#include "timelineview.h"
#include <QQmlContext>
#include <QQmlInfo>

struct TimelineViewItem
{
    TimelineViewItem(qint64 day, qint64 len, QQuickItem &qitem, TimelineView &view)
        : item(&qitem)
        , day(day)
    {
        item->setParentItem(&view);
        item->setPosition(QPointF(day * view.dayWidth(), 0.0));
        item->setSize(QSizeF(len * view.dayWidth(), view.height()));
        item->setVisible(true);
    }

    ~TimelineViewItem()
    {
        item->setVisible(false);
        item->setParent(nullptr);
    }

    qreal left() const { return item->x(); }
    qreal right() const { return item->x() + item->width(); }

    QQuickItem *item;
    const qint64 day;
};

TimelineView::TimelineView(QQuickItem *parent)
    : QQuickItem(parent)
    , m_dayWidth(24.0)
    , m_delegate(nullptr)
    , m_fromDate()
    , m_items()
    , m_reusableItems()
    , m_toDate()
    , m_viewportX(0)
    , m_prevViewportX(0)
    , m_viewportWidth(0)
    , m_prevViewportWidth(0)
{}

TimelineView::~TimelineView()
{
    clear();
    drainItems();
}

qreal TimelineView::dayWidth() const
{
    return m_dayWidth;
}

void TimelineView::setDayWidth(qreal width)
{
    if (width == m_dayWidth) {
        return;
    }
    m_dayWidth = width;
    emit dayWidthChanged(m_dayWidth);
    updateImplicitWidth();
    clear();
    populate();
}

QQmlComponent *TimelineView::delegate() const
{
    return m_delegate;
}

void TimelineView::setDelegate(QQmlComponent *delegate)
{
    if (delegate == m_delegate) {
        return;
    }
    m_delegate = delegate;
    emit delegateChanged(m_delegate);
    clear();
    drainItems();
    populate();
    update();
}

QDate TimelineView::fromDate() const
{
    return m_fromDate;
}

void TimelineView::setFromDate(QDate date)
{
    if (date == m_fromDate) {
        return;
    }
    m_fromDate = date;
    emit fromDateChanged(m_fromDate);
    updateImplicitWidth();
    populate();
}

QDate TimelineView::toDate() const
{
    return m_toDate;
}

void TimelineView::setToDate(QDate date)
{
    if (date == m_toDate) {
        return;
    }
    m_toDate = date;
    emit toDateChanged(m_toDate);
    updateImplicitWidth();
    populate();
}

qreal TimelineView::viewportX() const
{
    return m_viewportX;
}

void TimelineView::setViewportX(qreal x)
{
    if (x == m_viewportX) {
        return;
    }
    m_viewportX = x;
    emit viewportXChanged(m_viewportX);
    populate();
}

qreal TimelineView::viewportWidth() const
{
    return m_viewportWidth;
}

void TimelineView::setViewportWidth(qreal width)
{
    if (width == m_viewportWidth) {
        return;
    }
    m_viewportWidth = width;
    emit viewportWidthChanged(m_viewportWidth);
    populate();
}

void TimelineView::componentComplete()
{
    QQuickItem::componentComplete();
    populate();
}

TimelineViewItem *TimelineView::createItem(qint64 day, qint64 len)
{
    QQuickItem *item = m_reusableItems.isEmpty() ? qobject_cast<QQuickItem *>(m_delegate->create(
                                                       m_delegate->creationContext()))
                                                 : m_reusableItems.takeLast();
    if (!item) {
        qmlWarning(m_delegate) << TimelineView::tr("Delegate must be of Item type");
        return nullptr;
    }
    auto *viewItem = new TimelineViewItem(day, len, *item, *this);
    return viewItem;
}

void TimelineView::releaseItem(TimelineViewItem *item)
{
    if (!item) {
        return;
    }
    qsizetype index = m_items.indexOf(item);
    if (index < 0) {
        return;
    }
    QQuickItem *qitem = item->item;
    if (!m_reusableItems.contains(qitem)) {
        m_reusableItems.append(qitem);
    }
    m_items.removeAt(index);
    delete item;
}

void TimelineView::drainItems()
{
    qDeleteAll(m_reusableItems);
    m_reusableItems.clear();
}

void TimelineView::clear()
{
    while (!m_items.isEmpty()) {
        releaseItem(m_items.last());
    }
}

void TimelineView::populate()
{
    if (!isComponentComplete() || !m_delegate) {
        return;
    }
    if (m_viewportX > m_prevViewportX) {
        // Delete from the left
        while (!m_items.isEmpty()) {
            TimelineViewItem *item = m_items.first();
            if (item->right() >= m_viewportX) {
                break;
            }
            releaseItem(item);
        }
    } else if (m_viewportX < m_prevViewportX) {
        // Insert from the left
        for (qint64 day = m_items.isEmpty() ? qCeil(m_prevViewportX / m_dayWidth) - 1
                                            : m_items.first()->day - 1,
                    len = 1,
                    lastDay = qMax(-1, qFloor((m_viewportX - (len * m_dayWidth)) / m_dayWidth));
             day > lastDay;
             day -= len) {
            TimelineViewItem *viewItem = createItem(day, len);
            if (!viewItem) {
                break;
            }
            m_items.prepend(viewItem);
        }
    }
    int currentRight = m_viewportX + m_viewportWidth;
    int prevRight = m_prevViewportX + m_prevViewportWidth;
    if (currentRight < prevRight) {
        // Delete from the right
        while (!m_items.isEmpty()) {
            TimelineViewItem *item = m_items.last();
            if (item->left() < currentRight) {
                break;
            }
            releaseItem(item);
        }
    } else if (currentRight > prevRight) {
        // Insert from the right
        for (qint64 day = m_items.isEmpty() ? qCeil(prevRight / m_dayWidth) - 1
                                            : m_items.last()->day + 1,
                    len = 1,
                    lastDay = qFloor((currentRight + (len * m_dayWidth)) / m_dayWidth);
             day < lastDay;
             day += len) {
            TimelineViewItem *viewItem = createItem(day, len);
            if (!viewItem) {
                break;
            }
            m_items.append(viewItem);
        }
    }
    m_prevViewportX = m_viewportX;
    m_prevViewportWidth = m_viewportWidth;
}

void TimelineView::updateImplicitWidth()
{
    setImplicitWidth(m_dayWidth * m_fromDate.daysTo(m_toDate));
}

#include "moc_timelineview.cpp"