//
//  HomeCommonAppsGridView.swift
//  suixinkan
//

import SnapKit
import UIKit

/// 首页常用应用网格。
final class HomeCommonAppsGridView: UIView {

    var onMenuSelected: ((HomeMenuItem) -> Void)?

    private enum Section { case main }
    private enum Item: Hashable { case menu(HomeMenuItem) }

    private var menus: [HomeMenuItem] = []
    private let titleLabel = UILabel()
    private lazy var collectionView: UICollectionView = {
        let itemSize = NSCollectionLayoutSize(
            widthDimension: .fractionalWidth(0.25),
            heightDimension: .absolute(88)
        )
        let item = NSCollectionLayoutItem(layoutSize: itemSize)
        let groupSize = NSCollectionLayoutSize(
            widthDimension: .fractionalWidth(1),
            heightDimension: .absolute(88)
        )
        let group = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize, subitems: [item])
        let section = NSCollectionLayoutSection(group: group)
        let layout = UICollectionViewCompositionalLayout(section: section)
        return UICollectionView(frame: .zero, collectionViewLayout: layout)
    }()

    private lazy var dataSource = UICollectionViewDiffableDataSource<Section, Item>(collectionView: collectionView) {
        collectionView, indexPath, item in
        let cell = collectionView.dequeueReusableCell(
            withReuseIdentifier: HomeMenuCell.reuseIdentifier,
            for: indexPath
        ) as! HomeMenuCell
        if case let .menu(menu) = item {
            cell.apply(menu: menu)
        }
        return cell
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        titleLabel.text = "常用应用"
        titleLabel.font = .app(.title)
        titleLabel.textColor = AppColor.textPrimary

        collectionView.backgroundColor = .clear
        collectionView.delegate = self
        collectionView.register(HomeMenuCell.self, forCellWithReuseIdentifier: HomeMenuCell.reuseIdentifier)

        addSubview(titleLabel)
        addSubview(collectionView)

        titleLabel.snp.makeConstraints { make in
            make.top.leading.trailing.equalToSuperview()
        }
        collectionView.snp.makeConstraints { make in
            make.top.equalTo(titleLabel.snp.bottom).offset(AppSpacing.sm)
            make.leading.trailing.bottom.equalToSuperview()
            make.height.equalTo(88)
        }
    }

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

    func apply(menus: [HomeMenuItem]) {
        self.menus = menus + [.moreFunctions]
        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
        snapshot.appendSections([.main])
        snapshot.appendItems(self.menus.map { Item.menu($0) })
        dataSource.apply(snapshot, animatingDifferences: false)
    }
}

extension HomeCommonAppsGridView: UICollectionViewDelegate {
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        guard indexPath.item < menus.count else { return }
        onMenuSelected?(menus[indexPath.item])
    }
}

/// 首页菜单 cell。
final class HomeMenuCell: UICollectionViewCell {

    static let reuseIdentifier = "HomeMenuCell"

    private let iconView = UIImageView()
    private let titleLabel = UILabel()

    override init(frame: CGRect) {
        super.init(frame: frame)
        iconView.tintColor = AppColor.primary
        iconView.contentMode = .scaleAspectFit

        titleLabel.font = .app(.caption)
        titleLabel.textColor = AppColor.textPrimary
        titleLabel.textAlignment = .center
        titleLabel.numberOfLines = 2

        contentView.addSubview(iconView)
        contentView.addSubview(titleLabel)

        iconView.snp.makeConstraints { make in
            make.top.equalToSuperview().offset(AppSpacing.xs)
            make.centerX.equalToSuperview()
            make.width.height.equalTo(28)
        }
        titleLabel.snp.makeConstraints { make in
            make.top.equalTo(iconView.snp.bottom).offset(AppSpacing.xs)
            make.leading.trailing.equalToSuperview().inset(AppSpacing.xxs)
        }
    }

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

    func apply(menu: HomeMenuItem) {
        iconView.image = UIImage(systemName: menu.iconName)
        titleLabel.text = menu.title
    }
}