//
//  Pagination.swift
//  VDS
//
//  Created by Bandaru, Krishna Kishore on 01/03/24.
//

import Foundation
import VDSColorTokens
import Combine

@objc(VDSPagination)
open class Pagination: View {
    
    @Published var onPreviousTapped: PassthroughSubject<Int, Never> = PassthroughSubject()
    @Published var onNextTapped: PassthroughSubject<Int, Never> = PassthroughSubject()
    @Published var onPageWillChange: PassthroughSubject<Int, Never> = PassthroughSubject()
    @Published var onPageChanged: PassthroughSubject<Int, Never> = PassthroughSubject()
    
    public var total: Int = 0 {
        didSet {
            setNeedsUpdate()
        }
    }
    public var selectedPage: Int = 0 { didSet { setNeedsUpdate() } }
    private var numberOfRows: Int = 0 {
        didSet {
            collectionView.collectionViewLayout.invalidateLayout()
            setNeedsUpdate()
        }
    }
    private let pageItemCellSize: CGSize = .init(width: 20, height: 16)
    private let spacingBetweenCell: CGFloat = VDSLayout.Spacing.space1X.value
    private let buttonTintColorConfiguration = SurfaceColorConfiguration(VDSColor.paletteBlack, VDSColor.paletteWhite)
    private let buttonTextColorConfiguration = SurfaceColorConfiguration(VDSColor.paletteBlack, VDSColor.paletteWhite)
    
    private lazy var collectionView: UICollectionView = {
        let layout = UICollectionViewFlowLayout()
        layout.itemSize = pageItemCellSize
        layout.scrollDirection = .horizontal
        layout.minimumInteritemSpacing = spacingBetweenCell
        layout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize
        layout.minimumLineSpacing = spacingBetweenCell
        layout.sectionInset = .zero
        let collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
        collectionView.isScrollEnabled = false
        collectionView.translatesAutoresizingMaskIntoConstraints = false
        collectionView.delegate = self
        collectionView.dataSource = self
        collectionView.showsHorizontalScrollIndicator = false
        collectionView.showsVerticalScrollIndicator = false
        collectionView.register(PaginationCellItem.self, forCellWithReuseIdentifier: PaginationCellItem.identifier)
        collectionView.backgroundColor = .clear
        return collectionView
    }()
    
    //TODO: Need to check with textStyle with Matt as its getter only in ButtonBase
    private lazy var previousButton: ButtonBase = {
        let previousButton: ButtonBase
        if #available(iOS 15.0, *) {
            var configuration = ButtonBase.Configuration.plain()
            configuration.imagePadding = VDSLayout.Spacing.space2X.value
            configuration.attributedTitle = AttributedString("Previous", attributes: AttributeContainer([NSAttributedString.Key.font: TextStyle.boldBodySmall.font]))
            configuration.titleAlignment = .leading
            configuration.imagePlacement = .leading
            configuration.contentInsets = .zero
            previousButton = ButtonBase(configuration: configuration)
        } else {
            previousButton = ButtonBase()
            previousButton.imageEdgeInsets = .init(top: 0, left: 0, bottom: 0, right: VDSLayout.Spacing.space2X.value)
            previousButton.setTitle("Previous", for: .normal)
            previousButton.titleLabel?.font = TextStyle.boldBodySmall.font
        }
        previousButton.contentHorizontalAlignment = .leading
        previousButton.translatesAutoresizingMaskIntoConstraints = false
        previousButton.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
        previousButton.setImage(BundleManager.shared.image(for: "pagination-arrow-left")?.withRenderingMode(.alwaysTemplate), for: .normal)
        return previousButton
    }()
    
    private let nextButton: ButtonBase = {
        let nextButton: ButtonBase
        if #available(iOS 15.0, *) {
            var configuration = ButtonBase.Configuration.plain()
            configuration.imagePadding = VDSLayout.Spacing.space2X.value
            configuration.attributedTitle = AttributedString("Next", attributes: AttributeContainer([NSAttributedString.Key.font: TextStyle.boldBodySmall.font]))
            configuration.imagePlacement = .trailing
            configuration.titleAlignment = .trailing
            configuration.contentInsets = .zero
            nextButton = ButtonBase(configuration: configuration)
        } else {
            nextButton = ButtonBase()
            nextButton.imageEdgeInsets = .init(top: 0, left: 0, bottom: 0, right: VDSLayout.Spacing.space2X.value)
            nextButton.semanticContentAttribute = .forceRightToLeft
            nextButton.titleLabel?.font = TextStyle.boldBodySmall.font
            nextButton.setTitle("Next", for: .normal)
        }
        //nextButton.textStyle = .boldBodySmall
        nextButton.translatesAutoresizingMaskIntoConstraints = false
        nextButton.contentHorizontalAlignment = .trailing
        nextButton.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
        nextButton.setImage(BundleManager.shared.image(for: "pagination-arrow-right")?.withRenderingMode(.alwaysTemplate), for: .normal)
        return nextButton
    }()
    
    private let containerView: View = View().with {
        $0.translatesAutoresizingMaskIntoConstraints = false
    }
    
    open override func initialSetup() {
        super.initialSetup()
        
        addSubview(containerView)
        containerView.pinToSuperView()
        containerView.widthAnchor.constraint(greaterThanOrEqualToConstant: 288).activate()
        containerView.heightAnchor.constraint(equalToConstant: 44).activate()
        containerView.addSubview(previousButton)
        containerView.addSubview(collectionView)
        containerView.addSubview(nextButton)
        
        previousButton
            .pinTop()
            .pinBottom()
            .pinLeading()
        previousButton.trailingAnchor.constraint(greaterThanOrEqualTo: collectionView.leadingAnchor).activate()
        collectionView.heightAnchor.constraint(equalToConstant: VDSLayout.Spacing.space4X.value).activate()
        collectionView.centerYAnchor.constraint(equalTo: centerYAnchor).activate()
        collectionView.centerXAnchor.constraint(equalTo: centerXAnchor).activate()
        collectionView.trailingAnchor.constraint(greaterThanOrEqualTo: nextButton.leadingAnchor).activate()
        collectionView.widthAnchor.constraint(equalToConstant: 92).activate()
        nextButton
            .pinTop()
            .pinBottom()
            .pinTrailing()
        nextButton.onClick = onbuttonTapped
        previousButton.onClick = onbuttonTapped
        previousButton.isHidden = true
    }
    
    open override func updateView() {
        super.updateView()
        
        previousButton.tintColor = buttonTintColorConfiguration.getColor(surface)
        nextButton.tintColor = buttonTintColorConfiguration.getColor(surface)
        previousButton.setTitleColor(buttonTextColorConfiguration.getColor(surface), for: .normal)
        nextButton.setTitleColor(buttonTextColorConfiguration.getColor(surface), for: .normal)
        collectionView.reloadData()
    }
    
    private func onbuttonTapped(_ sender: UIButton) {
        let isNextAction = sender == nextButton
        if isNextAction {
            selectedPage += 1
        } else {
            selectedPage -= 1
        }
        updateSelection()
    }
    
    private func updateSelection() {
        collectionView.scrollToItem(at: IndexPath(row: max(selectedPage-1, 0), section: 0), at: .left, animated: false)
        previousButton.isHidden = selectedPage == 0
        nextButton.isHidden = selectedPage == total - 1
    }
}

extension Pagination: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
    
    public func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int { total }

    public func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: PaginationCellItem.identifier, for: indexPath) as? PaginationCellItem else { return UICollectionViewCell() }
        cell.update(selectedPage, currentIndex: indexPath.row, surface: surface)
        return cell
    }
    
    public func collectionView(_ collectionView: UICollectionView, shouldHighlightItemAt indexPath: IndexPath) -> Bool {
        onPageWillChange.send(selectedPage)
        return true
    }
    
    public func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        selectedPage = indexPath.row
        updateSelection()
        onPageChanged.send(indexPath.row)
    }
}

internal final class PaginationCellItem: UICollectionViewCell {
    
    static let identifier: String = String(describing: PaginationCellItem.self)
    private let textColorConfiguration = SurfaceColorConfiguration(VDSColor.elementsPrimaryOnlight, VDSColor.elementsPrimaryOndark)

    private var indexLabel: Label = Label().with {
        $0.translatesAutoresizingMaskIntoConstraints = false
        $0.textAlignment = .center
        $0.numberOfLines = 1
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        setUp()
    }
    
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setUp()
    }
    
    private func setUp() {
        let containerView = View()
        containerView.translatesAutoresizingMaskIntoConstraints = false
        containerView.addSubview(indexLabel)
        contentView.addSubview(containerView)
        containerView.pinToSuperView()
        indexLabel.pinToSuperView()
        indexLabel.widthAnchor.constraint(greaterThanOrEqualToConstant: VDSLayout.Spacing.space5X.value).activate()
        contentView.backgroundColor = .clear
        containerView.backgroundColor = .clear
        indexLabel.backgroundColor = .clear
    }
    
    internal func update(_ selectedIndex: Int, currentIndex: Int, surface: Surface) {
        indexLabel.textStyle = selectedIndex == currentIndex ? .boldBodySmall : .bodySmall
        indexLabel.text = "\(currentIndex)"
        indexLabel.textColor = textColorConfiguration.getColor(surface)
    }
}