//
//  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
    }

    //--------------------------------------------------
    // 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)
    }
    
    private var rightCaret: CaretLabelAttribute?
    private var leftCaret: Icon = Icon().with {
        $0.name = .leftCaretBold
        $0.size = .xsmall
    }
    
    //--------------------------------------------------
    // MARK: - Public Properties
    //--------------------------------------------------    
    /// Determines icon position of Caret.
    open var iconPosition: IconPosition = .right { didSet { setNeedsUpdate() } }
    
    open override var textAttributes: [any LabelAttributeModel]? {
        guard let rightCaret, iconPosition == .right else { return nil }
        return [rightCaret]
    }
    
    /// 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()
        accessibilityTraits = .link
        titleLabel?.lineBreakMode = .byWordWrapping
        titleLabel?.numberOfLines = 0

    }
    
    /// Used to make changes to the View based off a change events or from local properties.
    open override func updateView() {
        if iconPosition == .right {
            leftCaret.removeFromSuperview()
            rightCaret = CaretLabelAttribute(tintColor: textColor, position: .right)
            setImage(nil, for: .normal)
            titleEdgeInsets = .zero
            contentEdgeInsets = .zero
        } else {
            if let text, text.isEmpty {
                setImage(nil, for: .normal)
                titleEdgeInsets = .zero
                contentEdgeInsets = .zero
            } else {
                leftCaret.color = textColor
                if let image = leftCaret.imageView.image, let resized = resize(image: image, size: leftCaret.size.dimensions) {
                    contentVerticalAlignment = .top
                    setImage(resized, for: .normal)
                    imageEdgeInsets = .init(top: 5, left: 0, bottom: 0, right: VDSLayout.Spacing.space1X.value)
                    titleEdgeInsets = .init(top: 0, left: VDSLayout.Spacing.space1X.value, bottom: 0, right: 0)
                }
            }
            
        }
        super.updateView()
    }
    
    func resize(image: UIImage, size: CGSize) -> UIImage? {
        UIGraphicsBeginImageContextWithOptions(size, false, 0.0)
        image.draw(in: CGRect(origin: .zero, size: size))
        let resizedImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return resizedImage
    }

    /// 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.
    override open var intrinsicContentSize: CGSize {
        //get the labels size, if not the button
        return titleLabel?.intrinsicContentSize ?? super.intrinsicContentSize
    }
}

extension TextLinkCaret {
    struct CaretLabelAttribute: LabelAttributeModel {
        var id: UUID = .init()
        var location: Int = 0
        var length: Int = 1
        var tintColor: UIColor
        var position: IconPosition
        var spacerWidth: CGFloat = VDSLayout.Spacing.space1X.value
        var width: CGFloat { caretSize.width + spacerWidth }
        var caretSize: CGSize { Icon.Size.xsmall.dimensions }
        
        init(tintColor: UIColor, position: IconPosition) {
            self.tintColor = tintColor
            self.position = position
        }
        
        func setAttribute(on attributedString: NSMutableAttributedString) {
            let imageAttr = ImageLabelAttribute(location: location, imageName: "\(position.rawValue)-caret-bold", frame: .init(x: 0, y: 0, width: caretSize.width, height: caretSize.height), tintColor: tintColor)
            let spacer = NSAttributedString.spacer(for: spacerWidth)
            
            guard let image = try? imageAttr.getAttachment() else { return }
            
            if position == .right {
                attributedString.append(spacer)
                attributedString.append(NSAttributedString(attachment: image))
            } else {
                attributedString.insert(NSAttributedString(attachment: image), at: 0)
                attributedString.insert(spacer, at: 1)
            }
        }
        
        func isEqual(_ equatable: CaretLabelAttribute) -> Bool {
            return id == equatable.id && range == equatable.range
        }
        
    }
}