fix gif caching

Pocket Poster/Packages/GIFImage/Sources/domain/ImageLoader.swift

@@ -0,0 +1,80 @@
+//
+//  File.swift
+//  
+//
+//  Created by Igor Ferreira on 05/04/2022.
+//
+
+import Foundation
+
+/// Object responsible to load a `GIFSource` into a `ImageFrame` stream.
+public struct ImageLoader {
+    public let session: URLSession
+    public let cache: URLCache
+    public let fileManager: FileManager
+
+    public init(session: URLSession = .shared, cache: URLCache = .shared, fileManager: FileManager = .default) {
+        self.session = session
+        self.cache = cache
+        self.fileManager = fileManager
+    }
+
+    public func load(source: GIFSource) async throws -> CGImageSourceFrameSequence {
+        let data = try await source.loadData(session: session, cache: cache, fileManager: fileManager)
+        return try data.imageAsyncSequence()
+    }
+}
+
+private extension GIFSource {
+    func loadData(session: URLSession, cache: URLCache, fileManager: FileManager) async throws -> Data {
+        switch self {
+        case let .static(data): data
+        case .remote(let url), .remoteURL(let url): try await url.loadData(session: session, cache: cache)
+        case let .remoteRequest(request): try await request.loadData(session: session, cache: cache)
+        case let .local(filePath): try await filePath.loadData(fileManager: fileManager)
+        }
+    }
+}
+
+private extension String {
+    func loadData(fileManager: FileManager) async throws -> Data {
+        guard fileManager.fileExists(atPath: self) else {
+            throw URLError(.fileDoesNotExist)
+        }
+        guard let data = fileManager.contents(atPath: self) else {
+            throw URLError(.cannotOpenFile)
+        }
+        return data
+    }
+}
+
+private extension URL {
+    func loadData(session: URLSession, cache: URLCache) async throws -> Data {
+        let request = URLRequest(url: self)
+        return try await request.loadData(session: session, cache: cache)
+    }
+}
+
+private extension URLRequest {
+    func loadData(session: URLSession, cache: URLCache) async throws -> Data {
+        if let cache = cache.cachedResponse(for: self) {
+            return cache.data
+        }
+
+        let (data, response) = try await session.data(for: self)
+        guard let httpResponse = response as? HTTPURLResponse else {
+            throw URLError(.badServerResponse)
+        }
+        guard httpResponse.isSuccess else {
+            throw URLError(.init(rawValue: httpResponse.statusCode))
+        }
+        cache.storeCachedResponse(CachedURLResponse(response: response, data: data), for: self)
+        return data
+    }
+}
+
+private extension HTTPURLResponse {
+    var isSuccess: Bool {
+        200..<300 ~= statusCode
+    }
+}