/*
 * 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.juneau.microservice.resources;

import java.io.*;
import java.nio.charset.*;
import java.text.*;
import java.util.*;
import java.util.regex.*;

/**
 * Utility class for reading log files.
 *
 * <p>
 * Provides the capability of returning splices of log files based on dates and filtering based on thread and logger
 * names.
 */
public class LogParser implements Iterable<LogParser.Entry>, Iterator<LogParser.Entry>, Closeable {
   private BufferedReader br;
   LogEntryFormatter formatter;
   Date start, end;
   Set<String> loggerFilter, severityFilter;
   String threadFilter;
   private Entry next;

   /**
    * Constructor.
    *
    * @param formatter The log entry formatter.
    * @param f The log file.
    * @param start Don't return rows before this date.  If <jk>null</jk>, start from the beginning of the file.
    * @param end Don't return rows after this date.  If <jk>null</jk>, go to the end of the file.
    * @param thread Only return log entries with this thread name.
    * @param loggers Only return log entries produced by these loggers (simple class names).
    * @param severity Only return log entries with the specified severity.
    * @throws IOException Thrown by underlying stream.
    */
   public LogParser(LogEntryFormatter formatter, File f, Date start, Date end, String thread, String[] loggers, String[] severity) throws IOException {
      br = new BufferedReader(new InputStreamReader(new FileInputStream(f), Charset.defaultCharset()));
      this.formatter = formatter;
      this.start = start;
      this.end = end;
      this.threadFilter = thread;
      if (loggers != null)
         this.loggerFilter = new LinkedHashSet<>(Arrays.asList(loggers));
      if (severity != null)
         this.severityFilter = new LinkedHashSet<>(Arrays.asList(severity));

      // Find the first line.
      String line;
      while (next == null && (line = br.readLine()) != null) {
         Entry e = new Entry(line);
         if (e.matches())
            next = e;
      }
   }

   @Override /* Iterator */
   public boolean hasNext() {
      return next != null;
   }

   @Override /* Iterator */
   public Entry next() {
      Entry current = next;
      Entry prev = next;
      try {
         next = null;
         String line = null;
         while (next == null && (line = br.readLine()) != null) {
            Entry e = new Entry(line);
            if (e.isRecord) {
               if (e.matches())
                  next = e;
               prev = null;
            } else {
               if (prev != null)
                  prev.addText(e.line);
            }
         }
      } catch (IOException e) {
         throw new UncheckedIOException(e);
      }
      return current;
   }

   @Override /* Iterator */
   public void remove() {
      throw new NoSuchMethodError();
   }

   @Override /* Iterable */
   public Iterator<Entry> iterator() {
      return this;
   }

   @Override /* Closeable */
   public void close() throws IOException {
      br.close();
   }

   /**
    * Serializes the contents of the parsed log file to the specified writer and then closes the underlying reader.
    *
    * @param w The writer to write the log file to.
    * @throws IOException Thrown by underlying stream.
    */
   public void writeTo(Writer w) throws IOException {
      try {
         if (! hasNext())
            w.append("[EMPTY]");
         else for (LogParser.Entry le : this)
            le.append(w);
      } finally {
         close();
      }
   }

   /**
    * Represents a single line from the log file.
    */
   @SuppressWarnings("javadoc")
   public class Entry {
      public Date date;
      public String severity, logger;
      protected String line, text;
      protected String thread;
      protected List<String> additionalText;
      protected boolean isRecord;

      Entry(String line) throws IOException {
         try {
            this.line = line;
            Matcher m = formatter.getLogEntryPattern().matcher(line);
            if (m.matches()) {
               isRecord = true;
               String s = formatter.getField("date", m);
               if (s != null)
                  date = formatter.getDateFormat().parse(s);
               thread = formatter.getField("thread", m);
               severity = formatter.getField("level", m);
               logger = formatter.getField("logger", m);
               text = formatter.getField("msg", m);
               if (logger != null && logger.indexOf('.') > -1)
                  logger = logger.substring(logger.lastIndexOf('.')+1);
            }
         } catch (ParseException e) {
            throw new IOException(e);
         }
      }

      void addText(String t) {
         if (additionalText == null)
            additionalText = new LinkedList<>();
         additionalText.add(t);
      }

      public String getText() {
         if (additionalText == null)
            return text;
         int i = text.length();
         for (String s : additionalText)
            i += s.length() + 1;
         StringBuilder sb = new StringBuilder(i);
         sb.append(text);
         for (String s : additionalText)
            sb.append('\n').append(s);
         return sb.toString();
      }

      public String getThread() {
         return thread;
      }

      public Writer appendHtml(Writer w) throws IOException {
         w.append(toHtml(line)).append("<br>");
         if (additionalText != null)
            for (String t : additionalText)
               w.append(toHtml(t)).append("<br>");
         return w;
      }

      protected Writer append(Writer w) throws IOException {
         w.append(line).append('\n');
         if (additionalText != null)
            for (String t : additionalText)
               w.append(t).append('\n');
         return w;
      }

      boolean matches() {
         if (! isRecord)
            return false;
         if (start != null && date.before(start))
            return false;
         if (end != null && date.after(end))
            return false;
         if (threadFilter != null && ! threadFilter.equals(thread))
            return false;
         if (loggerFilter != null && ! loggerFilter.contains(logger))
            return false;
         if (severityFilter != null && ! severityFilter.contains(severity))
            return false;
         return true;
      }
   }

   static String toHtml(String s) {
      if (s.indexOf('<') != -1)
         return s.replaceAll("<", "&lt;");//$NON-NLS-2$
      return s;
   }
}