/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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.
 */
package org.apache.hadoop.hdfs.web.oauth2;

import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.RequestBody;
import com.squareup.okhttp.Response;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hdfs.web.URLConnectionFactory;
import org.apache.hadoop.util.Timer;
import org.apache.http.HttpStatus;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.ObjectReader;

import java.io.IOException;
import java.util.Map;
import java.util.concurrent.TimeUnit;

import static org.apache.hadoop.hdfs.DFSConfigKeys.OAUTH_CLIENT_ID_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.OAUTH_REFRESH_URL_KEY;
import static org.apache.hadoop.hdfs.web.oauth2.OAuth2Constants.ACCESS_TOKEN;
import static org.apache.hadoop.hdfs.web.oauth2.OAuth2Constants.CLIENT_CREDENTIALS;
import static org.apache.hadoop.hdfs.web.oauth2.OAuth2Constants.CLIENT_ID;
import static org.apache.hadoop.hdfs.web.oauth2.OAuth2Constants.CLIENT_SECRET;
import static org.apache.hadoop.hdfs.web.oauth2.OAuth2Constants.EXPIRES_IN;
import static org.apache.hadoop.hdfs.web.oauth2.OAuth2Constants.GRANT_TYPE;
import static org.apache.hadoop.hdfs.web.oauth2.OAuth2Constants.URLENCODED;
import static org.apache.hadoop.hdfs.web.oauth2.Utils.notNull;

/**
 * Obtain an access token via the credential-based OAuth2 workflow.  This
 * abstract class requires only that implementations provide the credential,
 * which the class then uses to obtain a refresh token.
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public abstract class CredentialBasedAccessTokenProvider
    extends AccessTokenProvider {
  private static final ObjectReader READER =
      new ObjectMapper().reader(Map.class);

  public static final String OAUTH_CREDENTIAL_KEY
      = "dfs.webhdfs.oauth2.credential";
  
  private AccessTokenTimer timer;
  
  private String clientId;
  
  private String refreshURL;
  
  private String accessToken;
  
  private boolean initialCredentialObtained = false;

  CredentialBasedAccessTokenProvider() {
    this.timer = new AccessTokenTimer();
  }
  
  CredentialBasedAccessTokenProvider(Timer timer) {
    this.timer = new AccessTokenTimer(timer);
  }
  
  public abstract String getCredential();

  @Override
  public void setConf(Configuration conf) {
    super.setConf(conf);
    clientId = notNull(conf, OAUTH_CLIENT_ID_KEY);
    refreshURL = notNull(conf, OAUTH_REFRESH_URL_KEY);
  }

  @Override
  public synchronized String getAccessToken() throws IOException {
    if(timer.shouldRefresh() || !initialCredentialObtained) {
      refresh();
      initialCredentialObtained = true;
    }
    
    return accessToken;
  }
  
  void refresh() throws IOException {
    try {
      OkHttpClient client = new OkHttpClient();
      client.setConnectTimeout(URLConnectionFactory.DEFAULT_SOCKET_TIMEOUT,
          TimeUnit.MILLISECONDS);
      client.setReadTimeout(URLConnectionFactory.DEFAULT_SOCKET_TIMEOUT,
          TimeUnit.MILLISECONDS);

      String bodyString = Utils.postBody(CLIENT_SECRET, getCredential(),
          GRANT_TYPE, CLIENT_CREDENTIALS,
          CLIENT_ID, clientId);

      RequestBody body = RequestBody.create(URLENCODED, bodyString);

      Request request = new Request.Builder()
          .url(refreshURL)
          .post(body)
          .build();
      Response responseBody = client.newCall(request).execute();

      if (responseBody.code() != HttpStatus.SC_OK) {
        throw new IllegalArgumentException("Received invalid http response: "
            + responseBody.code() + ", text = " + responseBody.toString());
      }

      Map<?, ?> response = READER.readValue(responseBody.body().string());

      String newExpiresIn = response.get(EXPIRES_IN).toString();
      timer.setExpiresIn(newExpiresIn);

      accessToken = response.get(ACCESS_TOKEN).toString();

    } catch (Exception e) {
      throw new IOException("Unable to obtain access token from credential", e);
    }
  }
}