Improve unknown usecase error message (#109)

Author: karulont

Sources/PIRService/Controllers/PIRServiceController.swift

@@ -66,11 +66,20 @@ struct PIRServiceController {
         }
 
         guard configRequest.existingConfigIds.isEmpty ||
-            configRequest.existingConfigIds.count == requestedUsecases.count
+            configRequest.existingConfigIds.count == configRequest.usecases.count
         else {
             throw HTTPError(.badRequest, message: """
                 Invalid existingConfigIds count \(configRequest.existingConfigIds.count). \
-                Expected 0 or \(requestedUsecases.count).
+                Expected 0 or \(configRequest.usecases.count).
+                """)
+        }
+
+        guard configRequest.usecases.isEmpty ||
+            configRequest.usecases.count == requestedUsecases.count
+        else {
+            throw await HTTPError(.notFound, message: """
+                One or more usecases not found. Requested usecases: \(configRequest.usecases).
+                Usecases available on the server: \(usecases.getAll().keys).
                 """)
         }
 

Tests/PIRServiceTests/PIRServiceControllerTests.swift

@@ -25,18 +25,18 @@ import Util
 
 @Suite
 struct PIRServiceControllerTests {
-    @Test
-    func noUserIdentifier() async throws {
-        // Error message returned by Hummingbird
-        struct ErrorMessage: Codable {
-            // swiftlint:disable:next nesting
-            struct Details: Codable {
-                let message: String
-            }
-
-            let error: Details
+    // Error message returned by Hummingbird
+    struct ErrorMessage: Codable {
+        // swiftlint:disable:next nesting
+        struct Details: Codable {
+            let message: String
         }
 
+        let error: Details
+    }
+
+    @Test
+    func noUserIdentifier() async throws {
         let app = try await buildApplication()
         try await app.test(.live) { client in
             try await client.execute(uri: "/key", method: .post) { response in
@@ -232,4 +232,27 @@ struct PIRServiceControllerTests {
             }
         }
     }
+
+    @Test
+    func configFetchWithUnknownUsecase() async throws {
+        let usecaseStore = UsecaseStore()
+        let exampleUsecase = ExampleUsecase.hundred
+        try await usecaseStore.set(name: "test", usecase: exampleUsecase)
+        let app = try await buildApplication(usecaseStore: usecaseStore)
+        let user = UserIdentifier()
+
+        let configRequest = Apple_SwiftHomomorphicEncryption_Api_Pir_V1_ConfigRequest.with { configReq in
+            configReq.usecases = ["other"]
+        }
+        try await app.test(.live) { client in
+            try await client.execute(uri: "/config", userIdentifier: user, message: configRequest) { response in
+                #expect(response.status == .notFound)
+                let errorMessage = try JSONDecoder().decode(ErrorMessage.self, from: response.body)
+                #expect(errorMessage.error.message == """
+                    One or more usecases not found. Requested usecases: ["other"].
+                    Usecases available on the server: ["test"].
+                    """)
+            }
+        }
+    }
 }