#!/usr/bin/env perl

use strict;
use warnings;

use Text::CSV;

my ($hr_file, $ad_file, $com_file) = qw{hr.txt ad.txt com.txt};

my (@col_index, %hr_record_for);

my $csv = Text::CSV::->new({quote_space => 0})
    or die "Can't instantiate a Text::CSV object: ",
            Text::CSV::->error_diag();

{
    open my $mem_fh, '<', canonicalise_file_in_memory($hr_file)
        or die "Can't read in-memory file: $!";

    @col_index = @{$csv->getline($mem_fh)};

    while (my $row = $csv->getline($mem_fh)) {
        $hr_record_for{$row->[0]} = $row;
    }
}

{
    open my $mem_fh, '<', canonicalise_file_in_memory($ad_file)
        or die "Can't read in-memory file: $!";
    open my $out_fh, '>', $com_file
        or die "Can't write '$com_file': $!";
    
    (undef) = $csv->getline($mem_fh);

    while (my $row = $csv->getline($mem_fh)) {
        for my $i (1 .. $#col_index) {
            if ($hr_record_for{$row->[0]}[$i] ne $row->[$i]) {
                $csv->say($out_fh, [
                    $row->[0], $col_index[$i],
                    $hr_record_for{$row->[0]}[$i]
                ]);
            }
        }
    }
}

sub canonicalise_file_in_memory {
    my ($file) = @_;

    open my $fh, '<', $file or die "Can't read '$file': $!";

    my $canon;

    while (<$fh>) {
        chomp if /,$/;
        $canon .= $_;
    }

    return \$canon;
}