#include "Visualization/VisualizationGraphRenderingDelegate.h"
#include "Visualization/qcustomplot.h"

#include <Common/DateUtils.h>

namespace {

const auto DATETIME_FORMAT = QStringLiteral("yyyy/MM/dd hh:mm:ss:zzz");

const auto TEXT_TRACER_FORMAT = QStringLiteral("key: %1\nvalue: %2");

/// Timeout after which a tracer is displayed
const auto TRACER_TIMEOUT = 500;

/// Formats a data value according to the axis on which it is present
QString formatValue(double value, const QCPAxis &axis)
{
    // If the axis is a time axis, formats the value as a date
    if (auto axisTicker = qSharedPointerDynamicCast<QCPAxisTickerDateTime>(axis.ticker())) {
        return DateUtils::dateTime(value, axisTicker->dateTimeSpec()).toString(DATETIME_FORMAT);
    }
    else {
        return QString::number(value);
    }
}

void initPointTracerStyle(QCPItemTracer &tracer) noexcept
{
    tracer.setInterpolating(false);
    tracer.setStyle(QCPItemTracer::tsPlus);
    tracer.setPen(QPen(Qt::black));
    tracer.setBrush(Qt::black);
    tracer.setSize(10);
}

void initTextTracerStyle(QCPItemText &tracer) noexcept
{
    tracer.setPen(QPen{Qt::gray});
    tracer.setBrush(Qt::white);
    tracer.setPadding(QMargins{6, 6, 6, 6});
    tracer.setPositionAlignment(Qt::AlignTop | Qt::AlignLeft);
    tracer.setTextAlignment(Qt::AlignLeft);
}

} // namespace

struct VisualizationGraphRenderingDelegate::VisualizationGraphRenderingDelegatePrivate {
    explicit VisualizationGraphRenderingDelegatePrivate(QCustomPlot &plot)
            : m_Plot{plot},
              m_PointTracer{new QCPItemTracer{&plot}},
              m_TextTracer{new QCPItemText{&plot}},
              m_TracerTimer{}
    {
        initPointTracerStyle(*m_PointTracer);
        initTextTracerStyle(*m_TextTracer);

        m_TracerTimer.setInterval(TRACER_TIMEOUT);
        m_TracerTimer.setSingleShot(true);
    }

    QCustomPlot &m_Plot;
    QCPItemTracer *m_PointTracer;
    QCPItemText *m_TextTracer;
    QTimer m_TracerTimer;
};

VisualizationGraphRenderingDelegate::VisualizationGraphRenderingDelegate(QCustomPlot &plot)
        : impl{spimpl::make_unique_impl<VisualizationGraphRenderingDelegatePrivate>(plot)}
{
}

void VisualizationGraphRenderingDelegate::onMouseMove(QMouseEvent *event) noexcept
{
    // Cancels pending refresh
    impl->m_TracerTimer.disconnect();

    auto showTracers = [ eventPos = event->pos(), this ]()
    {
        // Lambda function to display a tracer
        auto displayTracer = [this](auto &tracer) {
            // Tracer is set on top of the plot's main layer
            tracer.setLayer(impl->m_Plot.layer("main"));
            tracer.setVisible(true);
            impl->m_Plot.replot();
        };

        // Reinits tracers
        impl->m_PointTracer->setGraph(nullptr);
        impl->m_PointTracer->setVisible(false);
        impl->m_TextTracer->setVisible(false);
        impl->m_Plot.replot();

        // Gets the graph under the mouse position
        if (auto graph = qobject_cast<QCPGraph *>(impl->m_Plot.plottableAt(eventPos))) {
            auto mouseKey = graph->keyAxis()->pixelToCoord(eventPos.x());
            auto graphData = graph->data();

            // Gets the closest data point to the mouse
            auto graphDataIt = graphData->findBegin(mouseKey);
            if (graphDataIt != graphData->constEnd()) {
                auto key = formatValue(graphDataIt->key, *graph->keyAxis());
                auto value = formatValue(graphDataIt->value, *graph->valueAxis());
                impl->m_TextTracer->setText(TEXT_TRACER_FORMAT.arg(key, value));

                // Displays point tracer
                impl->m_PointTracer->setGraph(graph);
                impl->m_PointTracer->setGraphKey(graphDataIt->key);
                displayTracer(*impl->m_PointTracer);

                // Displays text tracer
                auto tracerPosition = impl->m_TextTracer->position;
                tracerPosition->setAxes(graph->keyAxis(), graph->valueAxis());
                tracerPosition->setCoords(impl->m_PointTracer->position->key(),
                                          impl->m_PointTracer->position->value());
                displayTracer(*impl->m_TextTracer);
            }
        }
    };

    // Starts the timer to display tracers at timeout
    QObject::connect(&impl->m_TracerTimer, &QTimer::timeout, showTracers);
    impl->m_TracerTimer.start();
}