first cut at an ImageCache

Signed-off-by: Matt Bruce <mbrucedogs@gmail.com>

EmployeeDirectory/Services/ImageCacheService.swift

@@ -0,0 +1,58 @@
+//
+//  ImageCacheService.swift
+//  EmployeeDirectory
+//
+//  Created by Matt Bruce on 1/20/25.
+//
+
+import Foundation
+import UIKit
+
+public class ImageCacheService {
+    public static let shared = ImageCacheService() // Default shared instance
+
+    private let memoryCache = NSCache<NSString, UIImage>()
+    private let fileManager = FileManager.default
+    private let cacheDirectory: URL = {
+       FileManager.default.urls(for: .cachesDirectory, in: .userDomainMask)[0]
+    }()
+    
+    public init() {}
+
+    public func loadImage(from url: URL) async -> UIImage? {
+        let uniqueKey = String(url.absoluteString.hashValue)
+        let cacheKey = uniqueKey as NSString
+    
+        if let cachedImage = memoryCache.object(forKey: cacheKey) {
+            return cachedImage
+        }
+        
+        let diskImagePath = cacheDirectory.appendingPathComponent(uniqueKey)
+        if let diskImage = UIImage(contentsOfFile: diskImagePath.path) {
+            memoryCache.setObject(diskImage, forKey: cacheKey)
+            return diskImage
+        }
+        
+        if let networkImage = await fetchFromNetwork(url: url) {
+            memoryCache.setObject(networkImage, forKey: cacheKey)
+            try? saveImageToDisk(image: networkImage, at: diskImagePath)
+            return networkImage
+        }
+        
+        return nil
+    }
+    
+    private func fetchFromNetwork(url: URL) async -> UIImage? {
+        do {
+            let (data, _) = try await URLSession.shared.data(from: url)
+            return UIImage(data: data)
+        } catch {
+            return nil
+        }
+    }
+    
+    private func saveImageToDisk(image: UIImage, at path: URL) throws {
+        guard let data = image.pngData() else { return }
+        try data.write(to: path)
+    }
+}