Add retry logic for download

Sources/XCRemoteCache/Network/NetworkClientImpl.swift

@@ -77,7 +77,12 @@ class NetworkClientImpl: NetworkClient {
     func download(_ url: URL, to location: URL, completion: @escaping (Result<Void, NetworkClientError>) -> Void) {
         var request = URLRequest(url: url)
         setupAuthenticationSignatureIfPresent(&request)
-        makeDownloadRequest(request, output: location, completion: completion)
+        makeDownloadRequest(
+            request,
+            output: location,
+            retries: maxRetries,
+            completion: completion
+        )
     }
 
     func upload(_ file: URL, as url: URL, completion: @escaping (Result<Void, NetworkClientError>) -> Void) {
@@ -125,7 +130,7 @@ class NetworkClientImpl: NetworkClient {
         dataTask.resume()
     }
 
-    private func makeDownloadRequest(_ request: URLRequest, output: URL, completion: @escaping (Result<Void, NetworkClientError>) -> Void) {
+    private func makeDownloadRequest(_ request: URLRequest, output: URL, retries: Int, completion: @escaping (Result<Void, NetworkClientError>) -> Void) {
         guard fileManager.fileExists(atPath: output.path) == false else {
             infoLog("Download file found in the destination, skipping download.")
             completion(.success(()))
@@ -135,6 +140,17 @@ class NetworkClientImpl: NetworkClient {
         let dataTask = session.downloadTask(with: request) { [fileManager] fileURL, _, error in
             guard let fileURL = fileURL else {
                 let networkError = error.map(NetworkClientError.build) ?? .inconsistentSession
+                if retries > 0 {
+                    infoLog("Download request failed with \(networkError). Left retries: \(retries).")
+                    self.retryDownload(
+                        request,
+                        output: output,
+                        retries: retries,
+                        completion: completion,
+                        after: self.retryDelay
+                    )
+                    return
+                }
                 errorLog("Download request failed: \(networkError)")
                 completion(.failure(networkError))
                 return
@@ -196,7 +212,24 @@ class NetworkClientImpl: NetworkClient {
     private func retryUpload(_ request: URLRequest, input: URL, retries: Int, completion: @escaping (Result<Void, NetworkClientError>) -> Void, after: TimeInterval) {
         DispatchQueue.global().asyncAfter(deadline: .now() + after) { [weak self] in
             guard let self = self else { return }
-            self.makeUploadRequest(request, input: input, retries: retries - 1, completion: completion)
+            self.makeUploadRequest(
+                request,
+                input: input,
+                retries: retries - 1,
+                completion: completion
+            )
+        }
+    }
+
+    private func retryDownload(_ request: URLRequest, output: URL, retries: Int, completion: @escaping (Result<Void, NetworkClientError>) -> Void, after: TimeInterval) {
+        DispatchQueue.global().asyncAfter(deadline: .now() + after) { [weak self] in
+            guard let self = self else { return }
+            self.makeDownloadRequest(
+                request,
+                output: output,
+                retries: retries - 1,
+                completion: completion
+            )
         }
     }
 }

Tests/XCRemoteCacheTests/Network/NetworkClientImplTests.swift

@@ -167,7 +167,7 @@ class NetworkClientImplTests: XCTestCase {
     func testUploadSuccessDoesntRetry() throws {
         client = NetworkClientImpl(
             session: session,
-            retries: 0,
+            retries: 2,
             retryDelay: 0,
             fileManager: fileManager,
             awsV4Signature: nil
@@ -178,6 +178,38 @@ class NetworkClientImplTests: XCTestCase {
         XCTAssertEqual(requests.map(\.url), [url], "Expected 1 request - original only")
     }
 
+    func testDownloadFilureWith400Retries() throws {
+        client = NetworkClientImpl(
+            session: session,
+            retries: 2,
+            retryDelay: 0,
+            fileManager: fileManager,
+            awsV4Signature: nil
+        )
+        responses[url] = nil
+        _ = try waitForResponse({ client.download(url, to: fileURL, completion: $0) }, timeout: 0.5)
+
+        XCTAssertEqual(
+            requests.map(\.url),
+            Array(repeating: url, count: 3),
+            "Expected 3 requests (original + 2 retries)"
+        )
+    }
+
+    func testDownloadSuccessDoesntRetry() throws {
+        client = NetworkClientImpl(
+            session: session,
+            retries: 2,
+            retryDelay: 0,
+            fileManager: fileManager,
+            awsV4Signature: nil
+        )
+        responses[url] = .success(successResponse, Data())
+        _ = try waitForResponse { client.download(url, to: fileURL, completion: $0) }
+
+        XCTAssertEqual(requests.map(\.url), [url], "Expected 1 request - original only")
+    }
+
     func testFileExits400CompletesWithFalse() throws {
         responses[url] = .success(failureResponse, Data())
         let response = try waitForResponse { client.fileExists(url, completion: $0) }