NAME
   Email::Store - Framework for database-backed email storage

SYNOPSIS
     use Email::Store 'dbi:mysql:mailstore';
     Email::Store->setup; # Do this once

     Email::Store::Mail->store( $rfc822 );
     Email::Store::Mail->retrieve( $msgid );

     ...

DESCRIPTION
   "Email::Store" is the ideal basis for any application which needs to
   deal with databases of email: archiving, searching, or even storing mail
   for implementing IMAP or POP3 servers.

   "Email::Store" itself is a very lightweight framework, meaning it does
   not provide very much functionality itself; in effect, it is merely a
   Class::DBI interface to a database schema which is designed for storing
   email. Incidentally, if you don't know much about "Class::DBI", you're
   going to need to in order to get much out of this.

   Despite its minimalist nature, "Email::Store" is incredibly powerful.
   Its power comes from its extensibility, through plugin modules and hooks
   which allow you to add new database tables and concepts to the system,
   and so access the mail store from a "different direction". In a sense,
   "Email::Store" is a blank canvas, onto which you can pick and choose (or
   even write!) the plugins which you want for your application.

   For instance, the core "Email::Store::Entity" plugin module addresses
   the idea of "people" in the email universe, allowing you to search for
   mails to or from particular people; (despite their changing names or
   email addresses) "Email::Store::Thread" interfaces "Email::Store" to
   "Mail::Thread" allowing you to navigate mails by their position in a
   mail thread; the planned non-core "Email::Store::Plucene" module plugs
   into the indexing process and stores information about emails in a
   Plucene search index for quick retrieval later, and so on.

Core "Email::Store" modules
   To get you started with a useful database, "Email::Store" provides a few
   core plugin modules which comprise the basics of a mailstore. Each of
   the modules provides one or more database tables, representing important
   concepts in the email world, and one or more relationships between these
   concepts and the other tables in the system. It's a little less
   complicated than that, as we'll see when we go through each module in
   turn. Here is a quick summary of what the core modules do:

   "Email::Store::Mail"
      This is, in a sense, the plugin of plugins. "Email::Store::Mail"
      encapsulates individual email messages. Its "store" method is the
      means in which emails are indexed and enter the mailstore. How this
      storing is done, however, is influenced by all the other plugins.

   "Email::Store::List"
      "List" is one of the easiest plugins to understand. To our concept of
      the mail, it adds the concept of a mailing list.

      "Email::Store::List" hooks into the indexing process and examines a
      mail to see if it came via a mailing list; if so, it associates the
      mail with one or more lists. This means you can ask a mail object for
      its "lists", and a list object for its "posts". Because of this,
      instead of looking at messages by their message ID, you can start by
      looking for a mailing list you're interested in and then navigate to
      the messages you want.

   "Email::Store::Entity"
      "Entity" is the most fundamental of the plugins but (or perhaps,
      "thus") the most complex. This module adds the concept of an
      addressing, which abstracts out the From, To, Cc and Bcc headers of
      an email. A "To" header, for instance, says that the mail is
      addressed to a particular name and address, but
      "Email::Store::Entity" also provides the potential for associating
      different names and addresses with the concept of an entity, a unique
      individual. That is, not all mails addressed to the name "Simon
      Cozens" are to me (due to the existence of multiple Simon Cozenses in
      the world) but all mails to ".*@simon-cozens.org" are, despite their
      being multiple email addresses which match that pattern.

      If that has you confused, (and believe me, it has me confused) ignore
      the "entity" bit and know that you can navigate from names, addresses
      and the intersection of the two, to emails involving them. More
      details in Email::Store::Entity as you'd expect.

   "Email::Store::Attachment"
      As you might be able to guess, this adds the concept of an
      attachment. It also ambushes the indexing process, and strips all the
      MIME attachments off an email, placing them in the attachments table.
      It then quietly slips the de-MIMEd email back into the mail table,
      and now you can ask a mail for its "attachments".

   All these modules have some degree of POD, so you should consult them
   for more details on the interface that they provide. Over time, there
   will be additional modules that you can install from CPAN.

USAGE
   When you use "Email::Store", you should pass a DBI connection string to
   its "use" statement:

       use Email::Store 'dbi:SQLite:dbname=mailstore.db';

   In order to create the tables used by the plugin modules, you should
   then say

       Email::Store->setup;

   You should do this on the initial set-up of your database, and then
   again on installing any additional plugin modules, to create the new
   tables they want to use. Note that this does not retroactively index
   existing mail with the new functions provided by the modules you've just
   installed! - a "reindex" method is planned, but is not there yet.

   This is all the functionality that "Email::Store" itself provides. See
   the documentation to the various plugins for their public interface,
   chiefly Email::Store::Mail.

THE PLUGIN SYSTEM
   If you want to write your own plugins, you will need to know how the
   plugin system works.

   The first thing to note is that when "Email::Store" indexes a mail,
   whether for the first time or when it re-indexes a mail it's seen
   before, it loads up all the modules it can find under the
   "Email::Store::*" hierarchy. Additionally, when "Email::Store->setup" is
   called, all the "Email::Store::*" modules are required. So, to register
   your new plugin, all you need to do is call it
   "Email::Store::"*something* and put it in Perl's include path in the
   usual way.

   Each plugin module should be a self-contained description of some
   concepts, the database schema that encapsulates them, their relationship
   to the rest of the system, and any hooks or additional functionality
   provided.

   Let us write a very simple plugin as a first example. This will
   introduce the concept of a mail annotation, an open-ended space where we
   can store "sticky notes" which relate to a particular email. We'll call
   the plugin "Email::Store::Annotation", and we start by putting the
   following in Email/Store/Annotation.pm:

       package Email::Store::Annotation;
       use base 'Email::Store::DBI';

   This makes us a "Class::DBI"-based package. Next we need to do the usual
   "Class::DBI" thing and ddeclare our table and columns:

       Email::Store::Annotation->table("mail_annotation");
       Email::Store::Annotation->columns(All => qw/id mail content/);

   Next we declare how this fits into the rest of the world: an
   "Email::Store::Mail" has many "annotations":

       Email::Store::Mail->has_many(annotations => "Email::Store::Annotation");

   Annotations are something that the utility which uses "Email::Store" is
   going to create, modify and delete manually; we can hardly auto-generate
   a user-defined annotation when a mail is indexed, so we don't need to
   define any hooks into the indexing process. In fact, this is all the
   code we need to write, so we end the package in the usual way:

       1;

   If we did need to hook into a different part of "Email::Store", we'd
   have to use Module::Pluggable::Ordered's plugin mechanism. See
   Email::Store::Mail for the hooks provided and how to hook into them.

   But where does this "mail_annotation" table come from? How does
   "Email::Store" know how to create it? The answer comes when we put the
   schema into the "__DATA__" section: "Email::Store->setup" reads all the
   "DATA" sections for the plugins that it finds, and executes them as SQL
   in the database. As pretty much every database's SQL is subtly
   different, the schema should be written in MySQL's SQL and
   "Email::Store" will magically translate it for the database in use:

       __DATA__
       CREATE TABLE IF NOT EXISTS mail_annotation (
           id INTEGER auto_increment NOT NULL PRIMARY KEY,
           mail INTEGER,
           content TEXT
       );

   With this module complete and installed, an "Email::Store" user can now
   say:

       my $mail = Email::Store::Mail->retrieve( $msg_id );
       $mail->add_to_annotations({ content => "I like this mail" });
       print "Things I know about this mail:\n";
       print $_->content, "\n" for $mail->annotations;

   The really big advantage of this architecture is that everything about a
   concept and its relationship to the mailstore is encapsulated in a
   single file and can be dropped in and out at will, without disturbing
   the rest of the code. This is fantastic extensibility. "Email::Store"
   does not need to define a schema of every single table you might
   possibly need up front, but everything is modularised.

   The really big disadvantage is that the interface of one part of the
   system, such as "Email::Store::Mail" isn't collected in one place, but
   gets added to by pretty much every other plugin that gets loaded up. If
   you look in the "Email::Store::Mail" POD you'll see nothing about the
   "add_to_annotations" method that we've just called.

   However, since every plugin should document its interface thoroughly and
   its relationship to other parts of the system, this should not really be
   a problem for end-users.

SEE ALSO
   Understanding Class::DBI is fundamental to using "Email::Store".

   The core modules: Email::Store::Mail, Email::Store::List,
   Email::Store::Entity, Email::Store::Thread, Email::Store::Attachment.
   Please do read through their documentation to see the whole of the
   "Email::Store" API.

   Any other "Email::Store::*" modules you find on CPAN.

   Module::Pluggable::Ordered is the pluggable hooks system used throughout
   "Email::Store". Those developing additional modules might want to look
   at its documentation to understand how to hook into the indexing,
   reindexing and other processes.

AUTHOR
   Simon Cozens, <[email protected]>

COPYRIGHT AND LICENSE
   Copyright 2004 by Simon Cozens

   This library is free software; you can redistribute it and/or modify it
   under the same terms as Perl itself.

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