#!/usr/bin/perl
# Author: Martin Dahlo
# Used to calculate debts
# Usage: perl skulder.pl <infile> <outfile>
# Ex.
# perl skulder.pl usa2010.txt resultat.txt

use strict;
use warnings;

# set the exchange rate, e.g 6.14 for usd -> sek, or 1 for no exchange rate
my $multiplicator = 1;

# define a usage message
my $usage = "Usage: perl skulder.pl <infile> <outfile>";

# get the file names
my $infile = shift or die $usage;
my $outfile = shift or die $usage;

# open the file handles
open IN, "<", $infile or die $!;
open OUT, ">", $outfile or die $!;

# initialize variables
my %balance;

# go through the debt file
while(<IN>){

    # only valid rows, e.g no commented rows
    if($_ =~ m/^([\d\.]+)\t(.+)\t(.+)\t(.+)$/){

        # save values to make everything more clear..
        my $sum = $1;
        my $creditor = $2;
        my $debtor = $3;
        my $what = $4;


        # check the number of people involved
        my @credArr = split(/,/,$creditor);  # create an array with all creditors
        my @debtArr = split(/,/,$debtor);  # create an array with all debtors
        my $nCred = $#credArr + 1;  # count number of creditors
        my $nDeb = $#debtArr + 1;  # count the number of debtors

        # increase creditors balance
        for(my $i = 0; $i < $nCred; $i++){
            # increase balance with 1/n of the sum
            $balance{$credArr[$i]} += $sum/$nCred;
        }

        # decrease debtors balance
        for(my $i = 0; $i < $nDeb; $i++){
            # decrease balance with 1/n of the sum
            $balance{$debtArr[$i]} -= $sum/$nDeb;
        }
    }
}

# initialize checksum
my $checksum = 0;

# print the results
foreach my $key (sort keys %balance){
    print OUT "$key:\t".$balance{$key}*$multiplicator."\n";
    print "$key:\t".$balance{$key}*$multiplicator."\n";
    $checksum += $balance{$key};
}

# should be zero if all is well. Or really really close to zero.. :)
print OUT "Checksum: $checksum\n";
print "Checksum: $checksum\n";