Simulate the sending of chain mail that depends on generations

chain-mail.rb

#a person will have, averagely, around double the specified value
#because when it's generated, everyone has to be friends with those
#who are friends with them
AMOUNT_OF_FRIENDS = 1
FRIEND_VARIANCE =   4
POPULATION =        7400 #7.4 billion in 1000's

def a(n)
    if n <= 1
        1
    else
        (1..(n-1)).reduce(:*)
    end
end

class Person
    attr_accessor :has_recieved_mail
    attr_accessor :has_to_send_mail
    attr_accessor :friends
    def _gen_friend_connections(amount_of_people, amount_of_friends)
        amount_of_friends.times do
            @friends << rand(amount_of_people)
        end
    end
    def initialize
        @has_recieved_mail = false
        @has_to_send_mail = false
        @friends = []
    end
end

def gen_world()
    world = []
    POPULATION.times do
        world << Person.new
    end
    world.each_with_index do |p, pI|
        variance = rand(FRIEND_VARIANCE)
        sign = rand(2) == 0 ? -1 : 1
        world[pI]._gen_friend_connections(POPULATION, AMOUNT_OF_FRIENDS + sign * variance)
    end
    world.each_with_index do |p, pI|
        #check to make sure that friend is friends with
        #someone who is friends with them
        p.friends.each do |friend|
            if !world[friend].friends.include?(pI)
                world[friend].friends << pI
            end
        end
    end
    #make one guy have the chain mail
    pI = rand(POPULATION)
    world[pI].has_recieved_mail = true
    world[pI].has_to_send_mail = true
    return world
end

def sim_world(world, gen)
    #make the mail be sent
    world.each_with_index do |p, pI|
        if p.has_to_send_mail
            recipients = p.friends.sample gen
            recipients.each do |friend|
                if !world[friend].has_recieved_mail
                    world[friend].has_recieved_mail = true
                    world[friend].has_to_send_mail = true
                end
            end
            world[pI].has_to_send_mail = false
        end
    end
    return world
end

def gen_stats(world)
    #new people, total people, untouched people
    stats = [0, 0, 0]
    world.each do |p|
        if p.has_to_send_mail
            stats[0] = stats[0] + 1
        elsif p.has_recieved_mail
            stats[1] = stats[1] + 1
        else
            stats[2] = stats[2] + 1
        end
    end
    return stats
end


def print_gen(*args)
    #puts " #{' '*(12 - gen.to_s.length)}#{gen} | #{' '*(12 - newPeople.to_s.length)}#{newPeople} | #{' '*(12 - totalPeople.to_s.length)}#{totalPeople} | #{' '*(12 - untouchedPeople.to_s.length)}#{untouchedPeople}"
    s = ""
    args.each do |n|
        s << " #{' '*(14 - n.to_s.length)}#{n} |"
    end
    puts s
end

puts "Generating world of #{POPULATION} with #{AMOUNT_OF_FRIENDS*2} +- #{FRIEND_VARIANCE} friends each..."
world = gen_world

puts " Generation     | New People     | Total People   | Untouched People "
puts ("-"*(`tput cols`.to_i))

1.step do |gen|
    newPeople, totalPeople, untouchedPeople = *gen_stats(world)
    print_gen(gen, newPeople, totalPeople, untouchedPeople)
    world = sim_world(world, gen)
    if newPeople == 0
        break
    end
end