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package io.grpc.stub;

import com.google.common.collect.Maps;

import io.grpc.Channel;
import io.grpc.ClientInterceptor;
import io.grpc.ClientInterceptors;
import io.grpc.MethodDescriptor;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.TimeUnit;

/**
 * Common base type for stub implementations.
 *
 * This is the base class of the stub classes from the generated code. It allows for
 * reconfiguration, e.g., attaching interceptors to the stub.
 *
 * @param  the concrete type of this stub.
 * @param  the service descriptor type
 */
public abstract class AbstractStub,
    C extends AbstractServiceDescriptor> {
  protected final Channel channel;
  protected final C config;

  /**
   * Constructor for use by subclasses.
   *
   * @param channel the channel that this stub will use to do communications
   * @param config defines the RPC methods of the stub
   */
  protected AbstractStub(Channel channel, C config) {
    this.channel = channel;
    this.config = config;
  }

  protected C getServiceDescriptor() {
    return config;
  }

  /**
   * Creates a builder for reconfiguring the stub.
   */
  public StubConfigBuilder configureNewStub() {
    return new StubConfigBuilder();
  }

  /**
   * The underlying channel of the stub.
   */
  public Channel getChannel() {
    return channel;
  }

  /**
   * Returns a new stub with the given channel for the provided method configurations.
   *
   * @param channel the channel that this stub will use to do communications
   * @param config defines the RPC methods of the stub
   */
  protected abstract S build(Channel channel, C config);

  /**
   * Utility class for (re) configuring the operations in a stub.
   */
  public class StubConfigBuilder {

    private final Map> methodMap;
    private final List interceptors = new ArrayList();
    private Channel stubChannel;

    private StubConfigBuilder() {
      this.stubChannel = AbstractStub.this.channel;
      methodMap = Maps.newHashMapWithExpectedSize(config.methods().size());
      for (MethodDescriptor method : AbstractStub.this.config.methods()) {
        methodMap.put(method.getName(), method);
      }
    }

    /**
     * Sets a timeout for all methods in the stub.
     */
    public StubConfigBuilder setTimeout(long timeout, TimeUnit unit) {
      for (Map.Entry> entry : methodMap.entrySet()) {
        entry.setValue(entry.getValue().withTimeout(timeout, unit));
      }
      return this;
    }

    /**
     * Set the channel to be used by the stub.
     */
    public StubConfigBuilder setChannel(Channel channel) {
      this.stubChannel = channel;
      return this;
    }

    /**
     * Adds a client interceptor to be attached to the channel of the reconfigured stub.
     */
    public StubConfigBuilder addInterceptor(ClientInterceptor interceptor) {
      interceptors.add(interceptor);
      return this;
    }

    /**
     * Create a new stub with the configurations made on this builder.
     */
    public S build() {
      return AbstractStub.this.build(ClientInterceptors.intercept(stubChannel, interceptors),
          config.build(methodMap));
    }
  }
}