=head1 NAME

cm_perl -- A Perl Plugin for Claws Mail

=head1 DESCRIPTION

This plugin provides an extended filtering engine for the email
client Claws Mail. It allows for the use of full Perl power
in email filters.

=head1 QUICK START

To get started, you can use the B<matcherrc2perlfilter.pl> script
in the B<tools>-directory to translate your old filtering rules to
Perl. Simply execute the script and follow the instructions.
(note that with recent versions of Claws Mail, this script might not
work due to upstream syntax changes. This will get updated in the
future. Send me an email if you have problems getting started).

However, you might want to consider reading the rest of this
manual and rewriting your rules if you choose to use the plugin,
since the Perl code produced by this script is not exactly
pretty.

Don't speak Perl? No problem, L<"perldoc perlintro"|perlintro>
should give you enough information to do fancy stuff.

=head1 USAGE

The Perl plugin expects a Perl script file called B<perl_filter>
in Claws Mail' config directory (usually $HOME/.claws-mail --
try `claws-mail --config-dir' if you're unsure). If that file
doesn't exist on plugin start, an empty one is created.  This
file, which doesn't need to start with a sha-bang (!#/bin/perl),
holds the Perl instructions for your email filters. To encourage
some good manners, the code is executed in a C<use strict;>
environment.

Both Claws Mail' filtering B<conditions> and B<actions> are
mapped to Perl functions with corresponding names, wherever this
is possible.

=head1 FUNCTION LISTING

For a detailed function description, see section L</"FUNCTION
DESCRIPTIONS">, below.

=over 4

=item Standard Filtering Conditions

 all, marked, unread, deleted, new, replied,
 forwarded, locked, ignore_thread, colorlabel,
 match, matchcase, regexp, S<regexpcase, test,
 size_greater, size_smaller, size_equal,
 score_greater, score_lower, score_equal, age_greater,
 age_lower, partial, tagged

=item Standard Filtering Actions

 mark, unmark, dele, mark_as_unread, mark_as_read,
 lock, unlock, move, copy, color, execute,
 hide, set_score, change_score, stop, forward,
 forward_as_attachment, redirect, set_tag, unset_tag,
 clear_tags

=item Fun stuff

 header, body, filepath, extract_addresses,
 move_to_trash, abort, addr_in_addressbook,
 from_in_addressbook, get_attribute_value, SA_is_spam,
 exit, manual, make_sure_folder_exists,
 filter_log, filter_log_verbosity,
 make_sure_tag_exists

=back

=head1 FUNCTION DESCRIPTIONS

In general, after the filtering invoked by the Perl script, the
mail is passed on to Claws' internal filtering engine, I<unless>
a B<final> rule was hit. Final rules stop not only the Perl
filtering script at the point of their occurrence, but also
prevent processing that email by Claws' internal filtering engine
(this might sound confusing, but you are already familiar with
that concept from standard filters: After an email was
e.g. I<move>d, the following rules don't apply anymore).

Also, be careful with the way you quote. In particular, remember
that the @-sign has a special meaning in Perl, and gets
interpolated inside double quotes. See L<perlop/"Quote and
Quote-like Operators"> to learn more about quoting and
interpolation.


=head2 Standard Filtering Conditions

=over 8

=item all

Returns a true value. Available for completeness only.

=item marked

Returns a true value if the marked flag is set, false otherwise.

=item unread

Returns a true value if the unread flag is set, false otherwise.

=item deleted

Returns a true value if the deleted flag is set, false otherwise.

=item new

Returns a true value if the new flag is set, false otherwise.

=item replied

Returns a true value if the replied flag is set, false otherwise.

=item forwarded

Returns a true value if the forwarded flag is set, false otherwise.

=item locked

Returns a true value if the locked flag is set, false otherwise.

=item ignore_thread

Returns a true value if the "Ignore Thread" flag is set, false otherwise.

=item colorlabel COLOR

=item colorlabel

Returns a true value if message has the color COLOR. COLOR can be
either a numeric value between 0 and 7 (with colors corresponding
to the internal filtering engine), or the english color name as
it is introduced in the filtering dialog (that is, one of: none,
orange, red, pink, sky blue, blue, green or brown, while upper
and lower case letters make no difference). If COLOR is omitted,
0 (none) is assumed.

=item size_greater SIZE

Returns a true value if message size is greater than SIZE, false otherwise.

=item size_smaller SIZE

Returns a true value if message size is smaller than SIZE, false otherwise.

=item size_equal SIZE

Returns a true value if message size is equal to SIZE, false otherwise.

=item score_greater SCORE

Returns a true value if message score is greater than SCORE, false otherwise.

=item score_lower SCORE

Returns a true value if message score is lower than SCORE, false otherwise.

=item score_equal SCORE

Returns a true value if message score is equal to SCORE, false otherwise.

=item age_greater AGE

Returns a true value if message age is greater than AGE, false otherwise.

=item age_lower AGE

Returns a true value if message age is lower than AGE, false otherwise.

=item partial

Returns a true value if message has only partially been
downloaded, false otherwise.

=item tagged

Returns a true value if the messages has one or more tags.

=item test

Corresponds the 'test' internal filtering rule. In particular, it
accepts the same symbols, namely:

=over

=item %%

%

=item %s

Subject

=item %f

From

=item %t

To

=item %c

Cc

=item %d

Date

=item %i

Message-ID

=item %n

Newsgroups

=item %r

References

=item %F

Filename -- should not be modified

=back

=item match WHERE WHAT

=item matchcase WHERE WHAT

=item regexp WHERE WHAT

=item regexpcase WHERE WHAT

The matching functions have a special syntax. The first argument
is either any of to_or_cc, body_part, headers_part, headers_cont,
message, to, from, subject, cc, newsgroups, inreplyto,
references, or tag (those strings may or may not be quoted), the
pattern matching works on that area. If it is any other string
(which must then be quoted), this string is taken to be the name
of a header field.

The second argument is the string to look for. For match,
matchcase, regexp and regexpcase we have case sensitive normal
matching, case insensitive normal matching, case sensitive
regular expression matching and case insensitive regular
expression pattern matching, respectively.

The functions return true if the pattern was found, false
otherwise.

Just as with the built-in filtering engine, the message body is
searched and provided as is - no character-set analysis is
done. Likewise, no HTML-tags are stripped. It should be possible
to use external modules or programs for these tasks though. If
you're doing that, drop me a message with your experiences.

With Perl having its strengths in pattern matching, using Perl's
builtin operators are usually a better option than using these
functions.

=back

=head2 Standard Filtering Actions

The actions return a true value upon success, and 'undef' when an
error occurred. I<Final> message rules are indicated. (See above
for a sketch what a final rule is)

=over 8

=item mark

Mark the message.

=item unmark

Unmark the message.

=item dele

Delete the message. Note the name change of Claws Mail'
"delete" to "dele". This is because "delete" is one of Perl's
builtin commands which cannot be redefined (if it can, tell me
how).

This is a I<final> rule.

=item mark_as_read

Mark the message as read

=item mark_as_unread

Mark the message as unread

=item lock

Lock the message

=item unlock

Remove the message lock

=item move DESTINATION

Move the message to folder DESTINATION. The folder notation is
the same that Claws Mail uses. You can copy & paste from the
move dialog of the normal filtering, until you get a feeling for
the notation.

This is a I<final> rule.

=item copy DESTINATION

Copy the message to folder DESTINATION. The folder notation is
the same that Claws Mail uses. You can copy & paste from the
move dialog of the normal filtering, until you get a feeling for
the notation.

=item execute COMMAND

This is the same as the test - rule from section L</"Standard
Filtering Conditions"> execpt that it always returns a true
value.

=item hide

Hide the message

=item set_score SCORE

Set message score to SCORE

=item change_score SCORE

Change message score by SCORE

=item stop

Stop Perl script at this point. Note that this is B<not> a final
rule, meaning that the email gets passed on to the internal
filtering engine. See "abort" below if you don't want that.

=item forward ACCOUNT, EMAIL

Forward the message to email address EMAIL, using the account ID
ACCOUNT as sender account. So far, you have to create a rule
in the normal filtering engine to find out that number.

=item forward_as_attachment, ACCOUNT EMAIL

Forward the message to email address EMAIL in an attachment,
using the account ID ACCOUNT as sender account. So far, you
have to create a rule in the normal filtering engine to find out
that number.

=item redirect ACCOUNT, EMAIL

Redirect the message to EMAIL, using the account ID ACCOUNT as
sender account. So far, you have to create a rule in the normal
filtering engine to find out that number.

=item set_tag TAG

Apply tag TAG. TAG must exist.

=item unset_tag TAG

Unset tag TAG.

=item clear_tags

Clear all tags.

=back

=head2 Fun stuff

=head3 Functions

=over 8

=item header ARG

=item header

If ARG is not given, returns a list of all header field names of
the mail.

If ARG is given, returns 'undef' if the header field ARG does not
exist in the email. Otherwise, it returns

=over

=item in scalar context

The value of the header field ARG.

=item in list context

A list of all available header field values. This is useful if a
header field occurs more than once in an email (eg the Received -
header).

=back

The header field "References" forms a special case. In a scalar context,
it returns the first reference. In a list context, it returns a list of
all references.

=item body

Returns the email body in a scalar.

=item filepath

Returns the file and path of the email that is currently filtered
(corresponds to the %F arguemnt in the 'test' rule).

=item extract_addresses

Extracts email addresses from a string and gives back a list of
addresses found. Currently an email address is found using the
regular expression '[-.+\w]+\@[-.+\w]+'. This will not find all
valid email addresses. Feel free to send me a better regexp.

=item move_to_trash

Move the email message to default trash folder.

This is a I<final> rule.

=item abort

Stop Perl script at this point.

In contrast to 'stop', this is a I<final> rule.

=item addr_in_addressbook EMAIL, ADDRESSBOOK

=item addr_in_addressbook EMAIL

Returns a true value if the email address EMAIL is in the addressbook
with the name ADDRESSBOOK. If ADDRESSBOOK is not given, returns
true if the email address is in any addressbook.

=item from_in_addressbook ADDRESSBOOK

=item from_in_addressbook

Checks if the email address found in the From-header is in
addressbook ADDRESSBOOK (or any, if omitted). It is implemented
as

 my ($from) = extract_addresses(header("from"));
 return 0 unless $from;
 return addr_in_addressbook($from,@_);

so the same restrictions as to extract_addresses apply.

=item get_attribute_value EMAIL, ATTRIBUTE, ADDRESSBOOK

=item get_attribute_value EMAIL, ATTRIBUTE

Looks through the addressbook ADDRESSBOOK (or all addressbooks,
if omitted) for a contact with the an email address EMAIL. If
found, the function checks if this contact has a user attribute
with name ATTRIBUTE. It returns the value of this attribute, or
an empty string if it was not found. As usual, 'undef' is
returned if an error occurred.

=item SA_is_spam

Is an alias to

not test 'spamc -c < %F > /dev/null'

=item exit

Has been redefined to be an alias to 'stop'. You shouldn't use
Perl's own 'exit' command, since it would exit Claws Mail.

=item manual

Returns a true value if the filter script was invoked manually,
that is, via the Tools menu.

=item make_sure_folder_exists IDENTIFIER

Returns a true value if the folder with id IDENTIFIER (e.g. #mh/Mail/foo/bar)
exists or could be created.

=item make_sure_tag_exists TAG

Returns a true value if the tag TAG exists or could be created.

=item filter_log SECTION, TEXT

=item filter_log TEXT

Writes TEXT to the filter logfile. SECTION can be any of

=over

=item *

"LOG_MANUAL"

=item *

"LOG_MATCH"

=item *

"LOG_ACTION"

=back

If the SECTION is omitted, "LOG_MANUAL" is assumed.

=item filter_log_verbosity VERBOSITY

=item filter_log_verbosity

Changes the filter log verbosity for the current mail. VERBOSITY
must be any of

=over 2

=item C<0>

Be silent

=item C<1>

Log MANUAL type

=item C<2>

Log Action type

=item C<3>

Log MATCH type

=back

For the meaning of those numbers, read section L</"LOGGING">. If
VERBOSITY is omitted, the filter logfile verbosity is not changed.

This function returns the filter_log_verbosity number before the
change (if any).

=back

=head3 Variables

=over 8

=item $permanent

This scalar keeps its value between filtered mail messages. On
plugin start, it is initialized to the empty string.

=back

=head1 LOGGING

To keep track of what has been done to the mails while filtering,
the plugin supports logging. Three verbosity levels are
recognized:

=over

=item C<0>

logging disabled

=item C<1>

log only manual messages, that is, messages introduced by the
C<filter_log> command in filter scripts

=item C<2>

log manual messages and filter actions

=item C<3>

log manual messages, filter actions and filter matches

=back

The messages are logged in Claws Mail' log window.
The default log level is 2. Log level 3 is not
recommended, because the matcher functions log a message if they
succeeded, and thus, if you have negative checks, you'll get
confusing entries. If you want to keep track of matching, do it
manually, using C<filter_log>, or do it by temporary enabling
matcher logging using C<filter_log_verbosity>.

The first time you unload this plugin (or shut down
Claws Mail), a section called B<[PerlPlugin]> will be created
in Claws Mail' configuration file B<clawsrc>, containing
one variable:

 * filter_log_verbosity

If you want to change the default behaviour, you can edit this
line. Make sure Claws Mail is not running while you do
this.

It will be possible to access these setting via the GUI, as soon
as I find the time to write a corresponding GTK plugin, or
somebody else is interested in contributing that.

=head1 EXAMPLE

This section lists a small example of a Perl script file. I'm
sure you get the idea..

 #-8<----------------------------------------------------
 # -*- perl -*-

 # local functions

 # Learn ham messages, and move them to specified folder. This is
 # useful for making sure a bayes filter sees ham as well.
 sub learn_and_move {
     execute('put command to learn ham here');
     move(@_);
 }

 # Two-stage spam filter. Every email that scores higher than 15
 # on SpamAssassin gets moved into the default trash folder.
 # All mails lower than that, but higher than SpamAssassin's
 # 'required_hits' go into  #mh/mail/Spam.
 sub spamcheck {
     my $surely_spam = 15;
     my $filepath = filepath;
     my $spamc = `spamc -c < $filepath`;
     my ($value,$threshold) = ($spamc =~ m|([-.,0-9]+)/([-.,0-9]+)|);
     if($value >= $surely_spam) {
        mark_as_read;
	move_to_trash;
     }
     if($value >= $threshold) {mark_as_read; move '#mh/mail/Spam';}
 }

 # Perl script execution starts here.

 # Some specific sorting
 learn_and_move '#mh/mail/MailLists/Claws Mail/user'
   if matchcase('sender','claws-mail-users-admin@lists.sourceforge.net');
 learn_and_move '#mh/mail/MailLists/Sylpheed'
   if matchcase('list-id','sylpheed.good-day.net');

 # Implement incoming folders using addressbook
 # attributes. Target folders for specific email addresses are
 # stored directly in the addressbook. This way, if an email
 # address changes, we only have to update the addressbook, not
 # the filter rules! Besides that, we can greatly unclutter the
 # filter script.

 # get the email address in the from header
 my $fromheader = header "from";
 my ($from) = extract_addresses $fromheader;

 # check if this email address has an associated attribute
 # called "incoming_folder". If if has, the value of this
 # attribute is supposed to be the target folder.
 my $value = get_attribute_value $from, "incoming_folder";
 learn_and_move($value) if $value;

 # An example of a whitelist: If the from-address is in my
 # "office" addressbook, move the mail to folder #mh/mail/office
 learn_and_move '#mh/mail/office' if from_in_addressbook("office");

 # If the from-address is in any other addressbook, move the
 # mail to folder #mh/mail/inbox/known
 learn_and_move '#mh/mail/inbox/known' if from_in_addressbook;

 # Feed the remaining mails through SpamAssassin.
 spamcheck;

 # mails that make it to the end of the script are passed on to
 # the internal filtering engine. If the internal rules don't say
 # otherwise, the mails end up in the default inbox.
 #-8<----------------------------------------------------


=head1 BUGS

=over 4

=item *

Do B<not> use this plugin together with other filtering plugins,
especially the B<Spamassassin> and B<ClamAV> plugins. They are
registered on the same hook and the order in which the plugins
are executed is not guaranteed.

=item *

The filter script is not (yet) updated automatically when a
folder gets renamed. The same applies for folder names in
addressbook user attributes.

=item *

This plugin has only be tested with POP3 accounts. If you have
experiences with IMAP or newsgroup accounts, drop me a message.

=item *

Warning during compile time:

 *** Warning: Linking the shared library perl_plugin.la against the
 *** static library
 /usr/lib/perl5/5.8.3/i586-linux-thread-multi/auto/DynaLoader/DynaLoader.a
 is not portable!

Ideas to solve this one are welcome :-)

=back

Please report comments, suggestions and bugreports to the address
given in the L</AUTHOR> section of this document.


=head1 LICENSE and (no) WARRANTY

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public
License as published by the Free Software Foundation;
either version 3 of the License, or (at your option) any later
version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see http://www.gnu.org/licenses/.

=head1 SEE ALSO

claws-mail(1), perl(1)


=head1 AUTHOR

Holger Berndt  <berndth@gmx.de>

=cut
