InteractiveTextView.swift

//
//  InteractiveLabel.swift
//  Hahow2C
//
//  Created by David on 2020/7/23.
//  Copyright © 2020 Hahow. All rights reserved.
//

import UIKit
import Siatke

// MARK: - Data modal of InteactiveTextView

public typealias TextComponentAction = (() -> Void)

public enum TextComponent {
    case text(String)
    case action(text: String, action: TextComponentAction)
}

fileprivate struct _TextComponent {
    let text: String
    let action: TextComponentAction?

    fileprivate init(text: String, action: TextComponentAction? = nil) {
        self.text = text
        self.action = action
    }
}

// MARK: - InteractiveTextView

final public class InteractiveTextView: UITextView {
    // MARK: - 📌 Constants

    // MARK: - 🔶 Properties

    private var actions: [(NSRange, TextComponentAction)] = []

    /// Components to display on label
    public var components: [TextComponent] = [] {
        didSet {
            renderContent(with: components)
        }
    }

    /// Determine if clickable range should have a underline indicates this is a clickable range.
    /// Default to true
    public var showUnderlineStyleOnActionRange: Bool = true {
        didSet { _reRenderContents() }
    }

    // MARK: - 🎨 Style

    public struct BaseStyle {
        public var fontStyle: UIFont.SteakerStyle = .body2
        public var textColor: UIColor = .hahow(.textPrimary)
        public var actionLabelColor: UIColor = .hahow(.textPrimary)
    }

    public var baseStyle = BaseStyle() {
        // re-render if style have changed
        didSet { _reRenderContents() }
    }

    public override var textAlignment: NSTextAlignment {
        didSet { _reRenderContents() }
    }

    public var lineBreakMode: NSLineBreakMode = .byWordWrapping {
        didSet {
            _reRenderContents()
        }
    }

    // MARK: - 🧩 Subviews

    // MARK: - 👆 Actions

    // MARK: - 🔨 Initialization

    public convenience init() {
        self.init(frame: .zero)
    }

    public override init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)

        setupUI()
    }

    required public init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    // MARK: - 🏗 UI

    private func setupUI() {
        isScrollEnabled = false
        textContainer.lineBreakMode = lineBreakMode
        adjustsFontForContentSizeCategory = true
        isUserInteractionEnabled = true
        backgroundColor = .clear

        textContainerInset = .zero
        textContainer.lineFragmentPadding = .zero

        addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(labelTapped(_:))))
    }

    public override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
        super.traitCollectionDidChange(previousTraitCollection)

        // TODO: re-render attributed text here
        renderContent(with: components)
    }

    // MARK: - 🚌 Public Methods

    private func renderContent(with components: [TextComponent]) {
        let string = NSMutableAttributedString()
        var range = NSRange(location: 0, length: 0)

        for item in components.mapStruct() {
            var attr: [NSAttributedString.Key: Any] = .steakerAttributes(
                for: baseStyle.fontStyle,
                textColor: baseStyle.textColor,
                textAlignment: textAlignment,
                lineBreakMode: lineBreakMode
            )
            range.location = range.location + range.length
            range.length = item.text.count
            if let action = item.action {
                attr[.foregroundColor] = baseStyle.actionLabelColor
                if showUnderlineStyleOnActionRange {
                    attr[.underlineStyle] = NSUnderlineStyle.single.rawValue
                }
                actions.append((range, action))
            }
            let attributedString = NSAttributedString(string: item.text, attributes: attr)
            string.append(attributedString)
        }

        attributedText = string
    }

    private func _reRenderContents() {
        renderContent(with: components)
    }

    // MARK: - 🔒 Private Methods

    @objc private func labelTapped(_ gesture: UITapGestureRecognizer) {
        guard let view = gesture.view as? UITextView else { return }

        var location = gesture.location(in: view)
        location.x -= view.textContainerInset.left
        location.y -= view.textContainerInset.top

        let indexOfCharacter = view.layoutManager.characterIndex(for: location, in: view.textContainer, fractionOfDistanceBetweenInsertionPoints: nil)

        for (range, action) in actions {
            if NSLocationInRange(indexOfCharacter, range) {
                action()
                break
            }
        }
    }
}

private extension TextComponent {
    func mapStruct() -> _TextComponent {
        switch self {
        case .text(let text):
            return _TextComponent(text: text)
        case let .action(text: text, action: action):
            return _TextComponent(text: text, action: action)
        }
    }
}

private extension Array where Element == TextComponent {
    func mapStruct() -> [_TextComponent] {
        map({ $0.mapStruct() })
    }
}