/*
 *   Copyright (C) 2007 Luca Gugelmann <lucag@student.ethz.ch>
 *
 *   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 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 "regiongrabber.h"

#include <QPainter>
#include <QMouseEvent>
#include <QApplication>
#include <QDesktopWidget>
#include <QToolTip>
#include <QTimer>

#include <klocale.h>
#include <KWindowSystem>

RegionGrabber::RegionGrabber( const QRect &startSelection ) :
    QWidget( 0, Qt::X11BypassWindowManagerHint | Qt::WindowStaysOnTopHint | Qt::FramelessWindowHint | Qt::Tool ),
    selection( startSelection ), mouseDown( false ), newSelection( false ),
    handleSize( 10 ), mouseOverHandle( 0 ),
    showHelp( true ), grabbing( false ),
    TLHandle(0,0,handleSize,handleSize), TRHandle(0,0,handleSize,handleSize),
    BLHandle(0,0,handleSize,handleSize), BRHandle(0,0,handleSize,handleSize),
    LHandle(0,0,handleSize,handleSize), THandle(0,0,handleSize,handleSize),
    RHandle(0,0,handleSize,handleSize), BHandle(0,0,handleSize,handleSize)
{
    handles << &TLHandle << &TRHandle << &BLHandle << &BRHandle
            << &LHandle << &THandle << &RHandle << &BHandle;
    setMouseTracking( true );
    int timeout = KWindowSystem::compositingActive() ? 200 : 50;
    QTimer::singleShot( timeout, this, SLOT(init()) );
}

RegionGrabber::~RegionGrabber()
{
}

void RegionGrabber::init()
{
    pixmap = QPixmap::grabWindow( QApplication::desktop()->winId() );
    resize( pixmap.size() );
    move( 0, 0 );
    setCursor( Qt::CrossCursor );
    show();
    grabMouse();
    grabKeyboard();
}

static void drawRect( QPainter *painter, const QRect &r, const QColor &outline, const QColor &fill = QColor() )
{
    QRegion clip( r );
    clip = clip.subtracted( r.adjusted( 1, 1, -1, -1 ) );

    painter->save();
    painter->setClipRegion( clip );
    painter->setPen( Qt::NoPen );
    painter->setBrush( outline );
    painter->drawRect( r );
    if ( fill.isValid() ) {
        painter->setClipping( false );
        painter->setBrush( fill );
        painter->drawRect( r.adjusted( 1, 1, -1, -1 ) );
    }
    painter->restore();
}

void RegionGrabber::paintEvent( QPaintEvent* e )
{
    Q_UNUSED( e );
    if ( grabbing ) // grabWindow() should just get the background
        return;

    QPainter painter( this );

    QPalette pal(QToolTip::palette());
    QFont font = QToolTip::font();

    QColor handleColor = pal.color( QPalette::Active, QPalette::Highlight );
    handleColor.setAlpha( 160 );
    QColor overlayColor( 0, 0, 0, 160 );
    QColor textColor = pal.color( QPalette::Active, QPalette::Text );
    QColor textBackgroundColor = pal.color( QPalette::Active, QPalette::Base );
    painter.drawPixmap(0, 0, pixmap);
    painter.setFont(font);

    QRect r = selection;
    if ( !selection.isNull() )
    {
        QRegion grey( rect() );
        grey = grey.subtracted( r );
        painter.setClipRegion( grey );
        painter.setPen( Qt::NoPen );
        painter.setBrush( overlayColor );
        painter.drawRect( rect() );
        painter.setClipRect( rect() );
        drawRect( &painter, r, handleColor );
    }

    if ( showHelp )
    {
        painter.setPen( textColor );
        painter.setBrush( textBackgroundColor );
        QString helpText = i18n( "Select a region using the mouse. To take the snapshot, press the Enter key or double click. Press Esc to quit." );
        helpTextRect = painter.boundingRect( rect().adjusted( 2, 2, -2, -2 ), Qt::TextWordWrap, helpText );
        helpTextRect.adjust( -2, -2, 4, 2 );
        drawRect( &painter, helpTextRect, textColor, textBackgroundColor );
        painter.drawText( helpTextRect.adjusted( 3, 3, -3, -3 ), helpText );
    }

    if ( selection.isNull() )
    {
        return;
    }

    // The grabbed region is everything which is covered by the drawn
    // rectangles (border included). This means that there is no 0px
    // selection, since a 0px wide rectangle will always be drawn as a line.
    QString txt = QString( "%1x%2" ).arg( selection.width() )
                  .arg( selection.height() );
    QRect textRect = painter.boundingRect( rect(), Qt::AlignLeft, txt );
    QRect boundingRect = textRect.adjusted( -4, 0, 0, 0);

    if ( textRect.width() < r.width() - 2*handleSize &&
         textRect.height() < r.height() - 2*handleSize &&
         ( r.width() > 100 && r.height() > 100 ) ) // center, unsuitable for small selections
    {
        boundingRect.moveCenter( r.center() );
        textRect.moveCenter( r.center() );
    }
    else if ( r.y() - 3 > textRect.height() &&
              r.x() + textRect.width() < rect().right() ) // on top, left aligned
    {
        boundingRect.moveBottomLeft( QPoint( r.x(), r.y() - 3 ) );
        textRect.moveBottomLeft( QPoint( r.x() + 2, r.y() - 3 ) );
    }
    else if ( r.x() - 3 > textRect.width() ) // left, top aligned
    {
        boundingRect.moveTopRight( QPoint( r.x() - 3, r.y() ) );
        textRect.moveTopRight( QPoint( r.x() - 5, r.y() ) );
    }
    else if ( r.bottom() + 3 + textRect.height() < rect().bottom() &&
              r.right() > textRect.width() ) // at bottom, right aligned
    {
        boundingRect.moveTopRight( QPoint( r.right(), r.bottom() + 3 ) );
        textRect.moveTopRight( QPoint( r.right() - 2, r.bottom() + 3 ) );
    }
    else if ( r.right() + textRect.width() + 3 < rect().width() ) // right, bottom aligned
    {
        boundingRect.moveBottomLeft( QPoint( r.right() + 3, r.bottom() ) );
        textRect.moveBottomLeft( QPoint( r.right() + 5, r.bottom() ) );
    }
    // if the above didn't catch it, you are running on a very tiny screen...
    drawRect( &painter, boundingRect, textColor, textBackgroundColor );

    painter.drawText( textRect, txt );

    if ( ( r.height() > handleSize*2 && r.width() > handleSize*2 )
         || !mouseDown )
    {
        updateHandles();
        painter.setPen( Qt::NoPen );
        painter.setBrush( handleColor );
        painter.setClipRegion( handleMask( StrokeMask ) );
        painter.drawRect( rect() );
        handleColor.setAlpha( 60 );
        painter.setBrush( handleColor );
        painter.setClipRegion( handleMask( FillMask ) );
        painter.drawRect( rect() );
    }
}

void RegionGrabber::resizeEvent( QResizeEvent* e )
{
    Q_UNUSED( e );
    if ( selection.isNull() )
        return;
    QRect r = selection;
    r.setTopLeft( limitPointToRect( r.topLeft(), rect() ) );
    r.setBottomRight( limitPointToRect( r.bottomRight(), rect() ) );
    if ( r.width() <= 1 || r.height() <= 1 ) //this just results in ugly drawing...
        selection = QRect();
    else
        selection = normalizeSelection(r);
}

void RegionGrabber::mousePressEvent( QMouseEvent* e )
{
    showHelp = !helpTextRect.contains( e->pos() );
    if ( e->button() == Qt::LeftButton )
    {
        mouseDown = true;
        dragStartPoint = e->pos();
        selectionBeforeDrag = selection;
        if ( !selection.contains( e->pos() ) )
        {
            newSelection = true;
            selection = QRect();
        }
        else
        {
            setCursor( Qt::ClosedHandCursor );
        }
    }
    else if ( e->button() == Qt::RightButton )
    {
        newSelection = false;
        selection = QRect();
        setCursor( Qt::CrossCursor );
    }
    update();
}

void RegionGrabber::mouseMoveEvent( QMouseEvent* e )
{
    bool shouldShowHelp = !helpTextRect.contains( e->pos() );
    if (shouldShowHelp != showHelp) {
        showHelp = shouldShowHelp;
        update();
    }

    if ( mouseDown )
    {
        if ( newSelection )
        {
            QPoint p = e->pos();
            QRect r = rect();
            selection = normalizeSelection(QRect( dragStartPoint, limitPointToRect( p, r ) ));
        }
        else if ( mouseOverHandle == 0 ) // moving the whole selection
        {
            QRect r = rect().normalized(), s = selectionBeforeDrag.normalized();
            QPoint p = s.topLeft() + e->pos() - dragStartPoint;
            r.setBottomRight( r.bottomRight() - QPoint( s.width(), s.height() ) + QPoint( 1, 1 ) );
            if ( !r.isNull() && r.isValid() )
                selection.moveTo( limitPointToRect( p, r ) );
        }
        else // dragging a handle
        {
            QRect r = selectionBeforeDrag;
            QPoint offset = e->pos() - dragStartPoint;

            if ( mouseOverHandle == &TLHandle || mouseOverHandle == &THandle
                 || mouseOverHandle == &TRHandle ) // dragging one of the top handles
            {
                r.setTop( r.top() + offset.y() );
            }

            if ( mouseOverHandle == &TLHandle || mouseOverHandle == &LHandle
                 || mouseOverHandle == &BLHandle ) // dragging one of the left handles
            {
                r.setLeft( r.left() + offset.x() );
            }

            if ( mouseOverHandle == &BLHandle || mouseOverHandle == &BHandle
                 || mouseOverHandle == &BRHandle ) // dragging one of the bottom handles
            {
                r.setBottom( r.bottom() + offset.y() );
            }

            if ( mouseOverHandle == &TRHandle || mouseOverHandle == &RHandle
                 || mouseOverHandle == &BRHandle ) // dragging one of the right handles
            {
                r.setRight( r.right() + offset.x() );
            }
            r.setTopLeft( limitPointToRect( r.topLeft(), rect() ) );
            r.setBottomRight( limitPointToRect( r.bottomRight(), rect() ) );
            selection = normalizeSelection(r);
        }
        update();
    }
    else
    {
        if ( selection.isNull() )
            return;
        bool found = false;
        foreach( QRect* r, handles )
        {
            if ( r->contains( e->pos() ) )
            {
                mouseOverHandle = r;
                found = true;
                break;
            }
        }
        if ( !found )
        {
            mouseOverHandle = 0;
            if ( selection.contains( e->pos() ) )
                setCursor( Qt::OpenHandCursor );
            else
                setCursor( Qt::CrossCursor );
        }
        else
        {
            if ( mouseOverHandle == &TLHandle || mouseOverHandle == &BRHandle )
                setCursor( Qt::SizeFDiagCursor );
            if ( mouseOverHandle == &TRHandle || mouseOverHandle == &BLHandle )
                setCursor( Qt::SizeBDiagCursor );
            if ( mouseOverHandle == &LHandle || mouseOverHandle == &RHandle )
                setCursor( Qt::SizeHorCursor );
            if ( mouseOverHandle == &THandle || mouseOverHandle == &BHandle )
                setCursor( Qt::SizeVerCursor );
        }
    }
}

void RegionGrabber::mouseReleaseEvent( QMouseEvent* e )
{
    mouseDown = false;
    newSelection = false;
    if ( mouseOverHandle == 0 && selection.contains( e->pos() ) )
        setCursor( Qt::OpenHandCursor );
    update();
}

void RegionGrabber::mouseDoubleClickEvent( QMouseEvent* )
{
    grabRect();
}

void RegionGrabber::keyPressEvent( QKeyEvent* e )
{
    QRect r = selection;
    if ( e->key() == Qt::Key_Escape )
    {
        emit regionUpdated( r );
        emit regionGrabbed( QPixmap() );
    }
    else if ( e->key() == Qt::Key_Enter || e->key() == Qt::Key_Return )
    {
        grabRect();
    }
    else
    {
        e->ignore();
    }
}

void RegionGrabber::grabRect()
{
    QRect r = selection;
    if ( !r.isNull() && r.isValid() )
    {
	grabbing = true;
        emit regionUpdated( r );
        emit regionGrabbed( pixmap.copy(r) );
    }
}

void RegionGrabber::updateHandles()
{
    QRect r = selection;
    int s2 = handleSize / 2;

    TLHandle.moveTopLeft( r.topLeft() );
    TRHandle.moveTopRight( r.topRight() );
    BLHandle.moveBottomLeft( r.bottomLeft() );
    BRHandle.moveBottomRight( r.bottomRight() );

    LHandle.moveTopLeft( QPoint( r.x(), r.y() + r.height() / 2 - s2) );
    THandle.moveTopLeft( QPoint( r.x() + r.width() / 2 - s2, r.y() ) );
    RHandle.moveTopRight( QPoint( r.right(), r.y() + r.height() / 2 - s2 ) );
    BHandle.moveBottomLeft( QPoint( r.x() + r.width() / 2 - s2, r.bottom() ) );
}

QRegion RegionGrabber::handleMask( MaskType type ) const
{
    // note: not normalized QRects are bad here, since they will not be drawn
    QRegion mask;
    foreach( QRect* rect, handles ) {
        if ( type == StrokeMask ) {
            QRegion r( *rect );
            mask += r.subtracted( rect->adjusted( 1, 1, -1, -1 ) );
        } else {
            mask += QRegion( rect->adjusted( 1, 1, -1, -1 ) );
        }
    }
    return mask;
}

QPoint RegionGrabber::limitPointToRect( const QPoint &p, const QRect &r ) const
{
    QPoint q;
    q.setX( p.x() < r.x() ? r.x() : p.x() < r.right() ? p.x() : r.right() );
    q.setY( p.y() < r.y() ? r.y() : p.y() < r.bottom() ? p.y() : r.bottom() );
    return q;
}

QRect RegionGrabber::normalizeSelection( const QRect &s ) const
{
    QRect r = s;
    if (r.width() <= 0) {
        int l = r.left();
        int w = r.width();
        r.setLeft(l + w - 1);
        r.setRight(l);
    }
    if (r.height() <= 0) {
        int t = r.top();
        int h = r.height();
        r.setTop(t + h - 1);
        r.setBottom(t);
    }
    return r;
}

#include "regiongrabber.moc"
