//
//  CalendarHeaderReusableView.swift
//  VDS
//
//  Created by Kanamarlapudi, Vasavi on 30/04/24.
//

import UIKit
import VDSTokens

/// Header view to display month and year along with days of week.
class CalendarHeaderReusableView: UICollectionReusableView {
    
    ///Identifier for the Calendar Header Reusable View.
    static let identifier: String = String(describing: CalendarHeaderReusableView.self)
    
    //--------------------------------------------------
    // MARK: - Public Properties
    //--------------------------------------------------
    /// A callback when the next button clicked.
    public var nextClicked: (() -> (Void))?
    
    /// A callback when the previous button clicked.
    public var previousClicked: (() -> (Void))?
    
    //--------------------------------------------------
    // MARK: - Private Properties
    //--------------------------------------------------
    internal var containerSize: CGSize { CGSize(width: 304, height: 88) }
    
    private lazy var stackView = UIStackView().with {
        $0.translatesAutoresizingMaskIntoConstraints = false
        $0.distribution = .fill
        $0.spacing = VDSLayout.space1X
        $0.axis = .vertical
        $0.backgroundColor = .clear
    }
    
    private lazy var topHeaderView = UIStackView().with {
        $0.translatesAutoresizingMaskIntoConstraints = false
        $0.distribution = .fill
        $0.spacing = VDSLayout.space1X
        $0.axis = .horizontal
        $0.backgroundColor = .clear
    }
    
    private lazy var daysCollectionView: UICollectionView = {
        let collectionView = UICollectionView(frame: .zero, collectionViewLayout: UICollectionViewFlowLayout())
        collectionView.isScrollEnabled = false
        collectionView.translatesAutoresizingMaskIntoConstraints = false
        collectionView.delegate = self
        collectionView.dataSource = self
        collectionView.showsHorizontalScrollIndicator = false
        collectionView.showsVerticalScrollIndicator = false
        collectionView.backgroundColor = .clear
        collectionView.register(collectionViewCell.self, forCellWithReuseIdentifier: collectionViewCell.identifier)
        return collectionView
    }()
    
    private var surface: Surface = .light
    private var displayDate: Date = Date()

    internal var previousMonthView = View()
    internal var nextMonthView = View()
    let viewSize = 40.0

    internal var previousButton = ButtonIcon().with {
        $0.kind = .ghost
        $0.iconName = .leftCaret
        $0.iconOffset = .init(x: -2, y: 0)
        $0.icon.size = .small
        $0.size = .small
    }
    
    internal var nextButton = ButtonIcon().with {
        $0.kind = .ghost
        $0.iconName = .rightCaret
        $0.iconOffset = .init(x: 2, y: 0)
        $0.icon.size = .small
        $0.size = .small
    }
    
    internal var headerTitle = Label().with {
        $0.translatesAutoresizingMaskIntoConstraints = false
        $0.textAlignment = .center
        $0.numberOfLines = 1
        $0.textStyle = .boldBodySmall
        $0.backgroundColor = .clear
        $0.isAccessibilityElement = true
    }
    
    internal let daysOfWeek = Date.capitalizedFirstLettersOfWeekdays
    internal let headerTitleTextColorConfiguration = SurfaceColorConfiguration(VDSColor.elementsPrimaryOnlight, VDSColor.elementsPrimaryOndark)

    //--------------------------------------------------
    // MARK: - Initializers
    //--------------------------------------------------
    override init(frame: CGRect) {
        super.init(frame: frame)
        setUp()
    }
    
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setUp()
    }
    
    //--------------------------------------------------
    // MARK: - Private Methods
    //--------------------------------------------------
    /// Configuring the cell with default setup.
    private func setUp() {
        isAccessibilityElement = false
        
        // stackview
        addSubview(stackView)
        stackView
            .pinTop()
            .pinBottom(VDSLayout.space1X)
            .pinLeading()
            .pinTrailing()
            .height(containerSize.height - VDSLayout.space1X)
            .width(containerSize.width)
        stackView.centerXAnchor.constraint(equalTo: centerXAnchor).activate()
        
        // top header stack view
        stackView.addArrangedSubview(topHeaderView)
        topHeaderView.heightAnchor.constraint(equalToConstant: viewSize).isActive = true
        topHeaderView.centerXAnchor.constraint(equalTo: centerXAnchor).activate()

        // previous button
        topHeaderView.addArrangedSubview(previousMonthView)
        previousMonthView.widthAnchor.constraint(equalToConstant: viewSize).activate()
        previousMonthView.addSubview(previousButton)
        previousButton.pinCenterY().pinCenterX()
        previousButton.onClick =  { _ in  self.previousButtonClick() }

        // month year label
        topHeaderView.addArrangedSubview(headerTitle)
        
        // next button
        topHeaderView.addArrangedSubview(nextMonthView)
        nextMonthView.widthAnchor.constraint(equalToConstant: viewSize).activate()
        nextMonthView.addSubview(nextButton)
        nextButton.pinCenterY().pinCenterX()
        nextButton.onClick =  { _ in  self.nextButtonClick() }

        // days Collection View
        stackView.addArrangedSubview(daysCollectionView)
        topHeaderView.heightAnchor.constraint(equalToConstant: viewSize).isActive = true
        daysCollectionView.centerXAnchor.constraint(equalTo: centerXAnchor).activate()
    }
    
    /// Updating UI based on next/previous clicks along with surface.
    /// Updating UI to enable/disable the next & previous buttons, updating header title.
    func update(with surface: Surface, date: Date, nextEnabled: Bool, previousEnabled: Bool) {
        self.surface = surface
        headerTitle.surface = surface
        previousButton.surface = surface
        nextButton.surface = surface
        nextButton.isEnabled = nextEnabled
        previousButton.isEnabled = previousEnabled
        daysCollectionView.reloadData()
        let labelText = date.getMonthName() + " \(date.yearInt)"
        headerTitle.text = labelText
        headerTitle.textColor = headerTitleTextColorConfiguration.getColor(surface)
    }
    
    func nextButtonClick() {
        nextClicked?()
    }
   
    func previousButtonClick() {
        previousClicked?()
    }
}

extension CalendarHeaderReusableView: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
    
    public func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return daysOfWeek.count
    }
    
    public func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: collectionViewCell.identifier, for: indexPath) as? collectionViewCell else { return UICollectionViewCell() }
        cell.updateTitle(text: daysOfWeek[indexPath.row], surface: self.surface)
        return cell
    }
    
    public func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: viewSize, height: viewSize)
    }
    
    public func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return VDSLayout.space1X
    }
    
    public func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return VDSLayout.space1X
    }
}

private class collectionViewCell: UICollectionViewCell {
    
    static let identifier: String = String(describing: collectionViewCell.self)
    
    private let textColorConfiguration = SurfaceColorConfiguration(VDSColor.elementsSecondaryOnlight, VDSColor.elementsSecondaryOndark)
    
    private var title = Label().with {
        $0.translatesAutoresizingMaskIntoConstraints = false
        $0.textAlignment = .center
        $0.numberOfLines = 1
        $0.textStyle = .bodySmall
        $0.backgroundColor = .clear
        $0.isAccessibilityElement = true
    }
    
    //--------------------------------------------------
    // MARK: - Initializers
    //--------------------------------------------------
    override init(frame: CGRect) {
        super.init(frame: frame)
        setupCell()
    }
    
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setupCell()
    }
    
    func setupCell() {
        addSubview(title)
        title.pinToSuperView()
    }
    
    func updateTitle(text: String, surface: Surface) {
        title.surface = surface
        title.text = text
        title.textColor = textColorConfiguration.getColor(surface)
    }
}