Handle expired signature GraphQL errors with ApolloAuthInterceptor

app/src/main/java/com/cornellappdev/uplift/data/auth/ApolloAuthInterceptor.kt

@@ -0,0 +1,76 @@
+package com.cornellappdev.uplift.data.auth
+
+import com.apollographql.apollo.ApolloClient
+import com.apollographql.apollo.api.ApolloRequest
+import com.apollographql.apollo.api.ApolloResponse
+import com.apollographql.apollo.api.ExecutionContext
+import com.apollographql.apollo.api.Operation
+import com.apollographql.apollo.interceptor.ApolloInterceptor
+import com.apollographql.apollo.interceptor.ApolloInterceptorChain
+import com.cornellappdev.uplift.RefreshAccessTokenMutation
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.emitAll
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.flow.flow
+import javax.inject.Inject
+import javax.inject.Named
+import javax.inject.Singleton
+
+/**
+ * Execution context to track retries.
+ */
+internal class RetryContext(val retryCount: Int) : ExecutionContext.Element {
+    override val key: ExecutionContext.Key<*> = Key
+
+    companion object Key : ExecutionContext.Key<RetryContext>
+}
+
+/**
+ * An Apollo Interceptor that handles token expiration errors that return as 200 OK with
+ * GraphQL errors (specifically "Signature has expired").
+ */
+@Singleton
+class ApolloAuthInterceptor @Inject constructor(
+    private val tokenManager: TokenManager,
+    private val sessionManager: SessionManager,
+    @Named("refresh") private val refreshClient: ApolloClient
+) : ApolloInterceptor {
+    override fun <D : Operation.Data> intercept(
+        request: ApolloRequest<D>,
+        chain: ApolloInterceptorChain
+    ): Flow<ApolloResponse<D>> = flow {
+        val response = chain.proceed(request).first()
+
+        val retryCount = request.executionContext[RetryContext]?.retryCount ?: 0
+        // TODO: replace string check with explicit error codes if backend implements
+        if (response.errors?.any { it.message.contains("Signature has expired") } == true && retryCount < 1) {
+            val refreshToken = tokenManager.getRefreshToken()
+            if (refreshToken != null) {
+                try {
+                    val mutationResponse = refreshClient.mutation(RefreshAccessTokenMutation())
+                        .addHttpHeader("Authorization", "Bearer $refreshToken")
+                        .execute()
+
+                    val newAccessToken = mutationResponse.data?.refreshAccessToken?.newAccessToken
+                    if (newAccessToken != null) {
+                        tokenManager.saveTokens(newAccessToken, refreshToken)
+                        // Retry the request with the new token
+                        val newRequest = request.newBuilder()
+                            .addExecutionContext(RetryContext(retryCount + 1))
+                            .build()
+                        emitAll(chain.proceed(newRequest))
+                        return@flow
+                    } else {
+                        sessionManager.logout()
+                    }
+                } catch (e: Exception) {
+                    sessionManager.logout()
+                }
+            } else {
+                sessionManager.logout()
+            }
+        }
+
+        emit(response)
+    }
+}

app/src/main/java/com/cornellappdev/uplift/di/AppModule.kt

@@ -3,6 +3,7 @@ package com.cornellappdev.uplift.di
 import com.apollographql.apollo.ApolloClient
 import com.apollographql.apollo.network.okHttpClient
 import com.cornellappdev.uplift.BuildConfig
+import com.cornellappdev.uplift.data.auth.ApolloAuthInterceptor
 import com.cornellappdev.uplift.data.auth.AuthInterceptor
 import com.cornellappdev.uplift.data.auth.TokenAuthenticator
 import dagger.Module
@@ -67,10 +68,14 @@ object AppModule {
     @Provides
     @Singleton
     @Named("main")
-    fun provideApolloClient(@Named("main") okHttpClient: OkHttpClient): ApolloClient {
+    fun provideApolloClient(
+        @Named("main") okHttpClient: OkHttpClient,
+        apolloAuthInterceptor: ApolloAuthInterceptor
+    ): ApolloClient {
         return ApolloClient.Builder()
             .serverUrl(BuildConfig.BACKEND_URL)
             .okHttpClient(okHttpClient)
+            .addInterceptor(apolloAuthInterceptor)
             .build()
     }