Update MultiplexImage

Sources/AsyncMultiplexImage/MultiplexImage.swift

@@ -2,6 +2,12 @@ import Foundation
 
 public struct MultiplexImage: Hashable, Sendable {
 
+  public enum URLContainer: Sendable {
+    case single(URL)
+    case multiple([URL])
+    case dynamic(@Sendable (borrowing Context) -> [URL])
+  }
+
   public struct Context: ~Copyable {
     public let targetSize: CGSize
     public let displayScale: CGFloat
@@ -25,27 +31,47 @@ public struct MultiplexImage: Hashable, Sendable {
 
   public let identifier: String
 
-  private let _urlsProvider: @Sendable (borrowing Context) -> [URL]
+  private let urlContainer: URLContainer
+
+  /**
+   User defined flag for any purpose.
+   */
+  public var flag: UInt64
 
   /**
     - Parameters:
       - identifier: The unique identifier of the image.
       - urlsProvider: The provider of the image URLs as the first item is the top priority.
    */
   public init(
+    flag: UInt64 = 0,
     identifier: String,
     urlsProvider: @escaping @Sendable (borrowing Context) -> [URL]
   ) {
+    self.flag = flag
     self.identifier = identifier
-    self._urlsProvider = urlsProvider
+    self.urlContainer = .dynamic(urlsProvider)
   }
 
-  public init(identifier: String, urls: [URL]) {
-    self.init(identifier: identifier, urlsProvider: { _ in urls })
+  public init(
+    flag: UInt64 = 0,
+    identifier: String,
+    urls: [URL]
+  ) {
+    self.flag = flag
+    self.identifier = identifier
+    self.urlContainer = .multiple(urls)
   }
 
   func makeURLs(context: borrowing Context) -> [URL] {
-    _urlsProvider(context)
+    switch urlContainer {
+    case .single(let url):
+      return [url]
+    case .multiple(let urls):
+      return urls
+    case .dynamic(let provider):
+      return provider(context)
+    }      
   }
 
 }
@@ -54,7 +80,8 @@ public struct MultiplexImage: Hashable, Sendable {
 extension MultiplexImage {
 
   public init(constant: URL) {
+    self.flag = 0
     self.identifier = constant.absoluteString
-    self._urlsProvider = { _ in [constant] }
+    self.urlContainer = .single(constant)
   }
 }