/*
 * Copyright 2014-present Facebook, Inc.
 *
 * 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.
 */

package com.facebook.buck.log;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Throwables;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;
import java.util.logging.Level;
import java.util.logging.LogRecord;
import javax.annotation.Nullable;

public class LogFormatter extends java.util.logging.Formatter {
  private static final int ERROR_LEVEL = Level.SEVERE.intValue();
  private static final int WARN_LEVEL = Level.WARNING.intValue();
  private static final int INFO_LEVEL = Level.INFO.intValue();
  private static final int DEBUG_LEVEL = Level.FINE.intValue();
  private static final int VERBOSE_LEVEL = Level.FINER.intValue();
  private final ThreadIdToCommandIdMapper mapper;
  private final ThreadLocal<SimpleDateFormat> simpleDateFormat;

  public LogFormatter() {
    this(
        GlobalStateManager.singleton().getThreadIdToCommandIdMapper(),
        Locale.US,
        TimeZone.getDefault());
  }

  @VisibleForTesting
  LogFormatter(ThreadIdToCommandIdMapper mapper, final Locale locale, final TimeZone timeZone) {
    this.mapper = mapper;
    simpleDateFormat =
        new ThreadLocal<SimpleDateFormat>() {
          @Override
          protected SimpleDateFormat initialValue() {
            SimpleDateFormat format = new SimpleDateFormat("[yyyy-MM-dd HH:mm:ss.SSS]", locale);
            format.setTimeZone(timeZone);
            return format;
          }
        };
  }

  @Override
  public String format(LogRecord record) {
    String timestamp = simpleDateFormat.get().format(new Date(record.getMillis()));

    // We explicitly don't use String.format here because this code is very
    // performance-critical: http://stackoverflow.com/a/1281651
    long tid = record.getThreadID();
    @Nullable String command = mapper.threadIdToCommandId(tid);
    StringBuilder sb =
        new StringBuilder(255)
            .append(timestamp)
            .append(formatRecordLevel(record.getLevel()))
            .append("[command:")
            .append(command)
            .append("][tid:");
    // Zero-pad on the left. We're currently assuming we have less than 100 threads.
    if (tid < 10) {
      sb.append("0").append(tid);
    } else {
      sb.append(tid);
    }
    sb.append("][").append(record.getLoggerName()).append("] ");
    if (record instanceof AppendableLogRecord) {
      // Avoid allocating then throwing away the formatted message and
      // params; just format directly to the StringBuilder.
      ((AppendableLogRecord) record).appendFormattedMessage(sb);
    } else {
      sb.append(formatMessage(record));
    }
    sb.append("\n");
    Throwable t = record.getThrown();
    if (t != null) {
      sb.append(Throwables.getStackTraceAsString(t)).append("\n");
    }
    return sb.toString();
  }

  private static String formatRecordLevel(Level level) {
    int l = level.intValue();
    if (l == ERROR_LEVEL) {
      return "[error]";
    } else if (l == WARN_LEVEL) {
      return "[warn ]";
    } else if (l == INFO_LEVEL) {
      return "[info ]";
    } else if (l == DEBUG_LEVEL) {
      return "[debug]";
    } else if (l == VERBOSE_LEVEL) {
      return "[vrbos]";
    } else {
      // We don't expect this to happen, so meh, let's use String.format for simplicity.
      return String.format("[%-5d]", l);
    }
  }
}