use strict;
use warnings;
package Email::Folder::Mbox;
{
  $Email::Folder::Mbox::VERSION = '0.858';
}
# ABSTRACT: reads raw RFC822 mails from an mbox file
use Carp;
use IO::File;
use Email::Folder::Reader;
use parent 'Email::Folder::Reader';


sub defaults {
    ( eol => "\n")
}

sub _open_it {
    my $self = shift;
    my $file = $self->{_file};

    # sanity checking
    croak "$file does not exist" unless (-e $file);
    croak "$file is not a file"  unless (-f $file);

    local $/ = $self->{eol};
    my $fh = $self->_get_fh($file);

    if ($self->{seek_to}) {
        # we were told to seek.  hope it all goes well
        seek $fh, $self->{seek_to}, 0;
    }
    else {
        my $firstline = <$fh>;
        if ($firstline) {
            croak "$file is not an mbox file" unless $firstline =~ /^From /;
        }
    }

    $self->{_fh} = $fh;
}

sub _get_fh {
    my $self = shift;
    my $file = shift;
    my $fh = IO::File->new($file) or croak "Cannot open $file";
    binmode($fh);
    return $fh;
}

use constant debug => 0;
my $count;

sub next_message {
    my $self = shift;

    my $fh = $self->{_fh} || $self->_open_it;
    local $/ = $self->{eol};

    my $mail = '';
    my $prev = '';
    my $inheaders = 1;
    ++$count;
    print "$count starting scanning at line $.\n" if debug;

    while (my $line = <$fh>) {
        if ($line eq $/ && $inheaders) { # end of headers
            print "$count end of headers at line $.\n" if debug;
            $inheaders = 0; # stop looking for the end of headers
            my $pos = tell $fh; # where to go back to if it goes wrong

            # look for a content length header, and try to use that
            if ($mail =~ m/^Content-Length: (\d+)$/mi) {
                $mail .= $prev;
                $prev = '';
                my $length = $1;
                print " Content-Length: $length\n" if debug;
                my $read = '';
                while (my $bodyline = <$fh>) {
                    last if length $read >= $length;
                    $read .= $bodyline;
                }
                # grab the next line (should be /^From / or undef)
                my $next = <$fh>;
                return "$mail$/$read"
                  if !defined $next || $next =~ /^From /;
                # seek back and scan line-by-line like the header
                # wasn't here
                print " Content-Length assertion failed '$next'\n" if debug;
                seek $fh, $pos, 0;
            }

            # much the same, but with Lines:
            if ($mail =~ m/^Lines: (\d+)$/mi) {
                $mail .= $prev;
                $prev = '';
                my $lines = $1;
                print " Lines: $lines\n" if debug;
                my $read = '';
                for (1 .. $lines) { $read .= <$fh> }
                <$fh>; # trailing newline
                my $next = <$fh>;
                return "$mail$/$read"
                  if !defined $next || $next =~ /^From /;
                # seek back and scan line-by-line like the header
                # wasn't here
                print " Lines assertion failed '$next'\n" if debug;
                seek $fh, $pos, 0;
            }
        }

        last if $prev eq $/ && ($line =~ $self->_from_line_re);

        $mail .= $prev;
        $prev = $line;
    }
    print "$count end of message line $.\n" if debug;
    return unless $mail;
    return $mail;
}

my @FROM_RE;
BEGIN {
  @FROM_RE = (
    # according to mutt:
    #   A valid message separator looks like:
    #   From [ <return-path> ] <weekday> <month> <day> <time> [ <tz> ] <year>
    qr/^From (?:\S+\s+)?(?:Mon|Tue|Wed|Thu|Fri|Sat|Sun)/,

    # though, as jwz rants, only this is reliable and portable
    qr/^From /,
  );
}

sub _from_line_re {
  return $FROM_RE[ $_[0]->{jwz_From_} ? 1 : 0 ];
}

sub tell {
    my $self = shift;
    return tell $self->{_fh};
}

1;

__END__

=pod

=encoding UTF-8

=head1 NAME

Email::Folder::Mbox - reads raw RFC822 mails from an mbox file

=head1 VERSION

version 0.858

=head1 SYNOPSIS

This isa Email::Folder::Reader - read about its API there.

=head1 DESCRIPTION

Does exactly what it says on the tin - fetches raw RFC822 mails from an
mbox.

The mbox format is described at http://www.qmail.org/man/man5/mbox.html

We attempt to read an mbox as through it's the mboxcl2 variant,
falling back to regular mbox mode if there is no C<Content-Length>
header to be found.

=head2 OPTIONS

The new constructor takes extra options.

=over

=item C<eol>

This indicates what the line-ending style is to be.  The default is
C<"\n">, but for handling files with mac line-endings you would want
to specify C<eol =E<gt> "\x0d">

=item C<jwz_From_>

The value is taken as a boolean that governs what is used match as a
message separator.

If false we use the mutt style

 /^From \S+\s+(?:Mon|Tue|Wed|Thu|Fri|Sat|Sun)/
 /^From (?:Mon|Tue|Wed|Thu|Fri|Sat|Sun)/;

If true we use

 /^From /

In deference to this extract from L<http://www.jwz.org/doc/content-length.html>

  Essentially the only safe way to parse that file format is to
  consider all lines which begin with the characters ``From ''
  (From-space), which are preceded by a blank line or
  beginning-of-file, to be the division between messages.  That is, the
  delimiter is "\n\nFrom .*\n" except for the very first message in the
  file, where it is "^From .*\n".

  Some people will tell you that you should do stricter parsing on
  those lines: check for user names and dates and so on.  They are
  wrong.  The random crap that has traditionally been dumped into that
  line is without bound; comparing the first five characters is the
  only safe and portable thing to do. Usually, but not always, the next
  token on the line after ``From '' will be a user-id, or email
  address, or UUCP path, and usually the next thing on the line will be
  a date specification, in some format, and usually there's nothing
  after that.  But you can't rely on any of this.

Defaults to false.

=item C<seek_to>

Seek to an offset when opening the mbox.  When used in combination with
->tell you may be able to resume reading, with a trailing wind.

=item C<tell>

This returns the current filehandle position in the mbox.

=back

=head1 AUTHORS

=over 4

=item *

Simon Wistow <simon@thegestalt.org>

=item *

Richard Clamp <richardc@unixbeard.net>

=back

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2006 by Simon Wistow.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut