/*
 * 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.geode.internal.admin.remote;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;

import org.apache.logging.log4j.Logger;

import org.apache.geode.DataSerializer;
import org.apache.geode.distributed.internal.DistributionConfig;
import org.apache.geode.distributed.internal.DistributionManager;
import org.apache.geode.distributed.internal.InternalDistributedSystem;
import org.apache.geode.distributed.internal.membership.InternalDistributedMember;
import org.apache.geode.internal.serialization.DeserializationContext;
import org.apache.geode.internal.serialization.SerializationContext;
import org.apache.geode.logging.internal.log4j.api.LogService;
import org.apache.geode.logging.internal.spi.LogFile;

public class TailLogResponse extends AdminResponse {
  private static final Logger logger = LogService.getLogger();

  private String tail;
  private String childTail;

  public static TailLogResponse create(DistributionManager dm,
      InternalDistributedMember recipient) {
    TailLogResponse m = new TailLogResponse();
    m.setRecipient(recipient);
    try {
      InternalDistributedSystem sys = dm.getSystem();
      if (sys.getLogFile().isPresent()) {
        LogFile logFile = sys.getLogFile().get();
        m.childTail = tailSystemLog(logFile.getChildLogFile());
        m.tail = tailSystemLog(sys.getConfig());
        if (m.tail == null) {
          m.tail =
              "No log file was specified in the configuration, messages will be directed to stdout.";
        }
      } else {
        m.childTail = tailSystemLog((File) null);
        m.tail = tailSystemLog(sys.getConfig());
        if (m.tail == null) {
          m.tail =
              "No log file was specified in the configuration, messages will be directed to stdout.";
        }
      }
    } catch (IOException e) {
      logger.warn("Error occurred while reading system log: {}", e.toString());
      m.tail = "";
    }
    return m;
  }

  @Override
  public int getDSFID() {
    return TAIL_LOG_RESPONSE;
  }

  @Override
  public void toData(DataOutput out,
      SerializationContext context) throws IOException {
    super.toData(out, context);
    DataSerializer.writeString(tail, out);
    DataSerializer.writeString(childTail, out);
  }

  @Override
  public void fromData(DataInput in,
      DeserializationContext context) throws IOException, ClassNotFoundException {
    super.fromData(in, context);
    tail = DataSerializer.readString(in);
    childTail = DataSerializer.readString(in);
  }

  public String getTail() {
    return tail;
  }

  public String getChildTail() {
    return childTail;
  }

  @Override
  public String toString() {
    return "TailLogResponse from " + this.getRecipient() + " <TAIL>" + getTail() + "</TAIL>";
  }

  public static String tailSystemLog(File logFile) throws IOException {
    if (logFile == null || logFile.equals(new File(""))) {
      return null;
    }
    int numLines = 30;
    int maxBuffer = 65500; // DataOutput.writeUTF will only accept 65535 bytes
    long fileLength = logFile.length();
    byte[] buffer = (fileLength > maxBuffer) ? new byte[maxBuffer] : new byte[(int) fileLength];
    int readSize = buffer.length;
    RandomAccessFile f = new RandomAccessFile(logFile, "r");
    f.seek(fileLength - readSize);
    f.read(buffer, 0, readSize);
    f.close();

    String messageString = new String(buffer);
    char[] text = messageString.toCharArray();
    for (int i = text.length - 1, j = 0; i >= 0; i--) {
      if (text[i] == '[')
        j++;
      if (j == numLines) {
        messageString = messageString.substring(i);
        break;
      }
    }
    return messageString.trim();
  }

  private static String tailSystemLog(DistributionConfig sc) throws IOException {
    File logFile = sc.getLogFile();
    if (logFile == null || logFile.equals(new File(""))) {
      return null;
    }
    if (!logFile.isAbsolute()) {
      logFile = new File(logFile.getAbsolutePath());
    }
    return tailSystemLog(logFile);
  }
}