/*
  Copyright © 2014 Uwe Rathmann

  This file is copied from Qwt project; you can redistribute it and/or modify it
  under the terms of the Qwt License, Version 1.0. You can obtain the original
  source code and the details of the Qwt License from the Qwt website:
  http://qwt.sourceforge.net/
*/

#include <qevent.h>
#include <qwt_plot_canvas.h>
#include <qwt_plot_layout.h>
#include <qwt_scale_engine.h>
#include <qwt_scale_widget.h>
#include "scrollbar.h"
#include "scrollzoomer.h"

class ScrollData
{
public:
    ScrollData():
        scrollBar( NULL ),
        position( ScrollZoomer::OppositeToScale ),
        mode( Qt::ScrollBarAsNeeded )
    {
    }

    ~ScrollData()
    {
        delete scrollBar;
    }

    ScrollBar *scrollBar;
    ScrollZoomer::ScrollBarPosition position;
    Qt::ScrollBarPolicy mode;
};

ScrollZoomer::ScrollZoomer( QWidget *canvas ):
    QwtPlotZoomer( canvas ),
    d_cornerWidget( NULL ),
    d_hScrollData( NULL ),
    d_vScrollData( NULL ),
    d_inZoom( false )
{
    xMin = 0.;
    xMax = 10000.;
    hViewSize = 10000;

    for ( int axis = 0; axis < QwtPlot::axisCnt; axis++ )
        d_alignCanvasToScales[ axis ] = false;

    if ( !canvas )
        return;

    d_hScrollData = new ScrollData;
    d_vScrollData = new ScrollData;
    hscrollmove = false;
    vscrollmove = false;
}

ScrollZoomer::~ScrollZoomer()
{
    delete d_cornerWidget;
    delete d_vScrollData;
    delete d_hScrollData;
}

void ScrollZoomer::setXLimits(double min, double max)
{
    xMin = min;
    xMax = max;
    setZoomBase();
}

void ScrollZoomer::setHViewSize(double size)
{
    hscrollmove = true;
    hViewSize = size;
    setZoomBase();
    hscrollmove = false;
}

void ScrollZoomer::setZoomBase(bool doReplot)
{
    QwtPlotZoomer::setZoomBase(doReplot);
    auto zb = zoomBase();
    auto zs = zoomStack();
    zb.setRight(xMax);
    if ((xMax - xMin) < hViewSize)
    {
        zb.setLeft(xMin);
    }
    else
    {
        zb.setLeft(xMax-hViewSize);
    }
    zs[0] = zb;
    setZoomStack(zs);
}

void ScrollZoomer::rescale()
{
    QwtScaleWidget *xScale = plot()->axisWidget( xAxis() );
    QwtScaleWidget *yScale = plot()->axisWidget( yAxis() );

    if ( zoomRectIndex() <= 0 )
    {
        if ( d_inZoom )
        {
            xScale->setMinBorderDist( 0, 0 );
            yScale->setMinBorderDist( 0, 0 );

            QwtPlotLayout *layout = plot()->plotLayout();

            for ( int axis = 0; axis < QwtPlot::axisCnt; axis++ )
                layout->setAlignCanvasToScale( axis, d_alignCanvasToScales[ axis ] );

            d_inZoom = false;
        }
    }
    else
    {
        if ( !d_inZoom )
        {
            /*
             We set a minimum border distance.
             Otherwise the canvas size changes when scrolling,
             between situations where the major ticks are at
             the canvas borders (requiring extra space for the label)
             and situations where all labels can be painted below/top
             or left/right of the canvas.
             */
            int start, end;

            xScale->getBorderDistHint( start, end );
            xScale->setMinBorderDist( start, end );

            yScale->getBorderDistHint( start, end );
            yScale->setMinBorderDist( start, end );

            QwtPlotLayout *layout = plot()->plotLayout();
            for ( int axis = 0; axis < QwtPlot::axisCnt; axis++ )
            {
                d_alignCanvasToScales[axis] = 
                    layout->alignCanvasToScale( axis );
            }

            layout->setAlignCanvasToScales( false );

            d_inZoom = true;
        }
    }

    // NOTE: Below snippet is copied from QwtPlotZoomer::rescale() just so that
    // we can refrain from updating y axis when moving horizontal scrollbar, so
    // that auto-scale isn't disrupted. Also we don't want to jump around in
    // x-axis when moving vertical scroll.
    {
        QwtPlot *plt = plot();
        if ( !plt )
            return;

        const QRectF &rect = zoomStack()[zoomRectIndex()];
        if ( rect != scaleRect() )
        {
            const bool doReplot = plt->autoReplot();
            plt->setAutoReplot( false );

            if (!vscrollmove)
            {
                double x1 = rect.left();
                double x2 = rect.right();
                if ( !plt->axisScaleDiv( xAxis() ).isIncreasing() )
                    qSwap( x1, x2 );

                plt->setAxisScale( xAxis(), x1, x2 );
            }

            if (!hscrollmove)
            {
                double y1 = rect.top();
                double y2 = rect.bottom();
                if ( !plt->axisScaleDiv( yAxis() ).isIncreasing() )
                    qSwap( y1, y2 );

                plt->setAxisScale( yAxis(), y1, y2 );

                plt->setAutoReplot( doReplot );
            }
            plt->replot();
        }
    }
    updateScrollBars();
}

ScrollBar *ScrollZoomer::scrollBar( Qt::Orientation orientation )
{
    ScrollBar *&sb = ( orientation == Qt::Vertical )
        ? d_vScrollData->scrollBar : d_hScrollData->scrollBar;

    if ( sb == NULL )
    {
        sb = new ScrollBar( orientation, canvas() );
        sb->hide();
        connect( sb,
            SIGNAL( valueChanged( Qt::Orientation, double, double ) ),
            SLOT( scrollBarMoved( Qt::Orientation, double, double ) ) );
    }
    return sb;
}

ScrollBar *ScrollZoomer::horizontalScrollBar() const
{
    return d_hScrollData->scrollBar;
}

ScrollBar *ScrollZoomer::verticalScrollBar() const
{
    return d_vScrollData->scrollBar;
}

void ScrollZoomer::setHScrollBarMode( Qt::ScrollBarPolicy mode )
{
    if ( hScrollBarMode() != mode )
    {
        d_hScrollData->mode = mode;
        updateScrollBars();
    }
}

void ScrollZoomer::setVScrollBarMode( Qt::ScrollBarPolicy mode )
{
    if ( vScrollBarMode() != mode )
    {
        d_vScrollData->mode = mode;
        updateScrollBars();
    }
}

Qt::ScrollBarPolicy ScrollZoomer::hScrollBarMode() const
{
    return d_hScrollData->mode;
}

Qt::ScrollBarPolicy ScrollZoomer::vScrollBarMode() const
{
    return d_vScrollData->mode;
}

void ScrollZoomer::setHScrollBarPosition( ScrollBarPosition pos )
{
    if ( d_hScrollData->position != pos )
    {
        d_hScrollData->position = pos;
        updateScrollBars();
    }
}

void ScrollZoomer::setVScrollBarPosition( ScrollBarPosition pos )
{
    if ( d_vScrollData->position != pos )
    {
        d_vScrollData->position = pos;
        updateScrollBars();
    }
}

ScrollZoomer::ScrollBarPosition ScrollZoomer::hScrollBarPosition() const
{
    return d_hScrollData->position;
}

ScrollZoomer::ScrollBarPosition ScrollZoomer::vScrollBarPosition() const
{
    return d_vScrollData->position;
}

void ScrollZoomer::setCornerWidget( QWidget *w )
{
    if ( w != d_cornerWidget )
    {
        if ( canvas() )
        {
            delete d_cornerWidget;
            d_cornerWidget = w;
            if ( d_cornerWidget->parent() != canvas() )
                d_cornerWidget->setParent( canvas() );

            updateScrollBars();
        }
    }
}

QWidget *ScrollZoomer::cornerWidget() const
{
    return d_cornerWidget;
}

bool ScrollZoomer::eventFilter( QObject *object, QEvent *event )
{
    if ( object == canvas() )
    {
        switch( event->type() )
        {
            case QEvent::Resize:
            {
                int left, top, right, bottom;
                canvas()->getContentsMargins( &left, &top, &right, &bottom );

                QRect rect;
                rect.setSize( static_cast<QResizeEvent *>( event )->size() );
                rect.adjust( left, top, -right, -bottom );

                layoutScrollBars( rect );
                break;
            }
            case QEvent::Show:
            {
                layoutScrollBars( canvas()->contentsRect() );
                break;
            }
            case QEvent::ChildRemoved:
            {
                const QObject *child =
                    static_cast<QChildEvent *>( event )->child();

                if ( child == d_cornerWidget )
                    d_cornerWidget = NULL;
                else if ( child == d_hScrollData->scrollBar )
                    d_hScrollData->scrollBar = NULL;
                else if ( child == d_vScrollData->scrollBar )
                    d_vScrollData->scrollBar = NULL;
                break;
            }
            default:
                break;
        }
    }
    return QwtPlotZoomer::eventFilter( object, event );
}

bool ScrollZoomer::needScrollBar( Qt::Orientation orientation ) const
{
    Qt::ScrollBarPolicy mode;
    double zoomMin, zoomMax, baseMin, baseMax;

    if ( orientation == Qt::Horizontal )
    {
        mode = d_hScrollData->mode;
        baseMin = xMin;
        baseMax = xMax;
        zoomMin = zoomRect().left();
        zoomMax = zoomRect().right();
    }
    else
    {
        mode = d_vScrollData->mode;
        baseMin = zoomBase().top();
        baseMax = zoomBase().bottom();
        zoomMin = zoomRect().top();
        zoomMax = zoomRect().bottom();
    }

    bool needed = false;
    switch( mode )
    {
        case Qt::ScrollBarAlwaysOn:
            needed = true;
            break;
        case Qt::ScrollBarAlwaysOff:
            needed = false;
            break;
        default:
        {
            if ( baseMin < zoomMin || baseMax > zoomMax )
                needed = true;
            break;
        }
    }
    return needed;
}

void ScrollZoomer::updateScrollBars()
{
    if ( !canvas() )
        return;

    const int xAxis = QwtPlotZoomer::xAxis();
    const int yAxis = QwtPlotZoomer::yAxis();

    int xScrollBarAxis = xAxis;
    if ( hScrollBarPosition() == OppositeToScale )
        xScrollBarAxis = oppositeAxis( xScrollBarAxis );

    int yScrollBarAxis = yAxis;
    if ( vScrollBarPosition() == OppositeToScale )
        yScrollBarAxis = oppositeAxis( yScrollBarAxis );


    QwtPlotLayout *layout = plot()->plotLayout();

    bool showHScrollBar = needScrollBar( Qt::Horizontal );
    if ( showHScrollBar )
    {
        ScrollBar *sb = scrollBar( Qt::Horizontal );
        sb->setPalette( plot()->palette() );
        sb->setInverted( !plot()->axisScaleDiv( xAxis ).isIncreasing() );
        sb->setBase( xMin, xMax );
        sb->moveSlider( zoomRect().left(), zoomRect().right() );

        if ( !sb->isVisibleTo( canvas() ) )
        {
            sb->show();
            layout->setCanvasMargin( layout->canvasMargin( xScrollBarAxis )
                + sb->extent(), xScrollBarAxis );
        }
    }
    else
    {
        if ( horizontalScrollBar() )
        {
            horizontalScrollBar()->hide();
            layout->setCanvasMargin( layout->canvasMargin( xScrollBarAxis )
                - horizontalScrollBar()->extent(), xScrollBarAxis );
        }
    }

    bool showVScrollBar = needScrollBar( Qt::Vertical );
    if ( showVScrollBar )
    {
        ScrollBar *sb = scrollBar( Qt::Vertical );
        sb->setPalette( plot()->palette() );
        sb->setInverted( plot()->axisScaleDiv( yAxis ).isIncreasing() );
        sb->setBase( zoomBase().top(), zoomBase().bottom() );
        sb->moveSlider( zoomRect().top(), zoomRect().bottom() );

        if ( !sb->isVisibleTo( canvas() ) )
        {
            sb->show();
            layout->setCanvasMargin( layout->canvasMargin( yScrollBarAxis )
                + sb->extent(), yScrollBarAxis );
        }
    }
    else
    {
        if ( verticalScrollBar() )
        {
            verticalScrollBar()->hide();
            layout->setCanvasMargin( layout->canvasMargin( yScrollBarAxis )
                - verticalScrollBar()->extent(), yScrollBarAxis );
        }
    }

    if ( showHScrollBar && showVScrollBar )
    {
        if ( d_cornerWidget == NULL )
        {
            d_cornerWidget = new QWidget( canvas() );
            d_cornerWidget->setAutoFillBackground( true );
            d_cornerWidget->setPalette( plot()->palette() );
        }
        d_cornerWidget->show();
    }
    else
    {
        if ( d_cornerWidget )
            d_cornerWidget->hide();
    }

    layoutScrollBars( canvas()->contentsRect() );
    plot()->updateLayout();
}

void ScrollZoomer::layoutScrollBars( const QRect &rect )
{
    int hPos = xAxis();
    if ( hScrollBarPosition() == OppositeToScale )
        hPos = oppositeAxis( hPos );

    int vPos = yAxis();
    if ( vScrollBarPosition() == OppositeToScale )
        vPos = oppositeAxis( vPos );

    ScrollBar *hScrollBar = horizontalScrollBar();
    ScrollBar *vScrollBar = verticalScrollBar();

    const int hdim = hScrollBar ? hScrollBar->extent() : 0;
    const int vdim = vScrollBar ? vScrollBar->extent() : 0;

    if ( hScrollBar && hScrollBar->isVisible() )
    {
        int x = rect.x();
        int y = ( hPos == QwtPlot::xTop )
            ? rect.top() : rect.bottom() - hdim + 1;
        int w = rect.width();

        if ( vScrollBar && vScrollBar->isVisible() )
        {
            if ( vPos == QwtPlot::yLeft )
                x += vdim;
            w -= vdim;
        }

        hScrollBar->setGeometry( x, y, w, hdim );
    }
    if ( vScrollBar && vScrollBar->isVisible() )
    {
        int pos = yAxis();
        if ( vScrollBarPosition() == OppositeToScale )
            pos = oppositeAxis( pos );

        int x = ( vPos == QwtPlot::yLeft )
            ? rect.left() : rect.right() - vdim + 1;
        int y = rect.y();

        int h = rect.height();

        if ( hScrollBar && hScrollBar->isVisible() )
        {
            if ( hPos == QwtPlot::xTop )
                y += hdim;

            h -= hdim;
        }

        vScrollBar->setGeometry( x, y, vdim, h );
    }
    if ( hScrollBar && hScrollBar->isVisible() &&
        vScrollBar && vScrollBar->isVisible() )
    {
        if ( d_cornerWidget )
        {
            QRect cornerRect(
                vScrollBar->pos().x(), hScrollBar->pos().y(),
                vdim, hdim );
            d_cornerWidget->setGeometry( cornerRect );
        }
    }
}

void ScrollZoomer::scrollBarMoved(
    Qt::Orientation o, double min, double max )
{
    Q_UNUSED( max );

    if ( o == Qt::Horizontal )
    {
        hscrollmove = true;
        moveTo( QPointF( min, zoomRect().top() ) );
        hscrollmove = false;
    }
    else
    {
        vscrollmove = true;
        moveTo( QPointF( zoomRect().left(), min ) );
        vscrollmove = false;
    }

    Q_EMIT zoomed( zoomRect() );
}

int ScrollZoomer::oppositeAxis( int axis ) const
{
    switch( axis )
    {
        case QwtPlot::xBottom:
            return QwtPlot::xTop;
        case QwtPlot::xTop:
            return QwtPlot::xBottom;
        case QwtPlot::yLeft:
            return QwtPlot::yRight;
        case QwtPlot::yRight:
            return QwtPlot::yLeft;
        default:
            break;
    }

    return axis;
}

void ScrollZoomer::moveTo( const QPointF &pos )
{
    // QwtPlotZoomer::moveTo(pos);
    // return;

    double x = pos.x();
    double y = pos.y();

    if ( x < xMin )
        x = xMin;
    if ( x > xMax - zoomRect().width() )
        x = xMax - zoomRect().width();

    if ( y < zoomBase().top() )
        y = zoomBase().top();
    if ( y > zoomBase().bottom() - zoomRect().height() )
        y = zoomBase().bottom() - zoomRect().height();

    if ( x != zoomRect().left() || y != zoomRect().top() )
    {
        auto zs = zoomStack();
        zs[zoomRectIndex()].moveTo( x, y );
        setZoomStack(zs, zoomRectIndex());
        rescale();
    }
}