/*
 * Copyright 2012-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.rules;

import com.facebook.buck.util.BuckConstant;
import com.facebook.buck.util.HumanReadableException;
import com.google.common.base.Throwables;
import com.google.common.eventbus.Subscribe;

import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
import java.util.logging.FileHandler;
import java.util.logging.Formatter;
import java.util.logging.Level;
import java.util.logging.LogRecord;
import java.util.logging.Logger;

/**
 * Logs build events to java.util.logging.
 */
public class JavaUtilsLoggingBuildListener {

  private final static Logger LOG = Logger.getLogger(JavaUtilsLoggingBuildListener.class.getName());
  private final static Level LEVEL = Level.INFO;

  public static void ensureLogFileIsWritten() {
    try {
      File dir = new File(BuckConstant.BIN_DIR);
      if (!dir.exists() && !dir.mkdirs()) {
        throw new HumanReadableException("Unable to create output directory: " + dir);
      }

      FileHandler handler = new FileHandler(
          String.format("%s/build.log", BuckConstant.BIN_DIR), /* append */ false);
      Formatter formatter = new BuildEventFormatter();
      handler.setFormatter(formatter);

      LOG.setUseParentHandlers(false);
      LOG.addHandler(handler);

      LOG.setLevel(LEVEL);

    } catch (IOException e) {
      throw Throwables.propagate(e);
    }
  }

  @Subscribe
  public void buildStarted(BuildStarted started) {
    LogRecord record = new LogRecord(LEVEL, "Build started");
    record.setMillis(started.getTimestamp());
    LOG.log(record);
  }

  @Subscribe
  public void buildFinished(BuildFinished finished) {
    LogRecord record = new LogRecord(LEVEL, "Build finished");
    record.setMillis(finished.getTimestamp());
    LOG.log(record);
  }

  @Subscribe
  public void ruleStarted(BuildRuleStarted started) {
    LogRecord record = new LogRecord(LEVEL, started.toString());
    record.setMillis(started.getTimestamp());
    LOG.log(record);
  }

  @Subscribe
  public void ruleFinished(BuildRuleFinished finished) {
    LogRecord record = new LogRecord(LEVEL, finished.toLogMessage());
    record.setMillis(finished.getTimestamp());
    LOG.log(record);
  }

  private static class BuildEventFormatter extends Formatter {

    private final ThreadLocal<SimpleDateFormat> dateFormat = new ThreadLocal<SimpleDateFormat>() {
      @Override protected SimpleDateFormat initialValue() {
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS");
        // Normalize all the times.
        format.setTimeZone(TimeZone.getTimeZone("UTC"));
        return format;
      }
    };

    @Override
    public String format(LogRecord logRecord) {
      StringBuilder builder = new StringBuilder();

      SimpleDateFormat format = dateFormat.get();
      builder.append(format.format(new Date(logRecord.getMillis())));

      builder.append("\t").append(logRecord.getLevel()).append("\t");
      builder.append(formatMessage(logRecord));
      builder.append("\n");

      return builder.toString();
    }
  }
}