#!/usr/bin/env perl

use strict;
use warnings;
use utf8;
use open OUT => ':utf8', ':std';

our $VERSION = '1.00';

# expect input data source at command line
@ARGV or die "Specify input source file or - for STDIN\n";

# skip everything until a character indented by 1 space (table start)
do {
	$_ = readline;
	defined or die "Premature input end";
} until /^\s\S/;

my @t = $_;  # add first line (already read, assume it's ok)

# read the rest of the character table
while ($_ = readline) {
	# check for table end (chapter 4)
	last if /^\d/;

	# parse table lines (ignore (unindented) page break)
	next unless s/^ //;
	chomp;

	# add the line to @t
	if (s/^ {15}/ /) {
		# continuation line (add to last entry)
		$t[-1] .= $_;
	}
	else {
		# add a new entry
		push @t, $_;
	}
}

# create a hash of desired input
my %di;
for (@t) {
	my ($mnem, $char, $name) = split / +/, $_, 3;
	next if length $mnem != 2;
	$di{$mnem} = hex $char;
}

# XXX
my %trans = (
	0xE001 => 0,  # join lines: not accepted
	0xE004 => 0,  # umlaut is no different from diaeresis 0x0308
	0xE005 => 0x0344, # discouraged
	0xE006 => 0x0300,
	0xE007 => 0x0301,
	0xE008 => 0x0302,
	0xE009 => 0x0303,
	0xE00A => 0x0304,
	0xE00B => 0x0306,
	0xE00C => 0x0307,
	0xE00D => 0x0308,
	0xE00E => 0x030A,
	0xE00F => 0x030B,
	0xE010 => 0x030C,
	0xE011 => 0x0327,
	0xE012 => 0x0328,
	0xE013 => 0x0332,
	0xE014 => 0x0333,
	0xE015 => 0x0338,
	0xE016 => 0x0345,
	0xE017 => 0x0314,
	0xE018 => 0x0313,
	0xE019 => 0x1FFE,
	0xE01A => 0x1FBF,
	0xE01B => 0x03D0,  # middle beta = curled beta?
	0xE01C => 0x25CB,
	0xE01D => 0x0192,
	0xE01E => 0x0292,
	0xE01F => 0x33C2,  # am, compatibility char
	0xE020 => 0x33D8,  # pm, compatibility char
	0xE021 => 0x2121,
	0xE022 => 0xFE8E,
	0xE023 => 0,  # dutch guilder 0192 is already encoded, and not very useful anyway
	0xE024 => 0x0393,
	0xE025 => 0x20D7,  # also 20D1; non-spacing
	0xE026 => 0x1FEF,
	0xE027 => 0x1FC0,
	0xE028 => 0x01F0, #but uppercase
);
for (values %di) {
	$_ >= 0xE000 or next;
	$_ = $trans{$_} if defined $trans{$_};
}

# output perl code of hash
# (assume no backslashes or curlies, so we can just q{} w/o escaping)
print "# automatically generated by $0\n";
print "use utf8;\n";
print "+{\n";
printf "q{%s}=>%s,\n", $_, $di{$_} for sort keys %di;
print "}\n";

__END__

=head1 NAME

mkdigraphs-rfc - Output digraph data from RFC-1345

=head1 SYNOPSIS

Extract digraphs from text specifications as a perl hash:

    mkdigraphs-rfc rfc1345.txt >digraphs-rfc.inc.pl

Input can be the literal RFC (or similar) document:

    curl http://www.ietf.org/rfc/rfc1345.txt | mkdigraphlist -

Test by printing the character for DO (should be a dollar sign):

    perl -e'$di = do "digraphs-rfc.inc.pl"; print chr $di->{DO}'

=head1 DESCRIPTION

Parses the official RFC-1345 document, searching the
'character mnemonic table' for all digraph definitions.
If successful, Perl code is output resulting in a hash
with Unicode code points keyed by digraph.
Obsolete values (references to private use area)
are converted to modern alternatives.
Any errors and warnings are given at STDERR.

=head1 AUTHOR

Mischa POSLAWSKY <perl@shiar.org>

=head1 LICENSE

Licensed under the GNU Affero General Public License version 3.