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

import Foundation
import UIKit
import VDSColorTokens
import Combine

/// A toggle is a control that lets customers instantly turn on
/// or turn off a single option, setting or function.
@objc(VDSToggle)
open class Toggle: Control, Changeable, FormFieldable {
    
    //--------------------------------------------------
    // 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: - Enums
    //--------------------------------------------------
    /// Enum for the size of text for the label.
    public enum TextSize: String, CaseIterable {
        case small, large
    }

    /// Enum to determine of the weight for the text style used for the label.
    public enum TextWeight: String, CaseIterable {
        case regular, bold
    }

    /// Enum for the text alignment in relation to the toggle view.
    public enum TextPosition: String, CaseIterable {
        case left, right
    }
    
    //--------------------------------------------------
    // MARK: - Constraints
    //--------------------------------------------------
    private var leftConstraints: [NSLayoutConstraint] = []
    private var rightConstraints: [NSLayoutConstraint] = []
    private var labelConstraints: [NSLayoutConstraint] = []

    //--------------------------------------------------
    // MARK: - Configuration
    //--------------------------------------------------
    private let toggleContainerSize = CGSize(width: 52, height: 44)
    private let spacingBetween = VDSLayout.Spacing.space3X.value
    
    /// TextStyle used to render the label.
    private var textStyle: TextStyle {
        if textSize == .small {
            if textWeight == .bold {
                return .boldBodySmall
            } else {
                return .bodySmall
            }
        } else {
            if textWeight == .bold {
                return .boldBodyLarge
            } else {
                return .bodyLarge
            }
        }
    }
    
    //--------------------------------------------------
    // MARK: - Private Properties
    //--------------------------------------------------
    private var showLabel: Bool {
        showText && !statusText.isEmpty
    }
    
    //--------------------------------------------------
    // MARK: - Public Properties
    //--------------------------------------------------
    open var onChangeSubscriber: AnyCancellable? {
        willSet {
            if let onChangeSubscriber {
                onChangeSubscriber.cancel()
            }
        }
    }
    
    /// Actual toggle used in this component.
    open var toggleView = ToggleView().with {
        $0.setContentCompressionResistancePriority(.defaultHigh, for: .horizontal)
        $0.isUserInteractionEnabled = false
        $0.isAccessibilityElement = false 
    }

    /// Used in showing the on/off text.
    open var label = Label().with {
        $0.setContentCompressionResistancePriority(.defaultHigh, for: .horizontal)
        $0.setContentHuggingPriority(.defaultHigh, for: .horizontal)

        $0.textColorConfiguration = ViewColorConfiguration().with {
            $0.setSurfaceColors(VDSColor.elementsSecondaryOnlight, VDSColor.elementsSecondaryOndark, forDisabled: true)
            $0.setSurfaceColors(VDSColor.elementsPrimaryOnlight, VDSColor.elementsPrimaryOndark, forDisabled: false)
        }.eraseToAnyColorable()
    }

    /// State of the toggle view.
    open var isOn: Bool {
        get { isSelected }
        set {
            if isSelected != newValue {
                toggleView.isOn = newValue
                isSelected = newValue
            }
        }
    }
    
    /// If set to true, the toggle view will include animation between state changes.
    open var isAnimated: Bool = true { didSet { setNeedsUpdate() } }

    /// If set to true, displays text either to the right or left of the toggle.
    open var showText: Bool = false { didSet { setNeedsUpdate() } }
        
    /// Text that will be shown in the status text when isOn is true
    open var onText: String = "On" { didSet { setNeedsUpdate() } }
    
    /// Text that will be shown in the status text when isOn is false
    open var offText: String = "Off" { didSet { setNeedsUpdate() } }
    
    /// Returns the correct text status based on the isOn state and correlates with onText or offText.
    open var statusText: String { isOn ? onText : offText }

    /// Changes the font size of the status text.
    open var textSize: TextSize = .small { didSet { setNeedsUpdate() } }
    
    /// Changes the font weight of the status text.
    open var textWeight: TextWeight = .regular { didSet { setNeedsUpdate() } }
    
    /// Positions status text to either the right or left of toggle.
    open var textPosition: TextPosition = .left { didSet { setNeedsUpdate() } }

    open var inputId: String? { didSet { setNeedsUpdate() } }

    open var value: AnyHashable? { didSet { setNeedsUpdate() } }
            
    /// The natural size for the receiving view, considering only properties of the view itself.
    open override var intrinsicContentSize: CGSize {
        if showLabel {
            label.sizeToFit()
            let size = CGSize(width: label.frame.width + spacingBetween +  toggleContainerSize.width,
                              height: max(toggleContainerSize.height, label.frame.height))
            return size
        } else {
            return toggleContainerSize
        }
    }
    
    open override var shouldHighlight: Bool { false }

    //--------------------------------------------------
    // MARK: - Overrides
    //--------------------------------------------------
    /// Executed on initialization for this View.
    open override func initialSetup() {
        super.initialSetup()
        onClick = { control in
            control.toggle()
        }
    }
    
    /// 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()
        
        isAccessibilityElement = true
        accessibilityTraits = .button
        addSubview(label)
        addSubview(toggleView)
                
        // Set up initial constraints for label and switch
        toggleView.centerYAnchor.constraint(equalTo: centerYAnchor).isActive = true

        labelConstraints = [
            height(constant: toggleContainerSize.height, priority: .defaultLow),
            heightGreaterThanEqualTo(constant: toggleContainerSize.height, priority: .defaultHigh),
            label.topAnchor.constraint(equalTo: topAnchor),
            label.bottomAnchor.constraint(equalTo: bottomAnchor),
        ]
        
        leftConstraints = [
            toggleView.leadingAnchor.constraint(equalTo: label.trailingAnchor, constant: spacingBetween),
            label.leadingAnchor.constraint(equalTo: leadingAnchor),
            toggleView.trailingAnchor.constraint(equalTo: trailingAnchor)
        ]
        
        rightConstraints = [
            toggleView.leadingAnchor.constraint(equalTo: leadingAnchor),
            label.leadingAnchor.constraint(equalTo: toggleView.trailingAnchor, constant: spacingBetween),
            label.trailingAnchor.constraint(lessThanOrEqualTo: trailingAnchor)
        ]

    }
    
    /// Resets to default settings.
    open override func reset() {
        super.reset()
        shouldUpdateView = false
        label.reset()
        isEnabled = true
        isOn = false
        isAnimated = true
        showText = false
        onText = "On"
        offText = "Off"
        textSize = .small
        textWeight = .regular
        textPosition = .left
        inputId = nil
        value = nil
        shouldUpdateView = true
        setNeedsUpdate()
    }
  
    /// Used to make changes to the View based off a change events or from local properties.
    open override func updateView() {
        super.updateView()
        
        updateLabel()
        toggleView.surface = surface
        toggleView.isEnabled = isEnabled
        toggleView.isOn = isOn
    }
    
    /// Used to update any Accessibility properties.
    open override func updateAccessibility() {
        super.updateAccessibility()
        if showText {
            accessibilityValue = isSelected ? onText : offText
        } else {
            accessibilityValue = isSelected ? "On" : "Off"
        }
    }

    /// This will change the state of the Selector and execute the actionBlock if provided.
    open func toggle() {
        isOn.toggle()
        sendActions(for: .valueChanged)
    }
    
    //--------------------------------------------------
    // MARK: - Private Methods
    //--------------------------------------------------
    private func updateLabel() {
        label.isHidden = !showLabel
        
        if showLabel {
            label.textAlignment = textPosition == .left ? .right : .left
            label.textStyle = textStyle
            label.text = statusText
            label.surface = surface
            label.isEnabled = isEnabled
            switch textPosition {
            case .left:
                NSLayoutConstraint.deactivate(rightConstraints)
                NSLayoutConstraint.activate(leftConstraints)
            case .right:
                NSLayoutConstraint.deactivate(leftConstraints)
                NSLayoutConstraint.activate(rightConstraints)
            }
            NSLayoutConstraint.activate(labelConstraints)
        } else {
            NSLayoutConstraint.deactivate(leftConstraints)
            NSLayoutConstraint.deactivate(rightConstraints)
            NSLayoutConstraint.deactivate(labelConstraints)
        }
    }
}