iOSGiphyCodeChallenge/LiveLikeGiphyChallenge/Utilities/ImageChache/LLCache.swift

//
//  LLCache.swift
//  LiveLikeGiphyChallenge
//
//  Created by Ljupco Nastevski on 30.1.22.
//

import Foundation
import UIKit

class LLCache: NSCache <NSString, UIImage> {
        
    static let shared: LLCache = LLCache()
    
    weak var activeTask: URLSessionDataTask?
        
    override init() {
        super.init()
        self.name = "com.livelike.gif_cache"
    }
    
    
    func retreiveDataFromUrl(url: URL, completion: @escaping (UIImage?) -> Void) {
        
        let path = url.path
        
        if let stored = self.object(forKey: path as NSString) {
            completion(stored)
            return
        }
        

        activeTask = GiphyApiManager.shared.getData(url: url) { [weak self] data in

            var preparedImage: UIImage?

            if let data = data {
                preparedImage = self?.prepareData(data: data)

                if preparedImage != nil {
                    self?.setObject(preparedImage!, forKey: path as NSString)
                }

            }

            completion(preparedImage)

        }
                
    }

    func cancelTaskFor(url: URL) {
        GiphyApiManager.shared.cancelDataTaskForUrl(url: url)
    }
    
    /*!
        Prepare the gif before saving it.
        The loading will be faster.
     */
    private func prepareData(data: Data) -> UIImage? {
        
        guard let source = CGImageSourceCreateWithData(data as CFData, nil) else { return nil }

        var images = [UIImage]()
        let imageCount = CGImageSourceGetCount(source)
        
        for i in 0 ..< imageCount {
            
            if let image = CGImageSourceCreateImageAtIndex(source, i, nil) {
                let img = self.drawInContext(image: UIImage(cgImage: image))
                images.append(img)
                
            }
        }

        let animatedImage = UIImage.animatedImage(with: images, duration: TimeInterval(images.count * (1/15)))

        return animatedImage
        
    }
    
    private func drawInContext(image: UIImage) -> UIImage {
        
        UIGraphicsBeginImageContextWithOptions(image.size, true, 1)
        image.draw(in: CGRect(x: 0, y: 0, width: image.size.width, height: image.size.height))
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return newImage!
    }

    
}