Add AsyncImage like API for WebImage

SDWebImageSwiftUI/Classes/WebImage2.swift

@@ -0,0 +1,103 @@
+//
+//  WebImage2.swift
+//
+//
+//  Created by Kyle on 2023/9/10.
+//
+
+import SwiftUI
+
+public struct WebImageEventContext {
+    // TODO, Configuration and Information of image
+}
+
+struct LoadingState {
+    var url: URL?
+    var phase: WebImagePhase
+    init() {
+        url = nil
+        phase = .empty
+    }
+
+    func load() {}
+}
+
+@available(iOS 14.0, macOS 11.0, tvOS 14.0, watchOS 7.0, *)
+public struct WebImage2<Content>: View where Content: View {
+    var url: URL?
+    var scale: CGFloat
+    var transaction: Transaction
+    var content: (WebImagePhase) -> Content
+
+    @State private var loadingState = LoadingState()
+
+    public init(url: URL?, scale: CGFloat = 1) where Content == Image {
+        self.init(url: url, scale: scale) { phase in
+            phase.image ?? Image("")
+        }
+    }
+
+    public init<I, P>(url: URL?, scale: CGFloat = 1, @ViewBuilder content: @escaping (Image) -> I, @ViewBuilder placeholder: @escaping () -> P) where Content == _ConditionalContent<I, P>, I: View, P: View {
+        self.init(url: url, scale: scale) { phase in
+            if let i = phase.image {
+                content(i)
+            } else {
+                placeholder()
+            }
+        }
+    }
+
+    public init(url: URL?, scale: CGFloat = 1, transaction: Transaction = Transaction(), @ViewBuilder content: @escaping (WebImagePhase) -> Content) {
+        self.url = url
+        self.scale = scale
+        self.transaction = transaction
+        self.content = { phase in
+            content(phase)
+        }
+    }
+
+    public var body: some View {
+        content(loadingState.phase)
+            .onAppear {
+                load(url)
+            }
+            .onDisappear {}
+            .onChange(of: url) { load($0) }
+    }
+
+    private func load(_: URL?) {}
+}
+
+@available(iOS 13.0, *)
+struct LoadingError: Error {}
+
+@available(iOS 13.0, *)
+public enum WebImagePhase {
+    /// No image is loaded.
+    case empty
+
+    /// An image succesfully loaded.
+    case success(Image)
+
+    /// An image failed to load with an error.
+    case failure(Error)
+
+    public var image: Image? {
+        switch self {
+        case let .success(image):
+            image
+        case .empty, .failure:
+            nil
+        }
+    }
+
+    /// The error that occurred when attempting to load an image, if any.
+    public var error: Error? {
+        switch self {
+        case .empty, .success:
+            nil
+        case let .failure(error):
+            error
+        }
+    }
+}