ProfilePictureGroupView.swift

//
//  ProfilePictureGroupView.swift
//  Vault
//
//  Created by Cole Potrocky on 1/24/19.
//  Copyright © 2019 Vault. All rights reserved.
//

import UIKit

final class ProfilePictureGroupView: UIView {
  struct Wrapper: AutoEquatable {
    let profilePictures: [ProfilePictureViewModel]
  }

  var preferredSize: CGSize = .zero {
    didSet {
      guard preferredSize != oldValue else { return }
      invalidateIntrinsicContentSize()
    }
  }

  override var intrinsicContentSize: CGSize {
    return preferredSize
  }

  var wrapper: Wrapper?
  var needsRerender: Bool = false

  func setImages(profilePictures: [ProfilePictureViewModel]) {
    let newWrapper = Wrapper(profilePictures: profilePictures)
    guard newWrapper != wrapper else { return }
    wrapper = newWrapper
    updateImageLayout()
  }

  func updateImageLayout() {
    guard frame != .zero else {
      needsRerender = true
      return
    }

    defer {
      needsRerender = false
      layoutSubviews()
    }

    subviews.forEach { $0.removeFromSuperview() }
    let views = wrapper?.profilePictures
      .map { vm -> ProfilePictureView in
        let view = ProfilePictureView()
        view.setImage(for: vm)
        view.layer.borderColor = UIColor.white.cgColor
        view.layer.borderWidth = 2
        return view
      }

    _ = views?.reduce(nil) { prev, view -> ProfilePictureView in
      self.insertSubview(view, at: 0)
      view.snp.makeConstraints { make in
        make.height.equalToSuperview()
        make.width.equalTo(view.snp.height)

        guard view != views?.first, let prev = prev else {
          make.left.equalToSuperview()
          return
        }

        make.left.equalTo(prev.snp.right).inset(frame.height * 0.55)
      }

      return view
    }
  }

  override func layoutSubviews() {
    super.layoutSubviews()

    guard !needsRerender else {
      updateImageLayout()
      return
    }

    let minX = subviews.reduce(0) { acc, v in min(acc, v.frame.minX) }
    let maxX = subviews.reduce(0) { acc, v in max(acc, v.frame.maxX) }
    let width = max(ceil(maxX - minX), preferredSize.width)

    preferredSize = CGSize(
      width: width,
      height: frame.height
    )
  }
}