#!/usr/bin/perl
use warnings;
use strict;

die "Usage: $0 filter_file input_file\n" unless @ARGV == 2;

my @filters;

my %dispatch;
for my $op (qw/== != <= >= <  >
               eq ne le ge lt gt/) {
    $dispatch{$op} = eval qq{ sub { \$_[0] $op \$_[1] } };
}

use constant {
    COLUMN => 0,
    REL    => 1,
    VAL    => 2,
    TYPE   => 3, # Ignored at the moment
    ACTION => 4
};

open my $DATA, '<', pop or die $!;
my @col_names_arr = split ' ', <$DATA>;
my %col_names;
$col_names{$col_names_arr[$_]} = $_ for 0 .. $#col_names_arr;

open my $FILTER, '<', pop or die $!;
<$FILTER>; # Skip header line
while (<$FILTER>) {
    my ($column, $rel, $val, $type, $action, $order, $rest) = split;

    die "Ivalid format at line $.\n"          if $rest;
    die "Duplicate order $order at line $.\n" if $filters[$order - 1];
    die "Unknown column $column at line $.\n" unless exists $col_names
+{$column};

    $filters[$order - 1] = [$column, $rel, $val, $type, $action];
}
close $FILTER;

while (<$DATA>) {
    my @data = split;

  FILTER:
    for my $f (@filters) {
        my $sub = $dispatch{$f->[REL]};
        die "Unknown operator $f->[REL]\n" unless ref $sub;
        my $result = $sub->($data[$col_names{$f->[COLUMN]}], $f->[VAL]
+);
        if ($result) {
            last FILTER if 'filter' eq $f->[ACTION];
            if ('append' eq $f->[ACTION]) {
                print;
            } else {
                die "Unknown action $f->[ACTION]\n";
            }
        }
    }
}
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