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)
    }
}