import Foundation
import UIKit
import VDSCoreTokens
import Combine

/// A dropdown select is an expandable menu of predefined options that allows a customer to make a single selection.
@objc(VDSDatePicker)
open class DatePicker: EntryFieldBase {
    //--------------------------------------------------
    // MARK: - Initializers
    //--------------------------------------------------
    required public init() {
        super.init(frame: .zero)
    }
    
    public override init(frame: CGRect) {
        super.init(frame: .zero)
    }
    
    public required init?(coder: NSCoder) {
        super.init(coder: coder)
    }
    
    //--------------------------------------------------
    // MARK: - Public Properties
    //--------------------------------------------------
    /// A callback when the selected option changes. Passes parameters (option).
    open var onDateSelected: ((Date, DatePicker) -> Void)?
        
    //--------------------------------------------------
    // MARK: - Private Properties
    //--------------------------------------------------
    internal override var responder: UIResponder? { hiddenView }
    internal var hiddenView = UITextView().with { $0.width(0) }
    internal var minWidthDefault = 186.0
    internal var popoverView: UIScrollView!
    internal var popoverVisible = false
    internal var outsideTapGesture: UITapGestureRecognizer?
    internal var outsidePanGesture: UIPanGestureRecognizer?
    internal var overlayView = UIView().with {
        $0.backgroundColor = .clear;
        $0.isHidden = true
    }
    
    internal var bottomStackView: UIStackView = {
        return UIStackView().with {
            $0.translatesAutoresizingMaskIntoConstraints = false
            $0.axis = .vertical
            $0.distribution = .fill
            $0.alignment = .top
            $0.spacing = VDSLayout.space2X
        }
    }()

    //--------------------------------------------------
    // MARK: - Public Properties
    //--------------------------------------------------
    open var calendarIcon = Icon().with {
        $0.name = .calendar
        $0.size = .medium
    }
    
    open var selectedDate: Date? { didSet { setNeedsUpdate() } }
    
    open var calendarModel: CalendarModel = .init() { didSet { setNeedsUpdate() } }
    
    open override var value: String? {
        get { selectedDateLabel.text }
        set { }
    }
    
    open var selectedDateLabel = Label().with {
        $0.setContentCompressionResistancePriority(.required, for: .vertical)
        $0.textAlignment = .left
        $0.textStyle = .bodyLarge
        $0.lineBreakMode = .byCharWrapping
    }
    
    public enum DateFormat: String, CaseIterable, CustomStringConvertible {
        case shortNumeric
        case longAlphabetic
        case mediumNumeric
        case consiseNumeric
        
        public var format: String {
            switch self {
            case .shortNumeric: "MM/dd/yy"
            case .longAlphabetic: "MMMM d, yyyy"
            case .mediumNumeric: "MM/dd/yyyy"
            case .consiseNumeric: "M/d/yyyy"
            }
        }
        
        public var description: String {
            return format
        }
    }
    
    open var dateFormat: DateFormat = .shortNumeric { didSet{ setNeedsUpdate() } }

    //--------------------------------------------------
    // MARK: - Configuration Properties
    //--------------------------------------------------
    internal override var containerSize: CGSize { CGSize(width: minWidthDefault, height: 44) }

    //--------------------------------------------------
    // MARK: - Overrides
    //--------------------------------------------------
    
    /// Called once when a view is initialized and is used to Setup additional UI or other constants and configurations.
    open override func setup() {
        super.setup()

        // setting color config
        selectedDateLabel.textColorConfiguration = primaryColorConfiguration.eraseToAnyColorable()
              
        // tap gesture
        containerView
            .publisher(for: UITapGestureRecognizer())
            .sink { [weak self] _ in
                guard let self else { return }
                if isEnabled && !isReadOnly {
                    showPopover()
                }
            }
            .store(in: &subscribers)
        
        NotificationCenter.default
            .publisher(for: UIDevice.orientationDidChangeNotification).sink {  [weak self] _ in
                guard let self else { return }
                hidePopoverView()
            }
            .store(in: &subscribers)

    }
    
    open override func getFieldContainer() -> UIView {
        // stackview for controls in EntryFieldBase.controlContainerView
        let controlStackView = UIStackView().with {
            $0.translatesAutoresizingMaskIntoConstraints = false
            $0.axis = .horizontal
            $0.spacing = VDSLayout.space3X
        }
        controlStackView.addArrangedSubview(calendarIcon)
        controlStackView.addArrangedSubview(selectedDateLabel)
        controlStackView.addArrangedSubview(hiddenView)
        return controlStackView
    }
        
    /// Used to make changes to the View based off a change events or from local properties.
    open override func updateView() {
        super.updateView()
        
        if let selectedDate {
            formatDate(selectedDate)
        }
        
        selectedDateLabel.surface = surface
        selectedDateLabel.isEnabled = isEnabled
        calendarIcon.color = iconColorConfiguration.getColor(self)
    }
 
    /// Resets to default settings.
    open override func reset() {
        super.reset()
        selectedDateLabel.textStyle = .bodyLarge
    }
    
    internal func formatDate(_ date: Date) {
        let formatter = DateFormatter()
        formatter.dateFormat = dateFormat.format
        selectedDateLabel.text = formatter.string(from: date)
    }
}

extension DatePicker {
    private func showPopover() {
        guard let viewController = UIApplication.topViewController(), let parentView = viewController.view else { return }
        if popoverVisible {
            hidePopoverView()
        } else {
            let calendar = CalendarBase()
            calendar.activeDates = calendarModel.activeDates
            calendar.hideContainerBorder = calendarModel.hideContainerBorder
            calendar.hideCurrentDateIndicator = calendarModel.hideCurrentDateIndicator
            calendar.inactiveDates = calendarModel.inactiveDates
            calendar.indicators = calendarModel.indicators
            calendar.maxDate = calendarModel.maxDate
            calendar.minDate = calendarModel.minDate
            calendar.surface = calendarModel.surface
            calendar.setNeedsLayout()
            calendar.layoutIfNeeded()
            calendar.onChange = { [weak self] control in
                guard let self else { return }
                selectedDate = control.selectedDate
                sendActions(for: .valueChanged)
                UIAccessibility.post(notification: .layoutChanged, argument: containerView)
                hidePopoverView()
            }
            
            outsideTapGesture = UITapGestureRecognizer()
            outsidePanGesture = UIPanGestureRecognizer()
            
            overlayView.publisher(for: outsideTapGesture!).sink { [weak self] _ in
                guard let self else { return }
                hidePopoverView()
            }.store(in: &subscribers)
            parentView.publisher(for: outsidePanGesture!).sink { [weak self] _ in
                guard let self else { return }
                hidePopoverView()
            }.store(in: &subscribers)
            
            overlayView.frame = parentView.bounds
            overlayView.isHidden = false

            parentView.addSubview(overlayView)

            popoverView = UIScrollView()
            popoverView.backgroundColor = .green
            popoverView.clipsToBounds = true
            popoverView.backgroundColor = .clear
            popoverView.isHidden = true
            popoverView.addSubview(calendar)
            calendar.pinToSuperView()
            parentView.addSubview(popoverView)
            

            let spacing: CGFloat = 4
            let popoverSize: CGSize = .init(width: calendar.frame.width, height: calendar.frame.height)
            popoverView.contentSize = CGSize(width: popoverSize.width, height: popoverSize.height)
            
            let (popoverX, popoverY, adjustedHeight) = calculatePopoverPosition(relativeTo: containerView, in: parentView, size: popoverSize, with: spacing)
            //let adjustedX = adjustedHeight != popoverSize.height ? popoverX - 10 : popoverX
            let adjustedWidth = adjustedHeight != popoverSize.height ? popoverSize.width + 10 : popoverSize.width
            popoverView.frame = CGRect(x: popoverX, y: popoverY, width: adjustedWidth, height: adjustedHeight)

            parentView.layoutIfNeeded()
            popoverView.alpha = 0
            popoverView.transform = CGAffineTransform(scaleX: 0.9, y: 0.9)
            popoverView.isHidden = false
            popoverVisible = true
            _ = responder?.becomeFirstResponder()
            updateContainerView()
            UIView.animate(withDuration: 0.3,
                           delay: 0,
                           usingSpringWithDamping: 0.8,
                           initialSpringVelocity: 0.2,
                           options: .curveEaseOut,
                           animations: { [weak self] in
                guard let self else { return }
                popoverView.alpha = 1
                popoverView.transform = CGAffineTransform.identity
                if popoverSize.height > adjustedHeight {
                    popoverView.flashScrollIndicators()
                }
                UIAccessibility.post(notification: .layoutChanged, argument: calendar)
                parentView.layoutIfNeeded()
            })
        }
    }
    
    private func hidePopoverView() {
        overlayView.isHidden = true
        overlayView.removeFromSuperview()
        outsideTapGesture = nil
        outsidePanGesture = nil
        UIView.animate(withDuration: 0.2,
                       animations: {[weak self] in
            guard let self else { return }
            popoverView.alpha = 0
            popoverView.transform = CGAffineTransform(scaleX: 0.9, y: 0.9)
        }) { [weak self] _ in
            guard let self else { return }
            popoverView.isHidden = true
            popoverView.removeFromSuperview()
            popoverVisible = false
            responder?.resignFirstResponder()
            setNeedsUpdate()
            UIAccessibility.post(notification: .layoutChanged, argument: containerView)
        }
        
    }
       
    private func calculatePopoverPosition(relativeTo sourceView: UIView, in parentView: UIView, size: CGSize, with spacing: CGFloat) -> (CGFloat, CGFloat, CGFloat) {
        let sourceFrameInParent = sourceView.convert(sourceView.bounds, to: parentView)
        let parentBounds = parentView.bounds
        let safeAreaInsets = parentView.safeAreaInsets
        let popoverWidth = size.width
        let popoverHeight = size.height
       
        var popoverX: CGFloat = 0
        var popoverY: CGFloat = 0
        var adjustedHeight = popoverHeight
       
        // Calculate horizontal position
        if sourceFrameInParent.width < popoverWidth {
            if sourceFrameInParent.midX - popoverWidth / 2 < 0 {
                // Align to left
                popoverX = sourceFrameInParent.minX
            } else if sourceFrameInParent.midX + popoverWidth / 2 > parentBounds.width {
                // Align to right
                popoverX = sourceFrameInParent.maxX - popoverWidth
            } else {
                // Center on source view
                popoverX = sourceFrameInParent.midX - popoverWidth / 2
            }
        } else {
            popoverX = sourceFrameInParent.midX - popoverWidth / 2
        }
       
        // Ensure the popover is within the parent's bounds horizontally
        popoverX = max(0, min(popoverX, parentBounds.width - popoverWidth))
       
        // Calculate vertical position and height
        let availableSpaceAbove = sourceFrameInParent.minY - safeAreaInsets.top - spacing
        let availableSpaceBelow = parentBounds.height - sourceFrameInParent.maxY - safeAreaInsets.bottom - spacing
        let totalAvailableHeight = parentBounds.height - safeAreaInsets.top - safeAreaInsets.bottom
        
        if availableSpaceAbove >= popoverHeight {
            // Show above without adjusting height
            popoverY = sourceFrameInParent.minY - popoverHeight - spacing
        } else if availableSpaceBelow >= popoverHeight {
            // Show below without adjusting height
            popoverY = sourceFrameInParent.maxY + spacing
            
        } else if totalAvailableHeight >= popoverHeight {
            // check if the total
            if availableSpaceAbove > availableSpaceBelow {
                popoverY = safeAreaInsets.top
            } else {
                popoverY = parentBounds.height - safeAreaInsets.bottom - popoverHeight
            }
        } else {
            popoverY = safeAreaInsets.top
            adjustedHeight = totalAvailableHeight
        }
       
        return (popoverX, popoverY, adjustedHeight)
    }
}