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Brave: Core Libary
There is a newer version: 6.0.3
/*
 * Copyright 2013-2020 The OpenZipkin Authors
 *
 * Licensed 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 brave.internal.propagation;

import brave.propagation.Propagation;
import brave.propagation.TraceContext.Extractor;
import brave.propagation.TraceContext.Injector;
import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

/**
 * This supports the deprecated {@link Propagation.Factory#create(KeyFactory)}.
 *
 * Here's how to integrate:
 *
 * 
First, override {@link Propagation.Factory#get()} with your actual implementation. Then,
 * dispatch {@link Propagation.Factory#create(KeyFactory)} to your implementation via {@link
 * #create(Propagation, KeyFactory)}:
 *
 * 
{@code
 * @Override public Propagation get() {
 *   return new YourPropagation(this);
 * }
 *
 * @Deprecated public  Propagation create(KeyFactory keyFactory) {
 *   return StringPropagationAdapter.create(get(), keyFactory);
 * }
 * }
 *
 * This is internal, and will be removed in Brave 6. However, it won't be removed
 * before Brave 6. If you wish to use this, use "maven-shade-plugin" with the following
 * configuration, or something similar.
 *
 * 
{@code
 * 
 * false
 * 
 *   
 *     io.zipkin.brave:brave
 *   
 * 
 * 
 *   
 *     io.zipkin.brave:brave
 *     
 *       brave/internal/propagation/StringPropagationAdapter*.class
 *     
 *   
 * 
 * 
 *   
 *     brave.internal.propagation
 *     YOUR_PACKAGE.brave_internal
 *   
 * 
 * }
 *
 * @since 5.12
 */
public final class StringPropagationAdapter implements Propagation {
  public static  Propagation create(Propagation delegate, KeyFactory keyFactory) {
    if (delegate == null) throw new NullPointerException("delegate == null");
    if (keyFactory == null) throw new NullPointerException("keyFactory == null");
    if (keyFactory == KeyFactory.STRING) return (Propagation) delegate;
    return new StringPropagationAdapter<>(delegate, keyFactory);
  }

  final Propagation delegate;
  final KeyFactory keyFactory;
  final Map map;
  final List keysList;

  StringPropagationAdapter(Propagation delegate, KeyFactory keyFactory) {
    this.delegate = delegate;
    this.keyFactory = keyFactory;
    this.map = new LinkedHashMap<>();
    this.keysList = toKeyList(delegate.keys(), keyFactory);
  }

  List toKeyList(List keyNames, KeyFactory keyFactory) {
    int length = keyNames.size();
    K[] keys = (K[]) new Object[length];
    for (int i = 0; i < length; i++) {
      String keyName = keyNames.get(i);
      K key = keyFactory.create(keyName);
      keys[i] = key;
      map.put(keyName, key);
    }
    return Collections.unmodifiableList(Arrays.asList(keys));
  }

  @Override public List keys() {
    return keysList;
  }

  @Override public  Injector injector(Setter setter) {
    // No check if Setter is a RemoteSetter because this instance cannot have String keys while
    // RemoteSetter must have String keys
    return delegate.injector(new SetterAdapter<>(setter, map));
  }

  @Override public  Extractor extractor(Getter getter) {
    // No check if Setter is a RemoteGetter because this instance cannot have String keys while
    // RemoteGetter must have String keys
    return delegate.extractor(new GetterAdapter<>(getter, map));
  }

  @Override public int hashCode() {
    return delegate.hashCode();
  }

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

  @Override public boolean equals(Object obj) {
    if (obj instanceof StringPropagationAdapter) {
      return delegate.equals(((StringPropagationAdapter) obj).delegate);
    } else if (obj instanceof Propagation) {
      return delegate.equals(obj);
    }
    return false;
  }

  static final class GetterAdapter implements Getter {
    final Getter getter;
    final Map map;

    GetterAdapter(Getter getter, Map map) {
      if (getter == null) throw new NullPointerException("getter == null");
      this.getter = getter;
      this.map = map;
    }

    @Override public String get(R request, String keyName) {
      K key = map.get(keyName);
      if (key == null) return null;
      return getter.get(request, key);
    }

    @Override public int hashCode() {
      return getter.hashCode();
    }

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

    @Override public boolean equals(Object obj) {
      if (obj instanceof GetterAdapter) {
        return getter.equals(((GetterAdapter) obj).getter);
      } else if (obj instanceof Getter) {
        return getter.equals(obj);
      }
      return false;
    }
  }

  static final class SetterAdapter implements Setter {
    final Setter setter;
    final Map map;

    SetterAdapter(Setter setter, Map map) {
      if (setter == null) throw new NullPointerException("setter == null");
      this.setter = setter;
      this.map = map;
    }

    @Override public void put(R request, String keyName, String value) {
      K key = map.get(keyName);
      if (key == null) return;
      setter.put(request, key, value);
    }

    @Override public int hashCode() {
      return setter.hashCode();
    }

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

    @Override public boolean equals(Object obj) {
      if (obj instanceof SetterAdapter) {
        return setter.equals(((SetterAdapter) obj).setter);
      } else if (obj instanceof Setter) {
        return setter.equals(obj);
      }
      return false;
    }
  }
}