/*
 * 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.lucene.util;


import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Map;

Helper methods for constructing nested resource descriptions
and debugging RAM usage.
 toString(Accountable} can be used to quickly debug the nested structure of any Accountable. 
 The namedAccountable and namedAccountables methods return type-safe, point-in-time snapshots of the provided resources. /** 
 * Helper methods for constructing nested resource descriptions
 * and debugging RAM usage.
 * <p>
 * {@code toString(Accountable}} can be used to quickly debug the nested
 * structure of any Accountable.
 * <p>
 * The {@code namedAccountable} and {@code namedAccountables} methods return
 * type-safe, point-in-time snapshots of the provided resources.
 */
public class Accountables {
  private Accountables() {}
  
  
Returns a String description of an Accountable and any nested resources.
This is intended for development and debugging.
/** 
   * Returns a String description of an Accountable and any nested resources.
   * This is intended for development and debugging.
   */
  public static String toString(Accountable a) {
    StringBuilder sb = new StringBuilder();
    toString(sb, a, 0);
    return sb.toString();
  }
  
  private static StringBuilder toString(StringBuilder dest, Accountable a, int depth) {
    for (int i = 1; i < depth; i++) {
      dest.append("    ");
    }
    
    if (depth > 0) {
      dest.append("|-- ");
    }
    
    dest.append(a.toString());
    dest.append(": ");
    dest.append(RamUsageEstimator.humanReadableUnits(a.ramBytesUsed()));
    dest.append(System.lineSeparator());
    
    for (Accountable child : a.getChildResources()) {
      toString(dest, child, depth + 1);
    }
    
    return dest;
  }
  
  
Augments an existing accountable with the provided description.
 The resource description is constructed in this format: description [toString()] 

This is a point-in-time type safe view: consumers 
will not be able to cast or manipulate the resource in any way.
/**
   * Augments an existing accountable with the provided description.
   * <p>
   * The resource description is constructed in this format:
   * {@code description [toString()]}
   * <p>
   * This is a point-in-time type safe view: consumers 
   * will not be able to cast or manipulate the resource in any way.
   */
  public static Accountable namedAccountable(String description, Accountable in) {
    return namedAccountable(description + " [" + in + "]", in.getChildResources(), in.ramBytesUsed());
  }
  
  
Returns an accountable with the provided description and bytes.
/** 
   * Returns an accountable with the provided description and bytes.
   */
  public static Accountable namedAccountable(String description, long bytes) {
    return namedAccountable(description, Collections.<Accountable>emptyList(), bytes);
  }
  
  
Converts a map of resources to a collection. 
 The resource descriptions are constructed in this format: prefix 'key' [toString()] 

This is a point-in-time type safe view: consumers 
will not be able to cast or manipulate the resources in any way.
/** 
   * Converts a map of resources to a collection. 
   * <p>
   * The resource descriptions are constructed in this format:
   * {@code prefix 'key' [toString()]}
   * <p>
   * This is a point-in-time type safe view: consumers 
   * will not be able to cast or manipulate the resources in any way.
   */
  public static Collection<Accountable> namedAccountables(String prefix, Map<?,? extends Accountable> in) {
    List<Accountable> resources = new ArrayList<>();
    for (Map.Entry<?,? extends Accountable> kv : in.entrySet()) {
      resources.add(namedAccountable(prefix + " '" + kv.getKey() + "'", kv.getValue()));
    }
    Collections.sort(resources, new Comparator<Accountable>() {
      @Override
      public int compare(Accountable o1, Accountable o2) {
        return o1.toString().compareTo(o2.toString());
      }
    });
    return Collections.unmodifiableList(resources);
  }
  
  
Returns an accountable with the provided description, children and bytes.
 The resource descriptions are constructed in this format: description [toString()] 

This is a point-in-time type safe view: consumers 
will not be able to cast or manipulate the resources in any way, provided
that the passed in children Accountables (and all their descendants) were created
with one of the namedAccountable functions.
/** 
   * Returns an accountable with the provided description, children and bytes.
   * <p>
   * The resource descriptions are constructed in this format:
   * {@code description [toString()]}
   * <p>
   * This is a point-in-time type safe view: consumers 
   * will not be able to cast or manipulate the resources in any way, provided
   * that the passed in children Accountables (and all their descendants) were created
   * with one of the namedAccountable functions.
   */
  public static Accountable namedAccountable(final String description, final Collection<Accountable> children, final long bytes) {
    return new Accountable() {
      @Override
      public long ramBytesUsed() {
        return bytes;
      }

      @Override
      public Collection<Accountable> getChildResources() {
        return children;
      }

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