//
//  ProfileHeaderCollectionViewCell.swift
//  Tusker
//
//  Created by Shadowfacts on 10/10/22.
//  Copyright © 2022 Shadowfacts. All rights reserved.
//

import UIKit

class ProfileHeaderCollectionViewCell: UICollectionViewCell {
    
    private var state: State = .unloaded
    
    var view: ProfileHeaderView? {
        if case .view(let view) = state {
            return view
        } else {
            return nil
        }
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        
        contentView.backgroundColor = .appBackground
        isOpaque = true
        contentView.isOpaque = true
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    func addHeader(_ header: ProfileHeaderView) {
        switch state {
        case .unloaded, .placeholder(heightConstraint: _):
            header.translatesAutoresizingMaskIntoConstraints = false
            contentView.embedSubview(header)
            self.state = .view(header)
        case .view(_):
            fatalError("profile header collection view cell already has view")
        }
    }
    
    func addConstraint(height: CGFloat) -> ProfileHeaderView? {
        switch state {
        case .unloaded:
            let constraint = contentView.heightAnchor.constraint(equalToConstant: height)
            constraint.isActive = true
            state = .placeholder(heightConstraint: constraint)
            return nil
        case .placeholder(let heightConstraint):
            heightConstraint.constant = height
            return nil
        case .view(let header):
            let constraint = contentView.heightAnchor.constraint(equalToConstant: height)
            constraint.isActive = true
            state = .placeholder(heightConstraint: constraint)
            return header
        }
    }
    
    // overrides an internal method
    // when the super impl is used, preferredLayoutAttributesFitting(_:) isn't called while the view is offscreen (i.e., window == nil)
    // and so the collection view imposes a height of 44pts which breaks the layout
    @objc func _preferredLayoutAttributesFittingAttributes(_ attributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
        return preferredLayoutAttributesFitting(attributes)
    }
    
    enum State {
        case unloaded
        case placeholder(heightConstraint: NSLayoutConstraint)
        case view(ProfileHeaderView)
    }
    
}