#! /usr/bin/env ruby

# Usage: ruby bill_generator.rb data.yml 2008-1-1 2008-12-31

# Params: data file, begin date, end date
# begin and end date is in the format yyyy-mm-dd

# Sample data.yml file entries
# Date format is [yyyy, mm, dd]
#
# # Paid every two weeks
# Income1:
#     amount: 1000
#     start: [2008, 1, 18]
#     repeat: daily
#     freq: 14
#
# # Paid twice a month on the 15th and the last day
# Income2:
#     amount: 1000
#     start: [ [2008, 1, 15], [2008, 1, -1] ]
#     repeat: monthly
#     freq: 1
#
# # Weekly food expense
# Food:
#     amount: -100
#     start: [2008, 1, 6]
#     repeat: weekly
#     freq: 1
#
# # Quarterly bill
# Water:
#     amount: -100
#     start: [2008, 1, 20]
#     repeat: monthly
#     freq: 3
#
# # Monthly bill
# Home:
#     amount: -1000
#     start: [2008, 1, 1]
#     repeat: monthly
#     freq: 1

# v0.1

# TODO: Date parser for better dates in the yaml file
# TODO: Extract bill class out into separate file
# TODO: Use command line params lib

require 'yaml'
require 'date'

class Bill

  def initialize(name, params)
    @name = name
    @amount = params['amount']
    @start_dates = params['start']
    @repeat = params['repeat']
    @freq = params['freq'].to_i
  end

  attr_accessor :name, :amount

  def due?(current_date)
    due = false
    if @start_dates[0].is_a? Array
      @start_dates.each do |start_date|
        # No need to check others if it matches
        next if due == true
        due = check_for_repeat_type(current_date, start_date)
      end
    else
      due = check_for_repeat_type(current_date, @start_dates)
    end
    due
  end

  private

  def check_for_repeat_type(current_date, start_date)
    case @repeat
    when "daily"
      compare_daily(current_date, start_date)
    when "weekly"
      compare_daily(current_date, start_date, @freq * 7)
    when "monthly"
      compare_monthly(current_date, start_date)
    when "yearly"
      compare_yearly(current_date, start_date)
    else
      raise ArgumentError, "Invalid repeat option. Must be one of daily, weekly, monthly, or yearly"
    end
  end

  def compare_daily(current_date, start_date, freq = @freq)
    # Custom freq allows us to convert weekly to daily
    start_date = convert_date(start_date)
    ((current_date - start_date) % freq) == 0
  end

  def compare_monthly(current_date, start_date)
    # Check for end of month comparison
    if start_date[2].to_i == -1
      start_date = convert_date(start_date)
      ((current_date.month - start_date.month) % @freq == 0) && current_date.day == end_of_month_day(current_date)
    else
      start_date = convert_date(start_date)
      ((current_date.month - start_date.month) % @freq == 0) && current_date.day == start_date.day
    end
  end

  def compare_yearly(current_date, start_date)
    ((current_date.year - start_date.year) % @freq == 0) && current_date.month == start_date.month && current_date.day == start_date.day
  end

  # Accepts format of [year, month, day]
  def convert_date(date)
    Date.new(*date)
  end

  def end_of_month_day(current_date)
    Date.new(current_date.year, current_date.month, -1).day
  end
end

# Begin script

file = ARGV[0]
date_start = Date.parse(ARGV[1].to_s)
date_end = Date.parse(ARGV[2].to_s)

bills = YAML.load_file(file)

(date_start..date_end).each do |date|
  bills.each do |name, info|
    bill = Bill.new(name, info)
    puts "#{bill.name}, #{date.to_s.strip}, #{bill.amount}" if bill.due? date
  end
end