gistfile1.rb

require 'date'


#
# My infinite monkeys just wrote the complete works of Shakespeare. Just can't find it
# amongst these infinite monkeys.
#
# That's right MONKEY PATCHING.....
#
class Date
  def quarter
    (((self.month + 5) % 12) / 3.0).floor + 1
  end
end

module Enumerable
  
  def sum( symbol = nil )
    if symbol.nil?
      self
    else
      self.collect {|i| i.send(symbol)}
    end.inject( 0, :+ )
  end
  
  
  # Nicked from activesupport
  def group_by
    assoc = Hash.new

    each do |element|
      key = yield(element)

      if assoc.has_key?(key)
        assoc[key] << element
      else
        assoc[key] = [element]
      end
    end

    assoc
  end unless [].respond_to?(:group_by)

end




module Expensify

  class Expense
    attr_accessor :amount, :date, :category, :for, :gst, :income, :work
  
    def quarter
      date.quarter
    end
  
    def gst_amount
      return 0 unless gst
      (amount * (income / 100.0)) / 11.0
    end
    
    def income_amount
      (amount * ((income || 0) / 100.0))
    end
  
  
    # The amount deductible as a work expense. Includes
    # GST as you can't claim that proportion of the GST
    # in a BAS.
    def work_deductible
      amount * (work / 100.0)
    end
  
  
    # The amount deductible as a business expense. Does NOT
    # include GST.
    def business_deductible
      income_amount - gst_amount
    end
    
    
    # Total deductible amount for the expense (used mostly for
    # calculating NET income).
    def deductible
      work_deductible + business_deductible
    end
  
  end

  class Income
    attr_accessor :amount, :date, :gst
  
    def initialize( amount, date, gst = true )
      @amount = amount
      @date = date
      @gst = gst
    end
    
    def gst_free
      amount * (gst ? (10/11.0) : 1.0)
    end
  end



  # This is the DSL such as it is for constructing the accounts object
  class Builder
    def initialize( accounts )
      @accounts = accounts
      @expense_defaults = {}
      @income_defaults = {}
      @expense_definitions = {}
    end
    
    
    
    def define_expense( name, options )
      @expense_definitions[name] = options
    end
    
    def method_missing( method, *args )
      if @expense_definitions[method] && args.size > 1
        options = @expense_definitions[method]
        options = options.merge(args[2]) if args.size > 2
        expense args[0], args[1], options
      else
        super
      end
    end
  
    def expense_defaults( defaults_hash )
      @expense_defaults = defaults_hash
    end
  
    def income_defaults( defaults_hash )
      @income_defaults = defaults_hash
    end
  
  
  
    def income( amount, date, details )
      details = @income_defaults.merge( details )
    
      i = Income.new( amount, date, details[:gst] )
      @accounts.add_income(i )
    end
  
    def expense( amount, date, details )
      e = Expense.new
      e.amount = amount
      e.date = date
    
      details = @expense_defaults.merge( details )
    
      e.income = details[:income] || 0
      e.work = details[:work] || 0
      e.category = details[:cat]
      e.for = details[:for]
      e.gst = details[:gst]
    
      @accounts.add_expense( e )
    end
  
    def expenses
      @expenses
    end
  end

  class Accounts
  
    def initialize
      @expenses = []
      @income = []
    end
    def add_expense(e)
      @expenses << e
    end

    def add_income( i )
      @income << i
    end
  
  
    def gst_report
      quarters = {1 => [], 2 => [], 3 => [], 4 => []}
    
      @expenses.each {|e| quarters[e.quarter] << e}
    
    
      (1..4).each do |q|
        expenses = quarters[q]
        income = @income.select {|i| i.date.quarter == q}
      
        g1 = income.sum :amount
        
        income_without_gst = income.select {|i| !i.gst}
        
        g2 = income_without_gst.sum :amount
        g3 = 0
        g4 = 0
        g5 = g2 + g3 + g4
        g6 = g1 - (g5)
        g7 = 0.0
        g8 = g6 + g7
        g9 = g8 / 11
      
        g10 = 0
        g11 = expenses.sum( :income_amount )
        g12 = g10 + g11
      
        g13 = 0 # purchases for making input taxed sales
      
        purchases_without_gst = expenses.select {|e| !e.gst}
      
        g14 = purchases_without_gst.sum( :income_amount )
      
        g15 = 0.0 # private use - already taken into account with income amount
      
        g16 = g13 + g14 + g15
      
        g17 = g12 - g16 # total purchases subject to GST
        g18 = 0.0 # adjustments
      
        g19 = g17 + g18 # total purchases subject to GST after adjustments
      
        g20 = (g19 / 11)
      
        puts "\n\nQ#{q}:"
      
  
        report_line "G1", g1.floor, "Total Sales (including any GST)"
        report_line "G2", g2.floor, "Export Sales"
        report_line "G3", g3.floor, "Other GST-free Sales"
        report_line "G10", g10.floor, "Capital Purchases (including any GST)"
        report_line "G11", g11.floor, "Non-Capital Purchases (including any GST)"
        report_line "G12", g12.floor, "G10 + G11"
        report_line "G13", g13.floor, "Purchases for making input taxed sales"
        report_line "G14", g14.floor, "Purchases without GST in the price"
        report_line "G15", g15.floor, "Estimate purchases for private use on not income tax deductible"
        report_line "G16", g16.floor, "G13 + G14 + G15"
        report_line "G17", g17.floor, "Total Purchases subject to GST"
        report_line "1A", g9.floor, "GST on Sales"
        report_line "1B", g20.floor, "GST on purchases"
        report_line "-",    (g9 > g20) ? "PAY" : "REFUND", "Payment or refund?"
        report_line "AMNT", (g9 - g20).floor.abs, "Amount"
      
      end
    
    

    
    end
  
    def report_line( column, amount, description )
      puts( "#{column.rjust(5)}: #{amount.to_s.rjust(6)}  : #{description}")
    end
    
    def income_report_line( column, amount )
      puts( "#{column.ljust(20)}: #{amount.to_s.rjust(6)}")
    end
    
    
    def income_report
      total = @income.sum :gst_free
      
      puts "\n\n\nINCOME"
      
      income_report_line "Ex GST", total.floor
      
      categories =  @expenses.group_by { |e| e.category }
      
      puts "\n\nWORK RELATED"
      categories.keys.sort.each do |k|
        total = categories[k].sum :work_deductible
        income_report_line k, total.floor
      end
      
      
      puts "\n\nBUSINESS RELATED"
      categories.keys.sort.each do |k|
        total = categories[k].sum :business_deductible
        income_report_line k, total.floor
      end
      

      puts
      puts
      income_report_line "TOTAL EXPENSES", @expenses.sum( :deductible ).floor
      
    end
  end

  def self.expenses(&block)
    accounts = Accounts.new
    builder = Builder.new( accounts )
  
    builder.instance_exec(&block)
  
    accounts
  end

end


# Sample


# require 'lib/expensify'


acc = Expensify::expenses do
  
  expense_defaults :gst => true, :income => 100, :cat => "unknown"
  income_defaults  :gst => true
  
  
  define_expense :internet, :for => 'Internode: Internet', :income => 70, :cat => 'internet'
  define_expense :github,   :for => 'Github', :gst => false, :cat => 'services'
  define_expense :phone,    :for => 'Telstra: iPhone4', :cat => 'phone'
  
  
  income 1000000, Date.new(2010, 7, 13), :from => "Holding world to ransom"

  expense 200.00, Date.new(2010, 8, 3), :for => 'Evil Corp: Shark head laser mounting kit', :cat => 'equipment'
  expense 7.76, Date.new(2010, 8, 12), :for => 'Officeworks: Tudor Eco Notebook', :cat => 'stationary'
  expense 5.99, Date.new(2010, 8, 12), :for => 'Officeworks: Sharpie pen', :cat => 'stationary'
  expense 14.68, Date.new(2010, 8, 12), :for => 'Officeworks: Pk 300 System Cards', :cat => 'stationary'
  
  internet 49.95, Date.new(2010, 7, 14)
  internet 59.95, Date.new(2010, 8, 17)
  internet 69.95, Date.new(2010, 9, 14)
  
  github 8.08, Date.new( 2010, 7, 29 )
  github 8.13, Date.new( 2010, 8, 27 )
    
  phone 106.84, Date.new( 2010, 9, 15 )
   
end

acc.gst_report
acc.income_report