package Log::Procmail;

require 5.005;
use strict;
use IO::File;
use IO::Select;
use Carp;
use UNIVERSAL ();

use vars qw/ $VERSION /;
local $^W = 1;

$VERSION = '0.11';

my %month;
@month{qw/ Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec /} = ( 0 .. 11 );

my $DATE = qr/(?:Mon|Tue|Wed|Thu|Fri|Sat|Sun) (Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec) ([ \d]\d) (\d\d):(\d\d):(\d\d) .*(\d\d\d\d)/;

sub new {
    my $class = shift;
    return bless {
        fh     => new IO::File,
        files  => [@_],
        errors => 0,
        buffer => [],
    }, $class;
}

sub next {
    my $log = shift;    # who needs $self?

    # try to read a record (3 lines)
    my $fh  = $log->fh();
  READ:
    {
        my $read;

      LINE:
        while (<$fh>) {
            $read++;

            # should carp if doesn't get what's expected
            # (From, then Subject, then Folder)

            # From create a new Abstract
            /^From (.+?) +($DATE)$/o && do {
                push @{$log->{buffer}}, Log::Procmail::Abstract->new();

                # assert: $read == 1;
                $log->{buffer}[-1]->from($1);
                $log->{buffer}[-1]->date($2);

                # return ASAP
                last READ if @{$log->{buffer}} > 1;
                next LINE;
            };

            # assert: $read == 2;
            /^ Subject:\s*(.*)/i && do {
                push @{$log->{buffer}}, Log::Procmail::Abstract->new()
                    unless @{$log->{buffer}};
                $log->{buffer}[0]->subject($1);
                next LINE;
            };

            # procmail tabulates with tabs and spaces... :-(
            # assert: $read == 3;
            # Folder means the end of this record
            /^  Folder:\s*(.*?)\s+(\d+)$/ && do {
                push @{$log->{buffer}}, Log::Procmail::Abstract->new()
                  unless @{$log->{buffer}};

                # assert: $read == 3;
                $log->{buffer}[0]->folder($1);
                $log->{buffer}[0]->size($2);
                last READ;
            };

            # fall through: some error message
            # shall we ignore it?
            next LINE unless $log->{errors};

            # or return it?
            chomp;
            push @{$log->{buffer}}, $_;
            last LINE;
        }

        # in case we couldn't read the first line
        if ( !$read or @{$log->{buffer}} == 0 ) {

            # return ASAP
            last READ if @{$log->{buffer}};

            # go to next file
            redo READ if $log->_open_next;

            # unless it's the last one
            return;
        }
    }

    # we have an abstract
    my $rec = shift @{$log->{buffer}};
    if(UNIVERSAL::isa( $rec, 'Log::Procmail::Abstract')) {
        # the folder field is required
        goto READ unless defined $rec->folder;
        $rec->{source} = $log->{source};
    }

    return $rec;
}

sub push {
    my $log = shift;
    push @{ $log->{files} }, @_;
}

sub errors {
    my $self = shift;
    return @_ ? $self->{errors} = shift() : $self->{errors};
}

sub fh {
    my $log = shift;
    $log->_open_next unless $log->{fh}->opened();
    return $log->{fh};
}

sub select {
    my $log = shift;
    $log->fh(); # make sure the file is correctly opened and select is updated
    return $log->{select};
}

# *internal method*
# opens a file or replace the old filehandle by the new one
# push() can therefore accept refs to typeglobs, IO::Handle, or filenames
sub _open_next {
    my ( $log ) = @_;
    my $file;

    if ( @{ $log->{files} } ) {
        $file = shift @{ $log->{files} };
    } else { return 0 };

    if ( ref $file eq 'GLOB' ) {
        $log->{fh} = *$file{IO};
        carp "Closed filehandle $log->{fh}" unless $log->{fh}->opened;
    }
    elsif ( ref $file && $file->isa('IO::Handle') ) {
        $log->{fh} = $file;
    }
    else {
        $log->{fh}->open($file) or carp "Can't open $file: $!";
    }
    $log->{source} = $file;
    $log->{select} = ( grep $^O eq $_, qw(MSWin32 NetWare dos VMS riscos beos) )
                   ? undef
                   : IO::Select->new( $log->{fh} );
    1;
}

sub DESTROY {
    my $self = shift;
    if ( $self->{fh} && $self->{fh}->opened ) { $self->{fh}->close }
}

#
# a small class for the abstracts themselves
#
package Log::Procmail::Abstract;

use Carp;

sub new {
    my $class = shift;
    return bless {@_}, $class;
}

for my $attr (qw( from date subject size folder source ) ) {
    no strict 'refs';
    *$attr = sub {
        my $self = shift;
        @_ ? $self->{$attr} = shift: $self->{$attr};
    }
}

sub ymd {
    my $self = shift;
    croak("Log::Procmail::Abstract::ymd cannot be used to set the date")
      if @_;
    return undef unless defined $self->{date};
    $self->{date} =~ /^$DATE$/o;
    return undef unless $1;
    return sprintf( "%04d%02d%02d$3$4$5", $6, $month{$1} + 1, $2 );
}

1;

__END__

=head1 NAME

Log::Procmail - Perl extension for reading procmail logfiles.

=head1 SYNOPSIS

    use Log::Procmail;

    my $log = new Log::Procmail 'procmail.log';

    # loop on every abstract
    while(my $rec = $log->next) {
        # do something with $rec->folder, $rec->size, etc.
    }

=head1 DESCRIPTION

=head2 Log::Procmail

Log::Procmail reads procmail(1) logfiles and returns the abstracts one by one.

=over 4

=item $log = Log::Procmail->new( @files );

Constructor for the procmail log reader.  Returns a reference to a
Log::Procmail object.

The constructor accepts a list of file as parameter. This allows you to
read records from several files in a row:

    $log = Log::Procmail->new( "$ENV{HOME}/.procmail/log.2",
                               "$ENV{HOME}/.procmail/log.1",
                               "$ENV{HOME}/.procmail/log", );

When $log reaches the end of the file "log", it doesn't close the file.
So, after B<procmail> processes some incoming mail, the next call to next()
will return the new records.

=item $rec = $log->next

Return a Log::Procmail::Abstract object that represent an entry in the log
file. Return undef if there is no record left in the file.

When the Log::Procmail object reaches the end of a file, and this file is
not the last of the stack, it closes the current file and opens the next
one.

When it reaches the end of the last file, the file is not closed. Next
time the record method is called, it will check again in case new abstracts
were appended.

Procmail(1) log look like the following:

    From karen644552@btinternet.com  Fri Feb  8 20:37:24 2002
     Subject: Stock Market Volatility Beating You Up? (18@2)
      Folder: /var/spool/mail/book						   2840

Some informational messages can be put by procmail(1) in the log file.
If the C<errors> attribute is true, these lines are returned one at a time.

With errors enabled, you have to check that next() actually returns a
Log::Procmail::Abstract object. Here is an example:

    $log->errors(1);

    # fetch data
    while ( $rec = $log->next ) {

        # if it's an error line
        if ( !ref $rec ) {
            # this is not a log, but an informational message
            # do something with it
            next;
        }

        # normal log processing
    }

=item $log->push( $file [, $file2 ...] );

Push one or more files on top of the list of log files to examine.
When Log::Procmail runs out of abstracts to return (i.e. it reaches the
end of the file), it transparently opens the next file (if there is one)
and keeps returning new abstracts.

=item $log->errors( [bool] );

Set or get the error flag. If set, when the next() method will return
the string found in the log file, instead of ignoring it. Be careful:
it is a simple string, not a Log::Procmail::Abstract object.

Default is to return no error.

=item $fh = $log->fh()

Returns the currently opened filehandle, from which the next call to
C<next()> will try to read a record.

=item $select = $log->select()

Return a IO::Select object that watches the currently opened filehandle.

B<You are not supposed to use C<add()> or C<remove()> on the returned
IO::Select object.>

B<Additional warning for C<MSWin32>, C<NetWare>, C<dos>, C<VMS>, C<riscos>
and C<beos>:> on those systems, C<select()> returns C<undef>.
(Check F<ext/IO/t/io_sel.t> in the Perl sources for details.
Hint: look for the message I<4-arg select is only valid on sockets>.)

=back

=head2 Log::Procmail::Abstract

Log::Procmail::Abstract is a class that hold the abstract information.
Since the abstract hold From, Date, Subject, Folder and Size information,
all this can be accessed and modified through the from(), date(), subject(),
folder() and size() methods.

Log::Procmail::next() returns a Log::Procmail::Abstract object.

=over 4

=item Log::Procmail::Abstract accessors

The Log::Procmail::Abstract object accessors are named from(), date(),
subject(), folder() and size(). They return the relevant information
when called without argument, and set it to their first argument
otherwise.

    # count mail received per folder
    while( $rec = $log->next ) { $folder{ $rec->folder }++ }

The source() accessor returns the name of the log file or the string
representation of the handle, if a filehandle was given.

=item $rec->ymd()

Return the date in the form C<yyyymmmddhhmmss> where each field is what
you think it is. C<;-)> This method is read-only.

=back

=head1 EXAMPLES

Here is an example procmail biff-like script, courtesy of Ian Langworth:

    #/usr/bin/perl -w
    use strict;
    use Log::Procmail;

    use constant LOGFILE       => "$ENV{HOME}/procmail.log";
    use constant VALID_FOLDERS => [qw( agent inbox perl systems )];
    my $format = "\%8s: \%-30.30s / %s\n";

    my $log = Log::Procmail->new( LOGFILE );
    $log->errors(1);

    while ( $log->select->can_read ) {
        my $rec = $log->next;

        # error?
        warn "$rec\n", next unless ref $rec;

        # ignore mailboxes we don't care about
        next unless grep { $_ eq $rec->folder } @{ VALID_FOLDERS() };

        # print data
        printf $format, From    => $rec->from;
        printf $format, Subject => $rec->subject, $rec->folder;
    }

=head1 TODO

The Log::Procmail object should be able to read from STDIN.

=head1 BUGS

=over 4

=item *

Sometimes procmail(1) logs are mixed up. When this happens, I've chosen
to accept them the way mailstat(1) does: they are discarded unless they
have a C<Folder> line.

=item *

If you use Log::Procmail and the select() method to follow a live logfile
as in the above example, please not that Log::Procmail will not detect
when the file is rotated.

=back

Please report all bugs through the rt.cpan.org interface:

L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=Log-Procmail>

=head1 AUTHOR

Philippe "BooK" Bruhat <book@cpan.org>.

=head1 ACKNOWLEDGMENTS

Thanks to Briac "Oeufmayo" Pilpré and David "Sniper" Rigaudiere for early
comments on irc. Thanks to Olivier "rs" Poitrey for giving me his huge
procmail log file (51 Mb spanning over a two-year period) and for probably
being the first user of this module. Many thanks to Michael Schwern for
insisting so much on the importance of tests and documentation.

Many thanks to "Les Mongueurs de Perl" for making cvs.mongueurs.net
available for Log::Procmail and many other projects.

=head1 COPYRIGHT 

Copyright (c) 2002-2004, Philippe Bruhat. All Rights Reserved.

=head1 LICENSE

This module is free software. It may be used, redistributed
and/or modified under the terms of the Perl Artistic License
(see http://www.perl.com/perl/misc/Artistic.html)

=head1 SEE ALSO

perl(1), procmail(1).

=cut

