[#12] 응답 검증과 디코딩 파이프라인을 구성한다

Nexa/Sources/Nexa/Runtime/NXResponsePipeline.swift

@@ -0,0 +1,65 @@
+//
+//  NXResponsePipeline.swift
+//  Nexa
+//
+//  Created by 최윤진 on 4/13/26.
+//
+
+import Foundation
+
+enum NXResponsePipeline {
+    static func validate(
+        clientConfiguration: NXClientConfiguration,
+        requestSpec: RequestSpec,
+        rawResponse: NXRawResponse
+    ) throws {
+        let statusCode = rawResponse.response.statusCode
+
+        guard requestSpec.validationPolicy.allows(statusCode: statusCode) else {
+            if let serverError = clientConfiguration.serverErrorDecoder.decodeServerError(
+                data: rawResponse.data,
+                response: rawResponse.response,
+                decoder: clientConfiguration.decoder
+            ) {
+                throw NXError.server(statusCode: statusCode, data: rawResponse.data, underlying: serverError)
+            }
+
+            throw NXError.invalidStatus(statusCode: statusCode, data: rawResponse.data)
+        }
+    }
+
+    static func decode<T: Decodable>(
+        clientConfiguration: NXClientConfiguration,
+        rawResponse: NXRawResponse,
+        responseType: T.Type
+    ) throws -> T {
+        do {
+            return try clientConfiguration.decoder.decode(responseType, from: rawResponse.data)
+        } catch {
+            throw NXError.decoding(error, data: rawResponse.data)
+        }
+    }
+
+    static func map(error: any Error) -> NXError {
+        if let nxError = error as? NXError {
+            return nxError
+        }
+
+        if let urlError = error as? URLError {
+            switch urlError.code {
+            case .timedOut:
+                return .timeout
+            case .cancelled:
+                return .cancelled
+            default:
+                return .transport(urlError)
+            }
+        }
+
+        if error is CancellationError {
+            return .cancelled
+        }
+
+        return .unknown(error)
+    }
+}

Nexa/Tests/NexaTests/NXResponsePipelineTests.swift

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+//
+//  NXResponsePipelineTests.swift
+//  Nexa
+//
+//  Created by 최윤진 on 4/13/26.
+//
+
+import Foundation
+import Testing
+@testable import Nexa
+
+@Suite("응답 검증과 디코딩 파이프라인 테스트")
+struct NXResponsePipelineTests {
+    @Test("응답 검증은 허용된 상태코드를 통과시킨다")
+    func validateAllowsExpectedStatusCode() throws {
+        let configuration = makeConfiguration()
+        let requestSpec = RequestSpec(method: .get, path: "/users")
+        let rawResponse = makeRawResponse(statusCode: 200, body: "{}")
+
+        try NXResponsePipeline.validate(
+            clientConfiguration: configuration,
+            requestSpec: requestSpec,
+            rawResponse: rawResponse
+        )
+    }
+
+    @Test("응답 검증은 서버 에러 디코더를 우선 사용한다")
+    func validateUsesServerErrorDecoderFirst() {
+        let configuration = makeConfiguration(serverErrorDecoder: MockServerErrorDecoder())
+        let requestSpec = RequestSpec(method: .get, path: "/users")
+        let rawResponse = makeRawResponse(statusCode: 400, body: "{\"message\":\"bad request\"}")
+
+        #expect {
+            try NXResponsePipeline.validate(
+                clientConfiguration: configuration,
+                requestSpec: requestSpec,
+                rawResponse: rawResponse
+            )
+        } throws: { error in
+            guard let nxError = error as? NXError,
+                  case let .server(statusCode, _, underlying) = nxError else {
+                return false
+            }
+
+            return statusCode == 400 &&
+                (underlying as? MockAPIError)?.message == "bad request"
+        }
+    }
+
+    @Test("응답 디코딩은 디코더를 사용해 모델을 반환한다")
+    func decodeReturnsDecodedModel() throws {
+        let configuration = makeConfiguration()
+        let rawResponse = makeRawResponse(statusCode: 200, body: "{\"id\":1,\"name\":\"opfic\"}")
+
+        let user = try NXResponsePipeline.decode(
+            clientConfiguration: configuration,
+            rawResponse: rawResponse,
+            responseType: PipelineUser.self
+        )
+
+        #expect(user.id == 1)
+        #expect(user.name == "opfic")
+    }
+
+    @Test("응답 디코딩 실패는 NXError.decoding으로 매핑한다")
+    func decodeMapsDecodingFailure() {
+        let configuration = makeConfiguration()
+        let rawResponse = makeRawResponse(statusCode: 200, body: "{\"unexpected\":true}")
+
+        #expect {
+            _ = try NXResponsePipeline.decode(
+                clientConfiguration: configuration,
+                rawResponse: rawResponse,
+                responseType: PipelineUser.self
+            )
+        } throws: { error in
+            guard let nxError = error as? NXError, case .decoding = nxError else {
+                return false
+            }
+            return true
+        }
+    }
+
+    @Test("에러 매핑은 URLError와 NXError를 적절한 케이스로 변환한다")
+    func mapConvertsKnownErrors() {
+        let timeoutError = NXResponsePipeline.map(error: URLError(.timedOut))
+        guard case .timeout = timeoutError else {
+            Issue.record("Expected timeout mapping")
+            return
+        }
+
+        let nxError = NXResponsePipeline.map(error: NXError.authenticationRequired)
+        guard case .authenticationRequired = nxError else {
+            Issue.record("Expected passthrough NXError")
+            return
+        }
+    }
+
+    private func makeConfiguration(
+        serverErrorDecoder: any NXServerErrorDecoder = NXDefaultServerErrorDecoder()
+    ) -> NXClientConfiguration {
+        NXClientConfiguration(
+            baseURL: URL(string: "https://example.com")!,
+            serverErrorDecoder: serverErrorDecoder
+        )
+    }
+}
+
+private struct PipelineUser: Decodable {
+    let id: Int
+    let name: String
+}
+
+private struct MockAPIError: Error {
+    let message: String
+}
+
+private struct MockServerErrorDecoder: NXServerErrorDecoder {
+    func decodeServerError(data: Data, response: HTTPURLResponse, decoder: JSONDecoder) -> (any Error)? {
+        let object = try? decoder.decode(ServerErrorEnvelope.self, from: data)
+        guard let message = object?.message else {
+            return nil
+        }
+        return MockAPIError(message: message)
+    }
+}
+
+private struct ServerErrorEnvelope: Decodable {
+    let message: String
+}
+
+private func makeRawResponse(statusCode: Int, body: String) -> NXRawResponse {
+    let response = HTTPURLResponse(
+        url: URL(string: "https://example.com")!,
+        statusCode: statusCode,
+        httpVersion: nil,
+        headerFields: nil
+    )!
+    return NXRawResponse(data: Data(body.utf8), response: response)
+}