//
//  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 = url.uniqueIdentifier
        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)
    }
}