credit calc

creadit-calc.pl

#!/usr/bin/env perl

use v5.10;
use strict;
use warnings;
use Time::Piece;
use Time::Seconds;

use constant {
    LOAN        => 500000,
    PERCENT     => 25,
    START_DATE  => '2025-03-26',
    DATE_FORMAT => '%Y-%m-%d"',
};

my $start_date = Time::Piece->strptime(START_DATE, DATE_FORMAT);

open my $fh, '<payments' or die $!;

my $remaining = LOAN;

for my $str (<$fh>, Time::Piece->new->strftime(DATE_FORMAT) . ' ' . 0) {
    my ($date, $sum) = split /\s+/, $str;
    $date = Time::Piece->strptime($date, DATE_FORMAT) if !ref $date;

    my $days_diff = int Time::Seconds->new($date - $start_date)->days;
    $remaining -= $sum - $remaining * PERCENT / 100 / 365 * $days_diff;

    $start_date = $date;
}

say $remaining;