foundation                *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU Library General Public License for more details.                  *
 *                                                                         *
 *   You should have received a copy of the GNU Library General Public     *
 *   License along with this program; if not, write to the                 *
 *   Free Software Foundation, Inc.,                                       *
 *   51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.         *
 ***************************************************************************/

#include "kgamerenderedobjectitem.h"
#include "kgamerenderer.h"

#include <QtMath>
#include <QGraphicsView>

class KGameRenderedObjectItemPrivate : public QGraphicsPixmapItem
{
	public:
		KGameRenderedObjectItemPrivate(KGameRenderedObjectItem* parent);
		bool adjustRenderSize(); //returns whether an adjustment was made; WARNING: only call when m_primaryView != 0
		void adjustTransform();

		//QGraphicsItem reimplementations (see comment below for why we need all of this)
		bool contains(const QPointF& point) const override;
		bool isObscuredBy(const QGraphicsItem* item) const override;
		QPainterPath opaqueArea() const override;
		void paint(QPainter* painter, const QStyleOptionGraphicsItem* option, QWidget* widget = nullptr) override;
		QPainterPath shape() const override;
	public:
		KGameRenderedObjectItem* m_parent;
		QGraphicsView* m_primaryView;
		QSize m_correctRenderSize;
		QSizeF m_fixedSize;
};

KGameRenderedObjectItemPrivate::KGameRenderedObjectItemPrivate(KGameRenderedObjectItem* parent)
	: QGraphicsPixmapItem(parent)
	, m_parent(parent)
	, m_primaryView(nullptr)
	, m_correctRenderSize(0, 0)
	, m_fixedSize(-1, -1)
{
}

static inline int vectorLength(const QPointF& point)
{
	return qSqrt(point.x() * point.x() + point.y() * point.y());
}

bool KGameRenderedObjectItemPrivate::adjustRenderSize()
{
	Q_ASSERT(m_primaryView);
	//create a polygon from the item's boundingRect
	const QRectF itemRect = m_parent->boundingRect();
	QPolygonF itemPolygon(3);
	itemPolygon[0] = itemRect.topLeft();
	itemPolygon[1] = itemRect.topRight();
	itemPolygon[2] = itemRect.bottomLeft();
	//determine correct render size
	const QPolygonF scenePolygon = m_parent->sceneTransform().map(itemPolygon);
	const QPolygon viewPolygon = m_primaryView->mapFromScene(scenePolygon);
	m_correctRenderSize.setWidth(qMax(vectorLength(viewPolygon[1] - viewPolygon[0]), 1));
	m_correctRenderSize.setHeight(qMax(vectorLength(viewPolygon[2] - viewPolygon[0]), 1));
	//ignore fluctuations in the render size which result from rounding errors
	const QSize diff = m_parent->renderSize() - m_correctRenderSize;
	if (qAbs(diff.width()) <= 1 && qAbs(diff.height()) <= 1)
	{
		return false;
	}
	m_parent->setRenderSize(m_correctRenderSize);
	adjustTransform();
	return true;
}

void KGameRenderedObjectItemPrivate::adjustTransform()
{
	//calculate new transform for this item
	QTransform t;
	t.scale(m_fixedSize.width() / m_correctRenderSize.width(), m_fixedSize.height() / m_correctRenderSize.height());
	//render item
	m_parent->prepareGeometryChange();
	setTransform(t);
	m_parent->update();
}

KGameRenderedObjectItem::KGameRenderedObjectItem(KGameRenderer* renderer, const QString& spriteKey, QGraphicsItem* parent)
	: QGraphicsObject(parent)
	, KGameRendererClient(renderer, spriteKey)
	, d(new KGameRenderedObjectItemPrivate(this))
{
	setPrimaryView(renderer->defaultPrimaryView());
}

KGameRenderedObjectItem::~KGameRenderedObjectItem()
{
	delete d;
}

QPointF KGameRenderedObjectItem::offset() const
{
	return d->pos();
}

void KGameRenderedObjectItem::setOffset(const QPointF& offset)
{
	if (d->pos() != offset)
	{
		prepareGeometryChange();
		d->setPos(offset);
		update();
	}
}

void KGameRenderedObjectItem::setOffset(qreal x, qreal y)
{
	setOffset(QPointF(x, y));
}

QSizeF KGameRenderedObjectItem::fixedSize() const
{
	return d->m_fixedSize;
}

void KGameRenderedObjectItem::setFixedSize(const QSizeF& fixedSize)
{
	if (d->m_primaryView)
	{
		d->m_fixedSize = fixedSize.expandedTo(QSize(1, 1));
		d->adjustTransform();
	}
}

QGraphicsView* KGameRenderedObjectItem::primaryView() const
{
	return d->m_primaryView;
}

void KGameRenderedObjectItem::setPrimaryView(QGraphicsView* view)
{
	if (d->m_primaryView != view)
	{
		d->m_primaryView = view;
		if (view)
		{
			if (!d->m_fixedSize.isValid())
			{
				d->m_fixedSize = QSize(1, 1);
			}
			//determine render size and adjust coordinate system
			d->m_correctRenderSize = QSize(-10, -10); //force adjustment to be made
			d->adjustRenderSize();
		}
		else
		{
			d->m_fixedSize = QSize(-1, -1);
			//reset transform to make coordinate systems of this item and the private item equal
			prepareGeometryChange();
			d->setTransform(QTransform());
			update();
		}
	}
}

void KGameRenderedObjectItem::receivePixmap(const QPixmap& pixmap)
{
	prepareGeometryChange();
	d->setPixmap(pixmap);
	update();
}

//We want to make sure that all interactional events are sent ot this item, and
//not to the contained QGraphicsPixmapItem which provides the visual
//representation (and the metrics calculations).
//At the same time, we do not want the contained QGraphicsPixmapItem to slow
//down operations like QGraphicsScene::collidingItems().
//So the strategy is to use the QGraphicsPixmapItem implementation from
//KGameRenderedObjectItemPrivate for KGameRenderedObjectItem.
//Then the relevant methods in KGameRenderedObjectItemPrivate are reimplemented empty
//to effectively clear the item and hide it from any collision detection. This
//strategy allows us to use the nifty QGraphicsPixmapItem logic without exposing
//a QGraphicsPixmapItem subclass (which would conflict with QGraphicsObject).

//BEGIN QGraphicsItem reimplementation of KGameRenderedObjectItem

QRectF KGameRenderedObjectItem::boundingRect() const
{
	return d->mapRectToParent(d->QGraphicsPixmapItem::boundingRect());
}

bool KGameRenderedObjectItem::contains(const QPointF& point) const
{
	return d->QGraphicsPixmapItem::contains(d->mapFromParent(point));
}

bool KGameRenderedObjectItem::isObscuredBy(const QGraphicsItem* item) const
{
	return d->QGraphicsPixmapItem::isObscuredBy(item);
}

QPainterPath KGameRenderedObjectItem::opaqueArea() const
{
	return d->mapToParent(d->QGraphicsPixmapItem::opaqueArea());
}

void KGameRenderedObjectItem::paint(QPainter* painter, const QStyleOptionGraphicsItem* option, QWidget* widget)
{
	Q_UNUSED(painter) Q_UNUSED(option) Q_UNUSED(widget)
}

QPainterPath KGameRenderedObjectItem::shape() const
{
	return d->mapToParent(d->QGraphicsPixmapItem::shape());
}

//END QGraphicsItem reimplementation of KGameRenderedObjectItem
//BEGIN QGraphicsItem reimplementation of KGameRenderedObjectItemPrivate

bool KGameRenderedObjectItemPrivate::contains(const QPointF& point) const
{
	Q_UNUSED(point)
	return false;
}

bool KGameRenderedObjectItemPrivate::isObscuredBy(const QGraphicsItem* item) const
{
	Q_UNUSED(item)
	return false;
}

QPainterPath KGameRenderedObjectItemPrivate::opaqueArea() const
{
	return QPainterPath();
}

void KGameRenderedObjectItemPrivate::paint(QPainter* painter, const QStyleOptionGraphicsItem* option, QWidget* widget)
{
	//Trivial stuff up to now. The fun stuff starts here. ;-)
	//There is no way to get informed when the viewport's coordinate system
	//(relative to this item's coordinate system) has changed, so we're checking
	//the renderSize in each paintEvent coming from the primary view.
	if (m_primaryView)
	{
		if (m_primaryView == widget || m_primaryView->isAncestorOf(widget))
		{
			const bool isSimpleTransformation = !painter->transform().isRotating();
			//If an adjustment was made, do not paint now, but wait for the next
			//painting. However, paint directly if the transformation is
			//complex, in order to avoid flicker.
			if (adjustRenderSize())
			{
				if (isSimpleTransformation)
				{
					return;
				}
			}
			if (isSimpleTransformation)
			{
				//draw pixmap directly in physical coordinates
				const QPoint basePos = painter->transform().map(QPointF()).toPoint();
				painter->save();
				painter->setTransform(QTransform());
				painter->drawPixmap(basePos, pixmap());
				painter->restore();
				return;
			}
		}
	}
	QGraphicsPixmapItem::paint(painter, option, widget);
}

QPainterPath KGameRenderedObjectItemPrivate::shape() const
{
	return QPainterPath();
}

//END QGraphicsItem reimplementation of KGameRenderedObjectItemPrivate