/*
 Copyright © 2017 Hasan Yavuz Özderya

 This file is part of serialplot.

 serialplot is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 serialplot 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 General Public License
 along with serialplot. If not, see <http://www.gnu.org/licenses/>.
*/

#include <QEvent>
#include <QMouseEvent>
#include <QPainter>
#include <qwt_scale_widget.h>
#include <qwt_scale_map.h>
#include <qwt_scale_div.h>
#include <qwt_text.h>
#include <math.h>

#include "scalepicker.h"

// minimum size for pick (in pixels)
#define MIN_PICK_SIZE (2)

#define SNAP_DISTANCE (5)

class PlotOverlay : public QwtWidgetOverlay
{
public:
 PlotOverlay(QWidget* widget, ScalePicker* picker);

protected:
 virtual void drawOverlay(QPainter*) const;

private:
 ScalePicker* _picker;
};

PlotOverlay::PlotOverlay(QWidget* widget, ScalePicker* picker) :
 QwtWidgetOverlay(widget)
{
 _picker = picker;
}

void PlotOverlay::drawOverlay(QPainter* painter) const
{
 _picker->drawPlotOverlay(painter);
}

class ScaleOverlay : public QwtWidgetOverlay
{
public:
 ScaleOverlay(QWidget* widget, ScalePicker* picker);

protected:
 virtual void drawOverlay(QPainter*) const;

private:
 ScalePicker* _picker;
};

ScaleOverlay::ScaleOverlay(QWidget* widget, ScalePicker* picker) :
 QwtWidgetOverlay(widget)
{
 _picker = picker;
}

void ScaleOverlay::drawOverlay(QPainter* painter) const
{
 _picker->drawScaleOverlay(painter);
}

ScalePicker::ScalePicker(QwtScaleWidget* scaleWidget, QWidget* canvas) :
 QObject(scaleWidget)
{
 _scaleWidget = scaleWidget;
 _canvas = canvas;
 scaleWidget->installEventFilter(this);
 scaleWidget->setMouseTracking(true);
 pickerOverlay = new PlotOverlay(canvas, this);
 scaleOverlay = new ScaleOverlay(scaleWidget, this);
 started = false;
 pressed = false;
}

bool ScalePicker::eventFilter(QObject* object, QEvent* event)
{
 if (event->type() == QEvent::MouseButtonPress ||
 event->type() == QEvent::MouseButtonRelease ||
 event->type() == QEvent::MouseMove)
 {
 updateSnapPoints();

 QMouseEvent* mouseEvent = (QMouseEvent*) event;
 int posPx = this->positionPx(mouseEvent);

 // do snapping unless Shift is pressed
 if (! (mouseEvent->modifiers() & Qt::ShiftModifier))
 {
 for (auto sp : snapPoints)
 {
 if (std::abs(posPx-sp) <= SNAP_DISTANCE)
 {
 posPx = sp;
 break;
 }
 }
 }

 double pos = this->position(posPx);
 currentPosPx = posPx;

 if (event->type() == QEvent::MouseButtonPress &&
 mouseEvent->button() == Qt::LeftButton)
 {
 pressed = true; // not yet started
 firstPos = pos;
 firstPosPx = posPx;
 }
 else if (event->type() == QEvent::MouseMove)
 {
 // make sure pick size is big enough, so that just
 // clicking won't trigger pick
 if (!started && pressed && (fabs(posPx-firstPosPx) > MIN_PICK_SIZE))
 {
 started = true;
 }
 pickerOverlay->updateOverlay();
 scaleOverlay->updateOverlay();
 }
 else // event->type() == QEvent::MouseButtonRelease
 {
 pressed = false;
 if (started)
 {
 // finalize
 started = false;
 if (firstPos != pos) // ignore 0 width zoom
 {
 emit picked(firstPos, pos);
 }
 }
 pickerOverlay->updateOverlay();
 scaleOverlay->updateOverlay();
 }
 return true;
 }
 else if (event->type() == QEvent::Leave)
 {
 scaleOverlay->updateOverlay();
 pickerOverlay->updateOverlay();
 return true;
 }
 else
 {
 return QObject::eventFilter(object, event);
 }
}

const int TEXT_MARGIN = 4;

void ScalePicker::drawPlotOverlay(QPainter* painter)
{
 const double FILL_ALPHA = 0.2;

 painter->save();
 painter->setPen(_pen);

 if (started)
 {
 QColor color = _pen.color();
 color.setAlphaF(FILL_ALPHA);
 painter->setBrush(color);

 QRect rect;
 QwtText text = trackerText();
 auto tSize = text.textSize(painter->font());

 if (_scaleWidget->alignment() == QwtScaleDraw::BottomScale ||
 _scaleWidget->alignment() == QwtScaleDraw::TopScale)
 {
 int canvasHeight = painter->device()->height();
 int pickWidth = currentPosPx-firstPosPx;
 rect = QRect(posCanvasPx(firstPosPx), 0, pickWidth, canvasHeight);
 }
 else // vertical
 {
 int canvasWidth = painter->device()->width();
 int pickHeight = currentPosPx-firstPosPx;
 rect = QRect(0, posCanvasPx(firstPosPx), canvasWidth, pickHeight);
 }
 painter->drawRect(rect);
 text.draw(painter, pickTrackerTextRect(painter, rect, tSize));
 }
 else if (_scaleWidget->underMouse())
 {
 // draw tracker text centered on cursor
 QwtText text = trackerText();
 auto tsize = text.textSize(painter->font());
 text.draw(painter, trackerTextRect(painter, currentPosPx, tsize));
 }
 painter->restore();
}

QwtText ScalePicker::trackerText() const
{
 double pos;
 // use stored value if snapped to restore precision
 if (snapPointMap.contains(currentPosPx))
 {
 pos = snapPointMap[currentPosPx];
 }
 else
 {
 pos = position(currentPosPx);
 }

 return QwtText(QString("%1").arg(pos));
}

QRectF ScalePicker::trackerTextRect(QPainter* painter, int posPx, QSizeF textSize) const
{
 int canvasPosPx = posCanvasPx(posPx);
 QPointF topLeft;

 if (_scaleWidget->alignment() == QwtScaleDraw::BottomScale ||
 _scaleWidget->alignment() == QwtScaleDraw::TopScale)
 {
 int left = canvasPosPx - textSize.width() / 2;
 int canvasWidth = painter->device()->width();
 left = std::max(TEXT_MARGIN, left);
 left = std::min(double(left), canvasWidth - textSize.width() - TEXT_MARGIN);
 int top = 0;
 if (_scaleWidget->alignment() == QwtScaleDraw::BottomScale)
 {
 top = painter->device()->height() - textSize.height();
 }
 topLeft = QPointF(left, top);
 }
 else // left/right scales
 {
 int top = canvasPosPx-textSize.height() / 2;
 int canvasHeight = painter->device()->height();
 top = std::max(0, top);
 top = std::min(double(top), canvasHeight - textSize.height());
 int left = TEXT_MARGIN;
 if (_scaleWidget->alignment() == QwtScaleDraw::RightScale)
 {
 left = painter->device()->width() - textSize.width();
 }
 topLeft = QPointF(left, top);
 }
 return QRectF(topLeft, textSize);
}

QRectF ScalePicker::pickTrackerTextRect(QPainter* painter, QRect pickRect, QSizeF textSize) const
{
 qreal left = 0;
 int pickLength = currentPosPx - firstPosPx;
 QPointF topLeft;

 if (_scaleWidget->alignment() == QwtScaleDraw::BottomScale ||
 _scaleWidget->alignment() == QwtScaleDraw::TopScale)
 {
 int canvasWidth = painter->device()->width();

 if (pickLength > 0)
 {
 left = pickRect.right() + TEXT_MARGIN;
 }
 else
 {
 left = pickRect.right() - (textSize.width() + TEXT_MARGIN);
 }

 // make sure text is not off the canvas
 if (left < TEXT_MARGIN)
 {
 left = std::max(0, pickRect.right()) + TEXT_MARGIN;
 }
 else if (left + textSize.width() + TEXT_MARGIN > canvasWidth)
 {
 left = std::min(pickRect.right(), canvasWidth) - (textSize.width() + TEXT_MARGIN);
 }

 if (_scaleWidget->alignment() == QwtScaleDraw::BottomScale)
 {
 int canvasHeight = painter->device()->height();
 topLeft = QPointF(left, canvasHeight - textSize.height());
 }
 else // top scale
 {
 topLeft = QPointF(left, 0);
 }
 }
 else // left/right scale
 {
 int canvasHeight = painter->device()->height();

 int top = 0;
 if (pickLength > 0)
 {
 top = pickRect.bottom();
 }
 else
 {
 top = pickRect.bottom() - textSize.height();
 }

 // make sure text is not off the canvas
 if (top < 0)
 {
 top = std::max(0, pickRect.bottom());
 }
 else if (top + textSize.height() > canvasHeight)
 {
 top = std::min(canvasHeight, pickRect.bottom()) - textSize.height();
 }

 if (_scaleWidget->alignment() == QwtScaleDraw::LeftScale)
 {
 topLeft = QPointF(TEXT_MARGIN, top);
 }
 else // right scale
 {
 int canvasWidth = painter->device()->width();
 topLeft = QPointF(canvasWidth - textSize.width() - TEXT_MARGIN, top);
 }
 }
 return QRectF(topLeft, textSize);
}

void ScalePicker::drawScaleOverlay(QPainter* painter)
{
 painter->save();

 // rotate & adjust coordinate system for vertical drawing
 if (_scaleWidget->alignment() == QwtScaleDraw::LeftScale ||
 _scaleWidget->alignment() == QwtScaleDraw::RightScale) // vertical
 {
 int width = painter->device()->width();
 painter->rotate(90);
 painter->translate(0, -width);
 }

 // draw the indicators
 if (started) drawTriangle(painter, firstPosPx);
 if (started || _scaleWidget->underMouse())
 {
 drawTriangle(painter, currentPosPx);
 }

 painter->restore();
}

void ScalePicker::drawTriangle(QPainter* painter, int position)
{
 const double tan60 = 1.732;
 const double trsize = 10;
 const int TRIANGLE_NUM_POINTS = 3;
 const int MARGIN = 2;
 const QPointF points[TRIANGLE_NUM_POINTS] =
 {
 {0, 0},
 {-trsize/tan60 , trsize},
 {trsize/tan60 , trsize}
 };

 painter->save();
 painter->setPen(Qt::NoPen);
 painter->setBrush(_scaleWidget->palette().windowText());
 painter->setRenderHint(QPainter::Antialiasing);

 painter->translate(position, MARGIN);
 painter->drawPolygon(points, TRIANGLE_NUM_POINTS);

 painter->restore();
}

void ScalePicker::setPen(QPen pen)
{
 _pen = pen;
}

// convert the position of the click to the plot coordinates
double ScalePicker::position(double posPx) const
{
 return _scaleWidget->scaleDraw()->scaleMap().invTransform(posPx);
}

int ScalePicker::positionPx(QMouseEvent* mouseEvent)
{
 double pos;
 if (_scaleWidget->alignment() == QwtScaleDraw::BottomScale ||
 _scaleWidget->alignment() == QwtScaleDraw::TopScale)
 {
 pos = mouseEvent->pos().x();
 }
 else // left or right scale
 {
 pos = mouseEvent->pos().y();
 }
 return pos;
}

/*
 * Scale widget and canvas widget is not always aligned. Especially
 * when zooming scaleWidget moves around. This causes irregularities
 * when drawing the tracker lines. This function maps scale widgets
 * pixel coordinate to canvas' coordinate.
 */
double ScalePicker::posCanvasPx(double pos) const
{
 // assumption: scale.width < canvas.width && scale.x > canvas.x
 if (_scaleWidget->alignment() == QwtScaleDraw::BottomScale ||
 _scaleWidget->alignment() == QwtScaleDraw::TopScale)
 {
 return pos + (_scaleWidget->x() - _canvas->x());
 }
 else // left or right scale
 {
 return pos + (_scaleWidget->y() - _canvas->y());
 }
 return pos;
}

void ScalePicker::updateSnapPoints()
{
 auto allTicks = _scaleWidget->scaleDraw()->scaleDiv().ticks(QwtScaleDiv::MajorTick) +
 _scaleWidget->scaleDraw()->scaleDiv().ticks(QwtScaleDiv::MediumTick) +
 _scaleWidget->scaleDraw()->scaleDiv().ticks(QwtScaleDiv::MinorTick);

 snapPoints.clear();
 snapPointMap.clear();
 for(auto t : allTicks)
 {
 // `round` is used because `allTicks` is double but `snapPoints` is int
 int p = round(_scaleWidget->scaleDraw()->scaleMap().transform(t));
 snapPoints << p;
 snapPointMap[p] = t;
 }
}