vds_ios/VDS/Components/Label/Label.swift

//
//  VDSLabel.swift
//  VDS
//
//  Created by Matt Bruce on 7/28/22.
//

import Foundation
import UIKit
import VDSColorTokens
import Combine

open class Label: UILabel, ModelHandlerable, Initable, Resettable {
    
    //--------------------------------------------------
    // MARK: - Combine Properties
    //--------------------------------------------------
    @Published public var model: LabelModel = DefaultLabelModel()
    private var cancellable: AnyCancellable?

    //--------------------------------------------------
    // MARK: - Properties
    //--------------------------------------------------
    @Proxy(\.model.fontSize)
    public var fontSize: FontSize
    
    @Proxy(\.model.textPosition)
    public var textPosition: TextPosition
    
    @Proxy(\.model.fontWeight)
    public var fontWeight: FontWeight
    
    @Proxy(\.model.fontCategory)
    public var fontCategory: FontCategory
    
    @Proxy(\.model.surface)
    public var surface: Surface

    //--------------------------------------------------
    // MARK: - Initializers
    //--------------------------------------------------
    required public convenience init() {
        self.init(frame: .zero)
    }
    
    public required convenience init(with model: LabelModel) {
        self.init()
        self.model = model
        set(with: model)
    }
    
    public override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }
    
    required public init?(coder: NSCoder) {
        super.init(coder: coder)
        setup()
    }
    
    //--------------------------------------------------
    // MARK: - Public Functions
    //--------------------------------------------------
    open func setup() {
        backgroundColor = .clear
        numberOfLines = 0
        lineBreakMode = .byWordWrapping
        translatesAutoresizingMaskIntoConstraints = false
        accessibilityCustomActions = []
        accessibilityTraits = .staticText
        cancellable = $model.debounce(for: .seconds(Constants.ModelStateDebounce), scheduler: RunLoop.main).sink { [weak self] viewModel in
            self?.onStateChange(viewModel: viewModel)
        }
    }
    
    public func reset() {
        text = nil
        attributedText = nil
        textColor = .black
        font = FontStyle.RegularBodyLarge.font
        textAlignment = .left
        accessibilityCustomActions = []
        accessibilityTraits = .staticText
        numberOfLines = 0
    }
    
    //Modelable
    open func set(with model: LabelModel) {
        self.model = model
    }
    
    //--------------------------------------------------
    // MARK: - State
    //--------------------------------------------------
    /// Follow the SwiftUI View paradigm
    /// - Parameter viewModel: state
    open func onStateChange(viewModel: LabelModel) {
        textAlignment = viewModel.textPosition.textAlignment
        textColor = getTextColor(for: viewModel.disabled, surface: viewModel.surface)
       
        if let vdsFont = try? FontStyle.font(for: viewModel.fontCategory, fontWeight: viewModel.fontWeight, fontSize: viewModel.fontSize) {
            font = vdsFont
        } else {
            font = FontStyle.RegularBodyLarge.font
        }
        
        if let attributes = viewModel.attributes, let text = model.text, let font = font, let textColor = textColor {
            let startingAttributes = [NSAttributedString.Key.font: font, NSAttributedString.Key.foregroundColor: textColor]
            let mutableText = NSMutableAttributedString(string: text, attributes: startingAttributes)
            for attribute in attributes {
                attribute.setAttribute(on: mutableText)
                if let actionable = attribute as? LabelAttributeActionable{
                    actions.append(actionable)
                }
            }
            attributedText = mutableText
        } else {
            text = viewModel.text
        }
    }

    //--------------------------------------------------
    // MARK: - Private Functions
    //--------------------------------------------------
    private func getTextColor(for disabled: Bool, surface: Surface) -> UIColor {
        if disabled {
            if surface == .light {
                return VDSColor.elementsSecondaryOnlight
            } else {
                return VDSColor.elementsSecondaryOndark
            }
        } else {
            if surface == .light {
                return VDSColor.elementsPrimaryOnlight
            } else {
                return VDSColor.elementsPrimaryOndark
            }
        }
    }
        
    //--------------------------------------------------
    // MARK: - Actionable
    //--------------------------------------------------
    private var tapGesture: UITapGestureRecognizer?
    private var actions: [LabelAttributeActionable] = [] {
        didSet {
            isUserInteractionEnabled = !actions.isEmpty
            if actions.isEmpty {
                if let tapGesture = tapGesture {
                    removeGestureRecognizer(tapGesture)
                }
            } else {
                //add tap gesture
                if tapGesture == nil {
                    let singleTap = UITapGestureRecognizer(target: self, action: #selector(textLinkTapped))
                    singleTap.numberOfTapsRequired = 1
                    addGestureRecognizer(singleTap)
                    tapGesture = singleTap
                }
                if actions.count > 1 {
                    actions.sort { first, second in
                        return first.range.location < second.range.location
                    }
                }
            }
        }
    }
    
    @objc private func textLinkTapped(_ gesture: UITapGestureRecognizer) {
        for actionable in actions {
            // This determines if we tapped on the desired range of text.
            if gesture.didTapAttributedTextInLabel(self, inRange: actionable.range) {
                actionable.action()
                return
            }
        }
    }
}