Class: InterestCalc::LineOfCreditCalculator

Inherits:
Object
  • Object
show all
Defined in:
lib/interest_calc/calculators/line_of_credit_calculator.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(interest_rate = 0.05) ⇒ LineOfCreditCalculator

Returns a new instance of LineOfCreditCalculator.



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# File 'lib/interest_calc/calculators/line_of_credit_calculator.rb', line 15

def initialize(interest_rate = 0.05)
  @interest_rate = interest_rate
  @logger = Logger.new(STDOUT)
end

Instance Attribute Details

#interest_rate ⇒ Object

Returns the value of attribute interest_rate.



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# File 'lib/interest_calc/calculators/line_of_credit_calculator.rb', line 12

def interest_rate
  @interest_rate
end

#logger ⇒ Object

Returns the value of attribute logger.



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# File 'lib/interest_calc/calculators/line_of_credit_calculator.rb', line 13

def logger
  @logger
end

Instance Method Details

#calculate(data) ⇒ Object 



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# File 'lib/interest_calc/calculators/line_of_credit_calculator.rb', line 20

def calculate(data)
  return_values = []
  nitem = nil
  changes = data[:changes]
  end_date = data[:end_date]

  if changes.nil? || changes.count < 1
    raise Exception.new "No changes to the line of credit provided. Please provide an array of changes data[:changes]"
  end

  changes.reverse!
  citem = changes.pop
  cdate = citem[:date]
  camount = citem[:amount]

  
  interest = 0
  nitem = changes.pop

  logger.debug "#{self.class.name}##{__method__}:calculation starts: #{cdate.at_beginning_of_month}"

  while(cdate <= cdate.at_end_of_month) do

    # amount has changed
    if(!nitem.nil? && nitem[:date] == cdate)
      logger.debug "#{self.class.name}##{__method__}: amount changing. OLD:#{camount} -- change:#{nitem[:amount]} -- NEW:#{camount + nitem[:amount]}"
      camount += nitem[:amount]
      nitem = changes.pop # pops nil if changes.empty?
    end

    interest += camount * interest_rate / 365.0

    if(cdate == cdate.at_end_of_month)
      return_values << {
        interest: interest,
        year: cdate.year,
        month: cdate.month
      }

      interest = 0
      logger.debug "#{self.class.name}##{__method__}: stored:#{return_values.last}"

      # if there are no further changes and this month is over, abort
      break if nitem.nil? && (end_date.nil? || cdate >= end_date)
    end

    

    cdate = cdate + 1.day
  end
  
  return return_values

end

#calculate_old(data) ⇒ Object

calculates the interest per month for an open line of credit



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# File 'lib/interest_calc/calculators/line_of_credit_calculator.rb', line 77

def calculate_old(data)

  return_values = []
  nitem = nil
  changes = data[:changes]

  if changes.nil? || changes.count < 1
    raise Exception.new "No changes to the line of credit provided. Please provide an array of changes data[:changes]"
  end

  changes = changes.reverse # allows us to use #pop
  citem = changes.pop
  cdate = citem[:date]
  camount = citem[:amount]

  puts "#{self.class.name}##{__method__}:calculation starts: #{cdate.at_beginning_of_month}"


  return_values << {year: cdate.year,
    month: cdate.month,
    interest: self.calculate_interest(camount, cdate)
  }

  # after this point the calculations for the first month are done

  cdate = cdate.at_beginning_of_month # normalize value to always be the first of the month
  i = 0

  # at the start changes won't be empty and
  # when all the changes have been popped from the stack nitem won't be empty
  while(!changes.empty? || !nitem.nil?)
    puts
    puts
    puts "#{self.class.name}##{__method__}: RUN #{i}"
    i+=1
    # only pop the next item if the previously popped item was used
    nitem = nitem || changes.pop
    ndate = nitem[:date]
    cdate = cdate.next_month
    new_return_value = {year: cdate.year, month: cdate.month}
    # the whole month needs to be calculated at the old amount
    if(ndate.at_beginning_of_month != cdate)
      puts "#{self.class.name}##{__method__}: FULL month calculation"
      return_values << {
        year: cdate.year,
        month: cdate.month,
        interest: self.calculate_interest(camount,cdate)
      }
    else # withdrawal/deposit within this month
      puts "#{self.class.name}##{__method__}: SPLIT month calculation"
      # calculate for first half of month with the old amount

      interest = calculate_interest(camount, cdate, ndate )
      puts "#{self.class.name}##{__method__}: amount changing. OLD:#{camount} -- change:#{nitem[:amount]} -- NEW:#{camount + nitem[:amount]}"
      # change the calculation amount by adding the withdrawal/deposit
      camount += nitem[:amount]

      # calculate interest for 2nd half of month
      interest += calculate_interest(camount, ndate)

      return_values << {
        year: cdate.year,
        month: cdate.month,
        interest: interest
      }

      # reset these variables to pop the next changes-item from the stack
      ndate = nil
      nitem = nil

      # do NOT change cdate as this is already on the 1st of the month and will
      # increase in the while loop

    end


  end # while !changes.empty?
  cdate = cdate.next_month
  # add one final month after the last month with changes
  # so that users know how much interest is per month going forward
  return_values << {year: cdate.year,
    month: cdate.month,
    interest: self.calculate_interest(camount, cdate)
  }

  return return_values

end

#print(data) ⇒ Object 



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# File 'lib/interest_calc/calculators/line_of_credit_calculator.rb', line 167

def print(data)
  values = calculate data

  total_interest = 0.0

  puts "--------------------------------------"
  puts "|    year-month  |     interest      |"
  puts "--------------------------------------"
  values.each do |item|
    ym = "#{item[:year]}-#{item[:month]}".ljust(16)
    i = item[:interest].to_f.round(2).to_s.rjust(19)
    puts "|#{ym}|#{i}|"

    total_interest += item[:interest].to_f
  end
  puts "|#{"2022".ljust(16)}|#{total_interest.round(2).to_s.rjust(19)}|"
  puts "--------------------------------------"
  return values
end