#! /usr/bin/perl
#
#  xcfview: a wrapper script that uses xcftools and an external viewer
#  to display XCF images. The external viewer is found through the
#  mailcap(5) database (q.v.).
#
#  Written by Henning Makholm <henning@makholm.net>
#  Derived from the run-mailcap script by Brian White <bcwhite@pobox.com>
#
#  This script has been placed in the public domain (by both authors)
#
#  We cannot use run-mailcap as-is because we can supply the flattened
#  image either as PNG and PPM, and we need to find the highest-ranked
#  viewer that can handle _one_ of these two. If everything else is equal
#  we try to prefer a PNG viewer such that transparency is handled properly.
#

use strict ;
use warnings ;

my $debug=0;
my $quotedsemi = "\001" ;
my $quotedprct = "\002" ;

sub ReadMailcap {
	my($file) = @_;
	my $line = "";

	return unless -r $file;

	print STDERR " - Reading mailcap file \"$file\"...\n" if $debug;
	open(MAILCAP,"<$file") || die "Error: could not read \"$file\" -- $!\n";
        my @mailcap ;
        
	while (<MAILCAP>) {
		chomp;
		s/^\s+// if $line;
		$line .= $_;
		next unless $line;
		if ($line =~ m/^\s*\#/) {
			$line = "";
			next;
		}
		if ($line =~ m/\\$/) {
			$line =~ s/\\$//;
		} else {
			$line =~ s/\\;/$quotedsemi/go;
			$line =~ s/\\%/$quotedprct/go;
			push @mailcap,$line;
			$line = "";
		}
	}
	close MAILCAP;

        return @mailcap ;
}

sub TempFile {
	my($match) = @_;
	my($cmd,$head,$tail,$tmpfile);

        ($head,$tail) = split(/%s/,$1,2)
            if ($match =~ m/nametemplate=(.*?)\s*($|;)/);

	$cmd  = "tempfile --mode=600";
	$cmd .= " --prefix $head" if $head;
	$cmd .= " --suffix $tail" if $tail;

	$tmpfile = `$cmd`;
	chomp($tmpfile);

	return $tmpfile;
}

my ($useline,$usecomm,$useprogram,$usetype,@converter) ;
foreach my $mailcap ( $ENV{MAILCAPS} ? split(/:/,$ENV{MAILCAPS}) :
                      ( "$ENV{HOME}/.mailcap",
                        qw( /etc/mailcap
                            /usr/local/etc/mailcap
                            /usr/share/etc/mailcap
                            /usr/etc/mailcap
                            ) ) ) {
    foreach ( ReadMailcap($mailcap) ) {
        my ($type,$comm,$program,$rest)
            = m"^image/(png|x-portable-pixmap)\s*;\s*((\S*).*?)\s*($|;.*)"
            or next ;
        print STDERR " - checking $mailcap entry \"$_\"\n" if $debug;
        next if $rest =~ /;\s*needsterminal\s*($|;)/ ;
        next if $rest =~ /;\s*copiousoutput\s*($|;)/ ;
        if( $rest =~ m/;\s*test=(.*?)\s*($|;)/ ) {
            my $test;
            print STDERR " - running test: $1 " if $debug;
            $test   = system "$1 >/dev/null 2>&1";
            $test >>= 8;
            print STDERR " (result=$test=",($test!=0?"false":"true"),")\n"
                if $debug;
            next if $test ;
        }
        # If we get down here, we have a possible hit.
        if( $type ne 'png' ) {
            # Save for later; if there is a PNG definition for the same
            # command, we will prefer PNG
            ($useline,$usecomm,$useprogram,$usetype,@converter)
                = ($rest,$comm,$program,$type,"xcf2pnm","-c","'-#'")
                unless @converter ;
            next ;
        } else {
            # use this definition _unless_ we have already seen and saved
            # a definition for a _different_ program (which must have been PPM)
            ($useline,$usecomm,$useprogram,$usetype,@converter)
                = ($rest,$comm,$program,$type,"xcf2png")
                unless @converter && $comm eq $useprogram ;
            last ;
        }
    }
    last if @converter ;
}

unless( @converter ) {
    print STDERR "$0: No appropriate way to display PPM or PNG images in mailcap\n" ;
    exit 1 ;
}

sub finishcomm() {
    $usecomm =~ s!([^%])%t!$1$usetype!g;
    $usecomm =~ s!%{(.*?)}!$_="'$ENV{$1}'";s/\`//g;$_!ge;
    $usecomm =~ s!\\(.)!$1!g;
    $usecomm =~ s!\'\'!\'!g;
    $usecomm =~ s!$quotedsemi!;!go;
    $usecomm =~ s!$quotedprct!%!go;
}

# quote arguments for converter
for( @ARGV ) {
    next if m{^[-a-z0-9,.:/@%^+=_]+$}i ;
    s/'/\\'/ ;
    $_ = "'$_'" ;
}

if( $usecomm =~ /[^%]%s/ ) {
    my $tempfile = TempFile($useline);
    $usecomm =~ s/([^%])%s/$1$tempfile/g ;
    finishcomm() ;
    my $retcode = 0 ;
    for my $comm ( join(" ",@converter,"-o",$tempfile,@ARGV),
                   $usecomm ) {
        print STDERR " - executing: $comm\n" if $debug ;
        my $res = system $comm;
        $res = int($res/256);
        if ($res != 0) {
            print STDERR "Warning: program returned non-zero exit code \#$res\n";
            $retcode = $res;
            last ;
        }
    }
    unlink $tempfile ;
    exit $retcode ;
} else {
    finishcomm() ;
    exec( join(@converter," ",@ARGV) . " | " . $usecomm )
        or print STDERR "Couldn't exec pipeline: $!\n" ;
    exit 1 ;
}