/*
 * 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.accumulo.server;

import static com.google.common.base.Preconditions.checkArgument;

import java.io.IOException;

import org.apache.accumulo.core.client.AccumuloException;
import org.apache.accumulo.core.client.AccumuloSecurityException;
import org.apache.accumulo.core.client.Connector;
import org.apache.accumulo.core.client.Instance;
import org.apache.accumulo.core.client.ZooKeeperInstance;
import org.apache.accumulo.core.client.impl.ClientContext;
import org.apache.accumulo.core.client.impl.ConnectorImpl;
import org.apache.accumulo.core.client.impl.Credentials;
import org.apache.accumulo.core.client.security.tokens.PasswordToken;
import org.apache.accumulo.core.conf.AccumuloConfiguration;
import org.apache.accumulo.core.conf.Property;
import org.apache.accumulo.core.rpc.SslConnectionParams;
import org.apache.accumulo.core.util.DeprecationUtil;
import org.apache.accumulo.server.client.HdfsZooInstance;
import org.apache.accumulo.server.conf.ServerConfigurationFactory;
import org.apache.accumulo.server.rpc.SaslServerConnectionParams;
import org.apache.accumulo.server.rpc.ThriftServerType;
import org.apache.accumulo.server.security.SecurityUtil;
import org.apache.accumulo.server.security.SystemCredentials;
import org.apache.accumulo.server.security.delegation.AuthenticationTokenSecretManager;
import org.apache.hadoop.security.UserGroupInformation;

/**
 * Provides a server context for Accumulo server components that operate with the system credentials and have access to the system files and configuration.
 */
public class AccumuloServerContext extends ClientContext {

  private final ServerConfigurationFactory confFactory;
  private AuthenticationTokenSecretManager secretManager;

  /**
   * Construct a server context from the server's configuration
   */
  public AccumuloServerContext(ServerConfigurationFactory confFactory) {
    this(confFactory, null);
  }

  /**
   * Construct a server context from the server's configuration
   */
  public AccumuloServerContext(ServerConfigurationFactory confFactory, AuthenticationTokenSecretManager secretManager) {
    super(confFactory.getInstance(), getCredentials(confFactory.getInstance()), confFactory.getSystemConfiguration());
    this.confFactory = confFactory;
    this.secretManager = secretManager;
    if (null != getSaslParams()) {
      // Server-side "client" check to make sure we're logged in as a user we expect to be
      enforceKerberosLogin();
    }
  }

  /**
   * A "client-side" assertion for servers to validate that they are logged in as the expected user, per the configuration, before performing any RPC
   */
  // Should be private, but package-protected so EasyMock will work
  void enforceKerberosLogin() {
    final AccumuloConfiguration conf = confFactory.getSiteConfiguration();
    // Unwrap _HOST into the FQDN to make the kerberos principal we'll compare against
    final String kerberosPrincipal = SecurityUtil.getServerPrincipal(conf.get(Property.GENERAL_KERBEROS_PRINCIPAL));
    UserGroupInformation loginUser;
    try {
      // The system user should be logged in via keytab when the process is started, not the currentUser() like KerberosToken
      loginUser = UserGroupInformation.getLoginUser();
    } catch (IOException e) {
      throw new RuntimeException("Could not get login user", e);
    }

    checkArgument(loginUser.hasKerberosCredentials(), "Server does not have Kerberos credentials");
    checkArgument(kerberosPrincipal.equals(loginUser.getUserName()), "Expected login user to be " + kerberosPrincipal + " but was " + loginUser.getUserName());
  }

  /**
   * Get the credentials to use for this instance so it can be passed to the superclass during construction.
   */
  private static Credentials getCredentials(Instance instance) {
    if (DeprecationUtil.isMockInstance(instance)) {
      return new Credentials("mockSystemUser", new PasswordToken("mockSystemPassword"));
    }
    return SystemCredentials.get(instance);
  }

  /**
   * Retrieve the configuration factory used to construct this context
   */
  public ServerConfigurationFactory getServerConfigurationFactory() {
    return confFactory;
  }

  /**
   * Retrieve the SSL/TLS configuration for starting up a listening service
   */
  public SslConnectionParams getServerSslParams() {
    return SslConnectionParams.forServer(getConfiguration());
  }

  @Override
  public SaslServerConnectionParams getSaslParams() {
    AccumuloConfiguration conf = getServerConfigurationFactory().getSiteConfiguration();
    if (!conf.getBoolean(Property.INSTANCE_RPC_SASL_ENABLED)) {
      return null;
    }
    return new SaslServerConnectionParams(conf, getCredentials().getToken(), secretManager);
  }

  /**
   * Determine the type of Thrift server to instantiate given the server's configuration.
   *
   * @return A {@link ThriftServerType} value to denote the type of Thrift server to construct
   */
  public ThriftServerType getThriftServerType() {
    AccumuloConfiguration conf = getConfiguration();
    if (conf.getBoolean(Property.INSTANCE_RPC_SSL_ENABLED)) {
      if (conf.getBoolean(Property.INSTANCE_RPC_SASL_ENABLED)) {
        throw new IllegalStateException("Cannot create a Thrift server capable of both SASL and SSL");
      }

      return ThriftServerType.SSL;
    } else if (conf.getBoolean(Property.INSTANCE_RPC_SASL_ENABLED)) {
      if (conf.getBoolean(Property.INSTANCE_RPC_SSL_ENABLED)) {
        throw new IllegalStateException("Cannot create a Thrift server capable of both SASL and SSL");
      }

      return ThriftServerType.SASL;
    } else {
      // Lets us control the type of Thrift server created, primarily for benchmarking purposes
      String serverTypeName = conf.get(Property.GENERAL_RPC_SERVER_TYPE);
      return ThriftServerType.get(serverTypeName);
    }
  }

  public void setSecretManager(AuthenticationTokenSecretManager secretManager) {
    this.secretManager = secretManager;
  }

  public AuthenticationTokenSecretManager getSecretManager() {
    return secretManager;
  }

  // Need to override this from ClientContext to ensure that HdfsZooInstance doesn't "downcast"
  // the AccumuloServerContext into a ClientContext (via the copy-constructor on ClientContext)
  @Override
  public Connector getConnector() throws AccumuloException, AccumuloSecurityException {
    // avoid making more connectors than necessary
    if (conn == null) {
      if (inst instanceof ZooKeeperInstance || inst instanceof HdfsZooInstance) {
        // reuse existing context
        conn = new ConnectorImpl(this);
      } else {
        Credentials c = getCredentials();
        conn = getInstance().getConnector(c.getPrincipal(), c.getToken());
      }
    }
    return conn;
  }
}