metatext/Views/UIKit/AnnouncementReactionsCollectionView.swift

// Copyright © 2021 Metabolist. All rights reserved.

import UIKit

final class AnnouncementReactionsCollectionView: UICollectionView {

    init() {
        super.init(frame: .zero, collectionViewLayout: Self.layout())

        backgroundColor = .clear
        isScrollEnabled = false
        showsVerticalScrollIndicator = false
        showsHorizontalScrollIndicator = false
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func layoutSubviews() {
        super.layoutSubviews()

        if bounds.size != intrinsicContentSize {
            invalidateIntrinsicContentSize()
        }
    }

    override var intrinsicContentSize: CGSize {
        CGSize(width: UIView.noIntrinsicMetric, height: max(contentSize.height, .minimumButtonDimension))
    }
}

private extension AnnouncementReactionsCollectionView {
    static func layout() -> UICollectionViewLayout {
        let itemSize = NSCollectionLayoutSize(
            widthDimension: .estimated(.minimumButtonDimension),
            heightDimension: .estimated(.minimumButtonDimension))
        let item = NSCollectionLayoutItem(layoutSize: itemSize)
        let groupSize = NSCollectionLayoutSize(
            widthDimension: .fractionalWidth(1),
            heightDimension: .estimated(.minimumButtonDimension))
        let group = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize, subitems: [item])

        group.interItemSpacing = .flexible(.defaultSpacing)

        let section = NSCollectionLayoutSection(group: group)

        section.interGroupSpacing = .defaultSpacing

        return UICollectionViewCompositionalLayout(section: section)
    }
}