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?
    
    var statusID: String!
    var attachments: [Attachment]!
    
    let attachmentViews: NSHashTable<AttachmentView> = .weakObjects()
    
    var blurView: UIVisualEffectView?
    var hideButton: UIButton?
    var contentHidden: Bool! {
        didSet {
            guard let blurView = blurView,
                let hideButton = hideButton else { return }
            
            blurView.alpha = contentHidden ? 0 : 1
            hideButton.alpha = contentHidden ? 1 : 0
            UIView.animate(withDuration: 0.2) {
                blurView.alpha = self.contentHidden ? 1 : 0
                hideButton.alpha = self.contentHidden ? 0 : 1
            }
        }
    }
    
    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) {
        self.statusID = status.id
        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:
                fillView(createAttachmentView(index: 0))
            case 2:
                let left = createAttachmentView(index: 0)
                fillView(createAttachmentsStack(axis: .horizontal, arrangedSubviews: [
                    left,
                    createAttachmentView(index: 1)
                ]))
                NSLayoutConstraint.activate([
                    left.halfWidth()
                ])
            case 3:
                let left = createAttachmentView(index: 0)
                let topRight = createAttachmentView(index: 1)
                fillView(createAttachmentsStack(axis: .horizontal, arrangedSubviews: [
                    left,
                    createAttachmentsStack(axis: .vertical, arrangedSubviews: [
                        topRight,
                        createAttachmentView(index: 2)
                    ])
                ]))
                NSLayoutConstraint.activate([
                    left.halfWidth(),
                    topRight.halfHeight(),
                ])
            case 4:
                let topLeft = createAttachmentView(index: 0)
                let left = createAttachmentsStack(axis: .vertical, arrangedSubviews: [
                    topLeft,
                    createAttachmentView(index: 2)
                ])
                let topRight = createAttachmentView(index: 1)
                fillView(createAttachmentsStack(axis: .horizontal, arrangedSubviews: [
                    left,
                    createAttachmentsStack(axis: .vertical, arrangedSubviews: [
                        topRight,
                        createAttachmentView(index: 3)
                    ])
                ]))
                NSLayoutConstraint.activate([
                    left.halfWidth(),
                    topLeft.halfHeight(),
                    topRight.halfHeight(),
                ])
            default: // more than 4
                let moreView = UIView()
                moreView.backgroundColor = .secondarySystemBackground
                moreView.translatesAutoresizingMaskIntoConstraints = false
                moreView.isUserInteractionEnabled = true
                moreView.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(moreViewTapped)))
                let moreLabel = UILabel()
                moreLabel.text = "\(attachments.count - 3) more..."
                moreLabel.textColor = .secondaryLabel
                moreLabel.textAlignment = .center
                moreLabel.translatesAutoresizingMaskIntoConstraints = false
                moreView.addSubview(moreLabel)

                let topLeft = createAttachmentView(index: 0)
                let left = createAttachmentsStack(axis: .vertical, arrangedSubviews: [
                    topLeft,
                    createAttachmentView(index: 2)
                ])
                let topRight = createAttachmentView(index: 1)
                fillView(createAttachmentsStack(axis: .horizontal, arrangedSubviews: [
                    left,
                    createAttachmentsStack(axis: .vertical, arrangedSubviews: [
                        topRight,
                        moreView
                    ])
                ]))
                NSLayoutConstraint.activate([
                    left.halfWidth(),
                    topLeft.halfHeight(),
                    topRight.halfHeight(),
                    moreView.leadingAnchor.constraint(equalTo: moreLabel.leadingAnchor),
                    moreLabel.trailingAnchor.constraint(equalTo: moreView.trailingAnchor),
                    moreView.topAnchor.constraint(equalTo: moreLabel.topAnchor),
                    moreLabel.bottomAnchor.constraint(equalTo: moreView.bottomAnchor),
                ])
            }
        } else {
            self.isHidden = true
        }
        
        if status.sensitive {
            contentHidden = true
            createBlurView()
            createHideButton()
        }
    }
    
    private func createAttachmentView(index: Int) -> AttachmentView {
        let attachmentView = AttachmentView(attachment: attachments[index], index: index)
        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 createBlurView() {
        let blur = UIBlurEffect(style: .dark)
        let blurView = UIVisualEffectView(effect: blur)
        blurView.effect = blur
        blurView.translatesAutoresizingMaskIntoConstraints = false
        fillView(blurView)
        let vibrancyView = UIVisualEffectView(effect: UIVibrancyEffect(blurEffect: blur, style: .label))
        vibrancyView.translatesAutoresizingMaskIntoConstraints = false
        fillView(vibrancyView, in: blurView.contentView)
        blurView.contentView.addSubview(vibrancyView)
        
        let image = UIImage(systemName: "eye")!
        let imageView = UIImageView(image: image)
        imageView.translatesAutoresizingMaskIntoConstraints = false
        let label = UILabel()
        label.text = "Sensitive Content"
        let stack = UIStackView(arrangedSubviews: [
            imageView,
            label
            ])
        stack.axis = .vertical
        stack.alignment = .center
        stack.translatesAutoresizingMaskIntoConstraints = false
        vibrancyView.contentView.addSubview(stack)
        NSLayoutConstraint.activate([
            imageView.widthAnchor.constraint(equalTo: imageView.heightAnchor, multiplier: image.size.width / image.size.height),
            imageView.widthAnchor.constraint(equalTo: widthAnchor, multiplier: 0.2),
            stack.centerXAnchor.constraint(equalTo: centerXAnchor),
            stack.centerYAnchor.constraint(equalTo: centerYAnchor),
            stack.widthAnchor.constraint(equalTo: widthAnchor)
        ])
        
        self.blurView = blurView
        
        blurView.isUserInteractionEnabled = true
        blurView.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(blurViewTapped)))
    }
    
    private func createHideButton() {
        let hideButton = UIButton()
        hideButton.translatesAutoresizingMaskIntoConstraints = false
        hideButton.alpha = 0
        hideButton.layer.cornerRadius = 2
        hideButton.layer.masksToBounds = true
        hideButton.setImage(UIImage(systemName: "eye.slash.fill"), for: .normal)
        hideButton.addTarget(self, action: #selector(hideButtonTapped), for: .touchUpInside)
        
        addSubview(hideButton)
        NSLayoutConstraint.activate([
            hideButton.topAnchor.constraint(equalTo: topAnchor, constant: 8),
            hideButton.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 8)
        ])
        
        self.hideButton = hideButton
    }
    
    private func fillView(_ view: UIView, in parentView: UIView? = nil) {
        let parentView = parentView ?? self
        parentView.addSubview(view)
        NSLayoutConstraint.activate([
            view.leadingAnchor.constraint(equalTo: parentView.leadingAnchor),
            view.trailingAnchor.constraint(equalTo: parentView.trailingAnchor),
            view.topAnchor.constraint(equalTo: parentView.topAnchor),
            view.bottomAnchor.constraint(equalTo: parentView.bottomAnchor)
        ])
    }
    
    // MARK: - Interaction
    
    @objc func blurViewTapped() {
        contentHidden = false
    }
    
    @objc func hideButtonTapped() {
        contentHidden = true
    }
    
    @objc func showSensitiveContent() {
        guard let blurView = blurView else { return }
        
        blurView.alpha = 1
        UIView.animate(withDuration: 0.2) {
            blurView.alpha = 0
        }
    }
    
    @objc func hideSensitiveContent() {
        guard let blurView = self.blurView else { return }
        
        blurView.alpha = 0
        UIView.animate(withDuration: 0.2) {
            blurView.alpha = 1
        }
    }
    
    @objc func moreViewTapped() {
        guard attachments.count > 4 else { return }
        // the more view shows up in place of the fourth attachemtn view, show tapping it should start at the fourth attachment
        delegate?.showAttachmentsGallery(startingAt: 3)
    }

}

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)
    }
}