//
//  RoundedCellViewHeader.swift
//  App
//
//  Created by me on 16/06/2020.
//  Copyright © 2020. All rights reserved.
//

import UIKit
import SnapKit

class RoundedCellViewHeader: UIView {

    enum LeftViewType {
        case none, textSizeSlider((Float) -> ()), title(String), titleAndIcon(String, UIImage)
        
        var shouldExpandHorizontally: Bool {
            switch self {
            case .title(_), .titleAndIcon(_, _): return true
            default: return false
            }
        }
    }
    
    // MARK: - Attributes
    
    /// The title label of the cell view.
    private lazy var titleLabel = CustomLabel(font: Fonts.body_small_bold)
    
    private lazy var iconImageView: UIImageView = {
        let iconImageView = UIImageView()
        iconImageView.contentMode = .scaleAspectFit
        return iconImageView
    }()
    
    /// The (optional) text size slider.
    private lazy var textSizeSlider: TextSizeSlider = {
        let textSizeSlider = TextSizeSlider(value: WritePreferencesManager.currentFontSizeAsClampedValue)
        textSizeSlider.addTarget(self, action: #selector(textSizeSliderChanged), for: .valueChanged)
        return textSizeSlider
    }()

    private lazy var textSizeSliderWithIcons = TextSizeSliderWithIcons(slider: textSizeSlider)

    /// The help button.
    private lazy var helpButton: UIButton = {
        let helpButton = IconButton(icon: R.image.info()!)
        helpButton.layer.cornerRadius = 18
        helpButton.addTarget(self, action: #selector(helpButtonPressed), for: .touchUpInside)
        helpButton.accessibilityIdentifier = "Help"
        return helpButton
    }()

    /// The helper text label.
    private lazy var helperDescriptionLabel: UILabel = {
        let helperDescriptionLabel = CustomLabel(font: Fonts.body_small_medium)
        return helperDescriptionLabel
    }()

    private lazy var subtitleLabel = CustomLabel(font: Fonts.body_small_medium, style: .transparent)

    /// Header constraints for expanding
    private var closedHeaderConstraint: Constraint?
    private var openHeaderConstraint: Constraint?

    /// Stores if the header should be black when opened.
    private var shouldMakeHeaderBlack: Bool

    /// Tracks if the cell view has a help feature (help button and description) or not.
    private var hasHelp: Bool

    /// Tracks if the help description view is open or not.
    private var isHelpOpen = false

    /// The callback to call when the text slider changes.
    private var textSliderCallback: ((Float) -> ())?

    private(set) var leftViewType: LeftViewType
    
    var subtitle: String {
        get { return subtitleLabel.text ?? "" }
        set { subtitleLabel.text = newValue }
    }
    
    // MARK: - Setup
    
    init(leftViewType: LeftViewType, leftViewIsTransparent: Bool = true, subtitle: String? = nil, helperText: String?, shouldMakeHeaderBlack: Bool = false) {
        self.hasHelp = helperText != nil
        self.leftViewType = leftViewType
        self.shouldMakeHeaderBlack = shouldMakeHeaderBlack
        super.init(frame: .zero)
        let insets = Spaces.roundedCellInsets
        
        helperDescriptionLabel.text = helperText
        
        clipsToBounds = true
        layer.cornerRadius = 16

        // this layout guide allows to vertically center content while having an offset from the top (useful for internal header)
        let layoutGuide = UILayoutGuide()
        addLayoutGuide(layoutGuide)
        layoutGuide.snp.makeConstraints { make in
            make.top.equalToSuperview().inset(insets.top-11)
            make.left.right.equalToSuperview()
            if subtitle == nil { closedHeaderConstraint = make.bottom.equalToSuperview().constraint }
            make.height.equalTo(36)
        }

        if let subtitle = subtitle {
            subtitleLabel.text = subtitle
            addSubview(subtitleLabel)
            subtitleLabel.snp.makeConstraints { make in
                make.left.equalToSuperview().inset(insets.left)
                make.right.equalToSuperview().inset(insets.right)
                make.top.equalTo(layoutGuide.snp.bottom).offset(2)
                closedHeaderConstraint = make.bottom.equalToSuperview().inset(10).constraint
            }
        }
        
        // help button and description (we don't add it if there is a subtitle)
        if hasHelp && subtitle == nil {
            addSubview(helpButton)
            helpButton.snp.makeConstraints { make in
                make.width.height.equalTo(36)
                make.right.equalTo(layoutGuide).inset(insets.right-11)
                make.top.bottom.equalTo(layoutGuide)
            }

            addSubview(helperDescriptionLabel)
            helperDescriptionLabel.snp.makeConstraints { make in
                make.top.equalTo(layoutGuide.snp.bottom).offset(16)
                openHeaderConstraint = make.bottom.equalToSuperview().inset(20).constraint
                make.left.equalToSuperview().inset(insets.left)
                make.right.equalToSuperview().inset(insets.right)
            }
            helperDescriptionLabel.setContentCompressionResistancePriority(.required, for: .vertical) // prevent label from being shrinked
        }
            
        // left view (uilabel or text size slider)
        var leftView: UIView? = nil
        switch leftViewType {
        case .textSizeSlider(let callback):
            leftView = textSizeSliderWithIcons
            textSliderCallback = callback

        case .title(let title):
            leftView = titleLabel
            titleLabel.text = title

        case .titleAndIcon(let title, let icon):
            leftView = iconAndTitle(title: title, icon: icon)
            
        case .none:
            break
        }

        if let view = leftView {
            view.alpha = leftViewIsTransparent ? Constants.transparentAlpha : 1.0
            
            addSubview(view)
            view.snp.makeConstraints { make in
                make.left.equalTo(layoutGuide).inset(insets.left)
                make.top.bottom.equalTo(layoutGuide)
                if leftViewType.shouldExpandHorizontally { // extend width if label
                    if hasHelp { make.right.equalTo(helpButton.snp.left).offset(-8) }
                    else { make.right.equalTo(layoutGuide).inset(insets.right) }
                }
            }
        }
        
        setHelp(open: false, triggerLayout: false)
    }
    
    /// This should not be called, since we are not using Storyboard or XIB.
    @available(*, unavailable) required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    private func iconAndTitle(title: String, icon: UIImage) -> UIView {
        let view = UIView()
        
        view.addSubview(iconImageView)
        iconImageView.image = icon
        iconImageView.snp.makeConstraints { make in
            make.height.width.equalTo(20)
            make.centerY.equalToSuperview()
            make.height.lessThanOrEqualToSuperview()
            make.left.equalToSuperview()
        }
        iconImageView.fixImageSizeCompressionHugging()

        view.addSubview(titleLabel)
        titleLabel.text = title
        titleLabel.snp.makeConstraints { make in
            make.centerY.equalToSuperview()
            make.height.lessThanOrEqualToSuperview()
            make.left.equalTo(iconImageView.snp.right).offset(10)
            make.right.equalToSuperview()
        }
        
        return view
    }
    
    
    // MARK: - Methods
    
    /// Called when the text size slider changes.
    @objc func textSizeSliderChanged() {
        textSliderCallback?(textSizeSlider.value)
    }

    /// Called when the help button is pressed.
    @objc func helpButtonPressed() {
        if isHelpOpen {
            self.setHelp(open: !self.isHelpOpen)
        }
        else {
            UIView.animate(withDuration: 0.3, delay: 0, options: .curveEaseOut, animations: {
                self.setHelp(open: !self.isHelpOpen)
            }, completion: nil)
        }
    }
    
    /// Opens or closes the helper description view.
    func setHelp(open: Bool, triggerLayout: Bool = true) {
        guard hasHelp || !open else { return }
        isHelpOpen = open
        
        if shouldMakeHeaderBlack {
            backgroundColor = open ? UIColor(white: 0, alpha: 0.4) : .clear
        }
//        titleLabel.transform = open ? CGAffineTransform(translationX: 0, y: 7) : .identity
        
        helperDescriptionLabel.alpha = open ? 1 : 0
        
        helpButton.alpha = open ? 1 : Constants.transparentAlpha
        helpButton.backgroundColor = open ? .white : .clear
        helpButton.tintColor = open ? .black : .white
        
        // Update constraints
        if open {
            closedHeaderConstraint?.deactivate()
            openHeaderConstraint?.activate()
        }
        else {
            openHeaderConstraint?.deactivate()
            closedHeaderConstraint?.activate()
        }
        
        if triggerLayout {
            (superview as? RoundedCellView)?.layoutIfNeeded()
        }
    }


}