$TOTAL = 0.0
PERSONS = {}
PAYMENTS = {}
PURPOSES = {}

class Person
  def initialize(name)
    @name = name
  end

  def leave!
    PERSONS.delete @name
  end

  def pay(amount, comment)
    $TOTAL += amount
    (PURPOSES[@name] ||= []) << comment

    (PERSONS.keys-[@name]).each { |ot|
      pay = amount/PERSONS.size
      
      na = @name
      if na.to_i > ot.to_i
        other, name = na, ot
        pay = -pay
      else
        name, other = na, ot
      end
      
      PAYMENTS[name] ||= {}
      PAYMENTS[name][other] ||= 0
      PAYMENTS[name][other] += pay
    }
  end
end

def person(name)
  Object.const_set name, PERSONS[name] = Person.new(name)
end

def cashing_up!
  puts PAYMENTS.map { |don, v|
    v.map { |rec, n|
      if n == 0
        nil
      elsif n > 0
        "%s -> %s: %.2f" % [rec, don, n]
      else
        "%s -> %s: %.2f" % [don, rec, -n]
      end
    }
  }.flatten.compact.sort
  puts

  PAYMENTS.each { |name, v|
    v.each { |other, w|
      v[other] = 0.0
    }
  }
end

load ARGV.first

avg = $TOTAL / PERSONS.size

puts "%d people, %.2f pro person (Cashflow: %.2f)" % [PERSONS.size, avg, $TOTAL]
PURPOSES.each { |name, purp|
  unless purp.empty?
    puts "#{name}: #{purp.join ', '}"
  end
}