/****************************************************************************
**
** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the examples of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the Technology Preview License Agreement accompanying
** this package.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights.  These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
**
**
**
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include <QPainter>

#include "edge.h"
#include "node.h"

#include <math.h>

static const double Pi = 3.14159265358979323846264338327950288419717;
static double TwoPi = 2.0 * Pi;

Edge::Edge(Node *sourceNode, Node *destNode)
    : arrowSize(10)
{
    setAcceptedMouseButtons(0);
    source = sourceNode;
    dest = destNode;
    source->addEdge(this);
    dest->addEdge(this);
    adjust();
}

Edge::~Edge()
{
}

Node *Edge::sourceNode() const
{
    return source;
}

void Edge::setSourceNode(Node *node)
{
    source = node;
    adjust();
}

Node *Edge::destNode() const
{
    return dest;
}

void Edge::setDestNode(Node *node)
{
    dest = node;
    adjust();
}

void Edge::adjust()
{
    if (!source || !dest)
        return;

    QLineF line(mapFromItem(source, 0, 0), mapFromItem(dest, 0, 0));
    qreal length = line.length();

    prepareGeometryChange();

    if (length > qreal(20.)) {
        QPointF edgeOffset((line.dx() * 10) / length, (line.dy() * 10) / length);
        sourcePoint = line.p1() + edgeOffset;
        destPoint = line.p2() - edgeOffset;
    } else {
        sourcePoint = destPoint = line.p1();
    }
}

QRectF Edge::boundingRect() const
{
    if (!source || !dest)
        return QRectF();

    qreal penWidth = 1;
    qreal extra = (penWidth + arrowSize) / 2.0;

    return QRectF(sourcePoint, QSizeF(destPoint.x() - sourcePoint.x(),
                                      destPoint.y() - sourcePoint.y()))
        .normalized()
        .adjusted(-extra, -extra, extra, extra);
}

void Edge::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *)
{
    if (!source || !dest)
        return;

    QLineF line(sourcePoint, destPoint);
    if (qFuzzyCompare(line.length(), qreal(0.)))
        return;

    // Draw the line itself
    painter->setPen(QPen(Qt::black, 1, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin));
    painter->drawLine(line);

    // Draw the arrows
    double angle = ::acos(line.dx() / line.length());
    if (line.dy() >= 0)
        angle = TwoPi - angle;

    QPointF sourceArrowP1 = sourcePoint + QPointF(sin(angle + Pi / 3) * arrowSize,
                                                  cos(angle + Pi / 3) * arrowSize);
    QPointF sourceArrowP2 = sourcePoint + QPointF(sin(angle + Pi - Pi / 3) * arrowSize,
                                                  cos(angle + Pi - Pi / 3) * arrowSize);   
    QPointF destArrowP1 = destPoint + QPointF(sin(angle - Pi / 3) * arrowSize,
                                              cos(angle - Pi / 3) * arrowSize);
    QPointF destArrowP2 = destPoint + QPointF(sin(angle - Pi + Pi / 3) * arrowSize,
                                              cos(angle - Pi + Pi / 3) * arrowSize);

    painter->setBrush(Qt::black);
    painter->drawPolygon(QPolygonF() << line.p1() << sourceArrowP1 << sourceArrowP2);
    painter->drawPolygon(QPolygonF() << line.p2() << destArrowP1 << destArrowP2);        
}
