/****************************************************************************

**

** 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.

**

**

**

** $QT_END_LICENSE$

**

****************************************************************************/

#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();

}

Node *Edge::sourceNode() const

{

    return source;

}

Node *Edge::destNode() const

{

    return dest;

}

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);        

}