refactor: (first draft) Introduce error/exception types and abstract …

…HttpRequest attempts

src/main/java/dev/openfga/sdk/api/auth/OAuth2Client.java

@@ -12,23 +12,18 @@
 
 package dev.openfga.sdk.api.auth;
 
-import com.fasterxml.jackson.databind.ObjectMapper;
 import dev.openfga.sdk.api.client.ApiClient;
 import dev.openfga.sdk.api.configuration.*;
 import dev.openfga.sdk.errors.ApiException;
 import dev.openfga.sdk.errors.FgaInvalidParameterException;
 import java.io.IOException;
-import java.net.HttpURLConnection;
-import java.net.http.HttpClient;
 import java.net.http.HttpRequest;
-import java.net.http.HttpResponse;
 import java.time.Instant;
 import java.util.concurrent.CompletableFuture;
 
 public class OAuth2Client {
-    private final HttpClient httpClient;
+    private final ApiClient apiClient;
     private final Credentials credentials;
-    private final ObjectMapper mapper;
     private final AccessToken token = new AccessToken();
     private final CredentialsFlowRequest authRequest;
     private final String apiTokenIssuer;
@@ -37,14 +32,11 @@ public class OAuth2Client {
      * Initializes a new instance of the {@link OAuth2Client} class
      *
      * @param configuration Configuration, including credentials, that can be used to retrieve an access tokens
-     * @param httpClient Http client
      */
-    public OAuth2Client(Configuration configuration, HttpClient httpClient, ObjectMapper mapper)
-            throws FgaInvalidParameterException {
+    public OAuth2Client(Configuration configuration, ApiClient apiClient) throws FgaInvalidParameterException {
         this.credentials = configuration.getCredentials();
 
-        this.httpClient = httpClient;
-        this.mapper = mapper;
+        this.apiClient = apiClient;
         this.apiTokenIssuer = credentials.getClientCredentials().getApiTokenIssuer();
         this.authRequest = new CredentialsFlowRequest();
         this.authRequest.setClientId(credentials.getClientCredentials().getClientId());
@@ -78,27 +70,14 @@ public CompletableFuture<String> getAccessToken() throws FgaInvalidParameterExce
     private CompletableFuture<CredentialsFlowResponse> exchangeToken()
             throws ApiException, FgaInvalidParameterException {
         try {
-            byte[] body = mapper.writeValueAsBytes(authRequest);
+            byte[] body = apiClient.getObjectMapper().writeValueAsBytes(authRequest);
 
             Configuration config = new Configuration().apiUrl("https://" + apiTokenIssuer);
 
             HttpRequest request = ApiClient.requestBuilder("POST", "/oauth/token", body, config)
                     .build();
 
-            return httpClient
-                    .sendAsync(request, HttpResponse.BodyHandlers.ofString())
-                    .thenCompose(httpResponse -> {
-                        if (httpResponse.statusCode() != HttpURLConnection.HTTP_OK) {
-                            return CompletableFuture.failedFuture(new ApiException("exchangeToken", httpResponse));
-                        }
-                        try {
-                            CredentialsFlowResponse response =
-                                    mapper.readValue(httpResponse.body(), CredentialsFlowResponse.class);
-                            return CompletableFuture.completedFuture(response);
-                        } catch (Exception e) {
-                            return CompletableFuture.failedFuture(e);
-                        }
-                    });
+            return ApiClient.attemptHttpRequest(apiClient, "exchangeToken", request, CredentialsFlowResponse.class);
         } catch (IOException e) {
             throw new ApiException(e);
         }

src/main/java/dev/openfga/sdk/api/client/ApiClient.java

@@ -20,9 +20,11 @@
 import com.fasterxml.jackson.databind.SerializationFeature;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
 import dev.openfga.sdk.api.configuration.Configuration;
-import dev.openfga.sdk.errors.FgaInvalidParameterException;
+import dev.openfga.sdk.errors.*;
 import dev.openfga.sdk.util.Pair;
+import java.io.IOException;
 import java.io.InputStream;
+import java.net.HttpURLConnection;
 import java.net.URI;
 import java.net.URLEncoder;
 import java.net.http.HttpClient;
@@ -35,7 +37,9 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.StringJoiner;
+import java.util.concurrent.CompletableFuture;
 import java.util.function.Consumer;
+import java.util.function.Supplier;
 import java.util.stream.Collectors;
 import org.openapitools.jackson.nullable.JsonNullableModule;
 
@@ -239,6 +243,73 @@ protected HttpClient.Builder createDefaultHttpClientBuilder() {
         return HttpClient.newBuilder();
     }
 
+    // Static for testability reasons
+    public static <T> CompletableFuture<T> attemptHttpRequest(
+            ApiClient apiClient, String name, HttpRequest request, Class<T> clazz) throws ApiException {
+        Supplier<CompletableFuture<HttpResponse<String>>> callOnce =
+                () -> apiClient.getHttpClient().sendAsync(request, HttpResponse.BodyHandlers.ofString());
+
+        return callOnce.get().thenCompose(response -> {
+            int status = response.statusCode();
+            String responseBody = response.body();
+
+            try {
+                checkStatus(name, response);
+            } catch (FgaApiRateLimitExceededError | FgaApiInternalError e) {
+                // TODO handle retry
+                return CompletableFuture.failedFuture(e);
+            } catch (Exception e) {
+                return CompletableFuture.failedFuture(e);
+            }
+
+            if (status != HttpURLConnection.HTTP_OK && status != HttpURLConnection.HTTP_CREATED) {
+                return CompletableFuture.failedFuture(new ApiException(name, response));
+            }
+
+            try {
+                T body = apiClient.getObjectMapper().readValue(responseBody, clazz);
+                return CompletableFuture.completedFuture(body);
+            } catch (IOException e) {
+                return CompletableFuture.failedFuture(new ApiException(e));
+            }
+        });
+    }
+
+    private static void checkStatus(String name, HttpResponse<String> response)
+            throws FgaApiValidationError, FgaApiAuthenticationError, FgaApiNotFoundError, FgaApiRateLimitExceededError,
+                    FgaApiInternalError {
+
+        int status = response.statusCode();
+        String body = response.body();
+
+        switch (status) {
+            case HttpURLConnection.HTTP_BAD_REQUEST:
+            case 422: // HTTP 422 Unprocessable Entity
+                throw new FgaApiValidationError(name, status, response.headers(), body);
+
+            case HttpURLConnection.HTTP_UNAUTHORIZED:
+            case HttpURLConnection.HTTP_FORBIDDEN:
+                throw new FgaApiAuthenticationError(name, status, response.headers(), body);
+
+            case HttpURLConnection.HTTP_NOT_FOUND:
+                throw new FgaApiNotFoundError(name, status, response.headers(), body);
+
+            case 429: // HTTP 429 Too Many Requests
+                throw new FgaApiRateLimitExceededError(name, status, response.headers(), body);
+
+            case HttpURLConnection.HTTP_INTERNAL_ERROR:
+                throw new FgaApiInternalError(name, status, response.headers(), body);
+        }
+    }
+
+    //    public static <T> CompletableFuture<T> retryHttpRequest(
+    //            String name,
+    //            HttpClient httpClient,
+    //            HttpRequest.Builder requestBuilder,
+    //            Class<T> clazz,
+    //            ObjectMapper mapper) {
+    //    }
+
     /**
      * Set a custom {@link HttpClient.Builder} object to use when creating the
      * {@link HttpClient} that is used by the API client.

src/main/java/dev/openfga/sdk/errors/FgaApiAuthenticationError.java

@@ -0,0 +1,14 @@
+package dev.openfga.sdk.errors;
+
+import java.net.http.HttpHeaders;
+
+public class FgaApiAuthenticationError extends ApiException {
+    public FgaApiAuthenticationError(
+            String message, Throwable throwable, int code, HttpHeaders responseHeaders, String responseBody) {
+        super(message, code, responseHeaders, responseBody);
+    }
+
+    public FgaApiAuthenticationError(String message, int code, HttpHeaders responseHeaders, String responseBody) {
+        this(message, (Throwable) null, code, responseHeaders, responseBody);
+    }
+}

src/main/java/dev/openfga/sdk/errors/FgaApiInternalError.java

@@ -0,0 +1,14 @@
+package dev.openfga.sdk.errors;
+
+import java.net.http.HttpHeaders;
+
+public class FgaApiInternalError extends ApiException {
+    public FgaApiInternalError(
+            String message, Throwable throwable, int code, HttpHeaders responseHeaders, String responseBody) {
+        super(message, code, responseHeaders, responseBody);
+    }
+
+    public FgaApiInternalError(String message, int code, HttpHeaders responseHeaders, String responseBody) {
+        this(message, (Throwable) null, code, responseHeaders, responseBody);
+    }
+}

src/main/java/dev/openfga/sdk/errors/FgaApiNotFoundError.java

@@ -0,0 +1,14 @@
+package dev.openfga.sdk.errors;
+
+import java.net.http.HttpHeaders;
+
+public class FgaApiNotFoundError extends ApiException {
+    public FgaApiNotFoundError(
+            String message, Throwable throwable, int code, HttpHeaders responseHeaders, String responseBody) {
+        super(message, code, responseHeaders, responseBody);
+    }
+
+    public FgaApiNotFoundError(String message, int code, HttpHeaders responseHeaders, String responseBody) {
+        this(message, (Throwable) null, code, responseHeaders, responseBody);
+    }
+}

src/main/java/dev/openfga/sdk/errors/FgaApiRateLimitExceededError.java

@@ -0,0 +1,14 @@
+package dev.openfga.sdk.errors;
+
+import java.net.http.HttpHeaders;
+
+public class FgaApiRateLimitExceededError extends ApiException {
+    public FgaApiRateLimitExceededError(
+            String message, Throwable throwable, int code, HttpHeaders responseHeaders, String responseBody) {
+        super(message, code, responseHeaders, responseBody);
+    }
+
+    public FgaApiRateLimitExceededError(String message, int code, HttpHeaders responseHeaders, String responseBody) {
+        this(message, (Throwable) null, code, responseHeaders, responseBody);
+    }
+}

src/main/java/dev/openfga/sdk/errors/FgaApiValidationError.java

@@ -0,0 +1,14 @@
+package dev.openfga.sdk.errors;
+
+import java.net.http.HttpHeaders;
+
+public class FgaApiValidationError extends ApiException {
+    public FgaApiValidationError(
+            String message, Throwable throwable, int code, HttpHeaders responseHeaders, String responseBody) {
+        super(message, code, responseHeaders, responseBody);
+    }
+
+    public FgaApiValidationError(String message, int code, HttpHeaders responseHeaders, String responseBody) {
+        this(message, (Throwable) null, code, responseHeaders, responseBody);
+    }
+}

src/test/java/dev/openfga/sdk/api/OpenFgaApiTest.java

@@ -207,7 +207,7 @@ public void createStore_400() throws Exception {
 
         // Then
         mockHttpClient.verify().post("https://localhost/stores").called(1);
-        ApiException exception = assertInstanceOf(ApiException.class, execException.getCause());
+        FgaApiValidationError exception = assertInstanceOf(FgaApiValidationError.class, execException.getCause());
         assertEquals(400, exception.getCode());
         assertEquals(
                 "{\"code\":\"validation_error\",\"message\":\"Generic validation error\"}",

src/test/java/dev/openfga/sdk/api/auth/OAuth2ClientTest.java

@@ -2,9 +2,12 @@
 
 import static org.hamcrest.Matchers.is;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.pgssoft.httpclient.HttpClientMock;
+import dev.openfga.sdk.api.client.ApiClient;
 import dev.openfga.sdk.api.configuration.*;
 import dev.openfga.sdk.errors.FgaInvalidParameterException;
 import org.junit.jupiter.api.BeforeEach;
@@ -36,7 +39,11 @@ public void setup() throws FgaInvalidParameterException {
 
         var configuration = new Configuration().apiUrl("").credentials(credentials);
 
-        oAuth2 = new OAuth2Client(configuration, mockHttpClient, mapper);
+        var apiClient = mock(ApiClient.class);
+        when(apiClient.getHttpClient()).thenReturn(mockHttpClient);
+        when(apiClient.getObjectMapper()).thenReturn(mapper);
+
+        oAuth2 = new OAuth2Client(configuration, apiClient);
     }
 
     @Test