UIImagable.swift

//
//  UIImagable.swift
//  Landscape
//
//  Created by Cameron Deardorff on 1/31/20.
//  Copyright © 2020 Cameron Deardorff. All rights reserved.
//

import UIKit
import Photos

fileprivate enum UIImagableSource {
    // image in a user's photo collection
    case photos(asset: PHAsset)
    // url of image on disk or internet
    case path(url: URL)
    
    var identifier: String {
        switch self {
        case .photos(let asset):
            return asset.localIdentifier
        case .path(let url):
            return url.absoluteString
        }
    }
}

struct UIImagable {
    
    private var source: UIImagableSource
    var id: String {
        return source.identifier
    }
    
    init(asset: PHAsset) {
        source = .photos(asset: asset)
    }
    init(url: URL) {
        source = .path(url: url)
    }
    
    func getImage(with size: CGSize, completion: @escaping (UIImage?) -> ()) {
        DispatchQueue.global(qos: .userInteractive).async {
            
            switch self.source {
            case .photos(let asset):
                let imageRequestOptions = PHImageRequestOptions()
                imageRequestOptions.isSynchronous = false
                imageRequestOptions.isNetworkAccessAllowed = true
                        
                let greaterDetailSize = size.applying(.init(scaleX: 3, y: 3))
                PHImageManager.default().requestImage(for: asset, targetSize: greaterDetailSize, contentMode: .aspectFit, options: imageRequestOptions, resultHandler: { image, metadata in
                    
                    guard let image = image else { return }
                    completion(image)
                })
                
            case .path(let url):
                guard let data = try? Data(contentsOf: url) else {
                    completion(nil)
                    return
                }
                completion(UIImage(data: data))
            }
        }
    }
}