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/*
 * Copyright © 2021-present Arcade Data Ltd ([email protected])
 *
 * 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.
 *
 * SPDX-FileCopyrightText: 2021-present Arcade Data Ltd ([email protected])
 * SPDX-License-Identifier: Apache-2.0
 */
package com.arcadedb.engine;

import com.arcadedb.database.Binary;
import com.arcadedb.database.DatabaseInternal;
import com.arcadedb.exception.ConfigurationException;
import com.arcadedb.exception.TransactionException;
import com.arcadedb.log.LogManager;
import com.arcadedb.utility.FileUtils;
import com.arcadedb.utility.LockContext;

import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.concurrent.atomic.*;
import java.util.logging.*;

public class WALFile extends LockContext {
  public enum FLUSH_TYPE {
    NO, YES_NOMETADATA, YES_FULL
  }

  // TXID (long) + TIMESTAMP (long) + PAGES (int) + SEGMENT_SIZE (int)
  private static final int TX_HEADER_SIZE = Binary.LONG_SERIALIZED_SIZE + Binary.LONG_SERIALIZED_SIZE + Binary.INT_SERIALIZED_SIZE + Binary.INT_SERIALIZED_SIZE;
  // SEGMENT_SIZE (int) + MAGIC_NUMBER (long)
  private static final int TX_FOOTER_SIZE = Binary.INT_SERIALIZED_SIZE + Binary.LONG_SERIALIZED_SIZE;

  // FILE_ID (int) + PAGE_NUMBER (int) + DELTA_FROM (int) + DELTA_TO (int) + CURR_PAGE_VERSION (int)+ CURR_PAGE_SIZE (int)
  private static final int PAGE_HEADER_SIZE =
      Binary.INT_SERIALIZED_SIZE + Binary.INT_SERIALIZED_SIZE + Binary.INT_SERIALIZED_SIZE + Binary.INT_SERIALIZED_SIZE + Binary.INT_SERIALIZED_SIZE
          + Binary.INT_SERIALIZED_SIZE;

  public static final long MAGIC_NUMBER = 9371515385058702L;

  private final    RandomAccessFile file;
  private final    String           filePath;
  private final    FileChannel      channel;
  private volatile boolean          active            = true;
  private volatile boolean          open;
  private final    AtomicInteger    pagesToFlush      = new AtomicInteger();
  private          long             statsPagesWritten = 0;
  private          long             statsBytesWritten = 0;
  // STATIC BUFFERS USED FOR RECOVERY
  private final    ByteBuffer       bufferLong        = ByteBuffer.allocate(Binary.LONG_SERIALIZED_SIZE);
  private final    ByteBuffer       bufferInt         = ByteBuffer.allocate(Binary.INT_SERIALIZED_SIZE);

  public static class WALTransaction {
    public long      txId;
    public long      timestamp;
    public WALPage[] pages;
    public long      startPositionInLog;
    public long      endPositionInLog;
  }

  public static class WALPage {
    public int    fileId;
    public int    pageNumber;
    public int    changesFrom;
    public int    changesTo;
    public Binary currentContent;
    public int    currentPageVersion;
    public int    currentPageSize;

    @Override
    public String toString() {
      return "WALPage(fileId=" + fileId + " pageNumber=" + pageNumber + ")";
    }
  }

  public WALFile(final String filePath) throws FileNotFoundException {
    this.filePath = filePath;
    this.file = new RandomAccessFile(filePath, "rw");
    this.channel = file.getChannel();
    this.open = true;
  }

  public synchronized void close() throws IOException {
    this.open = false;
    if (channel != null)
      channel.close();

    if (file != null)
      file.close();
  }

  public boolean isOpen() {
    return open;
  }

  public synchronized void drop() throws IOException {
    close();
    FileUtils.deleteFile(new File(filePath));
  }

  public WALTransaction getFirstTransaction() throws WALException {
    return getTransaction(0);
  }

  public int getPendingPagesToFlush() {
    return pagesToFlush.get();
  }

  /**
   * If the WAL is still active, execute the callback. This avoids closing a file where a thread is still writing to it.
   *
   * @return true if acquired, otherwise false
   */
  public synchronized boolean acquire(final Callable