//
//  Toggle.swift
//  VDS
//
//  Created by Matt Bruce on 7/22/22.
//

import Foundation
import UIKit
import VDSColorTokens
import Combine
/**
 A custom implementation of Apple's UISwitch.
 
 By default this class begins in the off state.
 
 Container: The background of the toggle control.
 Knob: The circular indicator that slides on the container.
 */
@objcMembers open class VDSToggle: VDSControl, Modelable, Changable {

    public typealias ModelType = VDSToggleModel
    @Published open var model: ModelType = DefaultToggleModel()
    private var cancellable: AnyCancellable?

    //--------------------------------------------------
    // MARK: - Private Properties
    //--------------------------------------------------
    private var toggleTintColor: (on: UIColor, off: UIColor) {
       return getToggleColor(for: disabled, surface: surface)
    }
    
    private var knobTintColor: (on: UIColor, off: UIColor) {
       return getKnobColor(for: disabled, surface: surface)
    }
    
    private func getToggleColor(for disabled: Bool, surface: Surface) -> (on: UIColor, off: UIColor) {
        if disabled {
            if surface == .light {
                return (on: VDSColor.elementsDisabledOnlight, off: VDSColor.elementsDisabledOnlight)
            } else {
                return (on: VDSColor.elementsDisabledOnDark, off: VDSColor.elementsDisabledOnDark)
            }
        } else {
            if surface == .light {
                return (on: VDSColor.paletteGreen26, off: VDSColor.elementsSecondaryOnlight)
            } else {
                return (on: VDSColor.paletteGreen34, off: VDSColor.paletteGray44)
            }
        }
    }
    
    private func getKnobColor(for disabled: Bool, surface: Surface) -> (on: UIColor, off: UIColor) {
        if disabled {
            if surface == .light {
                return (on: VDSColor.paletteGray95, off: VDSColor.paletteGray95)
            } else {
                return (on: VDSColor.paletteGray44, off: VDSColor.paletteGray44)
            }
        } else {
            if surface == .light {
                return (on: VDSColor.elementsPrimaryOndark, off: VDSColor.elementsPrimaryOndark)
            } else {
                return (on: VDSColor.elementsPrimaryOndark, off: VDSColor.elementsPrimaryOndark)
            }
        }
    }
    
    private var showTextSpacing: CGFloat {
        showText ? 12 : 0
    }
    
    private var stackView: UIStackView = {
       let stackView = UIStackView()
        stackView.translatesAutoresizingMaskIntoConstraints = false
        stackView.axis = .horizontal
        stackView.distribution = .fillProportionally
        return stackView
    }()
    
    private var label: VDSLabel = {
        let label = VDSLabel()
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }()
    
    private var toggleView: UIView = {
        let view = UIView()
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()

    private var knobView: UIView = {
        let view = UIView()
        view.translatesAutoresizingMaskIntoConstraints = false
        view.backgroundColor = .white
        return view
    }()
    
    
    //--------------------------------------------------
    // MARK: - Public Properties
    //--------------------------------------------------
    public var onChange: Blocks.ActionBlock?
    
    //--------------------------------------------------
    // MARK: - Static Properties
    //--------------------------------------------------
    // Sizes are from InVision design specs.
    public static var toggleSize = CGSize(width: 52, height: 24)
    public static var knobSize = CGSize(width: 20, height: 20)
    
    //--------------------------------------------------
    // MARK: - Computed Properties
    //--------------------------------------------------
    @Proxy(\.model.showText)
    public var showText: Bool {
        didSet {
            if oldValue != showText {
                ensureLabel()
            }
        }
    }
    
    @Proxy(\.model.onText)
    public var onText: String
    
    @Proxy(\.model.offText)
    public var offText: String

    @Proxy(\.model.textPosition)
    public var textPosition: VDSTextPosition {
        didSet {
            if oldValue != textPosition {
                ensureLabel()
            }
        }
    }
    
    @Proxy(\.model.fontSize)
    public var fontSize: VDSFontSize
    
    @Proxy(\.model.fontWeight)
    public var fontWeight: VDSFontWeight
    
    @Proxy(\.model.surface)
    public var surface: Surface

    @Proxy(\.model.on)
    open var isOn: Bool
    
    @Proxy(\.model.disabled)
    open var disabled: Bool
    
    open override var isEnabled: Bool {
        get { !model.disabled }
        set {
            //create local vars for clear coding
            let disabled = !newValue
            if model.disabled != disabled {
                model.disabled = disabled
            }
        }
    }
       
    //--------------------------------------------------
    // MARK: - Constraints
    //--------------------------------------------------
    
    private var knobLeadingConstraint: NSLayoutConstraint?
    private var knobTrailingConstraint: NSLayoutConstraint?
    private var knobHeightConstraint: NSLayoutConstraint?
    private var knobWidthConstraint: NSLayoutConstraint?
    private var toggleHeightConstraint: NSLayoutConstraint?
    private var toggleWidthConstraint: NSLayoutConstraint?
    
    //--------------------------------------------------
    // MARK: - Initializers
    //--------------------------------------------------
    public required init?(coder: NSCoder) {
        super.init(coder: coder)
        setup()
    }
    
    public override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }

    public convenience override init() {
        self.init(frame: .zero)
        setup()
    }
    
    func setup() {
        cancellable = $model.debounce(for: .seconds(ModelStateDebounce), scheduler: RunLoop.main).sink { [weak self] viewModel in
            self?.onStateChange(viewModel: viewModel)
        }
    }
    
    //functions
    //--------------------------------------------------
    // MARK: - Lifecycle
    //--------------------------------------------------
    
    public override func updateView(_ size: CGFloat) {
        super.updateView(size)
        
        let toggleSize = Self.toggleSize
        let knobSize = Self.knobSize

        toggleHeightConstraint?.constant = toggleSize.height
        toggleWidthConstraint?.constant = toggleSize.width
        
        knobHeightConstraint?.constant = knobSize.height
        knobWidthConstraint?.constant = knobSize.width
        
        toggleView.layer.cornerRadius = toggleSize.height / 2.0
        knobView.layer.cornerRadius = toggleSize.height / 2.0
        
        ensureLabel()
        
    }
    
    public override func setupView() {
        super.setupView()

        isAccessibilityElement = true
        accessibilityTraits = .button
        addSubview(stackView)
               
        let toggleSize = Self.toggleSize
        let knobSize = Self.knobSize

        toggleHeightConstraint = toggleView.heightAnchor.constraint(equalToConstant: toggleSize.height)
        toggleHeightConstraint?.isActive = true
        
        toggleWidthConstraint = toggleView.widthAnchor.constraint(equalToConstant: toggleSize.width)
        toggleWidthConstraint?.isActive = true
        
        toggleView.layer.cornerRadius = toggleSize.height / 2.0
        knobView.layer.cornerRadius = knobSize.height / 2.0
        
        toggleView.backgroundColor = toggleTintColor.off
        
        toggleView.addSubview(knobView)
        
        knobHeightConstraint = knobView.heightAnchor.constraint(equalToConstant: knobSize.height)
        knobHeightConstraint?.isActive = true
        knobWidthConstraint = knobView.widthAnchor.constraint(equalToConstant: knobSize.width)
        knobWidthConstraint?.isActive = true
        knobView.centerYAnchor.constraint(equalTo: toggleView.centerYAnchor).isActive = true
        knobView.topAnchor.constraint(greaterThanOrEqualTo: toggleView.topAnchor).isActive = true
        toggleView.bottomAnchor.constraint(greaterThanOrEqualTo: knobView.bottomAnchor).isActive = true
     
        //setup stackview
        if showText {
            stackView.addArrangedSubview(label)
        }
        ensureLabel()
        stackView.addArrangedSubview(toggleView)
        stackView.topAnchor.constraint(equalTo: topAnchor).isActive = true
        stackView.leadingAnchor.constraint(equalTo: leadingAnchor).isActive = true
        stackView.trailingAnchor.constraint(equalTo: trailingAnchor).isActive = true
        stackView.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true

    }
    
    func ensureLabel() {
        stackView.spacing = showTextSpacing
        if showText {
            if textPosition == .left {
                stackView.insertArrangedSubview(label, at: 0)
            } else {
                stackView.addArrangedSubview(label)
            }
        } else if stackView.subviews.contains(label) {
            label.removeFromSuperview()
        }
    }
    
    public override func reset() {
        super.reset()
        
        toggleView.backgroundColor = toggleTintColor.off
        knobView.backgroundColor = knobTintColor.off
        setAccessibilityLabel()
        onChange = nil
    }
        
    //--------------------------------------------------
    // MARK: - Actions
    //--------------------------------------------------
    
    open override func sendAction(_ action: Selector, to target: Any?, for event: UIEvent?) {
        super.sendAction(action, to: target, for: event)
        toggleAndAction()
    }
    
    open override func sendActions(for controlEvents: UIControl.Event) {
        super.sendActions(for: controlEvents)
        toggleAndAction()
    }
    
    /// This will toggle the state of the Toggle and execute the actionBlock if provided.
    public func toggleAndAction() {
        isOn.toggle()
        onChange?()
    }
        
    override open func accessibilityActivate() -> Bool {
        // Hold state in case User wanted isAnimated to remain off.
        guard isUserInteractionEnabled else { return false }
        sendActions(for: .touchUpInside)
        return true
    }
    
    //--------------------------------------------------
    // MARK: - UIResponder
    //--------------------------------------------------
    
    open override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        
        UIView.animate(withDuration: 0.1, animations: {
            self.knobWidthConstraint?.constant += Constants.PaddingOne
            self.layoutIfNeeded()
        })
    }
    
    public override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        knobReformAnimation()
        // Action only occurs of the user lifts up from withing acceptable region of the toggle.
        let value = 20.0
        guard let coordinates = touches.first?.location(in: self) else { return }
        guard coordinates.x > -value else { return }
        
        sendActions(for: .touchUpInside)
    }
    
    open override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
        knobReformAnimation()
        sendActions(for: .touchCancel)
    }
    
    //--------------------------------------------------
    // MARK: - Animations
    //--------------------------------------------------
    
    public func knobReformAnimation() {
        UIView.animate(withDuration: 0.1, animations: {
            self.knobWidthConstraint?.constant = Self.knobSize.width
            self.layoutIfNeeded()
        }, completion: nil)
    }
        
    /// Follow the SwiftUI View paradigm
    /// - Parameter viewModel: state
    open func onStateChange(viewModel: ModelType) {
        let enabled = !viewModel.disabled
        
        label.set(with: viewModel)
        label.text = viewModel.on ? viewModel.onText : viewModel.offText
        
        setAccessibilityHint(!viewModel.disabled)
        setAccessibilityValue(viewModel.on)
        
        //private func
        func constrainKnob(){
            self.knobLeadingConstraint?.isActive = false
            self.knobTrailingConstraint?.isActive = false
            if viewModel.on {
                self.knobTrailingConstraint = self.toggleView.trailingAnchor.constraint(equalTo: self.knobView.trailingAnchor, constant: 2)
                self.knobLeadingConstraint = self.knobView.leadingAnchor.constraint(greaterThanOrEqualTo: self.toggleView.leadingAnchor)
            }  else {
                self.knobTrailingConstraint = self.toggleView.trailingAnchor.constraint(greaterThanOrEqualTo: self.knobView.trailingAnchor)
                self.knobLeadingConstraint = self.knobView.leadingAnchor.constraint(equalTo: self.toggleView.leadingAnchor, constant: 2)
            }
            self.knobTrailingConstraint?.isActive = true
            self.knobLeadingConstraint?.isActive = true
            self.knobWidthConstraint?.constant = Self.knobSize.width
            self.layoutIfNeeded()
        }
        
        let toggleColor = getToggleColor(for: viewModel.disabled, surface: viewModel.surface)
        let knobColor = getKnobColor(for: viewModel.disabled, surface: viewModel.surface)
        
        if viewModel.disabled {
            toggleView.backgroundColor = viewModel.on ? toggleColor.on : toggleColor.off
            knobView.backgroundColor = viewModel.on ? knobColor.on : knobColor.off
            constrainKnob()
        } else {
            UIView.animate(withDuration: 0.2, delay: 0.0, options: .curveEaseIn, animations: {
                self.toggleView.backgroundColor = viewModel.on ? toggleColor.on : toggleColor.off
                self.knobView.backgroundColor = viewModel.on ? knobColor.on : knobColor.off
            }, completion: nil)
            
            UIView.animate(withDuration: 0.33, delay: 0, usingSpringWithDamping: 0.7, initialSpringVelocity: 0.5, options: [], animations: {
                constrainKnob()
            }, completion: nil)
        }
        
        backgroundColor = viewModel.surface.color
        isUserInteractionEnabled = !viewModel.disabled
        
        setAccessibilityHint(enabled)
        setAccessibilityValue(viewModel.on)
        setAccessibilityLabel(viewModel.on)
        
        setNeedsLayout()
        layoutIfNeeded()
    }

    // MARK:- Modable
    open func set(with model: ModelType) {
        self.model = model
    }
}