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

import Foundation
import UIKit
import VDSCoreTokens
import Combine

/// Label is a standard view used to draw text with applying Typography through ``TextStyle`` as well
/// as other attributes using any implemetation of ``LabelAttributeModel``.
@objc(VDSLabel)
open class Label: UILabel, ViewProtocol, UserInfoable {
    
    //--------------------------------------------------
    // MARK: - Initializers
    //--------------------------------------------------
    required public init() {
        super.init(frame: .zero)
        initialSetup()
    }

    public override init(frame: CGRect) {
        super.init(frame: .zero)
        initialSetup()
    }
    
    public required init?(coder: NSCoder) {
        super.init(coder: coder)
        initialSetup()
    }
    
    //--------------------------------------------------
    // MARK: - Combine Properties
    //--------------------------------------------------
    /// Set of Subscribers for any Publishers for this Control.
    open var subscribers = Set<AnyCancellable>()
    
    //--------------------------------------------------
    // MARK: - Private Properties
    //--------------------------------------------------
    private enum TextSetMode {
        case text
        case attributedText
    }

    private var textSetMode: TextSetMode = .text

    private var initialSetupPerformed = false
    
    private var edgeInsets: UIEdgeInsets { textStyle.edgeInsets }

    private var tapGesture: UITapGestureRecognizer? {
        willSet {
            if let tapGesture = tapGesture, newValue == nil {
                removeGestureRecognizer(tapGesture)
            } else if let gesture = newValue, tapGesture == nil {
                addGestureRecognizer(gesture)
            }
        }
    }
    
    private var actions: [LabelAction] = [] {
        didSet {
            isUserInteractionEnabled = !actions.isEmpty
            if actions.isEmpty {
                tapGesture = nil

            } else {
                //add tap gesture
                if tapGesture == nil {
                    let singleTap = UITapGestureRecognizer(target: self, action: #selector(textLinkTapped))
                    singleTap.numberOfTapsRequired = 1
                    tapGesture = singleTap
                }
                if actions.count > 1 {
                    actions.sort { first, second in
                        return first.range.location < second.range.location
                    }
                }
            }
        }
    }

    //--------------------------------------------------
    // MARK: - Private Models
    //--------------------------------------------------
    private struct LabelAction {
        var range: NSRange
        var action: PassthroughSubject<Void, Never>
        var accessibilityId: Int = 0
        
        func performAction() {
            action.send()
        }
        
        init(range: NSRange, action: PassthroughSubject<Void, Never>, accessibilityID: Int = 0) {
            self.range = range
            self.action = action
            self.accessibilityId = accessibilityID
        }
    }

    //--------------------------------------------------
    // MARK: - Public Properties
    //--------------------------------------------------
    /// Key of whether or not updateView() is called in setNeedsUpdate()
    open var shouldUpdateView: Bool = true

    /// Will determine if a scaled font should be used for the font.
    open var useScaledFont: Bool = false { didSet { setNeedsUpdate() }}
    
    open var surface: Surface = .light { didSet { setNeedsUpdate() }}
    
    /// Array of LabelAttributeModel objects used in rendering the text.
    open var attributes: [any LabelAttributeModel]? { didSet { setNeedsUpdate() }}
    
    /// TextStyle used on the this label.
    open var textStyle: TextStyle = .defaultStyle  { didSet { setNeedsUpdate() }}
    
    /// The alignment of the text within the label.
    open override var textAlignment: NSTextAlignment { didSet { setNeedsUpdate() }}

    open var userInfo = [String: Primitive]()
    
    /// Number of lines the label can render out, default is set to 0.
    open override var numberOfLines: Int { didSet { setNeedsUpdate() }}
    
    /// Line break mode for the label, default is set to word wrapping.
    open override var lineBreakMode: NSLineBreakMode { didSet { setNeedsUpdate() }}
        
    /// Text that will be used in the label.
    private var _text: String!
    override open var text: String! {
        didSet {
            _text = text
            textSetMode = .text
            setNeedsUpdate()
        }
    }
    
    ///AttributedText that will be used in the label.
    override open var attributedText: NSAttributedString? {
        didSet {
            textSetMode = .attributedText
            setNeedsUpdate()
        }
    }
    
    override open var font: UIFont! {
        didSet {
            if let font, initialSetupPerformed {
                textStyle = TextStyle.convert(font: font)
            }
            setNeedsUpdate()
        }
    }
    
    override open var textColor: UIColor! {
        didSet {
            if let textColor, initialSetupPerformed {
                textColorConfiguration = SurfaceColorConfiguration(textColor, textColor).eraseToAnyColorable()
            }
            setNeedsUpdate()
        }
    }
    
    /// Whether the View is enabled or not.
    /// Since the UILabel itselfs draws a different color for the "disabled state", I have to track
    /// local variable to deal with color and always enforce this UILabel is always enabled.
    private var _fakeIsEnabled: Bool = true
    open override var isEnabled: Bool {
        get { true }
        set {
            _fakeIsEnabled = newValue
            setNeedsUpdate()
        }
    }

    //--------------------------------------------------
    // MARK: - Configuration Properties
    //--------------------------------------------------
    /// Color configuration use for text color.  This is a configuration that will provide a color based
    /// of local properties such as surface and isEnabled.
    open var textColorConfiguration: AnyColorable = ViewColorConfiguration().with {
        $0.setSurfaceColors(VDSColor.interactiveDisabledOnlight, VDSColor.interactiveDisabledOndark, forDisabled: true)
        $0.setSurfaceColors(VDSColor.elementsPrimaryOnlight, VDSColor.elementsPrimaryOndark, forDisabled: false)
    }.eraseToAnyColorable(){ didSet { setNeedsUpdate() }}
            
    //--------------------------------------------------
    // MARK: - Lifecycle
    //--------------------------------------------------
    open func initialSetup() {
        if !initialSetupPerformed {
            initialSetupPerformed = true
            //register for ContentSizeChanges
            NotificationCenter
                .Publisher(center: .default, name: UIContentSizeCategory.didChangeNotification)
                .sink { [weak self] notification in
                    self?.setNeedsUpdate()
                }.store(in: &subscribers)
            backgroundColor = .clear
            numberOfLines = 0
            lineBreakMode = .byTruncatingTail
            translatesAutoresizingMaskIntoConstraints = false
            accessibilityCustomActions = []
            isAccessibilityElement = true
            accessibilityTraits = .staticText
            textAlignment = .left
            setup()
            setNeedsUpdate()
       }
    }
   
    open func setup() {}
    
    open func reset() {
        shouldUpdateView = false
        surface = .light
        isEnabled = true
        attributes = nil
        textStyle = .defaultStyle
        textAlignment = .left
        text = nil
        attributedText = nil
        numberOfLines = 0
        backgroundColor = .clear
        shouldUpdateView = true
        setNeedsUpdate()
    }
    
    open func updateView() {
        restyleText()
        
        //force a drawText
        setNeedsDisplay()
        
        setNeedsLayout()
    }
    
    open func updateAccessibility() {
        accessibilityLabel = text
        if isEnabled {
            accessibilityTraits.remove(.notEnabled)
        } else {
            accessibilityTraits.insert(.notEnabled)
        }
    }
    
    //--------------------------------------------------
    // MARK: - Overrides
    //--------------------------------------------------
    /// We are drawing using edgeInsets based off the textStyle.
    open override func drawText(in rect: CGRect) {
        super.drawText(in: rect.inset(by: edgeInsets))
    }
    
    /// We are applying action attributes after the views layout to ensure correct positioning of the text.
    open override func layoutSubviews() {
        super.layoutSubviews()
        applyActions()
    }
    
    /// Addig custom accessibillty actions from the collection of attributes.
    open override func accessibilityActivate() -> Bool {
        
        guard let accessibleActions = accessibilityCustomActions else { return false }
        
        for actionable in actions {
            for action in accessibleActions {
                if action.hash == actionable.accessibilityId {
                    actionable.performAction()
                    return true
                }
            }
        }
        
        return false
    }
    
    //--------------------------------------------------
    // MARK: - Private Methods
    //--------------------------------------------------
    private func restyleText() {
        if textSetMode == .text {
            styleText(_text)
        } else {
            styleAttributedText(attributedText)
        }
    }
    
   
    private struct FakeEnabled: Enabling, Surfaceable {
        var surface: Surface
        var isEnabled: Bool
    }
    
    /// Var to deal with the UILabel.isEnabled property causing issues with
    /// textColor when it is false, I am now using a struct to draw and manage
    /// colors instead of this class itself and this class will always be enabled
    private var _textColor: UIColor {
        let fake = FakeEnabled(surface: surface, isEnabled: _fakeIsEnabled)
        return textColorConfiguration.getColor(fake)
    }
    
    private func styleText(_ newValue: String!) {
        defer { invalidateIntrinsicContentSize() }
        guard let newValue, !newValue.isEmpty else {
            // We don't need to use attributed text
            super.attributedText = nil
            super.text = newValue
            return
        }
        
        //clear out accessibility
        accessibilityElements?.removeAll()
        accessibilityCustomActions = []
        
        //create the primary string
        let mutableText = NSMutableAttributedString.mutableText(for: newValue,
                                                                textStyle: textStyle,
                                                                useScaledFont: useScaledFont,
                                                                textColor: _textColor,
                                                                alignment: textAlignment,
                                                                lineBreakMode: lineBreakMode)
        applyAttributes(mutableText)
                
        // Set attributed text to match typography
        super.attributedText = mutableText
    }

    private func styleAttributedText(_ newValue: NSAttributedString?) {
        defer { invalidateIntrinsicContentSize() }
        guard let newValue, !newValue.string.isEmpty else {
            // We don't need any additional styling
            super.attributedText = newValue
            return
        }
        
        //clear out accessibility
        accessibilityElements?.removeAll()
        accessibilityCustomActions = []

        let mutableText = NSMutableAttributedString(attributedString: newValue)

        applyAttributes(mutableText)
                
        // Modify attributed text to match typography
        super.attributedText = mutableText
    }

    private func applyAttributes(_ mutableAttributedString: NSMutableAttributedString) {
        actions = []
        
        if let attributes {
            mutableAttributedString.apply(attributes: attributes)
        }
    }
    
    private func applyActions() {
        actions = []
        guard let attributedText else { return }
        
        let mutableAttributedString = NSMutableAttributedString(attributedString: attributedText)
        
        if let attributes {
            //loop through the models attributes
            for attribute in attributes {
                
                //see if the attribute is Actionable
                if let actionable = attribute as? any ActionLabelAttributeModel, mutableAttributedString.isValid(range: actionable.range) {
                    //create a accessibleAction
                    let customAccessibilityAction = customAccessibilityAction(text: mutableAttributedString.string, range: actionable.range, accessibleText: actionable.accessibleText)
                    
                    //create a wrapper for the attributes range, block and
                    actions.append(LabelAction(range: actionable.range, action: actionable.action, accessibilityID: customAccessibilityAction?.hashValue ?? -1))
                }
            }
            
            if let accessibilityElements, !accessibilityElements.isEmpty {
                let staticText = UIAccessibilityElement(accessibilityContainer: self)
                staticText.accessibilityLabel = text
                staticText.accessibilityFrameInContainerSpace = bounds
                
                isAccessibilityElement = false
                self.accessibilityElements = accessibilityElements.compactMap{$0 as? UIAccessibilityElement}.filter { $0.accessibilityLabel != text }
                self.accessibilityElements?.insert(staticText, at: 0)
            }
        }
    }
    
    @objc private func textLinkTapped(_ gesture: UITapGestureRecognizer) {
        for actionable in actions {
            // This determines if we tapped on the desired range of text.
            if gesture.didTapActionInLabel(self, inRange: actionable.range) {
                actionable.performAction()
                return
            }
        }
    }

    private func customAccessibilityAction(text: String?, range: NSRange, accessibleText: String? = nil) -> UIAccessibilityCustomAction? {
        
        guard let text = text, let attributedText else { return nil }
        
        let actionText = accessibleText ?? (text.isValid(range: range) ? NSString(string:text).substring(with: range) : text)
               
        // Calculate the frame of the substring
        let layoutManager = NSLayoutManager()
        let textContainer = NSTextContainer(size: bounds.size)
        let textStorage = NSTextStorage(attributedString: attributedText)
        layoutManager.addTextContainer(textContainer)
        textStorage.addLayoutManager(layoutManager)

        var glyphRange = NSRange()
       
        // Convert the range for the substring into a range of glyphs
        layoutManager.characterRange(forGlyphRange: range, actualGlyphRange: &glyphRange)
       
        let substringBounds = layoutManager.boundingRect(forGlyphRange: glyphRange, in: textContainer)

        // Create custom accessibility element
        let element = UIAccessibilityElement(accessibilityContainer: self)
        element.accessibilityLabel = actionText
        element.accessibilityTraits = .link
        element.accessibilityFrameInContainerSpace = substringBounds
        
        //TODO: accessibilityHint for Label
//      element.accessibilityHint = MVMCoreUIUtility.hardcodedString(withKey: "swipe_to_select_with_action_hint")

        accessibilityElements = (accessibilityElements ?? []).compactMap{$0 as? UIAccessibilityElement}.filter { $0.accessibilityLabel != actionText }
        accessibilityElements?.append(element)

        let accessibleAction = UIAccessibilityCustomAction(name: actionText, target: self, selector: #selector(accessibilityCustomAction(_:)))
        accessibilityCustomActions?.append(accessibleAction)
        return accessibleAction
    }
    
    @objc private func accessibilityCustomAction(_ action: UIAccessibilityCustomAction) {
        
        for actionable in actions {
            if action.hash == actionable.accessibilityId {
                actionable.performAction()
                return
            }
        }
    }
}