# Vocabulary generation utilities
#
# Copyright (C) 2021 Ngô Ngọc Đức Huy
#
# This file is a part of CreLang-corelibs and was cherry-picked for this document.
#
# CreLang-corelibs is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# CreLang-corelibs is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with CreLang-corelibs.  If not, see <https://www.gnu.org/licenses/>.
use v6;

enum ParseCategoryError <LongLHS EmptyLHS EmptyRHS>;

sub get-categories ($raw-input) is export {
	my %categories;
	for $raw-input.lines -> $line {
		next unless $line;
		my ($left, $right) = $line.split("=");
		my $key = $left.trim;
		my @symbols = $right.words;
		die LongLHS if $key.chars > 1;
		die EmptyLHS if $key.chars == 0;
		die EmptyRHS if @symbols.elems == 0;
		%categories{$left.trim} = $right.words;
	}
	return %categories;
};

sub generate-words ($pattern, %categories) is export {
	my @generated-words;
	sub support ($to-do, $so-far) {
		if $to-do.chars == 0 {
			@generated-words.push: $so-far;
			return;
		}
		my $current = $to-do.substr(0, 1);
		my $remainder = $to-do.substr(1);

		die "Invalid category: $current" unless
			$current ∈ %categories.keys;
		for @(%categories{$current}) -> $char {
			support($remainder, $so-far ~ $char)
		}
	}
	support($pattern, "");
	return @generated-words;
}

sub rewrite ($rules, $word) {
	my $ret = $word;
	for $rules.lines -> $rule {
		my ($left, $right) = $rule.split(",");
		if $word.match($left) {
			$ret = $ret.subst($left, $right)
		}
	}
	return $ret
}

my $category-input = slurp "categories";
my $rewrite-rules = slurp "rewrite";
my $categories = get-categories($category-input);
my @possible-syllables;

for "patterns".IO.lines -> $pattern {
	@possible-syllables.append: generate-words($pattern, $categories);
}

sub MAIN($max-syllables, $n-outputs) {
	# my $output = open "output.txt", :w;

	for (1..$n-outputs) {
		my $word = '';
		my $n-syllables = $max-syllables.rand.ceiling;
		for (1..$n-syllables) {
			$word ~= @possible-syllables[@possible-syllables.elems.rand.floor];
		}
		# $output.say(rewrite($rewrite-rules, $word))
		say rewrite($rewrite-rules, $word)
	}
	# $output.close
}