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 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
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package org.elasticsearch.discovery.gce;

import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.LogManager;
import com.google.api.client.auth.oauth2.Credential;
import com.google.api.client.googleapis.testing.auth.oauth2.MockGoogleCredential;
import com.google.api.client.http.HttpBackOffIOExceptionHandler;
import com.google.api.client.http.HttpBackOffUnsuccessfulResponseHandler;
import com.google.api.client.http.HttpRequest;
import com.google.api.client.http.HttpRequestInitializer;
import com.google.api.client.http.HttpResponse;
import com.google.api.client.http.HttpUnsuccessfulResponseHandler;
import com.google.api.client.util.ExponentialBackOff;
import com.google.api.client.util.Sleeper;
import org.elasticsearch.cloud.gce.util.Access;
import org.elasticsearch.common.unit.TimeValue;

import java.io.IOException;
import java.util.Objects;

public class RetryHttpInitializerWrapper implements HttpRequestInitializer {
    private static final Logger logger = LogManager.getLogger(RetryHttpInitializerWrapper.class);

    // Intercepts the request for filling in the "Authorization"
    // header field, as well as recovering from certain unsuccessful
    // error codes wherein the Credential must refresh its token for a
    // retry.
    private final Credential wrappedCredential;

    // A sleeper; you can replace it with a mock in your test.
    private final Sleeper sleeper;

    private TimeValue maxWait;

    public RetryHttpInitializerWrapper(Credential wrappedCredential) {
        this(wrappedCredential, Sleeper.DEFAULT, TimeValue.timeValueMillis(ExponentialBackOff.DEFAULT_MAX_ELAPSED_TIME_MILLIS));
    }

    public RetryHttpInitializerWrapper(Credential wrappedCredential, TimeValue maxWait) {
        this(wrappedCredential, Sleeper.DEFAULT, maxWait);
    }

    // Use only for testing.
    RetryHttpInitializerWrapper(
            Credential wrappedCredential, Sleeper sleeper, TimeValue maxWait) {
        this.wrappedCredential = Objects.requireNonNull(wrappedCredential);
        this.sleeper = sleeper;
        this.maxWait = maxWait;
    }

    // Use only for testing
    static MockGoogleCredential.Builder newMockCredentialBuilder() {
        // TODO: figure out why GCE is so bad like this
        return Access.doPrivileged(MockGoogleCredential.Builder::new);
    }

    @Override
    public void initialize(HttpRequest httpRequest) {
        final HttpUnsuccessfulResponseHandler backoffHandler =
                new HttpBackOffUnsuccessfulResponseHandler(
                        new ExponentialBackOff.Builder()
                                .setMaxElapsedTimeMillis(((int) maxWait.getMillis()))
                                .build())
                        .setSleeper(sleeper);

        httpRequest.setInterceptor(wrappedCredential);
        httpRequest.setUnsuccessfulResponseHandler(
                new HttpUnsuccessfulResponseHandler() {
                    int retry = 0;

                    @Override
                    public boolean handleResponse(HttpRequest request, HttpResponse response, boolean supportsRetry) throws IOException {
                        if (wrappedCredential.handleResponse(
                                request, response, supportsRetry)) {
                            // If credential decides it can handle it,
                            // the return code or message indicated
                            // something specific to authentication,
                            // and no backoff is desired.
                            return true;
                        } else if (backoffHandler.handleResponse(
                                request, response, supportsRetry)) {
                            // Otherwise, we defer to the judgement of
                            // our internal backoff handler.
                            logger.debug("Retrying [{}] times : [{}]", retry, request.getUrl());
                            return true;
                        } else {
                            return false;
                        }
                    }
                });
        httpRequest.setIOExceptionHandler(
                new HttpBackOffIOExceptionHandler(
                        new ExponentialBackOff.Builder()
                                .setMaxElapsedTimeMillis(((int) maxWait.getMillis()))
                                .build())
                        .setSleeper(sleeper)
        );
    }
}

