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

import UIKit
import Pachyderm

class AttachmentsContainerView: UIView {

    static let supportedAttachmentTypes = [Attachment.Kind.image, .video, .audio]
    
    weak var delegate: AttachmentViewDelegate?
    
    var statusID: String!
    var attachments: [Attachment]!
    
    let attachmentViews: NSHashTable<AttachmentView> = .weakObjects()
    
    var blurView: UIVisualEffectView?
    var hideButtonView: UIVisualEffectView?
    var contentHidden: Bool! {
        didSet {
            guard let blurView = blurView,
                let hideButtonView = hideButtonView else { return }
            
            blurView.alpha = self.contentHidden ? 1 : 0
            hideButtonView.alpha = self.contentHidden ? 0 : 1
        }
    }
    
    override func awakeFromNib() {
        super.awakeFromNib()
        
        self.isUserInteractionEnabled = true
        
        createBlurView()
        createHideButton()
    }
    
    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 { AttachmentsContainerView.supportedAttachmentTypes.contains($0.kind) }
        
        attachmentViews.allObjects.forEach { $0.removeFromSuperview() }
        attachmentViews.removeAllObjects()

        if attachments.count > 0 {
            self.isHidden = false
            
            var accessibilityElements = [Any]()

            switch attachments.count {
            case 1:
                let attachmentView = createAttachmentView(index: 0)
                fillView(attachmentView)
                sendSubviewToBack(attachmentView)
                accessibilityElements.append(attachmentView)
            case 2:
                let left = createAttachmentView(index: 0)
                let right = createAttachmentView(index: 1)
                let stack = createAttachmentsStack(axis: .horizontal, arrangedSubviews: [
                    left,
                    right
                ])
                fillView(stack)
                sendSubviewToBack(stack)
                NSLayoutConstraint.activate([
                    left.halfWidth()
                ])
                accessibilityElements.append(left)
                accessibilityElements.append(right)
            case 3:
                let left = createAttachmentView(index: 0)
                let topRight = createAttachmentView(index: 1)
                let bottomRight = createAttachmentView(index: 2)
                let outerStack = createAttachmentsStack(axis: .horizontal, arrangedSubviews: [
                    left,
                    createAttachmentsStack(axis: .vertical, arrangedSubviews: [
                        topRight,
                        bottomRight
                    ])
                ])
                fillView(outerStack)
                sendSubviewToBack(outerStack)
                NSLayoutConstraint.activate([
                    left.halfWidth(),
                    topRight.halfHeight(),
                ])
                accessibilityElements.append(left)
                accessibilityElements.append(topRight)
                accessibilityElements.append(bottomRight)
            case 4:
                let topLeft = createAttachmentView(index: 0)
                let bottomLeft = createAttachmentView(index: 2)
                let left = createAttachmentsStack(axis: .vertical, arrangedSubviews: [
                    topLeft,
                    bottomLeft
                ])
                let topRight = createAttachmentView(index: 1)
                let bottomRight = createAttachmentView(index: 3)
                let outerStack = createAttachmentsStack(axis: .horizontal, arrangedSubviews: [
                    left,
                    createAttachmentsStack(axis: .vertical, arrangedSubviews: [
                        topRight,
                        bottomRight
                    ])
                ])
                fillView(outerStack)
                sendSubviewToBack(outerStack)
                NSLayoutConstraint.activate([
                    left.halfWidth(),
                    topLeft.halfHeight(),
                    topRight.halfHeight(),
                ])
                accessibilityElements.append(topLeft)
                accessibilityElements.append(topRight)
                accessibilityElements.append(bottomLeft)
                accessibilityElements.append(bottomRight)
            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)
                moreView.accessibilityLabel = moreLabel.text

                let topLeft = createAttachmentView(index: 0)
                let bottomLeft = createAttachmentView(index: 2)
                let left = createAttachmentsStack(axis: .vertical, arrangedSubviews: [
                    topLeft,
                    bottomLeft
                ])
                let topRight = createAttachmentView(index: 1)
                let outerStack = createAttachmentsStack(axis: .horizontal, arrangedSubviews: [
                    left,
                    createAttachmentsStack(axis: .vertical, arrangedSubviews: [
                        topRight,
                        moreView
                    ])
                ])
                fillView(outerStack)
                sendSubviewToBack(outerStack)
                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),
                ])
                accessibilityElements.append(topLeft)
                accessibilityElements.append(topRight)
                accessibilityElements.append(bottomLeft)
                accessibilityElements.append(moreView)
            }
            
            self.accessibilityElements = accessibilityElements
        } else {
            self.isHidden = true
        }

        contentHidden = Preferences.shared.blurAllMedia || status.sensitive
    }
    
    private func createAttachmentView(index: Int) -> AttachmentView {
        let attachmentView = AttachmentView(attachment: attachments[index], index: index)
        attachmentView.delegate = delegate
        attachmentView.translatesAutoresizingMaskIntoConstraints = false
        attachmentView.isAccessibilityElement = true
        attachmentView.accessibilityTraits = [.image, .button]
        attachmentView.accessibilityLabel = String(format: NSLocalizedString("Attachment %d", comment: "attachment at index accessiblity label"), index + 1)
        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.alpha = 0
        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 blurEffect = UIBlurEffect(style: .regular)
        let hideButtonBlurView = UIVisualEffectView(effect: blurEffect)
        hideButtonBlurView.translatesAutoresizingMaskIntoConstraints = false
        hideButtonBlurView.alpha = 1
        hideButtonBlurView.isUserInteractionEnabled = true
        hideButtonBlurView.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(hideButtonTapped)))
        addSubview(hideButtonBlurView)
        self.hideButtonView = hideButtonBlurView
        
        let maskLayer = CALayer()
        let image = UIImage(systemName: "eye.slash.fill")!
        maskLayer.contents = image.cgImage!
        maskLayer.frame = CGRect(origin: .zero, size: image.size)
        hideButtonBlurView.layer.mask = maskLayer

        let hideButtonVibrancyView = UIVisualEffectView(effect: UIVibrancyEffect(blurEffect: blurEffect, style: .label))
        hideButtonVibrancyView.translatesAutoresizingMaskIntoConstraints = false
        hideButtonBlurView.contentView.addSubview(hideButtonVibrancyView)
        let fillView = UIView()
        fillView.translatesAutoresizingMaskIntoConstraints = false
        fillView.backgroundColor = UIColor(displayP3Red: 0, green: 0, blue: 0, alpha: 0.5)
        hideButtonVibrancyView.contentView.addSubview(fillView)

        NSLayoutConstraint.activate([
            hideButtonBlurView.topAnchor.constraint(equalTo: topAnchor, constant: 8),
            hideButtonBlurView.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 8),
            hideButtonBlurView.widthAnchor.constraint(equalToConstant: image.size.width),
            hideButtonBlurView.heightAnchor.constraint(equalToConstant: image.size.height),
            hideButtonVibrancyView.leadingAnchor.constraint(equalTo: hideButtonBlurView.contentView.leadingAnchor),
            hideButtonVibrancyView.trailingAnchor.constraint(equalTo: hideButtonBlurView.contentView.trailingAnchor),
            hideButtonVibrancyView.topAnchor.constraint(equalTo: hideButtonBlurView.contentView.topAnchor),
            hideButtonVibrancyView.bottomAnchor.constraint(equalTo: hideButtonBlurView.contentView.bottomAnchor),
            fillView.leadingAnchor.constraint(equalTo: hideButtonBlurView.contentView.leadingAnchor),
            fillView.trailingAnchor.constraint(equalTo: hideButtonBlurView.contentView.trailingAnchor),
            fillView.topAnchor.constraint(equalTo: hideButtonBlurView.contentView.topAnchor),
            fillView.bottomAnchor.constraint(equalTo: hideButtonBlurView.contentView.bottomAnchor),
        ])
    }
    
    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() {
        UIView.animate(withDuration: 0.2) {
            self.contentHidden = false
        }
    }
    
    @objc func hideButtonTapped() {
        UIView.animate(withDuration: 0.2) {
            self.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)
    }
}