#! /usr/local/bin/perl

# $Id$

=head1 NAME

B<minc> - Incorporate mail from a maildir into mh folders.

=head1 SYNOPSIS

B<minc> [-B<dhns>]

=head1 DESCRIPTION

B<minc> is a program for incorporating mail from a maildir to a mh
folder hierarchy.  It takes mail from a maildir folder (not a maildir
folder hierarchy), optionally checks for spam with a user-defined
spam-checking function, and optionally filters mail into separate mh
folders.

The filtering is quite sophisticated, as it is done using real Perl
substitution (s//) commands.

=cut

use strict;
use warnings;

require 'sysexits.ph';

use Data::Dumper;
use Errno;
use Fcntl qw(O_WRONLY O_EXCL O_CREAT);
use File::Basename;
use Getopt::Std;
use Log::Dispatch;
use Log::Dispatch::File;
use POSIX qw(strftime WEXITSTATUS WIFEXITED);
use Tie::IxHash;

=head1 OPTIONS

=over 4

=item B<-d>

Dump (using Data::Dumper) the FILTERS hash and exit.  This is useful
for testing the syntax of .mincfilter.

=item B<-f>

Filter only, then exit.  This is useful after running B<minc -s>.

=item B<-h>

Show help.

=item B<-n>

Dry run; do not actually incorporate the mail, but log and report to
stdout/stderr as normal.

=item B<-s>

Process SPAM only, then exit, leaving all non-spam messages in the
maildir.

=back

=cut

my $dumpfilters = 0;
my $filteronly = 0;
our $run = 1;
my $spamonly = 0;

our $opt_d;
our $opt_f;
our $opt_h;
our $opt_n;
our $opt_s;                     # ;; # stupid cperl-mode

if (not getopts('dfhns')) {
    exit(&EX_USAGE);
}

if ($opt_d) {
    $dumpfilters = 1;
} elsif ($opt_h) {
    print("Sorry bub, no help.\n");
    exit(&EX_OK);
} elsif ($opt_n) {
    $run = 0;
}

if ($opt_f) {
    $filteronly = 1;
} elsif ($opt_s) {              # ))){ # stupid cperl-mode
    $spamonly = 1;
}

=head1 ENVIRONMENT

=over 4

=item HOME

Where configuration files (.mincfilter) are found.  Also,
$HOME/Maildir is used for the maildir if MAILDIR is not set.

=item MAILDIR

Where mail is delivered.

=back

=cut

use Env qw(HOME MAILDIR);

if (not $HOME) {
    die("HOME environment variable must be set.\n");
}
if (not $MAILDIR) {
    $MAILDIR = "$HOME/Maildir";
}

=head1 FILES

=over 4

=item $HOME/.mincfilter

This file is Perl code (included via the 'require' directive) which is
expected to define the FILTERS hash.

=item $HOME/.mincspam

If this file exists, minc will include it with the expectation that it
will define a B<is_spam> function.  This function takes a message
filename as an argument and returns 1 if the message is spam, else 0.
If this file does not exist, minc will define a simple function that
always returns 0.

One of minc's global variables is available to the user-defined
is_spam function: $run.  This boolean should be honored; is_spam
should only take real action (i.e. removing or creating files, running
external programs, etc.) if $run is non-zero.

XXX: need more details about the spam-handling process; for now read
the code.

=item `mhpath +`/logs/minc.log

Where minc logs what it does, unless in -n mode.

=item `mhpath +`/logs/dryrun.log

Where minc logs what it would do; used in -n mode.

=back

=cut

our %FILTERS;
tie(%FILTERS, 'Tie::IxHash');
require "$HOME/.mincfilter";

if (-f "$HOME/.mincspam") {
    require "$HOME/.mincspam";
} else {
    sub is_spam {
        return 0;
    }
}

my $mh;
my $logfile;

$mh = `mhpath +`;
chomp($mh);

if ($run) {
    $logfile = $mh . '/logs/minc.log';
} else {
    $logfile = $mh . '/logs/dryrun.log';
}


###############################################################################
# Logging

# debuglevels for the logger
use constant LOG_DEBUGLEVEL     => 'info';
use constant SCREEN_DEBUGLEVEL  => 'debug';

# characters used to wrap around the id field in the log so I can more
# easily parse the msg flow
use constant DEBUGCHAR          => '%';
use constant INFOCHAR           => '=';
use constant INCOMINGCHAR       => '<';
use constant SAVECHAR           => '>';
use constant WARNCHAR           => 'W';
use constant ERRORCHAR          => 'E';

my $logger = new Log::Dispatch;
$logger->add(new Log::Dispatch::File (name=>'logfile',
                                      filename=>$logfile,
                                      min_level=>'info',
                                      mode=>'append'));

# log alias, handles getting passed vars that are undef
sub mylog {
    my $level = shift;
    my $act = shift;
    my $timestamp = strftime('%b %e %H:%M:%S', localtime);
    my $msg;
    foreach my $part (@_) {
        if (defined($part)) {
            $msg .= $part;
        }
    }
    # no newlines in the log message, thanks
    $msg =~ s/\n/ /gm;
    $msg = sprintf("%s %s%s %s\n", $timestamp, $act, $act, $msg);
    $logger->log(level=>$level, message=>$msg);

    if ($act eq SAVECHAR) {
        $logger->log(level=>$level, message=>"\n");
    }
}

sub logincoming { mylog('info', INCOMINGCHAR, @_); }
sub logsave { mylog('notice', SAVECHAR, @_); }
sub loginfo { mylog('info', INFOCHAR, @_); }
sub logdebug { mylog('debug', DEBUGCHAR, @_); }
sub logwarn { mylog('warning', WARNCHAR, @_); }
sub logerr { mylog('error', ERRORCHAR, @_); }

sub log_headers {
    my %headers = @_;

    logincoming('From:       ', $headers{'return-path'});
    logincoming('To:         ', $headers{'to'});
    logincoming('Subject:    ', $headers{'subject'});
    logincoming('Message-Id: ', $headers{'message-id'});
}


###############################################################################
# Utility procedures

sub _errprint {
    printf('%s:%s', __FILE__, __LINE__);

    if (@_) {
        print(': ');
        foreach (@_) {
            print;
        }
    }
}

sub err {
    my $ex = shift;

    _errprint(@_);
    print(": $!\n");

    exit($ex);
}

sub errx {
    my $ex = shift;

    _errprint(@_);
    print("\n");

    exit($ex);
}

sub mkfolder {
    my $mhfolder = shift;
    my $folder;
    my $target;
    my $component;

    $folder = $mh . '/' . $mhfolder;
    $target = '';

    if (not -d $folder) {
        foreach $component (split('/', $folder)) {
            if (defined($component) and length($component) >= 1) {
                $target = $target . '/' . $component;
                if (-d $target or mkdir($target)) {
                    next;
                } else {
                    err(&EX_OSERR,
                        "Failed to create +$mhfolder ($component)");
                }
            }
        }
    }
}

sub getfiles {
    my $dir = shift;
    my @result;

    if (not opendir(DIR, $dir)) {
        err(&EX_OSERR, "Failed opendir($dir)");
    }

    # Initialize $! to 0 (success) because stupid stupid Perl provides
    # no way to distinguish an error from an empty directory; that
    # means setting $! to 0 and testing it afterwards is the only way
    # to detect an error.  Real Programmers don't handle errors,
    # right?  >sigh<
    $! = 0;
    @result = grep {
        ($_ ne '.' and $_ ne '..')
          and $_ = "$MAILDIR/new/$_"
      } readdir(DIR);

    if ($! != 0) {
        err(&EX_OSERR, "Failed readdir($dir)");
    }

    closedir(DIR);

    return @result;
}

sub get_highest_msgnum {
    my $mhfolder = shift;
    my $dir;
    my @list;
    my $highest;
    my $msgnum;

    $dir = "$mh/$mhfolder";
    if (not opendir(DIR, $dir)) {
        err(&EX_OSERR, "Failed opendir($dir)");
    }

    $! = 0;
    @list = readdir(DIR);

    if ($! != 0) {
        err(&EX_OSERR, "Failed readdir($dir)");
    }

    closedir(DIR);

    $highest = 0;
    foreach $msgnum (@list) {
        # Look for integers.
        if ($msgnum =~ /^[0-9]+$/) {
            if ($msgnum > $highest) {
                $highest = $msgnum;
            }
        }
    }

    return $highest;
}

# We want to print the name of each list that has new mail only once,
# so use this hash to store the lists that have already been printed.
# Start the list out with SPAM already in it, since we don't care when
# new messages are added to it.
my %FOLDERS = ('SPAM'=>1);

sub store_message {
    my $msg = shift;
    my $mhfolder = shift;
    my $msgnum;
    my $try;
    my $mhmsg;
    my $status;

    # We must do this even in -n mode because later steps fail without
    # it.  This should be harmless.
    mkfolder($mhfolder);

    # This loop is a modified version of the maildir delivery algorithm.
    $msgnum = get_highest_msgnum($mhfolder);
    for ($try = 0; ; $try++) {
        $msgnum++;
        $mhmsg = "$mh/$mhfolder/$msgnum";

        if (not stat($mhmsg)) {
            if ($!{ENOENT}) {
                # Now we have a non-existent file, let's try to create
                # it.  We must create a zero-byte file first because a
                # file my appear between our happy stat results and
                # our later rename(2), which would clobber said file.
                # So attempt to create a file with this name.  If it
                # succeeds, in just a bit here we'll knowingly clobber
                # this file with the rename(2) call.
                if ($run) {
                    if (sysopen(MSG, "$mhmsg",
                                O_WRONLY | O_EXCL | O_CREAT, 0600)) {
                        close(MSG);
                        last;
                    }
                } else {
                    last;
                }
            }
        }

        # This algorithm is different from the maildir one; let's make
        # 10 tries instead of 3.
        if ($try == 9) {
            errx(&EX_TEMPFAIL, "Attempted filename $mhmsg exists.");
        }

        # This algorithm is different; i don't think we need to sleep.
        #sleep(2);
    }

    logsave("+$mhfolder");

    if ($run) {
        if (not rename($msg, $mhmsg)) {
            err(&EX_OSERR, "Failed rename($msg, $mhmsg)");
        }

        # Mark each message as soon as we store it and bomb if that
        # fails.  While it is slow, it is not safe to store multiple
        # messages and then have a failure before marking some (or
        # all).
        if ($mhfolder ne 'SPAM') {
            $status = system("mark +$mhfolder $msgnum -sequence unseen -add");
            if (not WIFEXITED($status)) {
                err(&EX_OSERR, "Failed to run mark");
            } elsif (WEXITSTATUS($status) != 0) {
                errx(&EX_SOFTWARE, "Failed to mark message unseen.");
            }
        }
    }

    if (not $FOLDERS{$mhfolder}) {
        print("+$mhfolder\n");
        $FOLDERS{$mhfolder} = 1;
    }
}

sub get_headers {
    my $msg = shift;
    my %headers;
    my $current;                # current header, used for unfolding lines
    my $fieldname;              # unmolested header name

    open(MSG, $msg);
    while (<MSG>) {
        chomp;
        if (length == 0) {
            last;
        }

        if (/^\s/) {
            # folded header continuation

            if (not defined($current)) {
                print("Malformed message, cannot parse headers.\n");
                return ();
            }

            $headers{$current} .= $_;
        } else {
            ($fieldname) = split(/:/);
            $current = lc($fieldname);
            (undef, $headers{$current}) = split(/^\Q$fieldname\E:\s*/);
        }
    }
    close(MSG);

    return %headers;
}

###############################################################################
# Spam handling

sub kill_spam {
    my @msglist = @_;
    my @result;
    my $msg;
    my $i;

    @result = ();

    $i = 0;
    foreach $msg (@msglist) {
        printf('%sChecking for spam... %6d/%d',
               "\r", ++$i, scalar(@msglist));
        if (is_spam($msg)) {
            print(" SPAM\n");
            store_message($msg, 'SPAM');
        } else {
            push(@result, $msg);
        }
    }
    print("\nDone: ", scalar(@result), " survivors\n");

    return @result;
}


###############################################################################
# Filtering

sub find_mh_folder {
    my $msg = shift;
    my %headers;
    my $header;
    my $contents;
    my $regex;
    my $subst;
    my $try;

    %headers = get_headers($msg);
    if (not %headers) {
        return 'inbox';
    }

    log_headers(%headers);

    foreach $header (keys(%FILTERS)) {
        $contents = $headers{lc($header)};

        if (defined($contents)) {
            foreach $regex (keys(%{$FILTERS{$header}})) {
                $subst = $FILTERS{$header}->{$regex};

                $try = '$contents =~';
                $try .= " s|$regex|$subst|is";
                if (eval $try) {
                    return $contents;
                }
            }
        }
    }

    return 'inbox';
}

sub filter_mail {
    my @msglist = @_;
    my $msg;
    my $mhfolder;

    foreach $msg (@msglist) {
        $mhfolder = find_mh_folder($msg);
        store_message($msg, $mhfolder);
    }
}


MAIN: {
    my @msglist;

    if ($dumpfilters) {
        $Data::Dumper::Indent = 1;
        print(Dumper(\%FILTERS));
        exit(&EX_OK);
    }

    @msglist = getfiles("$MAILDIR/new");

    if (not $filteronly) {
        @msglist = kill_spam(@msglist);
    }

    if (not $spamonly) {
        filter_mail(@msglist);
    }
}

__END__

=head1 EXAMPLES

%FILTERS =
  ('List-Id:'=>
   {'.*<([[:graph:]]+)-([[:graph:]]+)\.lists\.sourceforge\.net>.*'=>'l/$1/$2',
    '.*<([[:graph:]]+?)(-list)?\.freedesktop\.org>.*'=>'l/freedesktop/$1',
    '.*<swig\.cs\.uchicago\.edu>.*'=>'l/swig'},

   'List-Post:'=>
   {'<mailto:([[:graph:]]+)+@([[:graph:]]+)\.apache\.org>'=>'l/apache/$2/$1'},

   'To:'=>
   {'root'=>'root'});

The first List-Id filter is a surprisingly effective one which creates
appropriate folder names (such as l/htdig/updates and l/rox/devel) for
all Sourceforge lists to which i subscribe.  Certainly there are lists
hosted at Sourceforge which do not work well with this, and this is
where it is important to remember that the first match is the one
uses.  Simply put the more specific rules before this one.

The next List-Id example is simple.  The swig example demonstrates
that the folder name does not have to use a portion of the matched
header; you can just hardcode the folder name.

The List-Post example is a nice one.  Most ASF projects have their own
apache.org subdomain, with mailing lists hosted there.  So, given a
list such as dev@httpd.apache.org, this filter will create the folder
name l/apache/httpd/dev.

For an example is_spam function, see
L<http:E<sol>E<sol>pretzelnet.orgE<sol>cvsE<sol>dotfilesE<sol>.mincspam>

=head1 AUTHORS

Written by Eric Gillespie <epg@pretzelnet.org> with logging code
stolen from Adam Lazur <adam@lazur.org>.

Design by Eric Gillespie and Doug Porter <dsp@waterspout.com>.

=cut