/*
    * 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
    *
    *      https://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.commons.net.examples.mail;
  
  import java.io.BufferedWriter;
  import java.io.IOException;
  import java.io.UncheckedIOException;
  import java.net.URI;
  import java.net.URISyntaxException;
  import java.nio.charset.Charset;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.nio.file.Paths;
  import java.nio.file.StandardOpenOption;
  import java.text.ParseException;
  import java.text.SimpleDateFormat;
  import java.util.ArrayList;
  import java.util.Date;
  import java.util.Iterator;
  import java.util.List;
  import java.util.TimeZone;
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  import org.apache.commons.io.IOUtils;
  import org.apache.commons.net.PrintCommandListener;
  import org.apache.commons.net.ProtocolCommandEvent;
  import org.apache.commons.net.imap.IMAP;
  import org.apache.commons.net.imap.IMAP.IMAPChunkListener;
  import org.apache.commons.net.imap.IMAPClient;
  import org.apache.commons.net.imap.IMAPReply;
  
  /**
   * This is an example program demonstrating how to use the IMAP[S]Client class. This program connects to a IMAP[S] server and exports selected messages from a
   * folder into an mbox file.
   * <p>
   * Usage: IMAPExportMbox imap[s]://user:password@host[:port]/folder/path <mboxfile> [sequence-set] [item-names]
   * <p>
   * An example sequence-set might be:
   * <ul>
   * <li>11,2,3:10,20:*</li>
   * <li>1:* - this is the default</li>
   * </ul>
   * <p>
   * Some example item-names might be:
   * <ul>
   * <li>BODY.PEEK[HEADER]</li>
   * <li>'BODY.PEEK[HEADER.FIELDS (SUBJECT)]'</li>
   * <li>ALL - macro equivalent to '(FLAGS INTERNALDATE RFC822.SIZE ENVELOPE)'</li>
   * <li>FAST - macro equivalent to '(FLAGS INTERNALDATE RFC822.SIZE)'</li>
   * <li>FULL - macro equivalent to '(FLAGS INTERNALDATE RFC822.SIZE ENVELOPE BODY)'</li>
   * <li>ENVELOPE X-GM-LABELS</li>
   * <li>'(INTERNALDATE BODY.PEEK[])' - this is the default</li>
   * </ul>
   * <p>
   * Macro names cannot be combined with anything else; they must be used alone.<br>
   * Note that using BODY will set the \Seen flag. This is why the default uses BODY.PEEK[].<br>
   * The item name X-GM-LABELS is a Google Mail extension; it shows the labels for a message.<br>
   * For example:<br>
   * IMAPExportMbox imaps://user:password@imap.googlemail.com/messages_for_export exported.mbox 1:10,20<br>
   * IMAPExportMbox imaps://user:password@imap.googlemail.com/messages_for_export exported.mbox 3 ENVELOPE X-GM-LABELS<br>
   * <p>
   * The sequence-set is passed unmodified to the FETCH command.<br>
   * The item names are wrapped in parentheses if more than one is provided. Otherwise, the parameter is assumed to be wrapped if necessary.<br>
   * Parameters with spaces must be quoted otherwise the OS shell will normally treat them as separate parameters.<br>
   * Also, the listener that writes the mailbox only captures the multi-line responses (e.g. ones that include BODY references). It does not capture the output
   * from FETCH commands using item names such as ENVELOPE or FLAGS that return a single line response.
   */
  public final class IMAPExportMbox {
  
      private static final class MboxListener implements IMAPChunkListener {
  
          private final BufferedWriter bufferedWriter;
          volatile AtomicInteger total = new AtomicInteger();
          volatile String lastFetched;
          volatile List<String> missingIds = new ArrayList<>();
          volatile long lastSeq = -1;
          private final String lineSeparator;
          private final SimpleDateFormat DATE_FORMAT // for mbox From_ lines
                  = new SimpleDateFormat("EEE MMM dd HH:mm:ss yyyy");
  
          // e.g. INTERNALDATE "27-Oct-2013 07:43:24 +0000"
          // for parsing INTERNALDATE
         private final SimpleDateFormat IDPARSE = new SimpleDateFormat("dd-MMM-yyyy HH:mm:ss Z");
         private final boolean printHash;
         private final boolean printMarker;
         private final boolean checkSequence;
 
         MboxListener(final BufferedWriter bufferedWriter, final String lineSeparator, final boolean printHash, final boolean printMarker,
                 final boolean checkSequence) {
             this.lineSeparator = lineSeparator;
             this.printHash = printHash;
             this.printMarker = printMarker;
             DATE_FORMAT.setTimeZone(TimeZone.getTimeZone("GMT"));
             this.bufferedWriter = bufferedWriter;
             this.checkSequence = checkSequence;
         }
 
         @Override
         public boolean chunkReceived(final IMAP imap) {
             final String[] replyStrings = imap.getReplyStrings();
             Date received = new Date();
             final String firstLine = replyStrings[0];
             Matcher m = PATID.matcher(firstLine);
             if (m.lookingAt()) { // found a match
                 final String date = m.group(PATID_DATE_GROUP);
                 try {
                     received = IDPARSE.parse(date);
                 } catch (final ParseException e) {
                     System.err.println(e);
                 }
             } else {
                 System.err.println("No timestamp found in: " + firstLine + "  - using current time");
             }
             String replyTo = "MAILER-DAEMON"; // default
             for (int i = 1; i < replyStrings.length - 1; i++) {
                 final String line = replyStrings[i];
                 if (line.startsWith("Return-Path: ")) {
                     final String[] parts = line.split(" ", 2);
                     if (!parts[1].equals("<>")) { // Don't replace default with blank
                         replyTo = parts[1];
                         if (replyTo.startsWith("<")) {
                             if (replyTo.endsWith(">")) {
                                 replyTo = replyTo.substring(1, replyTo.length() - 1); // drop <> wrapper
                             } else {
                                 System.err.println("Unexpected Return-path: '" + line + "' in " + firstLine);
                             }
                         }
                     }
                     break;
                 }
             }
             try {
                 // Add initial mbox header line
                 bufferedWriter.append("From ");
                 bufferedWriter.append(replyTo);
                 bufferedWriter.append(' ');
                 bufferedWriter.append(DATE_FORMAT.format(received));
                 bufferedWriter.append(lineSeparator);
                 // Debug
                 bufferedWriter.append("X-IMAP-Response: ").append(firstLine).append(lineSeparator);
                 if (printMarker) {
                     System.err.println("[" + total + "] " + firstLine);
                 }
                 // Skip first and last lines
                 for (int i = 1; i < replyStrings.length - 1; i++) {
                     final String line = replyStrings[i];
                     if (startsWith(line, PATFROM)) {
                         bufferedWriter.append('>'); // Escape a From_ line
                     }
                     bufferedWriter.append(line);
                     bufferedWriter.append(lineSeparator);
                 }
                 // The last line ends with the trailing closing ")" which needs to be stripped
                 final String lastLine = replyStrings[replyStrings.length - 1];
                 final int lastLength = lastLine.length();
                 if (lastLength > 1) { // there's some content, we need to save it
                     bufferedWriter.append(lastLine, 0, lastLength - 1);
                     bufferedWriter.append(lineSeparator);
                 }
                 bufferedWriter.append(lineSeparator); // blank line between entries
             } catch (final IOException e) {
                 e.printStackTrace();
                 throw new UncheckedIOException(e); // chunkReceived cannot throw a checked Exception
             }
             lastFetched = firstLine;
             total.incrementAndGet();
             if (checkSequence) {
                 m = PATSEQ.matcher(firstLine);
                 if (m.lookingAt()) { // found a match
                     final long msgSeq = Long.parseLong(m.group(PATSEQ_SEQUENCE_GROUP)); // Cannot fail to parse
                     if (lastSeq != -1) {
                         final long missing = msgSeq - lastSeq - 1;
                         if (missing != 0) {
                             for (long j = lastSeq + 1; j < msgSeq; j++) {
                                 missingIds.add(String.valueOf(j));
                             }
                             System.err.println("*** Sequence error: current=" + msgSeq + " previous=" + lastSeq + " Missing=" + missing);
                         }
                     }
                     lastSeq = msgSeq;
                 }
             }
             if (printHash) {
                 System.err.print(".");
             }
             return true;
         }
 
         public void close() throws IOException {
             IOUtils.close(bufferedWriter);
         }
     }
 
     private static final String CRLF = "\r\n";
     private static final String LF = "\n";
 
     private static final String EOL_DEFAULT = System.lineSeparator();
     private static final Pattern PATFROM = Pattern.compile(">*From "); // unescaped From_
     // e.g. * nnn (INTERNALDATE "27-Oct-2013 07:43:24 +0000" BODY[] {nn} ...)
     private static final Pattern PATID = // INTERNALDATE
             Pattern.compile(".*INTERNALDATE \"(\\d\\d-\\w{3}-\\d{4} \\d\\d:\\d\\d:\\d\\d [+-]\\d+)\"");
 
     private static final int PATID_DATE_GROUP = 1;
     private static final Pattern PATSEQ = Pattern.compile("\\* (\\d+) "); // Sequence number
 
     private static final int PATSEQ_SEQUENCE_GROUP = 1;
 
     // e.g. * 382 EXISTS
     private static final Pattern PATEXISTS = Pattern.compile("\\* (\\d+) EXISTS"); // Response from SELECT
 
     // AAAC NO [TEMPFAIL] FETCH Temporary failure on server [CODE: WBL]
     private static final Pattern PATTEMPFAIL = Pattern.compile("[A-Z]{4} NO \\[TEMPFAIL\\] FETCH .*");
     private static final int CONNECT_TIMEOUT = 10; // Seconds
 
     private static final int READ_TIMEOUT = 10;
 
     public static void main(final String[] args) throws IOException, URISyntaxException {
         int connect_timeout = CONNECT_TIMEOUT;
         int read_timeout = READ_TIMEOUT;
 
         int argIdx = 0;
         String eol = EOL_DEFAULT;
         boolean printHash = false;
         boolean printMarker = false;
         int retryWaitSecs = 0;
 
         for (argIdx = 0; argIdx < args.length; argIdx++) {
             if (args[argIdx].equals("-c")) {
                 connect_timeout = Integer.parseInt(args[++argIdx]);
             } else if (args[argIdx].equals("-r")) {
                 read_timeout = Integer.parseInt(args[++argIdx]);
             } else if (args[argIdx].equals("-R")) {
                 retryWaitSecs = Integer.parseInt(args[++argIdx]);
             } else if (args[argIdx].equals("-LF")) {
                 eol = LF;
             } else if (args[argIdx].equals("-CRLF")) {
                 eol = CRLF;
             } else if (args[argIdx].equals("-.")) {
                 printHash = true;
             } else if (args[argIdx].equals("-X")) {
                 printMarker = true;
             } else {
                 break;
             }
         }
 
         final int argCount = args.length - argIdx;
 
         if (argCount < 2) {
             System.err.println("Usage: IMAPExportMbox [-LF|-CRLF] [-c n] [-r n] [-R n] [-.] [-X]"
                     + " imap[s]://user:password@host[:port]/folder/path [+|-]<mboxfile> [sequence-set] [itemnames]");
             System.err.println("\t-LF | -CRLF set end-of-line to LF or CRLF (default is the line.separator system property)");
             System.err.println("\t-c connect timeout in seconds (default 10)");
             System.err.println("\t-r read timeout in seconds (default 10)");
             System.err.println("\t-R temporary failure retry wait in seconds (default 0; i.e. disabled)");
             System.err.println("\t-. print a . for each complete message received");
             System.err.println("\t-X print the X-IMAP line for each complete message received");
             System.err.println("\tthe mboxfile is where the messages are stored; use '-' to write to standard output.");
             System.err.println("\tPrefix file name with '+' to append to the file. Prefix with '-' to allow overwrite.");
             System.err.println("\ta sequence-set is a list of numbers/number ranges e.g. 1,2,3-10,20:* - default 1:*");
             System.err.println("\titemnames are the message data item name(s) e.g. BODY.PEEK[HEADER.FIELDS (SUBJECT)]"
                     + " or a macro e.g. ALL - default (INTERNALDATE BODY.PEEK[])");
             System.exit(1);
         }
 
         final String uriString = args[argIdx++];
         URI uri;
         try {
             uri = URI.create(uriString);
         } catch (final IllegalArgumentException e) { // cannot parse the path as is; let's pull it apart and try again
             final Matcher m = Pattern.compile("(imaps?://[^/]+)(/.*)").matcher(uriString);
             if (!m.matches()) {
                 throw e;
             }
             uri = URI.create(m.group(1)); // Just the scheme and auth parts
             uri = new URI(uri.getScheme(), uri.getAuthority(), m.group(2), null, null);
         }
         final String file = args[argIdx++];
         String sequenceSet = argCount > 2 ? args[argIdx++] : "1:*";
         final String itemNames;
         // Handle 0, 1 or multiple item names
         if (argCount > 3) {
             if (argCount > 4) {
                 final StringBuilder sb = new StringBuilder();
                 sb.append("(");
                 for (int i = 4; i <= argCount; i++) {
                     if (i > 4) {
                         sb.append(" ");
                     }
                     sb.append(args[argIdx++]);
                 }
                 sb.append(")");
                 itemNames = sb.toString();
             } else {
                 itemNames = args[argIdx++];
             }
         } else {
             itemNames = "(INTERNALDATE BODY.PEEK[])";
         }
 
         final boolean checkSequence = sequenceSet.matches("\\d+:(\\d+|\\*)"); // are we expecting a sequence?
         final MboxListener mboxListener;
         if (file.equals("-")) {
             mboxListener = null;
         } else if (file.startsWith("+")) {
             final Path mboxPath = Paths.get(file.substring(1));
             System.out.println("Appending to file " + mboxPath);
             mboxListener = new MboxListener(Files.newBufferedWriter(mboxPath, Charset.defaultCharset(), StandardOpenOption.CREATE, StandardOpenOption.APPEND),
                     eol, printHash, printMarker, checkSequence);
         } else if (file.startsWith("-")) {
             final Path mboxPath = Paths.get(file.substring(1));
             System.out.println("Writing to file " + mboxPath);
             mboxListener = new MboxListener(Files.newBufferedWriter(mboxPath, Charset.defaultCharset(), StandardOpenOption.CREATE), eol, printHash, printMarker,
                     checkSequence);
         } else {
             final Path mboxPath = Paths.get(file);
             if (Files.exists(mboxPath) && Files.size(mboxPath) > 0) {
                 throw new IOException("mailbox file: " + mboxPath + " already exists and is non-empty!");
             }
             System.out.println("Creating file " + mboxPath);
             mboxListener = new MboxListener(Files.newBufferedWriter(mboxPath, Charset.defaultCharset(), StandardOpenOption.CREATE), eol, printHash, printMarker,
                     checkSequence);
         }
 
         final String path = uri.getPath();
         if (path == null || path.length() < 1) {
             throw new IllegalArgumentException("Invalid folderPath: '" + path + "'");
         }
         final String folder = path.substring(1); // skip the leading /
 
         // suppress login details
         final PrintCommandListener listener = new PrintCommandListener(System.out, true) {
             @Override
             public void protocolReplyReceived(final ProtocolCommandEvent event) {
                 if (event.getReplyCode() != IMAPReply.PARTIAL) { // This is dealt with by the chunk listener
                     super.protocolReplyReceived(event);
                 }
             }
         };
 
         // Connect and login
         final IMAPClient imap = IMAPUtils.imapLogin(uri, connect_timeout * 1000, listener);
 
         String maxIndexInFolder = null;
 
         try {
 
             imap.setSoTimeout(read_timeout * 1000);
 
             if (!imap.select(folder)) {
                 throw new IOException("Could not select folder: " + folder);
             }
 
             for (final String line : imap.getReplyStrings()) {
                 maxIndexInFolder = matches(line, PATEXISTS, 1);
                 if (maxIndexInFolder != null) {
                     break;
                 }
             }
 
             if (mboxListener != null) {
                 imap.setChunkListener(mboxListener);
             } // else the command listener displays the full output without processing
 
             while (true) {
                 final boolean ok = imap.fetch(sequenceSet, itemNames);
                 // If the fetch failed, can we retry?
                 if (ok || retryWaitSecs <= 0 || mboxListener == null || !checkSequence) {
                     break;
                 }
                 final String replyString = imap.getReplyString(); // includes EOL
                 if (!startsWith(replyString, PATTEMPFAIL)) {
                     throw new IOException("FETCH " + sequenceSet + " " + itemNames + " failed with " + replyString);
                 }
                 System.err.println("Temporary error detected, will retry in " + retryWaitSecs + "seconds");
                 sequenceSet = mboxListener.lastSeq + 1 + ":*";
                 try {
                     Thread.sleep(retryWaitSecs * 1000);
                 } catch (final InterruptedException e) {
                     // ignored
                 }
             }
 
         } catch (final IOException ioe) {
             final String count = mboxListener == null ? "?" : mboxListener.total.toString();
             System.err.println("FETCH " + sequenceSet + " " + itemNames + " failed after processing " + count + " complete messages ");
             if (mboxListener != null) {
                 System.err.println("Last complete response seen: " + mboxListener.lastFetched);
             }
             throw ioe;
         } finally {
 
             if (printHash) {
                 System.err.println();
             }
 
             if (mboxListener != null) {
                 mboxListener.close();
                 final Iterator<String> missingIds = mboxListener.missingIds.iterator();
                 if (missingIds.hasNext()) {
                     final StringBuilder sb = new StringBuilder();
                     for (;;) {
                         sb.append(missingIds.next());
                         if (!missingIds.hasNext()) {
                             break;
                         }
                         sb.append(",");
                     }
                     System.err.println("*** Missing ids: " + sb.toString());
                 }
             }
             imap.logout();
             imap.disconnect();
         }
         if (mboxListener != null) {
             System.out.println("Processed " + mboxListener.total + " messages.");
         }
         if (maxIndexInFolder != null) {
             System.out.println("Folder contained " + maxIndexInFolder + " messages.");
         }
     }
 
     private static String matches(final String input, final Pattern pat, final int index) {
         final Matcher m = pat.matcher(input);
         if (m.lookingAt()) {
             return m.group(index);
         }
         return null;
     }
 
     private static boolean startsWith(final String input, final Pattern pat) {
         final Matcher m = pat.matcher(input);
         return m.lookingAt();
     }
 }