#!/usr/bin/perl
# Licensed under GPL v2 or greater
# (c) 2007 Patrick Winnertz <patrick.winnertz@skolelinux.org>

package IkiWiki::Plugin::teximg;
use warnings;
use strict;
use Digest::MD5 qw(md5_hex);
use File::Temp qw(tempdir);
use HTML::Entities;
use Encode;
use IkiWiki 3.00;

my $default_prefix = <<EOPREFIX;
\\documentclass{article}
\\usepackage[utf8]{inputenc}
\\usepackage{amsmath}
\\usepackage{amsfonts}
\\usepackage{amssymb}
\\pagestyle{empty}
\\begin{document}
EOPREFIX

my $default_postfix = '\\end{document}';

sub import {
	hook(type => "getsetup", id => "teximg", call => \&getsetup);
	hook(type => "preprocess", id => "teximg", call => \&preprocess);
}

sub getsetup () {
	return
		plugin => {
			safe => 1,
			rebuild => undef,
			section => "widget",
		},
		teximg_dvipng => {
			type => "boolean",
			description => "Should teximg use dvipng to render, or dvips and convert?",
			safe => 0,
			rebuild => undef,
		},
		teximg_prefix => {
			type => "string",
			example => $default_prefix,
			description => "LaTeX prefix for teximg plugin",
			safe => 0, # Not sure how secure LaTeX is...
			rebuild => 1,
		},
		teximg_postfix => {
			type => "string",
			example => $default_postfix,
			description => "LaTeX postfix for teximg plugin",
			safe => 0, # Not sure how secure LaTeX is...
			rebuild => 1,
		},
}

sub preprocess (@) {
	my %params = @_;
	
	my $height = $params{height};
	if (! defined $height || ! length $height) {
		$height = 12;
	}
	else {
		$height =~ s#(\d+)#$1#;
	}
	
	my $code = $params{code};
	if (! defined $code && ! length $code) {
		error gettext("missing tex code");
	}
	return create($code, check_height($height), \%params);
}

sub check_height ($) {
	# Since latex doesn't support unlimited scaling this function
	# returns the closest supported size.
	my $height =shift;

	my @allowed=(8,9,10,11,12,14,17,20);

	my $ret;
	my $fit;
	foreach my $val (@allowed) {
		my $f = abs($val - $height);
		if (! defined($fit) || $f < $fit ) {
			$ret=$val;
			$fit=$f;
		}
	}
	return $ret;
}

sub create ($$$) {
	# This function calls the image generating function and returns
	# the <img .. /> for the generated image.
	my $code = shift;
	my $height = shift;
	my $params = shift;

	if (! defined($height) and not length($height) ) {
		$height = 12;
	}

	my $digest = md5_hex(Encode::encode_utf8($code), $height);

	my $imglink= $params->{page} . "/$digest.png";
	my $imglog =  $params->{page} .  "/$digest.log";
	will_render($params->{page}, $imglink);
	will_render($params->{page}, $imglog);

	my $imgurl=urlto($imglink, $params->{destpage});
	my $logurl=urlto($imglog, $params->{destpage});
	
	if (-e "$config{destdir}/$imglink" ||
	    gen_image($code, $height, $digest, $params->{page})) {
		return qq{<img src="$imgurl" alt="}
			.(exists $params->{alt} ? $params->{alt} : encode_entities($code))
			.qq{" class="teximg" />};
	}
	else {
		error qq{<a href="$logurl">}.gettext("failed to generate image from code")."</a>";
	}
}

sub gen_image ($$$$) {
	# Actually creates the image.
	my $code = shift;
	my $height = shift;
	my $digest = shift;
	my $imagedir = shift;

	if (!defined $config{teximg_prefix}) {
		$config{teximg_prefix} = $default_prefix;
	}
	if (!defined $config{teximg_postfix}) {
		$config{teximg_postfix} = $default_postfix;
	}
	if (!defined $config{teximg_dvipng}) {
		$config{teximg_dvipng} = length `which dvipng 2>/dev/null`;
	}
	
	my $tex = $config{teximg_prefix};
	$tex .= '\['.$code.'\]';
	$tex .= $config{teximg_postfix};
	$tex =~ s!\\documentclass{article}!\\documentclass[${height}pt]{article}!g;
	$tex =~ s!\\documentclass{scrartcl}!\\documentclass[${height}pt]{scrartcl}!g;

	my $tmp = eval { create_tmp_dir($digest) };
	if (! $@ &&
	    writefile("$digest.tex", $tmp, $tex) &&
	    system("cd $tmp; shell_escape=f openout_any=p openin_any=p latex --interaction=nonstopmode $digest.tex < /dev/null > /dev/null") == 0 &&
	    # ensure destination directory exists
	    writefile("$imagedir/$digest.png", $config{destdir}, "") &&
	    (($config{teximg_dvipng} &&
	    	system("dvipng -D 120 -bg Transparent -T tight -o $config{destdir}/$imagedir/$digest.png $tmp/$digest.dvi > $tmp/$digest.log") == 0
	    ) || (!$config{teximg_dvipng} &&
	    	system("dvips -E $tmp/$digest.dvi -o $tmp/$digest.ps 2> $tmp/$digest.log") == 0 &&
	    	system("convert -density 120  -trim -transparent \"#FFFFFF\" $tmp/$digest.ps $config{destdir}/$imagedir/$digest.png > $tmp/$digest.log") == 0
	    ))) {
		return 1;
	}
	else {
		# store failure log
		my $log="";
		{
			if (open(my $f, '<', "$tmp/$digest.log")) {
				local $/=undef;
				$log = <$f>;
				close($f);
			}
		}
		writefile("$digest.log", "$config{destdir}/$imagedir", $log);

		return 0;
	}
}

sub create_tmp_dir ($) {
	# Create a temp directory, it will be removed when ikiwiki exits.
	my $base = shift;

	my $template = $base.".XXXXXXXXXX";
	my $tmpdir = tempdir($template, TMPDIR => 1, CLEANUP => 1);
	return $tmpdir;
}

1
