/****************************************************************************
**
** Copyright (C) 2006-2007 Trolltech ASA. All rights reserved.
**
** This file is part of the example classes of the Qt Toolkit.
**
** Licensees holding a valid Qt License Agreement may use this file in
** accordance with the rights, responsibilities and obligations
** contained therein.  Please consult your licensing agreement or
** contact sales@trolltech.com if any conditions of this licensing
** agreement are not clear to you.
**
** Further information about Qt licensing is available at:
** http://www.trolltech.com/products/qt/licensing.html or by
** contacting info@trolltech.com.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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****************************************************************************/

#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();
    QPointF edgeOffset((line.dx() * 15) / length, (line.dy() * 15) / length);

    prepareGeometryChange();
    sourcePoint = line.p1() + edgeOffset;
    destPoint = line.p2() - edgeOffset;
}

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;

    adjust();

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

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

    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.p2() << destArrowP1 << destArrowP2);        
}