From b44b23f79590d2bd9874985a253f247f33d03b20 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?John=20Ankarstr=C3=B6m?= <john@ankarstrom.se>
Date: Mon, 30 Nov 2020 22:26:50 +0100
Subject: Add 'mh' script

mh is a simple Perl script that translates troff-like source text
into HTML.
---
 mh | 119 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100755 mh

diff --git a/mh b/mh
new file mode 100755
index 0000000..cae73bf
--- /dev/null
+++ b/mh
@@ -0,0 +1,119 @@
+#!/usr/bin/perl
+
+use v5.12;
+use warnings;
+
+use Text::ParseWords qw/quotewords/;
+
+
+# 1  Definitions
+
+
+# 1.1  Global program state
+
+my $empty = ''; # currently buffered empty lines
+my $opel = ''; # currently opened element
+
+
+# 1.2  Elements
+
+# 1.2.1  Block elements
+my %blels = (
+	Pp_0 => '<p>%</p>',
+	Qp_0 => '<blockquote><p>%</p></blockquote>',
+	Pr_0 => '<pre>%</pre>',
+	Sh_0 => '<h3>%</h3>',
+	Sh_1 => '<h\\$1>%</h\\$1>',
+	Ti_0 => '<title>%</title>',
+);
+
+# 1.2.2  Inline elements
+my %inels = (
+	Au_1 => '<meta name="author" content="\\$1"/>',
+	Bd_0 => '\\$3<b>\\$1</b>\\$2',
+	br_0 => '<br/>',
+	Cd_0 => '\\$3<code>\\$1</code>\\$2',
+	Cs_1 => '<meta http-equiv="Content-Type" content="text/html; charset=\\$1"/>',
+	Em_0 => '\\$3<em>\\$1</em>\\$2',
+	Hy_0 => '<a href="\\$2">\\$1</a>',
+	Im_0 => '<img src="\\$1" alt="\\$2"/>',
+	It_0 => '\\$3<i>\\$1</i>\\$2',
+	St_0 => '\\$3<strong>\\$1</strong>\\$2',
+	Tt_0 => '\\$3<tt>\\$1</tt>\\$2',
+	Ul_0 => '\\$3<u>\\$1</u>\\$2',
+);
+
+
+# 1.3  Subroutines
+
+# 1.3.1  Handle element request
+sub request {
+	my ($el, $args) = @_;
+	my @argv = quotewords('\s+', 0, $args);
+	my $n = @argv;
+	my $elkey = "${el}_$n";
+
+	if (exists $blels{$elkey}) {
+		# Clear empty line buffer
+		$empty = '';
+
+		# Close currently open block element, open new
+		if (exists $blels{$opel}) {
+			print end($blels{$opel}) . "\n";
+			$opel = '';
+		}
+		$opel = $elkey;
+
+		print interpol(start($blels{$elkey}), @argv) . "\n";
+	} elsif (exists $inels{$elkey}) {
+		print interpol($inels{$elkey}, @argv) . "\n";
+	} else {
+		print STDERR "Error: $el/$n not implemented\n";
+		exit 1;
+	}
+}
+
+# 1.3.2  Interpolate \$n parameters
+sub interpol {
+	my $s = shift;
+	my $i = 1;
+	my $arg;
+	while ($arg = shift) {
+		$s =~ s/\\\$$i/$arg/g;
+		$i++;
+	}
+	return $s;
+}
+
+# 1.3.3  Retrieve first portion of block element string
+sub start {
+	return (split '%', shift)[0];
+}
+
+# 1.3.4  Retrieve second portion of block element string
+sub end {
+	return (split '%', shift)[1];
+}
+
+
+# 2  Program
+
+
+# 2.1  Translate mh source text to HTML
+while (<>) {
+	chomp;
+	if (/^\.([A-Za-z][a-z])\s*(.*)/) {
+		request($1, $2);
+	} elsif ($_ eq '') {
+		$empty .= "\n";
+	} else {
+		print $empty; $empty = '';
+		print "$_\n";
+	}
+}
+
+# 2.2  Close currently open block element
+if (exists $blels{$opel}) {
+	print end($blels{$opel}) . "\n";
+	$opel = '';
+}
-- 
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