#!/usr/bin/env perl

# urldecode - decode the game ID from x[a-f0-9]{12} form to [a-f0-9]{8} form
#
# useful for getting immediate logs of games from a.mjv.jp/log?etc
#
# 2008-08-19  bps   initial
# 2011-07-02  bps   added support for new encryption method

use strict;
use warnings;

# keys
my @t = (22136, 52719, 55146, 42104, 59591, 46934, 9248, 28891, 49597, 52974,
    62844, 4015, 18311, 50730, 43056, 17939, 64838, 38145, 27008, 39128, 35652,
    63407, 65535, 23473, 35164, 55230, 27536, 4386, 64920, 29075, 42617, 17294,
    18868, 2081);

sub urldecode {
    my $full = shift;
    $full =~ /((\d{10})gm-.*-)(x[a-f0-9]{12})/;
    my $pref = $1;
    my $date = $2;
    my $eid = $3;
    if(substr($eid, 0, 1) eq 'x') {
        my $a = hex substr $eid, 1, 4;
        my $b = hex substr $eid, 5, 4;
        my $c = hex substr $eid, 9, 4;
        my $l = (int($date) >= 2010041111) ?
            int("3".substr($date,4,6))%(17*2-int(substr($date,9,1))-1) : 0;
        $eid = sprintf "%x%x", ($a^$b^$t[$l]), ($b^$t[$l]^$c^$t[$l+1]);
    }
    $pref.$eid;
}

print urldecode($_)."\n" foreach @ARGV;

exit 0;