//
//  CarouselScrollbar.swift
//  VDS
//
//  Created by Kanamarlapudi, Vasavi on 12/03/24.
//

import Foundation
import UIKit
import VDSColorTokens
import VDSFormControlsTokens
import Combine

/// A carousel scrollbar is a control that allows to navigate between items in a carousel.
/// It's also a status indicator that conveys the relative amount of content in a carousel and a location within it.
@objc(VDSCarouselScrollbar)
open class CarouselScrollbar: View {
    
    //--------------------------------------------------
    // 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
    //--------------------------------------------------
    /// Used to set total number of slides within carousel
    open var numberOfSlides: Int? {
        get { return _numberOfSlides }
        set {
            if let newValue {
                _numberOfSlides = newValue
            } else {
                _numberOfSlides = 1
            }
            setThumbWidth()
            scrollThumbToPosition(position)
            setNeedsUpdate()
        }
    }
    
    /// The number of slides that can appear at once in a set in a carousel container.
    open var selectedLayout: Layout? {
        get { return _selectedLayout }
        set {
            if let newValue {
                _selectedLayout = newValue
            } else {
                _selectedLayout = .oneUP
            }
            setThumbWidth()
            scrollThumbToPosition(position)
            setNeedsUpdate()
        }
    }
    
    /// Enum used to describe the number of slides that can appear at once in a set in a carousel container.
    public enum Layout: String, CaseIterable {
        case oneUP = "1UP"
        case twoUP = "2UP"
        case threeUP = "3UP"
        case fourUP = "4UP"
        case fiveUP = "5UP"
        case sixUP = "6UP"
        case eightUP = "8UP"
        
        var value: Int {
            switch self {
            case .oneUP:
                1
            case .twoUP:
                2
            case .threeUP:
                3
            case .fourUP:
                4
            case .fiveUP:
                5
            case .sixUP:
                6
            case .eightUP:
                8
            }
        }
    }
    
    /// Used to set the position of the thumb(scrubber). This is used when the carousel container changes position, it will align the position of thumb(scrubber).
    open var position: Int? {
        get { return _position }
        set {
            if let newValue {
                checkPositions()
                _position = (newValue > totalPositions ?? 1) ? totalPositions : newValue
            } else {
                _position = 1
            }
            scrollThumbToPosition(position)
            setNeedsUpdate()
        }
    }
    
    /// Allows a unique id to be passed into the thumb and track of the thumb(scrubber).
    open var scrubberId: Int?  { didSet { setNeedsUpdate() } }
    
    /// A callback when the scrubber position changes. Passes parameters (position).
    open var onScrubberDidChange: ((Int) -> Void)?
    
    //--------------------------------------------------
    // MARK: - Private Properties
    //--------------------------------------------------
    // Sizes are from InVision design specs.
    internal var containerSize: CGSize { CGSize(width: 45, height: 44) }
    internal var _selectedLayout: Layout = .oneUP
    internal var _numberOfSlides: Int? = 1
    internal var heightConstraint: NSLayoutConstraint?
    internal var totalPositions: Int? = 1
    internal var _position: Int? = 1
    internal var trayOriginalCenter: CGPoint!
    
    private let trackViewWidth = 96
    private let trackViewHeight: CGFloat = 4
    private let minThumbWidth: Float = 16.0
    private var thumbWidth: Float = 16.0
    private var actualThumbWidth: Float = 0.0
    private let cornerRadius: CGFloat = 4.0
    private let activeOpacity: Float = 0.15
    private let defaultOpacity: Float = 1
    
    /// Track view with fixed width
    internal var trackView: UIView = {
        return UIView().with {
            $0.translatesAutoresizingMaskIntoConstraints = false
        }
    }()
    
    /// Left Active Track overlay with variable width
    internal var leftActiveOverlay: UIView = {
        return UIView().with {
            $0.translatesAutoresizingMaskIntoConstraints = false
            $0.tag = 2
        }
    }()
    
    /// Right Active Track overlay with variable width
    internal var rightActiveOverlay: UIView = {
        return UIView().with {
            $0.translatesAutoresizingMaskIntoConstraints = false
            $0.tag = 3
        }
    }()
    
    /// Thumb view with variable width
    internal var thumbView: UIView = {
        return UIView().with {
            $0.translatesAutoresizingMaskIntoConstraints = false
        }
    }()
    
    //--------------------------------------------------
    // MARK: - Configuration
    //--------------------------------------------------
    private var thumbColorConfiguration = SurfaceColorConfiguration(VDSColor.interactiveScrollthumbOnlight , VDSColor.interactiveScrollthumbOndark)
    private var trackColorConfiguration = SurfaceColorConfiguration(VDSColor.interactiveScrolltrackOnlight , VDSColor.interactiveScrolltrackOndark)
    private var activeOverlayColorConfiguration = SurfaceColorConfiguration(VDSColor.paletteBlack, VDSColor.paletteWhite)
    
    //--------------------------------------------------
    // MARK: - Lifecycle
    //--------------------------------------------------
    open override func initialSetup() {
        super.initialSetup()
    }
    
    open override func setup() {
        super.setup()
        accessibilityLabel = "Carousel Scrollbar"
        
        //create the wrapping view
        heightConstraint = self.heightAnchor.constraint(equalToConstant: containerSize.height)
        heightConstraint?.priority = .defaultHigh
        heightConstraint?.isActive = true
        
        //Trackview
        trackView.frame = CGRectMake(20, 20, CGFloat(trackViewWidth), trackViewHeight)
        trackView.layer.cornerRadius = cornerRadius
        addSubview(trackView)
        
        ///Left active overlay
        leftActiveOverlay.frame = CGRectMake(trackView.frame.origin.x, 20,  CGFloat(trackViewWidth), trackViewHeight)
        leftActiveOverlay.isUserInteractionEnabled = true
        leftActiveOverlay.layer.cornerRadius = cornerRadius
        let leftPressRecognizer = UILongPressGestureRecognizer(target: self, action: #selector(self.onThumbTouchStart(_:)))
        leftPressRecognizer.minimumPressDuration = 0
        leftActiveOverlay.addGestureRecognizer(leftPressRecognizer)
        addSubview(leftActiveOverlay)
        
        ///Right active overlay
        rightActiveOverlay.frame = CGRectMake(thumbView.frame.origin.x + thumbView.frame.size.width, 20,  CGFloat(trackViewWidth), trackViewHeight)
        rightActiveOverlay.isUserInteractionEnabled = true
        rightActiveOverlay.layer.cornerRadius = cornerRadius
        let rightPressRecognizer = UILongPressGestureRecognizer(target: self, action: #selector(self.onThumbTouchEnd(_:)))
        rightPressRecognizer.minimumPressDuration = 0
        rightActiveOverlay.addGestureRecognizer(rightPressRecognizer)
        addSubview(rightActiveOverlay)
        
        //Thumbview
        thumbView.frame = CGRectMake(20, 20, CGFloat(thumbWidth), trackViewHeight)
        thumbView.layer.cornerRadius = cornerRadius
        thumbView.addGestureRecognizer(UIPanGestureRecognizer(target: self, action:(#selector(self.onScrubberDrag(_:)))))
        addSubview(thumbView)
        updateActiveOverlays()
    }
    
    open override func updateView() {
        super.updateView()
        trackView.backgroundColor = trackColorConfiguration.getColor(surface)
        thumbView.backgroundColor = thumbColorConfiguration.getColor(surface)
    }
    
    open override func updateAccessibility() {
        super.updateAccessibility()
    }
    
    open override func reset() {
        for subview in subviews {
            for recognizer in subview.gestureRecognizers ?? [] {
                subview.removeGestureRecognizer(recognizer)
            }
        }
        super.reset()
    }
    
    //--------------------------------------------------
    // MARK: - Private Methods
    //--------------------------------------------------
    func onMoveBackward() {
        position = (position ?? 1) - 1
        scrollThumbToPosition(position)
    }
    
    func onMoveForward() {
        position = (position ?? 1) + 1
        scrollThumbToPosition(position)
    }
    
    // Drag scrollbar thumb to move it to the left or right.
    // Upon releases of drag, the scrollbar thumb snaps to the closest full position and the scrollbar returns to original size without delay.
    @objc func onScrubberDrag(_ sender: UIPanGestureRecognizer) {
        let translation = sender.translation(in: thumbView)
        if sender.state == UIGestureRecognizer.State.began {
            trayOriginalCenter = thumbView.center
        } else if sender.state == UIGestureRecognizer.State.changed {
            let draggedPositions = Int (ceil (Double(translation.x) / Double(actualThumbWidth)))
            setThumb(at: (position ?? 1) + draggedPositions)
        }
        else if sender.state == UIGestureRecognizer.State.cancelled || sender.state == UIGestureRecognizer.State.ended {
            let draggedPositions = Int (ceil (Double(translation.x) / Double(actualThumbWidth)))
            position = (((position ?? 1) + draggedPositions) < 1) ? 1 : ((position ?? 1) + draggedPositions)
        }
    }
    
    // Move the scrollbar thumb to the left while tapping on the left side of the scrubber.
    @objc func onThumbTouchStart(_ gesture: UILongPressGestureRecognizer) {
        if gesture.state == .began {
            leftActiveOverlay.backgroundColor = activeOverlayColorConfiguration.getColor(self)
            leftActiveOverlay.layer.opacity = activeOpacity
        } else if gesture.state == .cancelled {
            leftActiveOverlay.backgroundColor = .clear
            leftActiveOverlay.layer.opacity = defaultOpacity
        } else if gesture.state == .ended {
            leftActiveOverlay.backgroundColor = .clear
            leftActiveOverlay.layer.opacity = defaultOpacity
            self.onMoveBackward()
        }
    }
    
    // Move the scrollbar thumb to the right while tapping on the right side of the scrubber.
    @objc func onThumbTouchEnd(_ gesture: UILongPressGestureRecognizer) {
        if gesture.state == .began {
            rightActiveOverlay.backgroundColor = activeOverlayColorConfiguration.getColor(self)
            rightActiveOverlay.layer.opacity = activeOpacity
        } else if gesture.state == .cancelled {
            rightActiveOverlay.backgroundColor = .clear
            rightActiveOverlay.layer.opacity = defaultOpacity
        } else if gesture.state == .ended {
            rightActiveOverlay.backgroundColor = .clear
            rightActiveOverlay.layer.opacity = defaultOpacity
            self.onMoveForward()
        }
    }
    
    // Minimum thumb width applied
    // Incomplete set moves a shorter distance than the standard increment value.
    private func setThumbWidth() {
        let width = (Float(trackViewWidth) / Float(numberOfSlides ?? 1)) * Float(_selectedLayout.value)
        actualThumbWidth = (width > Float(trackViewWidth)) ? Float(trackViewWidth) : width
        thumbWidth = (width <= Float(trackViewWidth) && width > minThumbWidth) ? width : ((width > Float(trackViewWidth)) ? Float(trackViewWidth) : minThumbWidth)
        thumbView.frame.size.width = CGFloat(thumbWidth)
        thumbView.frame.origin.x = trackView.frame.origin.x
        checkPositions()
        updateActiveOverlays()
    }
    
    // Update active overlay frames according to thumb position.
    private func updateActiveOverlays() {
        // adjusting thumb position if it goes beyond trackView.
        let thumbPosition = thumbView.frame.origin.x + thumbView.frame.size.width
        let trackPosition = trackView.frame.origin.x + trackView.frame.size.width
        if thumbPosition > trackPosition {
            thumbView.frame.origin.x = trackPosition - thumbView.frame.size.width
        } else if thumbView.frame.origin.x < trackView.frame.origin.x {
            thumbView.frame.origin.x = trackView.frame.origin.x
        }
        
        //left active overlay position update
        leftActiveOverlay.frame.size.width = thumbView.frame.origin.x - trackView.frame.origin.x + cornerRadius
        
        //left active overlay position update
        rightActiveOverlay.frame.origin.x = thumbView.frame.origin.x + thumbView.frame.size.width - cornerRadius
        rightActiveOverlay.frame.size.width = (trackView.frame.origin.x + trackView.frame.size.width) - (thumbView.frame.origin.x + thumbView.frame.size.width) + cornerRadius
    }
    
    private func checkPositions() {
        totalPositions = Int (ceil (Double(numberOfSlides ?? 1) / Double(_selectedLayout.value)))
    }

    private func scrollThumbToPosition(_ position: Int?) {
        DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(100)) { [weak self] in
            self?.setThumb(at: position)
            self?.onScrubberDidChange?(position ?? 1)
        }
    }
    
    private func setThumb(at position: Int?) {
        thumbView.frame.origin.x = CGFloat(Float((position ?? 1) - 1) * actualThumbWidth) + trackView.frame.origin.x
        updateActiveOverlays()
    }
}