#!/usr/bin/env perl

use strict;
use warnings;
use 5.020;
use utf8;

use File::Slurp qw(read_file);
use JSON;
use List::Util qw(uniq);

sub show_usage {
	my ($exit_code) = @_;

	say STDERR
"Usage: umlauf-to-dot <wagenreihung.json> [line number] [limit] | dot -Tpng > umlauf.png";

	exit $exit_code;
}

sub contained_in {
	my ( $value, @list ) = @_;

	for my $elem (@list) {
		if ( $elem eq $value ) {
			return 1;
		}
	}
	return;
}

sub format_train {
	my ( $train_no, $train ) = @_;

	return sprintf( '"%s %d\n%s\n%s"',
		$train->{type} // $train->{raw} // 'Zug',
		$train_no,
		$train->{route}{start} // $train->{route}{preStart} // '?',
		$train->{route}{end}   // $train->{route}{postEnd}  // '?' );
}

binmode( STDOUT, ':encoding(utf-8)' );

if ( @ARGV < 1 ) {
	show_usage(1);
}

my ( $file, $line, $limit ) = @ARGV;

my $file_content = read_file($file);
my $json         = JSON->new->utf8->decode($file_content);

my $map = $json->{train};

sub build_cycle {
	my ( $line, $cycle_id ) = @_;
	my @queue = ( [ $line, 0 ] );
	my @train_numbers;

	while (@queue) {
		my ( $train_number, $distance ) = @{ pop @queue };
		push( @train_numbers, $train_number );

		if ( $limit and $distance > $limit ) {
			next;
		}

		my @candidates;

		my $train = $map->{$train_number};
		if ( my $c = $train->{cycle}{$cycle_id} ) {
			push( @candidates, @{ $c->{from} // [] } );
			push( @candidates, @{ $c->{to}   // [] } );
		}

		@candidates = uniq @candidates;
		@candidates
		  = grep { not contained_in( $_, @train_numbers, @queue ) } @candidates;

		if (@candidates) {
			printf( "# handle %s -> push %s\n",
				$train_number, join( " ", @candidates ) );
		}

		push( @queue, map { [ $_, $distance + 1 ] } @candidates );
	}

	my @output;

	for my $train_number (@train_numbers) {
		my $train = $map->{$train_number};
		if ( my $c = $train->{cycle}{$cycle_id} ) {
			for my $from ( @{ $c->{from} // [] } ) {
				push(
					@output,
					sprintf( "%s -> %s;",
						format_train( $from,         $map->{$from} ),
						format_train( $train_number, $map->{$train_number} ) )
				);
			}
			for my $to ( @{ $c->{to} // [] } ) {
				push(
					@output,
					sprintf( "%s -> %s;",
						format_train( $train_number, $map->{$train_number} ),
						format_train( $to,           $map->{$to} ) )
				);
			}
		}
		if ( $train_number != $line ) {
			push(
				@output,
				sprintf( "%s [shape=box];",
					format_train( $train_number, $map->{$train_number} ) )
			);
		}
	}

	return @output;
}

my @cycle_ids;

push( @cycle_ids, keys %{ $map->{$line}{cycle} // {} } );

say "digraph Umlauf {";

my @all_lines;
for my $cycle_id (@cycle_ids) {
	push( @all_lines, build_cycle( $line, $cycle_id ) );
}
say join( "\n", uniq @all_lines );

printf( "%s [style=bold];\n", format_train( $line, $map->{$line} ) );

say "}"