vds_ios/VDS/Components/Buttons/TextLinkCaret/TextLinkCaret.swift

//
//  TextLinkCaret.swift
//  VDS
//
//  Created by Matt Bruce on 11/1/22.
//

import Foundation
import UIKit
import VDSColorTokens
import VDSFormControlsTokens
import Combine

/// A text link caret is an interactive element that always brings a customer to another page. It's used for navigation,
/// like "Back", or a call-to-action for a product or feature, like "Shop smartphones".  This class can be used within a ``ButtonGroup``.
///
/// If you are using AutoLayoutConstraints you have a combination of Leading/Left and Trailing/Right NSLayoutConstraints,
/// you need to ensure that one of these Horizontal Contraints is not constraint of "equatTo".  If you are to pin the left/right edges
/// to its parent this object will stretch to the parent's width.
@objc(VDSTextLinkCaret)
open class TextLinkCaret: ButtonBase {
    //--------------------------------------------------
    // 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 used to describe the position of the icon in relation to the title label.
    public enum IconPosition: String, CaseIterable {
        case left, right
        var image: UIImage {
            UIImage.image(for: self == .left ? .leftCaretBold : .rightCaretBold)!
        }
    }
    
    //--------------------------------------------------
    // MARK: - Private Properties
    //--------------------------------------------------
    private var textColorConfiguration = ControlColorConfiguration().with {
        $0.setSurfaceColors(VDSColor.elementsPrimaryOnlight, VDSColor.elementsPrimaryOndark, forState: .normal)
        $0.setSurfaceColors(VDSColor.interactiveDisabledOnlight, VDSColor.interactiveDisabledOndark, forState: .disabled)
        $0.setSurfaceColors(VDSColor.interactiveActiveOnlight, VDSColor.interactiveActiveOndark, forState: .highlighted)
    }
    
    //--------------------------------------------------
    // MARK: - Public Properties
    //--------------------------------------------------
    /// Determines icon position of Caret.
    open var iconPosition: IconPosition = .right { didSet { setNeedsUpdate() } }
    
    /// UIColor used on the titleLabel text.
    open override var textColor: UIColor {
        textColorConfiguration.getColor(self)
    }
    
    open override var textStyle: TextStyle {
        TextStyle.boldBodyLarge
    }
    
    //--------------------------------------------------
    // 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()
        
        //left align titleLabel in case this is pinned leading/trailing
        //default is always set to center
        contentHorizontalAlignment = .left
        
        accessibilityTraits = .link
        titleLabel?.numberOfLines = 0
        titleLabel?.lineBreakMode = .byWordWrapping
    }
    
    /// Used to make changes to the View based off a change events or from local properties.
    open override func updateView() {
        setImage(iconPosition.image.withTintColor(textColor), for: .normal)
        super.updateView()
    }
    
    /// Resets to default settings.
    open override func reset() {
        super.reset()
        iconPosition = .right
        text = nil
    }
    
    /// The natural size for the receiving view, considering only properties of the view itself.
    // Property to specify the icon size
    private var imageSize: CGSize = Icon.Size.xsmall.dimensions
    
    open override func layoutSubviews() {
        super.layoutSubviews()
        guard let titleLabel = titleLabel, let imageView = imageView else { return }
        
        // Adjust imageView size based on the imageSize property
        imageView.frame.size = imageSize
        
        let space: CGFloat = 5 // Space between the icon and the text
        
        // Adjust icon and text positions based on the iconPosition
        switch iconPosition {
        case .left:
            imageView.frame.origin.x = bounds.minX + contentEdgeInsets.left
            imageView.frame.origin.y = titleLabel.frame.minY + (textStyle.lineHeight - imageSize.height) / 2.0
            titleLabel.frame.origin.x = imageView.frame.maxX + space
            
        case .right:

            guard let attribtedText = titleLabel.attributedText else { return }

            let textContainer = NSTextContainer(size: CGSize(width: titleLabel.bounds.width, height: CGFloat.greatestFiniteMagnitude))
            textContainer.lineFragmentPadding = 0

            let layoutManager = NSLayoutManager()
            layoutManager.addTextContainer(textContainer)

            let textStorage = NSTextStorage(attributedString: attribtedText)
            textStorage.addLayoutManager(layoutManager)

            let lastGlyphIndex = layoutManager.glyphIndexForCharacter(at: attribtedText.string.utf16.count - 1)
            var lastGlyphRect = layoutManager.boundingRect(forGlyphRange: NSRange(location: lastGlyphIndex, length: 1), in: textContainer)

            lastGlyphRect.origin.x += titleLabel.frame.origin.x
            lastGlyphRect.origin.y += titleLabel.frame.origin.y

            imageView.frame.origin.x = lastGlyphRect.maxX + space
            imageView.frame.origin.y = lastGlyphRect.midY - imageSize.height / 2

        }
        
        imageView.contentMode = .scaleAspectFit
    }
    
    private var space: CGFloat {
        return 5 // Space between the icon and text, used in multiple places
    }
}