Caps-iOS/CapCollector/Presentation/ImageSelector.swift

//
//  ListViewController.swift
//  CapFinder
//
//  Created by User on 22.02.18.
//  Copyright © 2018 User. All rights reserved.
//

import UIKit

class ImageSelector: UIViewController {

    // MARK: - Constants

    /// The number of items per row
    private let itemsPerRow: CGFloat = 3
    
    override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
        return .portrait
    }
    
    override var preferredInterfaceOrientationForPresentation: UIInterfaceOrientation {
        return .portrait
    }
    
    override var shouldAutorotate: Bool {
        return false
    }

    // MARK: - Variables
    
    private var titleLabel: UILabel!
    
    private var subtitleLabel: UILabel!

    private var images = [UIImage?]()

    var cap: Cap!

    @IBOutlet weak var collection: UICollectionView!
    
    private var titleText: String {
        "Cap \(cap.id) (\(cap.count) images)"
    }
    
    private var subtitleText: String {
        cap.name
    }

    // MARK: - Life cycle

    override func viewDidLoad() {
        super.viewDidLoad()

        collection.dataSource = self
        collection.delegate = self
        
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        downloadImages()
    }
    
    override func didMove(toParent parent: UIViewController?) {
        super.didMove(toParent: parent)

        guard parent != nil && self.navigationItem.titleView == nil else {
            return
        }
        initNavigationItemTitleView()
    }
    
    private func initNavigationItemTitleView() {
        self.titleLabel = UILabel()
        titleLabel.text = titleText
        titleLabel.font = .preferredFont(forTextStyle: .headline)
        titleLabel.textColor = .label

        self.subtitleLabel = UILabel()
        subtitleLabel.text = subtitleText
        subtitleLabel.font = .preferredFont(forTextStyle: .footnote)
        subtitleLabel.textColor = .secondaryLabel

        let stackView = UIStackView(arrangedSubviews: [titleLabel, subtitleLabel])
        stackView.distribution = .equalCentering
        stackView.alignment = .center
        stackView.axis = .vertical

        self.navigationItem.titleView = stackView
    }

    // MARK: Image download

    private func downloadImages() {
        images = [UIImage?](repeating: nil, count: cap.count)
        log("\(cap.count) images for cap \(cap.id)")
        for version in 0..<cap.count {
            if let image = app.storage.image(for: cap.id, version: version) {
                log("Image \(version) already downloaded")
                set(image, for: version)
            } else {
                log("Downloading image \(version)")
                app.database.downloadImage(for: cap.id, version: version) { image in
                    self.set(image, for: version)
                    if image != nil {
                        self.log("Downloaded version \(version)")
                    } else {
                        self.log("Failed to download image \(version)")
                    }
                }
            }
        }
    }
    
    private func set(_ image: UIImage?, for version: Int) {
        self.images[version] = image
        DispatchQueue.main.async {
            self.collection.reloadItems(at: [IndexPath(row: version, section: 0)])
        }
    }

    // MARK: Select

    private func selectedImage(nr: Int) {
        app.database.setMainImage(of: cap.id, to: nr)
    }
}

// MARK: - UICollectionViewDataSource

extension ImageSelector: UICollectionViewDataSource {

    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return images.count
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(
            withReuseIdentifier: "Image",
            for: indexPath) as! ImageCell

        cell.capView.image = images[indexPath.row] ?? UIImage(named: "launch")
        return cell
    }

    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        selectedImage(nr: indexPath.row)
        navigationController?.popViewController(animated: true)
    }
}

// MARK: - UICollectionViewDelegateFlowLayout

extension ImageSelector : UICollectionViewDelegateFlowLayout {

    func collectionView(_ collectionView: UICollectionView,
                        layout collectionViewLayout: UICollectionViewLayout,
                        sizeForItemAt indexPath: IndexPath) -> CGSize {
        let widthPerItem = collectionView.frame.width / itemsPerRow
        return CGSize(width: widthPerItem, height: widthPerItem)
    }

    func collectionView(_ collectionView: UICollectionView,
                        layout collectionViewLayout: UICollectionViewLayout,
                        insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
    }

    func collectionView(_ collectionView: UICollectionView,
                        layout collectionViewLayout: UICollectionViewLayout,
                        minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 0
    }
}

extension ImageSelector: Logger { }