Map auth errors to internal representation

app/src/main/java/gq/kirmanak/mealient/data/auth/AuthService.kt

@@ -1,6 +1,7 @@
 package gq.kirmanak.mealient.data.auth
 
 import gq.kirmanak.mealient.data.auth.impl.GetTokenResponse
+import retrofit2.Response
 import retrofit2.http.Field
 import retrofit2.http.FormUrlEncoded
 import retrofit2.http.POST
@@ -15,5 +16,5 @@ interface AuthService {
         @Field("scope") scope: String? = null,
         @Field("client_id") clientId: String? = null,
         @Field("client_secret") clientSecret: String? = null
-    ): GetTokenResponse
+    ): Response<GetTokenResponse>
 }

app/src/main/java/gq/kirmanak/mealient/data/auth/impl/AuthDataSourceImpl.kt

@@ -2,15 +2,25 @@ package gq.kirmanak.mealient.data.auth.impl
 
 import gq.kirmanak.mealient.data.auth.AuthDataSource
 import gq.kirmanak.mealient.data.auth.AuthService
+import gq.kirmanak.mealient.data.auth.impl.AuthenticationError.*
+import gq.kirmanak.mealient.data.impl.ErrorDetail
 import gq.kirmanak.mealient.data.impl.RetrofitBuilder
+import kotlinx.coroutines.CancellationException
 import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.SerializationException
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.decodeFromStream
+import retrofit2.HttpException
+import retrofit2.Response
 import retrofit2.create
 import timber.log.Timber
+import java.io.InputStream
 import javax.inject.Inject
 
 @ExperimentalSerializationApi
 class AuthDataSourceImpl @Inject constructor(
-    private val retrofitBuilder: RetrofitBuilder
+    private val retrofitBuilder: RetrofitBuilder,
+    private val json: Json,
 ) : AuthDataSource {
     override suspend fun authenticate(
         username: String,
@@ -19,8 +29,37 @@ class AuthDataSourceImpl @Inject constructor(
     ): String {
         Timber.v("authenticate() called with: username = $username, password = $password, baseUrl = $baseUrl")
         val authService = retrofitBuilder.buildRetrofit(baseUrl).create<AuthService>()
-        val response = authService.getToken(username, password)
-        Timber.d("authenticate() response is $response")
-        return response.accessToken
+
+        val accessToken = runCatching {
+            authService.getToken(username, password)
+        }.mapCatching {
+            Timber.d("authenticate() response is $it")
+            if (!it.isSuccessful) {
+                val cause = HttpException(it)
+                throw when (it.decodeErrorBodyOrNull<GetTokenResponse, ErrorDetail>()?.detail) {
+                    "Unauthorized" -> Unauthorized(cause)
+                    else -> NotMealie(cause)
+                }
+            }
+            checkNotNull(it.body()).accessToken // Can't be null here, would throw SerializationException
+        }.onFailure {
+            Timber.e(it, "authenticate: getToken failed")
+            throw when (it) {
+                is CancellationException, is AuthenticationError -> it
+                is SerializationException, is IllegalStateException -> NotMealie(it)
+                else -> NoServerConnection(it)
+            }
+        }.getOrThrow()
+
+        Timber.v("authenticate() returned: $accessToken")
+        return accessToken
     }
+
+    private inline fun <reified T, reified R> Response<T>.decodeErrorBodyOrNull(): R? =
+        errorBody()?.byteStream()?.let { json.decodeFromStreamOrNull<R>(it) }
+
+    private inline fun <reified T> Json.decodeFromStreamOrNull(stream: InputStream): T? =
+        runCatching { decodeFromStream<T>(stream) }
+            .onFailure { Timber.e(it, "decodeFromStreamOrNull: can't decode") }
+            .getOrNull()
 }

app/src/main/java/gq/kirmanak/mealient/data/auth/impl/AuthenticationError.kt

@@ -0,0 +1,7 @@
+package gq.kirmanak.mealient.data.auth.impl
+
+sealed class AuthenticationError(cause: Throwable) : RuntimeException(cause) {
+    class Unauthorized(cause: Throwable) : AuthenticationError(cause)
+    class NoServerConnection(cause: Throwable) : AuthenticationError(cause)
+    class NotMealie(cause: Throwable) : AuthenticationError(cause)
+}

app/src/main/java/gq/kirmanak/mealient/data/impl/ErrorDetail.kt

@@ -0,0 +1,7 @@
+package gq.kirmanak.mealient.data.impl
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+@Serializable
+data class ErrorDetail(@SerialName("detail") val detail: String? = null)