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/*
 * Copyright 2015, Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *    * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *    * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *
 *    * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.glowroot.agent.shaded.grpc;

import org.glowroot.agent.shaded.google.common.base.Preconditions;

import java.util.HashMap;

import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;

/**
 * An immutable type-safe container of attributes.
 */
@ExperimentalApi
@Immutable
public final class Attributes {

  private final HashMap data = new HashMap();

  public static final Attributes EMPTY = new Attributes();

  private Attributes() {
  }

  /**
   * Gets the value for the key, or {@code null} if it's not present.
   */
  @SuppressWarnings("unchecked")
  @Nullable
  public  T get(Key key) {
    return (T) data.get(key.name);
  }

  /**
   * Create a new builder.
   */
  public static Builder newBuilder() {
    return new Builder();
  }

  public static final class Key {
    private final String name;

    /**
     * Construct the key.
     *
     * @param name the name, which should be namespaced like com.foo.BarAttribute to avoid
     *             collision.
     */
    public Key(String name) {
      this.name = name;
    }

    @Override
    public String toString() {
      return name;
    }
  }

  @Override
  public String toString() {
    return data.toString();
  }

  public static final class Builder {
    private Attributes product;

    private Builder() {
      this.product = new Attributes();
    }

    public  Builder set(Key key, T value) {
      product.data.put(key.name, value);
      return this;
    }

    /**
     * Build the attributes. Can only be called once.
     */
    public Attributes build() {
      Preconditions.checkState(product != null, "Already built");
      Attributes result = product;
      product = null;
      return result;
    }
  }
}