/* Copyright (c) 2012-2016 Stanislaw Halik <sthalik@misaki.pl>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 */

#include "compat/util.hpp"
#include "spline-widget.hpp"
#include <QPainter>
#include <QPaintEvent>
#include <QPen>
#include <QPixmap>
#include <QList>
#include <QPointF>
#include <cmath>
#include <algorithm>

spline_widget::spline_widget(QWidget *parent) :
    QWidget(parent),
    _config(nullptr),
    moving_control_point_idx(-1),
    snap_x(0),
    snap_y(0),
    _draw_function(true),
    _preview_only(false)
{
    update_range();
    setMouseTracking(true);
}

void spline_widget::setConfig(spline* spl)
{
    if (spl != _config)
    {
        if (connection)
        {
            QObject::disconnect(connection);
            //connection = QMetaObject::Connection();
        }

        if (spl)
        {
            mem<spline::settings> s = spl->get_settings();
            connection = connect(s.get(), &spline::settings::recomputed,
                                 this, [this]() { reload_spline(); },
                                 Qt::QueuedConnection);
        }

        _config = spl;
        update_range();
    }
}

void spline_widget::set_preview_only(bool val)
{
    _preview_only = val;
}

bool spline_widget::is_preview_only() const
{
    return _preview_only;
}

void spline_widget::drawBackground()
{
    if (!_config)
        return;
    _background = QPixmap(width(), height());

    QPainter painter(&_background);
    painter.fillRect(rect(), QColor::fromRgb(204, 204, 204));

    QColor bg_color(112, 154, 209);
    if (!isEnabled() && !_preview_only)
        bg_color = QColor(176,176,180);
    painter.fillRect(pixel_bounds, bg_color);

    QFont font;
    font.setPointSize(8);
    painter.setFont(font);
    QFontMetrics metrics(font);

    QColor color__(176, 190, 209, 127);

    if (!isEnabled())
        color__ = QColor(70, 90, 100, 96);

    QPen pen(color__, 1, Qt::SolidLine);

    const int xstep = 10, ystep = 10;
    const qreal maxx = _config->maxInput();
    const qreal maxy = _config->maxOutput();

    // horizontal grid
    for (int i = 0; i <= maxy; i += xstep)
    {
        const qreal y = pixel_bounds.height() - i * c.y() + pixel_bounds.y();
        drawLine(&painter,
                 QPointF(pixel_bounds.x(), y),
                 QPointF(pixel_bounds.x() + pixel_bounds.width(), y),
                 pen);
        painter.drawText(QRectF(10,
                                y - metrics.height()/2,
                                pixel_bounds.left(),
                                metrics.height()),
                         QString::number(i));
    }

    // vertical grid
    for (int i = 0; i <= maxx; i += ystep)
    {
        const qreal x = pixel_bounds.x() + i * c.x();
        drawLine(&painter,
                 QPointF(x, pixel_bounds.y()),
                 QPointF(x, pixel_bounds.y() + pixel_bounds.height()),
                 pen);
        const QString text = QString::number(i);
        painter.drawText(QRectF(x - metrics.width(text)/2,
                                pixel_bounds.height() + 10 + metrics.height(),
                                metrics.width(text),
                                metrics.height()),
                         text);
    }
}

void spline_widget::drawFunction()
{
    if (!_config)
        return;

    _function = _background;
    QPainter painter(&_function);
    painter.setRenderHint(QPainter::Antialiasing, true);

    points_t points = _config->getPoints();

    const int alpha = !isEnabled() ? 64 : 120;
    if (!_preview_only)
    {
        for (int i = 0; i < points.size(); i++)
        {
            drawPoint(&painter,
                      point_to_pixel(points[i]),
                      QColor(200, 200, 210, alpha),
                      isEnabled() ? QColor(50, 100, 120, 200) : QColor(200, 200, 200, 96));
        }
    }

    QColor color = spline_color;

    if (!isEnabled() && !_preview_only)
    {
        const int avg = int(float(color.red() + color.green() + color.blue())/3);
        color = QColor(int(float(color.red() + avg) * .5f),
                       int(float(color.green() + avg) * .5f),
                       int(float(color.blue() + avg) * .5f),
                       96);
    }

    QPen pen(color, 1.2, Qt::SolidLine);

    const qreal step_ = line_length_pixels / c.x();
    const qreal step = std::max(1e-2, step_);
    const qreal max = _config->maxInput();

    painter.save();
    painter.setPen(pen);
    painter.setBrush(Qt::NoBrush);

    QPointF prev = point_to_pixel(QPointF(0, 0));
    for (qreal i = 0; i < max; i += step)
    {
        const qreal val = qreal(_config->getValue(i));
        QPointF cur = point_to_pixel(QPointF(i, val));
        painter.drawLine(prev, cur);
        prev = cur;
    }

    {
        const qreal val = qreal(_config->getValue(max));
        QPointF last = point_to_pixel(QPointF(max, val));
        painter.drawLine(prev, last);
    }

    painter.restore();
}

void spline_widget::paintEvent(QPaintEvent *e)
{
    QPainter p(this);

    if (_background.isNull())
    {
        _draw_function = true;
        drawBackground();
    }

    if (_draw_function)
    {
        _draw_function = false;
        drawFunction();
    }

    p.drawPixmap(e->rect(), _function);

    if (_config)
    {
        QPen pen(Qt::white, 1, Qt::SolidLine);
        points_t points = _config->getPoints();
        if (points.size() &&
            moving_control_point_idx >= 0 &&
            moving_control_point_idx < points.size())
        {
            if (points[0].x() > 1e-2)
                points.push_front(QPointF(0, 0));
            QPointF prev = point_to_pixel(points[0]);
            for (int i = 1; i < points.size(); i++)
            {
                auto tmp = point_to_pixel(points[i]);
                drawLine(&p, prev, tmp, pen);
                prev = tmp;
            }
        }

        // If the Tracker is active, the 'Last Point' it requested is recorded.
        // Show that point on the graph, with some lines to assist.
        // This new feature is very handy for tweaking the curves!
        QPointF last;
        if (_config->getLastPoint(last) && isEnabled())
        {
            QPointF pixel_pos = point_to_pixel(last);
            drawPoint(&p, pixel_pos, QColor(255, 0, 0, 120));
        }
    }
}

void spline_widget::drawPoint(QPainter *painter, const QPointF &pos, QColor colBG, QColor border)
{
    painter->save();
    painter->setPen(border);
    painter->setBrush( colBG );
    painter->drawEllipse(QRectF(pos.x() - point_size,
                                pos.y() - point_size,
                                point_size*2, point_size*2));
    painter->restore();
}

void spline_widget::drawLine(QPainter *painter, const QPointF &start, const QPointF &end, QPen &pen)
{
    painter->save();
    painter->setPen(pen);
    painter->setBrush(Qt::NoBrush);
    painter->drawLine(start, end);
    painter->restore();
}

void spline_widget::mousePressEvent(QMouseEvent *e)
{
    if (!_config || !isEnabled())
        return;
    points_t points = _config->getPoints();
    if (e->button() == Qt::LeftButton)
    {
        bool bTouchingPoint = false;
        moving_control_point_idx = -1;
        if (_config)
        {
            for (int i = 0; i < points.size(); i++)
            {
                if (point_within_pixel(points[i], e->pos()))
                {
                    bTouchingPoint = true;
                    moving_control_point_idx = int(i);
                    break;
                }
            }
            if (!bTouchingPoint)
            {
                bool too_close = false;
                const auto pos = e->pos();

                for (int i = 0; i < points.size(); i++)
                {
                    const QPointF pt = point_to_pixel(points[i]);
                    const qreal x = pt.x() - pos.x();
                    if (point_closeness_limit * point_closeness_limit >= x * x)
                    {
                        too_close = true;
                        break;
                    }
                }

                if (!too_close)
                    _config->addPoint(pixel_coord_to_point(e->pos()));
            }
        }
    }

    if (e->button() == Qt::RightButton)
    {
        if (_config)
        {
            int found_pt = -1;
            for (int i = 0; i < points.size(); i++)
            {
                if (point_within_pixel(points[i], e->pos()))
                {
                    found_pt = i;
                    break;
                }
            }

            if (found_pt != -1)
            {
                _config->removePoint(found_pt);
            }
            moving_control_point_idx = -1;
        }
    }
    _draw_function = true;
    update();
}

void spline_widget::mouseMoveEvent(QMouseEvent *e)
{
    if (!_config || !isEnabled())
        return;

    points_t points = _config->getPoints();

    if (moving_control_point_idx >= 0 &&
        moving_control_point_idx < points.size())
    {
        const int idx = moving_control_point_idx;

        setCursor(Qt::ClosedHandCursor);

        bool overlap = false;

        QPointF pix = e->pos();
        QPointF new_pt = pixel_coord_to_point(pix);

        for (int i = 0; i < 2; i++)
        {
            bool bad = false;
            if (idx + 1 < points.size())
            {
                auto other = points[idx+1];
                auto other_pix = point_to_pixel(other);
                bad = pix.x() + point_closeness_limit > other_pix.x();
                if (i == 0 && bad)
                {
                    pix.setX(other_pix.x() - point_closeness_limit);
                    new_pt = pixel_coord_to_point(pix);
                }
                else
                    overlap |= bad;
            }
            if (idx != 0)
            {
                auto other = points[idx-1];
                auto other_pix = point_to_pixel(other);
                bad = pix.x() - point_closeness_limit < other_pix.x();
                if (i == 0 && bad)
                {
                    pix.setX(other_pix.x() + point_closeness_limit);
                    new_pt = pixel_coord_to_point(pix);
                }
                else
                    overlap |= bad;
            }
            if (!bad)
                break;
        }

        if (!overlap)
        {
            points[idx] = new_pt;
            _config->movePoint(int(idx), new_pt);
            _draw_function = true;
            update();
        }
    }
    else
    {
        bool is_on_point = false;
        for (int i = 0; i < points.size(); i++)
        {
            const QPoint pos = e->pos();
            if (point_within_pixel(points[i], pos))
            {
                is_on_point = true;
                break;
            }
        }

        if (is_on_point)
        {
            setCursor(Qt::CrossCursor);
        }
        else
        {
            setCursor(Qt::ArrowCursor);
        }
    }
}

void spline_widget::mouseReleaseEvent(QMouseEvent *e)
{
    if (!_config || !isEnabled())
        return;

    if (e->button() == Qt::LeftButton)
    {
        mouseMoveEvent(e);
        setCursor(Qt::ArrowCursor);
        moving_control_point_idx = -1;

        _draw_function = true;
        update();
    }
}

void spline_widget::reload_spline()
{
    if (_config)
    {
        // don't recompute here as the value's just been recomputed
        update_range();
    }
}

void spline_widget::update_range()
{
    if (!_config)
        return;

    const int w = width(), h = height();
    const int mwl = 40, mhl = 20;
    const int mwr = 15, mhr = 35;

    pixel_bounds = QRectF(mwl, mhl, (w - mwl - mwr), (h - mhl - mhr));
    c = QPointF(pixel_bounds.width() / _config->maxInput(), pixel_bounds.height() / _config->maxOutput());
    _draw_function = true;

    _background = QPixmap();
    _function = QPixmap();

    update();
}

bool spline_widget::point_within_pixel(const QPointF &pt, const QPointF &pixel)
{
    QPointF tmp = pixel - point_to_pixel(pt);
    return sqrt(QPointF::dotProduct(tmp, tmp)) < point_size;
}

QPointF spline_widget::pixel_coord_to_point(const QPointF& point)
{
    if (!_config)
        return QPointF(-1, -1);

    using std::round;

    qreal x = round((point.x() - pixel_bounds.x()) / c.x());
    qreal y = round((pixel_bounds.height() - point.y() + pixel_bounds.y()) / c.y());

    if (snap_x > 0)
        x -= int(x) % snap_x;
    if (snap_y > 0)
        y -= int(y) % snap_y;

    if (x < 0)
        x = 0;
    if (x > _config->maxInput())
        x = _config->maxInput();

    if (y < 0)
        y = 0;
    if (y > _config->maxOutput())
        y = _config->maxOutput();

    return QPointF(x, y);
}

QPointF spline_widget::point_to_pixel(const QPointF& point)
{
    return QPointF(pixel_bounds.x() + point.x() * c.x(),
                   pixel_bounds.y() + pixel_bounds.height() - point.y() * c.y());
}

void spline_widget::resizeEvent(QResizeEvent *)
{
    update_range();
}