Date-based financial math

calendar_math.rb

#!/usr/bin/env ruby
require 'date'

puts "hi, I'm gonna do math!"

class CalendarItem
	attr_accessor :date
	attr_accessor :amount
	
	def initialize(date, amount)
		@date = date
		@amount = amount
	end
	
	def self.monthly(start_date, amount, month_count)
		month = start_date.month
		
		values = []
		month_count.times.each do
			date = Date.new(start_date.year, month, 1)
			values.push(CalendarItem.new(date, amount))
			month = month + 1
		end
		return values
	end
end

def sum(calendar_items)
	total = 0
	calendar_items.each do |item|
		total += item.amount
	end
	total
end

def summary(calendar_items, end_date = nil, goal = nil)
	debits = []
	credits = []
	total_items = []
	
	calendar_items.sort! { |a,b| a.date <=> b.date }
	calendar_items.each do |item|
		if(end_date && (item.date <=> end_date) != -1)
			break
		end
		
		if(item.amount > 0)
			credits.push(item)
		else
			debits.push(item)
		end
		total_items.push(item)
	end
	
	puts "Credits: $#{sum(credits)}"
	puts "Debits: $#{sum(debits)}"
	puts "Total: $#{sum(total_items)}"
	
	if(goal)
		money_needed = goal - sum(total_items)
		bonus_time_needed = ((money_needed)/500)*7
		puts "Bonus time needed: #{bonus_time_needed} hours for $#{money_needed}"
	end
end