NAME

Mail::Box::Thread::Manager - maintain threads within a set of folders

SYNOPSIS

 my $mgr     = Mail::Box::Thread::Manager->new;
 my $folder  = $mgr->open(folder => '/tmp/inbox');
 my $threads = $mgr->threads(folder => $folder);
 my $threads = $mgr->threads($folder);   # same

 foreach my $thread ($threads->all)
 {   $thread->print;
 }

 $threads->includeFolder($folder);
 $threads->removeFolder($folder);

DESCRIPTION

Read Mail::Box-Overview first. You need to understand the Mail::Box::Thread::Node too.

A (message-)thread is a message with links to messages which followed in reply of that message. And then the messages with replied to the messages, which replied the original message. And so on. Some threads are only one message long (never replied to), some threads are very long.

The Mail::Box::Thread::Manager is very powerful. Not only is it able to do a descent job on MH-like folders (makes a trade-off between perfection and speed), it also can maintain threads from messages residing in different opened folders. Both facilities are rare for mail-agents.

More details about the IMPLEMENTATION at the bottom of this man-page. BE WARNED: not all possibilities are tested in great detail.

METHOD INDEX

The general methods for Mail::Box::Thread::Manager objects:

      all                                  removeFolder FOLDERS
      folders                              sortedAll [PREPARE [COMPARE]]
      includeFolder FOLDERS                sortedKnown [PREPARE [,COMP...
      known                                thread MESSAGE
      new ARGS                             threadStart MESSAGE

METHODS

new ARGS

A Mail::Box::Thread::Manager-object is created by a Mail::Box::Manager. One manager can produce more than one of these objects. One thread-manager can combine messages from a set of folders, which may be partially overlapping with other objects of the same type.

The construction of thread administration accepts the following options:

• dummy_type => CLASS

  The type of dummy messages. Dummy messages are used to fill holes in detected threads: refered to by messages found in the folder, but itselves not in the folder. Defaults to Mail::Box::Message::Dummy.

• folder => FOLDER | REF-ARRAY-FOLDERS

• folders => FOLDER | REF-ARRAY-FOLDERS

  Specifies which folders are to be covered by the threads. You can specify one or more open folders. When you close a folder, the manager will automatically remove the messages of that folder from your threads.

• thread_type => CLASS

  Type of the threads, by default Mail::Box::Thread::Node

• threader_type => CLASS | OBJECT

  You can specify a module name (CLASS) or a prepared OBJECT, which can handle the basic actions required to detect threads. In both case, the class must be derived from Mail::Box::Thread::Manager.

• window => INTEGER|'ALL'

  The thread-window describes how many messages should be checked at maximum to fill `holes' in threads for folder which use delay-loading of message headers. The default value is 10.

  The constant 'ALL' will cause thread-detection not to stop trying to fill holes, but continue looking until the first message of the folder is reached. Gives the best quality results, but may perform bad.

• timespan => TIME | 'EVER'

  Specify how fast threads usually work: the amount of time between an answer and a reply. This is used in combination with the window option to determine when to give-up filling the holes in threads.

  See Mail::Box::timespan2seconds for the possibilities for TIME. The default is '3 days'. With 'EVER', the search for messages in a thread will only be limited by the window-size.

• thread_body => BOOL

  May thread-detection be based on the content of a message? This has a serious performance implication when there are many messages without In-Reply-To and References headers in the folder, because it will cause many messages to be parsed.

  NOT USED YET. Defaults to FALSE.

Example:

    use Mail::Box::Manager;
    my $mgr     = new Mail::Box::Manager;
    my $inbox   = $mgr->open(folder => $ENV{MAIL});
    my $read    = $mgr->open(folder => 'Mail/read');
    my $threads = $mgr->threads(folders => [$inbox, $read]);

    # longer alternative for last line:
    my $threads = $mgr->threads;
    $threads->includeFolder($inbox);
    $threads->includeFolder($read);

folders

Returns the folders as managed by this threader.

includeFolder FOLDERS

removeFolder FOLDERS

Add/Remove a folders to/from the list of folders whose messages are organized in the threads maintained by this object. Duplicated inclusions will not cause any problems.

From the folders, the messages which have their header-lines parsed (see Mail::Box about lazy extracting) will be immediately scanned. Messages of which the header is known only later will have to report this (see Mail:Box with toBeThreaded).

Example:

    $threads->includeFolder($inbox, $draft);
    $threads->removeFolder($draft);

thread MESSAGE

Returns the thread where this MESSAGE is the start of. However, there is a possibility that this message is a reply itself.

Usually, all messages which are in reply of this message are dated later than the specified one. All headers of messages later than this one are are getting parsed first, for each folder in this threads-object.

Example:

   my $threads = $mgr->threads(folder => $inbox);
   my $thread  = $threads->thread($inbox->message(3));
   print $thread->toString;

threadStart MESSAGE

Based on a message, and facts from previously detected threads, try to build solid knowledge about the thread where this message is in.

all

sortedAll [PREPARE [COMPARE]]

Returns all messages which start a thread. The list may contain dummy messages and messages which are scheduled for deletion.

To be able to return all threads, thread construction on each message is performed first, which may be slow for some folder-types because is will enforce parsing of message-bodies.

The sortedAll returns the threads by default sorted on timestamp.

known

sortedKnown [PREPARE [,COMPARE]]

Returns the list of all messages which are known to be the start of a thread. Threads containing messages which where not read from their folder (like often happends MH-folder messages) are not yet known, and hence will not be returned.

The list may contain dummy messages, and messages which are scheduled for deletion. Threads are detected based on explicitly calling inThread() and thread() with a messages from the folder.

Be warned that, each time a message's header is read from the folder, the return of the method can change.

The sortedKnown returns the threads by default sorted on timestamp.

IMPLEMENTATION

This module implements thread-detection on a folder. Messages created by the better mailers will include In-Reply-To and References lines, which are used to figure out how messages are related. If you prefer a better thread detection, they are implementable, but there may be a serious performance hit (depends on the type of folder used).

Maintaining threads

A Mail::Box::Thread::Manager-object is created by the Mail::Box::Manager, using its threads() method. Each object can monitor the thread-relations between messages in one or more folders. When more than one folder is specified, the messages are merged while reading the threads, although nothing changes in the folder-structure. Adding and removing folders which have to be maintained is permitted at any moment, although may be quite costly in performance.

An example of the maintained structure is shown below. The Mail::Box::Manager has two open folders, and a thread-builder which monitors them both. The combined folders have two threads, the second is two long (msg3 is a reply on msg2). Msg2 is in two folders at once.

       manager
        |    \
        |     `----------- threads
        |                  |     |
        |                thread thread---thread
        |                  |    /|        /
        |                  |   //        /
        +---- folder1      |  //        /
        |       |         /  //        /
        |       `-----msg1  //        /
        |       `-----msg2-'/        /
        |                  /        /
        `-----folder2     /        /
                |        /        /
                `-----msg2       /
                `-----msg3------'

Delayed thread detection

With all() you get the start-messages of each thread of this folder. When that message was not found in the folder (not saved or already removed), you get a message of the dummy-type. These thread descriptions are in perfect state: all messages of the folder are included somewhere, and each missing message of the threads (`holes') are filled by dummies.

However, to be able to detect all threads it is required to have the headers of all messages, which is very slow for some types of folders, especially MH and IMAP folders.

For interactive mail-readers, it is prefered to detect threads only on messages which are in the viewport of the user. This may be sloppy in some situations, but everything is preferable over reading an MH mailbox with 10k e-mails to read only the see most recent messages.

In this object, we take special care not to cause unnecessary parsing (loading) of messages. Threads will only be detected on command, and by default only the message headers are used.

The following reports the Mail::Box::Thread::Node object which is related to a message:

   my $thread = $message->thread;

When the message was not put in a thread yet, it is done now. But, more work is done to return the best thread. Based on various parameters, which where specified when the folder was created, the method walks through the folder to fill the holes which are in this thread.

Walking from back to front (recently arrived messages are usually in the back of the folder), message after message are triggered to be included in their thread. At a certain moment, the whole thread of the requested method is found, a certain maximum number of messages was tried, but that didn't help (search window bound reached), or the messages within the folder are getting too old. Then the search to complete the thread will end, although more messages of them might have been in the folder: we don't scan the whole folder for performance reasons.

Finally, for each message where the head is known, for instance for all messages in mbox-folders, the correct thread is determined immediately. Also, all messages where the head get loaded later, are automatically included.

SEE ALSO

Mail::Box-Overview

AUTHOR

Mark Overmeer (mailbox@overmeer.net). All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

VERSION

This code is beta, version 2.009.

Copyright (c) 2001 Mark Overmeer. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

cpanm Mail::Box

perl -MCPAN -e shell
install Mail::Box