/*
 * 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.index;


import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.lucene.index.DocValuesUpdate.BinaryDocValuesUpdate;
import org.apache.lucene.index.DocValuesUpdate.NumericDocValuesUpdate;
import org.apache.lucene.search.Query;
import org.apache.lucene.util.Accountable;
import org.apache.lucene.util.Counter;
import org.apache.lucene.util.RamUsageEstimator;

Holds buffered deletes and updates, by docID, term or query for a single segment. This is used to hold buffered pending deletes and updates against the to-be-flushed segment. Once the deletes and updates are pushed (on flush in DocumentsWriter), they are converted to a FrozenBufferedUpdates instance and pushed to the BufferedUpdatesStream. /** Holds buffered deletes and updates, by docID, term or query for a
 *  single segment. This is used to hold buffered pending
 *  deletes and updates against the to-be-flushed segment.  Once the
 *  deletes and updates are pushed (on flush in DocumentsWriter), they
 *  are converted to a {@link FrozenBufferedUpdates} instance and
 *  pushed to the {@link BufferedUpdatesStream}. */

// NOTE: instances of this class are accessed either via a private
// instance on DocumentWriterPerThread, or via sync'd code by
// DocumentsWriterDeleteQueue

class BufferedUpdates implements Accountable {

  /* Rough logic: HashMap has an array[Entry] w/ varying
     load factor (say 2 * POINTER).  Entry is object w/ Term
     key, Integer val, int hash, Entry next
     (OBJ_HEADER + 3*POINTER + INT).  Term is object w/
     String field and String text (OBJ_HEADER + 2*POINTER).
     Term's field is String (OBJ_HEADER + 4*INT + POINTER +
     OBJ_HEADER + string.length*CHAR).
     Term's text is String (OBJ_HEADER + 4*INT + POINTER +
     OBJ_HEADER + string.length*CHAR).  Integer is
     OBJ_HEADER + INT. */
  final static int BYTES_PER_DEL_TERM = 9*RamUsageEstimator.NUM_BYTES_OBJECT_REF + 7*RamUsageEstimator.NUM_BYTES_OBJECT_HEADER + 10*Integer.BYTES;

  /* Rough logic: del docIDs are List<Integer>.  Say list
     allocates ~2X size (2*POINTER).  Integer is OBJ_HEADER
     + int */
  final static int BYTES_PER_DEL_DOCID = 2*RamUsageEstimator.NUM_BYTES_OBJECT_REF + RamUsageEstimator.NUM_BYTES_OBJECT_HEADER + Integer.BYTES;

  /* Rough logic: HashMap has an array[Entry] w/ varying
     load factor (say 2 * POINTER).  Entry is object w/
     Query key, Integer val, int hash, Entry next
     (OBJ_HEADER + 3*POINTER + INT).  Query we often
     undercount (say 24 bytes).  Integer is OBJ_HEADER + INT. */
  final static int BYTES_PER_DEL_QUERY = 5*RamUsageEstimator.NUM_BYTES_OBJECT_REF + 2*RamUsageEstimator.NUM_BYTES_OBJECT_HEADER + 2*Integer.BYTES + 24;
  final AtomicInteger numTermDeletes = new AtomicInteger();
  final AtomicInteger numFieldUpdates = new AtomicInteger();

  final Map<Term,Integer> deleteTerms = new HashMap<>(); // TODO cut this over to FieldUpdatesBuffer
  final Map<Query,Integer> deleteQueries = new HashMap<>();
  final List<Integer> deleteDocIDs = new ArrayList<>();

  final Map<String, FieldUpdatesBuffer> fieldUpdates = new HashMap<>();
  

  public static final Integer MAX_INT = Integer.valueOf(Integer.MAX_VALUE);

  private final Counter bytesUsed = Counter.newCounter(true);
  final Counter fieldUpdatesBytesUsed = Counter.newCounter(true);

  private final static boolean VERBOSE_DELETES = false;

  long gen;

  final String segmentName;
  
  public BufferedUpdates(String segmentName) {
    this.segmentName = segmentName;
  }

  @Override
  public String toString() {
    if (VERBOSE_DELETES) {
      return "gen=" + gen + " numTerms=" + numTermDeletes + ", deleteTerms=" + deleteTerms
        + ", deleteQueries=" + deleteQueries + ", deleteDocIDs=" + deleteDocIDs + ", fieldUpdates=" + fieldUpdates
        + ", bytesUsed=" + bytesUsed;
    } else {
      String s = "gen=" + gen;
      if (numTermDeletes.get() != 0) {
        s += " " + numTermDeletes.get() + " deleted terms (unique count=" + deleteTerms.size() + ")";
      }
      if (deleteQueries.size() != 0) {
        s += " " + deleteQueries.size() + " deleted queries";
      }
      if (deleteDocIDs.size() != 0) {
        s += " " + deleteDocIDs.size() + " deleted docIDs";
      }
      if (numFieldUpdates.get() != 0) {
        s += " " + numFieldUpdates.get() + " field updates";
      }
      if (bytesUsed.get() != 0) {
        s += " bytesUsed=" + bytesUsed.get();
      }

      return s;
    }
  }

  public void addQuery(Query query, int docIDUpto) {
    Integer current = deleteQueries.put(query, docIDUpto);
    // increment bytes used only if the query wasn't added so far.
    if (current == null) {
      bytesUsed.addAndGet(BYTES_PER_DEL_QUERY);
    }
  }

  public void addDocID(int docID) {
    deleteDocIDs.add(Integer.valueOf(docID));
    bytesUsed.addAndGet(BYTES_PER_DEL_DOCID);
  }

  public void addTerm(Term term, int docIDUpto) {
    Integer current = deleteTerms.get(term);
    if (current != null && docIDUpto < current) {
      // Only record the new number if it's greater than the
      // current one.  This is important because if multiple
      // threads are replacing the same doc at nearly the
      // same time, it's possible that one thread that got a
      // higher docID is scheduled before the other
      // threads.  If we blindly replace than we can
      // incorrectly get both docs indexed.
      return;
    }

    deleteTerms.put(term, Integer.valueOf(docIDUpto));
    // note that if current != null then it means there's already a buffered
    // delete on that term, therefore we seem to over-count. this over-counting
    // is done to respect IndexWriterConfig.setMaxBufferedDeleteTerms.
    numTermDeletes.incrementAndGet();
    if (current == null) {
      bytesUsed.addAndGet(BYTES_PER_DEL_TERM + term.bytes.length + (Character.BYTES * term.field().length()));
    }
  }
 
  void addNumericUpdate(NumericDocValuesUpdate update, int docIDUpto) {
    FieldUpdatesBuffer buffer = fieldUpdates.computeIfAbsent(update.field, k -> new FieldUpdatesBuffer(fieldUpdatesBytesUsed, update, docIDUpto));
    if (update.hasValue) {
      buffer.addUpdate(update.term, update.getValue(), docIDUpto);
    } else {
      buffer.addNoValue(update.term, docIDUpto);
    }
    numFieldUpdates.incrementAndGet();
  }
  
  void addBinaryUpdate(BinaryDocValuesUpdate update, int docIDUpto) {
    FieldUpdatesBuffer buffer = fieldUpdates.computeIfAbsent(update.field, k -> new FieldUpdatesBuffer(fieldUpdatesBytesUsed, update, docIDUpto));
    if (update.hasValue) {
      buffer.addUpdate(update.term, update.getValue(), docIDUpto);
    } else {
      buffer.addNoValue(update.term, docIDUpto);
    }
    numFieldUpdates.incrementAndGet();
  }

  void clearDeleteTerms() {
    deleteTerms.clear();
    numTermDeletes.set(0);
  }
  
  void clear() {
    deleteTerms.clear();
    deleteQueries.clear();
    deleteDocIDs.clear();
    numTermDeletes.set(0);
    numFieldUpdates.set(0);
    fieldUpdates.clear();
    bytesUsed.addAndGet(-bytesUsed.get());
    fieldUpdatesBytesUsed.addAndGet(-fieldUpdatesBytesUsed.get());
  }
  
  boolean any() {
    return deleteTerms.size() > 0 || deleteDocIDs.size() > 0 || deleteQueries.size() > 0 || numFieldUpdates.get() > 0;
  }

  @Override
  public long ramBytesUsed() {
    return bytesUsed.get() + fieldUpdatesBytesUsed.get();
  }

  void clearDeletedDocIds() {
    deleteDocIDs.clear();
    bytesUsed.addAndGet(-deleteDocIDs.size() * BufferedUpdates.BYTES_PER_DEL_DOCID);
  }
}