/*
 * 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.bkd;

import java.io.Closeable;
import java.io.IOException;
import java.util.List;

import org.apache.lucene.codecs.CodecUtil;
import org.apache.lucene.store.ChecksumIndexInput;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.IOContext;
import org.apache.lucene.store.IndexOutput;

/** Writes points to disk in a fixed-with format.
 *
 * @lucene.internal */
public final class OfflinePointWriter implements PointWriter {

  final Directory tempDir;
  public final IndexOutput out;
  public final String name;
  final int packedBytesLength;
  final boolean singleValuePerDoc;
  long count;
  private boolean closed;
  // true if ords are written as long (8 bytes), else 4 bytes
  private boolean longOrds;
  private OfflinePointReader sharedReader;
  private long nextSharedRead;
  final long expectedCount;

  /** Create a new writer with an unknown number of incoming points */
  public OfflinePointWriter(Directory tempDir, String tempFileNamePrefix, int packedBytesLength,
                            boolean longOrds, String desc, long expectedCount, boolean singleValuePerDoc) throws IOException {
    this.out = tempDir.createTempOutput(tempFileNamePrefix, "bkd_" + desc, IOContext.DEFAULT);
    this.name = out.getName();
    this.tempDir = tempDir;
    this.packedBytesLength = packedBytesLength;
    this.longOrds = longOrds;
    this.singleValuePerDoc = singleValuePerDoc;
    this.expectedCount = expectedCount;
  }

  /** Initializes on an already written/closed file, just so consumers can use {@link #getReader} to read the file. */
  public OfflinePointWriter(Directory tempDir, String name, int packedBytesLength, long count, boolean longOrds, boolean singleValuePerDoc) {
    this.out = null;
    this.name = name;
    this.tempDir = tempDir;
    this.packedBytesLength = packedBytesLength;
    this.count = count;
    closed = true;
    this.longOrds = longOrds;
    this.singleValuePerDoc = singleValuePerDoc;
    this.expectedCount = 0;
  }
    
  @Override
  public void append(byte[] packedValue, long ord, int docID) throws IOException {
    assert packedValue.length == packedBytesLength;
    out.writeBytes(packedValue, 0, packedValue.length);
    out.writeInt(docID);
    if (singleValuePerDoc == false) {
      if (longOrds) {
        out.writeLong(ord);
      } else {
        assert ord <= Integer.MAX_VALUE;
        out.writeInt((int) ord);
      }
    }
    count++;
    assert expectedCount == 0 || count <= expectedCount;
  }

  @Override
  public PointReader getReader(long start, long length) throws IOException {
    assert closed;
    assert start + length <= count: "start=" + start + " length=" + length + " count=" + count;
    assert expectedCount == 0 || count == expectedCount;
    return new OfflinePointReader(tempDir, name, packedBytesLength, start, length, longOrds, singleValuePerDoc);
  }

  @Override
  public PointReader getSharedReader(long start, long length, List<Closeable> toCloseHeroically) throws IOException {
    if (sharedReader == null) {
      assert start == 0;
      assert length <= count;
      sharedReader = new OfflinePointReader(tempDir, name, packedBytesLength, 0, count, longOrds, singleValuePerDoc);
      toCloseHeroically.add(sharedReader);
      // Make sure the OfflinePointReader intends to verify its checksum:
      assert sharedReader.in instanceof ChecksumIndexInput;
    } else {
      assert start == nextSharedRead: "start=" + start + " length=" + length + " nextSharedRead=" + nextSharedRead;
    }
    nextSharedRead += length;
    return sharedReader;
  }

  @Override
  public void close() throws IOException {
    if (closed == false) {
      assert sharedReader == null;
      try {
        CodecUtil.writeFooter(out);
      } finally {
        out.close();
        closed = true;
      }
    }
  }

  @Override
  public void destroy() throws IOException {
    if (sharedReader != null) {
      // At this point, the shared reader should have done a full sweep of the file:
      assert nextSharedRead == count;
      sharedReader.close();
      sharedReader = null;
    }
    tempDir.deleteFile(name);
  }

  @Override
  public String toString() {
    return "OfflinePointWriter(count=" + count + " tempFileName=" + name + ")";
  }
}