Add ImageService with memory + disk cache

Sources/LuminateCore/ImageService.swift

@@ -0,0 +1,50 @@
+import Foundation
+#if canImport(FoundationNetworking)
+import FoundationNetworking
+#endif
+
+public actor ImageService {
+    private let cacheDir: URL
+    private let memoryCache = NSCache<NSString, NSData>()
+
+    public init(cacheDir: URL? = nil) {
+        let defaultCache = FileManager.default.urls(
+            for: .cachesDirectory, in: .userDomainMask
+        ).first!.appendingPathComponent("luminate/images")
+        self.cacheDir = cacheDir ?? defaultCache
+        try? FileManager.default.createDirectory(at: self.cacheDir, withIntermediateDirectories: true)
+    }
+
+    public func loadImage(url: URL) async throws -> Data {
+        let key = url.absoluteString as NSString
+        if let cached = memoryCache.object(forKey: key) {
+            return cached as Data
+        }
+        let diskKey = url.absoluteString.data(using: .utf8)!.base64EncodedString()
+            .replacingOccurrences(of: "/", with: "_")
+        let diskURL = cacheDir.appendingPathComponent(diskKey)
+        if let data = try? Data(contentsOf: diskURL) {
+            memoryCache.setObject(data as NSData, forKey: key)
+            return data
+        }
+        let (data, _) = try await URLSession.shared.data(from: url)
+        let nsData = data as NSData
+        memoryCache.setObject(nsData, forKey: key)
+        try? data.write(to: diskURL)
+        return data
+    }
+
+    public func prefetch(urls: [URL]) async {
+        await withTaskGroup(of: Void.self) { group in
+            for url in urls {
+                group.addTask { _ = try? await self.loadImage(url: url) }
+            }
+        }
+    }
+
+    public func clearCache() {
+        memoryCache.removeAllObjects()
+        try? FileManager.default.removeItem(at: cacheDir)
+        try? FileManager.default.createDirectory(at: cacheDir, withIntermediateDirectories: true)
+    }
+}