//
//  ItemCollectionViewCell.swift
//  Reader
//
//  Created by Shadowfacts on 1/9/22.
//

import UIKit

protocol ItemCollectionViewCellDelegate: AnyObject {
    func itemCellSelected(cell: ItemCollectionViewCell, item: Item)
}

class ItemCollectionViewCell: UICollectionViewListCell {
    
    weak var delegate: ItemCollectionViewCellDelegate?
    
    private let titleLabel = UILabel()
    private let feedTitleLabel = UILabel()
    private let contentLabel = UILabel()
    private var shouldInteractOnNextTouch = true
    
    private var item: Item!
    
    private lazy var feedbackGenerator = UISelectionFeedbackGenerator()
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        
        backgroundConfiguration = .clear()
        
        let descriptor = UIFontDescriptor.preferredFontDescriptor(withTextStyle: .title3).withSymbolicTraits(.traitBold)!.withDesign(.serif)!
        titleLabel.font = UIFont(descriptor: descriptor, size: 0)
        titleLabel.numberOfLines = 0
        
        feedTitleLabel.font = UIFont(descriptor: .preferredFontDescriptor(withTextStyle: .subheadline), size: 0)
        
        contentLabel.font = UIFont(descriptor: .preferredFontDescriptor(withTextStyle: .body).withDesign(.serif)!, size: 0)
        contentLabel.numberOfLines = 0
        
        let stack = UIStackView(arrangedSubviews: [
            titleLabel,
            feedTitleLabel,
            contentLabel,
        ])
        stack.translatesAutoresizingMaskIntoConstraints = false
        stack.spacing = 8
        stack.axis = .vertical
        addSubview(stack)
        NSLayoutConstraint.activate([
            stack.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 20),
            stack.trailingAnchor.constraint(equalTo: trailingAnchor, constant: -20),
            stack.topAnchor.constraint(equalTo: topAnchor, constant: 8),
            stack.bottomAnchor.constraint(equalTo: bottomAnchor, constant: -8),
            separatorLayoutGuide.leadingAnchor.constraint(equalTo: stack.leadingAnchor),
        ])
        
        let doubleTap = DoubleTapRecognizer(target: self, action: #selector(cellDoubleTapped))
        doubleTap.onTouchesBegan = onDoubleTapBegan
        addGestureRecognizer(doubleTap)
        
        let singleTap = UITapGestureRecognizer(target: self, action: #selector(cellSingleTapped))
        singleTap.require(toFail: doubleTap)
        addGestureRecognizer(singleTap)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    func updateUI(item: Item) {
        self.item = item
        
        titleLabel.text = item.title
        feedTitleLabel.text = item.feed!.title ?? item.feed!.url?.host
        if let excerpt = item.excerpt {
            contentLabel.text = excerpt
            contentLabel.isHidden = false
        } else {
            contentLabel.isHidden = true
        }
        
        updateColors()
    }
    
    func setRead(_ read: Bool, animated: Bool) {
        guard self.item.read != read else { return }
        self.item.read = read
        if animated {
            // i don't know why .transition works but .animate doesn't
            UIView.transition(with: self, duration: 0.2, options: .transitionCrossDissolve) {
                self.updateColors()
            }
        } else {
            updateColors()
        }
    }
    
    private func updateColors() {
        if item.read {
            titleLabel.textColor = .secondaryLabel
            feedTitleLabel.textColor = .secondaryLabel
            contentLabel.textColor = .secondaryLabel
        } else {
            titleLabel.textColor = .label
            feedTitleLabel.textColor = .tintColor
            contentLabel.textColor = .appContentPreviewLabel
        }
    }
    
    private func onDoubleTapBegan() {
        guard shouldInteractOnNextTouch else { return }
        shouldInteractOnNextTouch = false
        feedbackGenerator.prepare()
        UIView.animateKeyframes(withDuration: 0.4, delay: 0, options: .allowUserInteraction) {
            UIView.addKeyframe(withRelativeStartTime: 0, relativeDuration: 0.5) {
                self.backgroundColor = .appCellHighlightBackground
            }
            UIView.addKeyframe(withRelativeStartTime: 0.5, relativeDuration: 0.5) {
                self.backgroundColor = nil
            }
        }
    }
    
    @objc private func cellDoubleTapped() {
        setRead(!item.read, animated: true)
        shouldInteractOnNextTouch = true
        feedbackGenerator.selectionChanged()
    }
    
    @objc private func cellSingleTapped() {
        delegate?.itemCellSelected(cell: self, item: item)
        shouldInteractOnNextTouch = true
        feedbackGenerator.selectionChanged()
    }

}

private class DoubleTapRecognizer: UITapGestureRecognizer {
    var onTouchesBegan: (() -> Void)!
    
    override init(target: Any?, action: Selector?) {
        super.init(target: target, action: action)
        numberOfTapsRequired = 2
        delaysTouchesBegan = true
    }
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
        super.touchesBegan(touches, with: event)
        onTouchesBegan()
        // shorten the delay before the single tap is recognized
        DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(300)) { [weak self] in
            guard let self = self else { return }
            if self.state != .recognized {
                self.state = .failed
            }
        }
    }
}