Tusker/Tusker/Views/Attachments/AttachmentsContainerView.swift

//
//  AttachmentsContainerView.swift
//  Tusker
//
//  Created by Shadowfacts on 6/16/19.
//  Copyright © 2019 Shadowfacts. All rights reserved.
//

import UIKit
import Pachyderm

class AttachmentsContainerView: UIView {

    var delegate: AttachmentViewDelegate?
    
    let attachmentViews: NSHashTable<AttachmentView> = .weakObjects()
    
    override func awakeFromNib() {
        super.awakeFromNib()
        
        self.isUserInteractionEnabled = true
    }
    
    func getAttachmentView(for attachment: Attachment) -> AttachmentView? {
        return attachmentViews.allObjects.first { $0.attachment.id == attachment.id }
    }
    
    // MARK: - User Interaface
    
    func updateUI(status: Status) {
        let attachments = status.attachments.filter { $0.kind == .image }
        
        attachmentViews.removeAllObjects()
        subviews.forEach { $0.removeFromSuperview() }

        if attachments.count > 0 {
            self.isHidden = false
            
            switch attachments.count {
            case 1:
                makeMainView(createAttachmentView(attachments[0]))
            case 2:
                let left = createAttachmentView(attachments[0])
                makeMainView(createAttachmentsStack(axis: .horizontal, arrangedSubviews: [
                    left,
                    createAttachmentView(attachments[1])
                ]))
                NSLayoutConstraint.activate([
                    left.halfWidth()
                ])
            case 3:
                let left = createAttachmentView(attachments[0])
                let topRight = createAttachmentView(attachments[1])
                makeMainView(createAttachmentsStack(axis: .horizontal, arrangedSubviews: [
                    left,
                    createAttachmentsStack(axis: .vertical, arrangedSubviews: [
                        topRight,
                        createAttachmentView(attachments[2])
                    ])
                ]))
                NSLayoutConstraint.activate([
                    left.halfWidth(),
                    topRight.halfHeight(),
                ])
            case 4:
                let topLeft = createAttachmentView(attachments[0])
                let left = createAttachmentsStack(axis: .vertical, arrangedSubviews: [
                    topLeft,
                    createAttachmentView(attachments[2])
                ])
                let topRight = createAttachmentView(attachments[1])
                makeMainView(createAttachmentsStack(axis: .horizontal, arrangedSubviews: [
                    left,
                    createAttachmentsStack(axis: .vertical, arrangedSubviews: [
                        topRight,
                        createAttachmentView(attachments[3])
                    ])
                ]))
                NSLayoutConstraint.activate([
                    left.halfWidth(),
                    topLeft.halfHeight(),
                    topRight.halfHeight(),
                ])
            default:
                fatalError("Too many attachments")
            }
        } else {
            self.isHidden = true
        }
    }
    
    private func createAttachmentView(_ attachment: Attachment) -> AttachmentView {
        let attachmentView = AttachmentView(attachment: attachment)
        attachmentView.delegate = delegate
        attachmentView.translatesAutoresizingMaskIntoConstraints = false
        attachmentViews.add(attachmentView)
        return attachmentView
    }
    
    private func createAttachmentsStack(axis: NSLayoutConstraint.Axis, arrangedSubviews: [UIView]) -> UIStackView {
        let stack = UIStackView(arrangedSubviews: arrangedSubviews)
        stack.axis = axis
        stack.spacing = 4
        stack.translatesAutoresizingMaskIntoConstraints = false
        return stack
    }
    
    private func makeMainView(_ view: UIView) {
        addSubview(view)
        NSLayoutConstraint.activate([
            view.leadingAnchor.constraint(equalTo: leadingAnchor),
            view.trailingAnchor.constraint(equalTo: trailingAnchor),
            view.topAnchor.constraint(equalTo: topAnchor),
            view.bottomAnchor.constraint(equalTo: bottomAnchor)
        ])
    }
    
}

fileprivate extension UIView {
    enum RelativeSize {
        case full, half
        
        var multiplier: CGFloat {
            switch self {
            case .full:
                return 1
            case .half:
                return 0.5
            }
        }
    }
    
    func halfWidth(spacing: CGFloat = 4) -> NSLayoutConstraint {
        return widthAnchor.constraint(equalTo: superview!.widthAnchor, multiplier: 0.5, constant: -spacing / 2)
    }
    
    func halfHeight(spacing: CGFloat = 4) -> NSLayoutConstraint {
        return heightAnchor.constraint(equalTo: superview!.heightAnchor, multiplier: 0.5, constant: -spacing / 2)
    }
}