import AppKit

class ImageCache {
    static let shared = ImageCache()
    private let cache = NSCache<NSString, NSImage>()
    
    private init() {}
    
    func image(for url: URL) -> NSImage? {
        return cache.object(forKey: url.absoluteString as NSString)
    }
    
    func insertImage(_ image: NSImage, for url: URL) {
        cache.setObject(image, forKey: url.absoluteString as NSString)
    }
    
    func fetchImage(url: URL) async throws -> NSImage {
        if let cached = image(for: url) {
            return cached
        }
        
        let (data, _) = try await URLSession.shared.data(from: url)
        guard let image = NSImage(data: data) else {
            throw WallhavenError.decodingError(NSError(domain: "ImageCache", code: -1, userInfo: nil))
        }
        
        insertImage(image, for: url)
        return image
    }
}