#!/usr/bin/env perl
# Copyright (C) 2020 Daniel Friesel
#
# SPDX-License-Identifier: BSD-2-Clause

use strict;
use warnings;
use 5.020;

use File::Slurp qw(write_file);
use IPC::Run3;
use JSON;

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

	say STDERR "Usage: db-wagenreihung-to-json <wagenreihung.pdf>\n";
	say STDERR
"You can obtain the latest PDF from <https://data.deutschebahn.com/dataset/zugbildungsplanzugbildungsplan-zpar>";

	exit $exit_code;
}

if ( @ARGV == 0 ) {
	show_usage(1);
}

run3( [ "which", "pdftotext" ], \undef, \undef, \undef );
if ($?) {
	say STDERR
"Error: db-wagenreihung-to-json depends on the pdftotext utility, but could not find it on this system.\n";
	say STDERR
"On Debian and derivatives, it should be available in the 'poppler-utils' package.";
	exit 2;
}

my $wr_pdf = $ARGV[0];
my $wr_txt;
my $command = [ "pdftotext", "-layout", $wr_pdf, "/dev/stdout" ];

# stdin: /dev/null
# stdout: $wr_txt
# stderr: forwarded to terminal
run3( $command, \undef, \$wr_txt, undef );

if ($?) {
	my $exit_status = $? >> 8;
	say STDERR
	  "\nError: 'pdftotext $wr_pdf' failed (exit status: $exit_status)";
	exit 2;
}

my @lines = split( qr{\n}, $wr_txt );

my ( $type, $number );
my %map;

for my $line (@lines) {

	if ( $line
		=~ m{ ^ (?<type> [EINR][CJN][ A-Z-]{6}) (?<number> [ 0-9]{2,12}) }x )
	{
		$type = $+{type};
		$type =~ tr{ }{}d;
		$number = $+{number};
		$number =~ tr{ }{}d;

		if ( $number !~ m{ ^ \d+ $ }x ) {
			next;
		}

		#say "$type $number";
		$map{$number} = {
			raw => $type,
		};

		if ( $type eq 'ICE-A' ) {
			$map{$number}{type} = 'ICE 1/2/4';
		}
		elsif ( $type eq 'ICE-W' ) {
			$map{$number}{type}  = 'ICE 3';
			$map{$number}{short} = '3';
		}
		elsif ( $type eq 'ICE' ) {
			$map{$number}{type} = 'ICE 1/2/4';
		}
		elsif ( $type eq 'ICE-T' ) {
			$map{$number}{type}  = 'ICE T';
			$map{$number}{short} = 'T';
		}
		elsif ( $type eq 'IC-A' ) {
			$map{$number}{type}  = 'Metropolitan';
			$map{$number}{short} = 'M';
		}
		elsif ( $type eq 'IC-D' ) {
			$map{$number}{type}  = 'IC2';
			$map{$number}{short} = '2';
		}
		elsif ( $type eq 'IC-E' ) {
			$map{$number}{type}  = 'IC2 KISS';
			$map{$number}{short} = '2';
		}
		else {
			$map{$number}{type} = $type;
		}
	}
	elsif ( $line =~ m{^LPF} ) {

		# Not in passenger service ("Leehrfahrt"). Ignore it for now.
		# FWIW, LPF(T) can be further distinguished:
		# LPFT-A: ICE BR 401/402
		# LPFT-B: ICE BR 412
		# LPFT-T: ICE BR 411 / 415 / 605
		# LPFT-W: ICE BR 403 / 406
		$number = undef;
	}

	# ICE types can be further distinguished by rolling stock. For instance,
	# ICE 4 is the only ICE-A variant with restaurant and first-class seats
	# in the same wagon ("ARmz").
	elsif ( $number and $line =~ m{^\d*\s+ARmz} ) {
		if ( $map{$number}{type} eq 'ICE 1/2/4' ) {
			$map{$number}{type}  = 'ICE 4';
			$map{$number}{short} = '4';
		}
	}
	elsif ( $number and $line =~ m{^\d*\s+WRmz} ) {

		#say "ICE 1 / ICE 3 Redesign (WRmz)";
		if ( $map{$number}{type} eq 'ICE 1/2/4' ) {
			$map{$number}{type}  = 'ICE 1';
			$map{$number}{short} = '1';
		}
		elsif ( $map{$number}{type} eq 'ICE 3' ) {
			$map{$number}{type}  = 'ICE 3 Redesign';
			$map{$number}{short} = '3R';
		}
	}
	elsif ( $number and $line =~ m{^\d*\s+WRmbsz} ) {

		#say "ICE 2 (WRmbsz)";
		if ( $map{$number}{type} eq 'ICE 1/2/4' ) {
			$map{$number}{type}  = 'ICE 2';
			$map{$number}{short} = '2';
		}
	}
	elsif ( $number and $line =~ m{^\d*\s+Bpmbsz} ) {

		#say "ICE 3 Velaro";
		if ( $map{$number}{type} eq 'ICE 3' ) {
			$map{$number}{type}  = 'ICE 3 Velaro';
			$map{$number}{short} = '3V';
		}
	}

	if ( $number and $line =~ m{^\d*\s+(D?(A|AB|B|W)R?D?[impvw]\S*)} ) {
		$map{$number}{wagons}{$1} = \1;
	}
}

# use canonical output (i.e., sort hash keys) to allow for easy diffing.
say JSON->new->utf8->canonical->encode( {%map} );