#pragma once

#include "../../Widgets/Widget.h"
#include <cstddef>
#include <functional>
#include <memory>
#include <vector>

namespace UI {

class VirtualizingGridLayout : public Widget {
    std::size_t itemCount;
    float reasonableColumnWidth;
    float spacing;
    float maximumRowHeight;
    float overscan;
    std::function<Size(std::size_t)> itemSizeProvider;
    std::function<std::unique_ptr<Widget>(std::size_t)> itemFactory;
    std::vector<float> rowHeights;
    std::vector<float> rowOffsets;
    std::size_t columnCount = 1;
    std::size_t visibleStartRow = 0;
    std::size_t visibleEndRow = 0;
    float scrollOffset = 0.0f;
    bool hasVisibleRange = false;

    std::size_t CalculateColumnCount(float availableWidth) const;
    float CalculateColumnWidth(float availableWidth) const;
    void RebuildMetrics(float availableWidth);
    bool UpdateVisibleChildren();
    void ArrangeChildInCell(Widget* child, Rect cellBounds) const;

public:
    VirtualizingGridLayout(
        std::size_t itemCount,
        float reasonableColumnWidth,
        float spacing,
        float maximumRowHeight,
        float overscan,
        std::function<Size(std::size_t)> itemSizeProvider,
        std::function<std::unique_ptr<Widget>(std::size_t)> itemFactory
    );

    void Measure(Size availableSpace) override;
    void Arrange(Rect finalBounds) override;
    void SetScrollOffset(Point offset) override;
};

}