module FinancialMaths

# File lib/financial_maths.rb, line 145
def annuity_given_future(future_value, interest, term)
   (future_value.to_f * (interest.to_f / ((1 + interest) ** term)-1)).round(4)
end

# File lib/financial_maths.rb, line 139
def annuity_given_present(present_value, interest, term)
  interest = interest.to_f
   (present_value.to_f * ((interest * (1+interest) ** term) / (((1 + interest) ** term) -1))).round(4)
end

# File lib/financial_maths.rb, line 204
def anticipated_fixed_payment(present_value, rate, term)
              ((present_value.to_f) / ((1 - (1 - rate.to_f ) ** term ) / rate.to_f )).round(4)
end

# File lib/financial_maths.rb, line 73
def anticipated_fixed_payment_amortization(periods, amount, rate, payment)
  result = []
  result << {:period=> 0, :monthly_payment => nil,
             :interest => amount * rate, :payment => nil,
             :balance => amount}

  for i in 1..periods
    month_payment = payment * ((1-rate) ** (periods - i))
    interest = payment - month_payment
    amount -= month_payment
    #date += 1
    result << {:period=> i,
               :payment => payment,
               :interest => interest,
               :monthly_payment => month_payment,
               :balance => amount}
  end
  result
end

# File lib/financial_maths.rb, line 197
def anticipated_interest(rate, periods)
  (1 - (( 1 / ( rate.to_f + 1 )) ** (1.0 / periods)))
end

# File lib/financial_maths.rb, line 104
def anticipated_interest_amortization(periods, amount, rate)
  result = []

  for i in 0..(periods - 2) do  
    result << {period: i, monthly_payment: 0, interest: (amount * rate), payment: (amount * rate), balance: 0}
  end 

  result << {period: periods - 1, monthly_payment: amount , interest: amount * rate, payment: amount * rate + amount, balance: 0}
end

# File lib/financial_maths.rb, line 26
def anticipated_variable_payment_amortization(periods, amount, rate,  payment)
      result = []
  #result << {:period=> 0, :monthly_payment => nil, :interest => nil, :payment => nil, :balance => amount}

  for i in 0..periods-1
    interest = amount * rate
    month_payment = payment + interest
    if i == periods
      amount -= amount
    else
      amount -= payment
    end

    #date += 1
    result << {:period=> i,
               :payment => month_payment,
               :interest => interest,
               :monthly_payment => payment,
               :balance => amount}
  end
  result
end

# File lib/financial_maths.rb, line 50
def due_fixed_payment_amortization(periods, amount, rate, payment)
  result = []
  result << {:period=> 0, :monthly_payment => nil, :interest => nil, :payment => nil, :balance => amount}

  for i in 1..periods
    interest = amount * rate
    month_payment = payment - interest
    if i == periods
      amount -= amount
    else
      amount -= month_payment
    end
    
    #date += 1
    result << {:period=> i,
               :payment => payment,
               :interest => interest,
               :monthly_payment => month_payment,
               :balance => amount}
  end
  result
end

# File lib/financial_maths.rb, line 93
def due_interest_amortization(periods, amount, rate)
  result = []
  result << {:period=> 0, :monthly_payment => nil, :interest => nil, :payment => nil, :balance => amount}
  
  for i in 1..(periods - 1) do  
    result << {period: i, monthly_payment: 0, interest: (amount * rate), payment: (amount * rate), balance: amount}
  end 

  result << {period: periods, monthly_payment: amount , interest: amount * rate, payment: amount * rate + amount, balance: 0}
end

# File lib/financial_maths.rb, line 5
def due_variable_payment_amortization(periods, amount, rate,  payment)
  result = []
  result << {:period=> 0, :monthly_payment => nil, :interest => nil, :payment => nil, :balance => amount}

  for i in 1..periods
    interest = amount * rate
    month_payment = payment + interest
    if i == periods
      amount -= amount
    else
      amount -= payment
    end
    result << {:period=> i,
               :payment => month_payment,
               :interest => interest,
               :monthly_payment => payment,
               :balance => amount}
  end
  result
end

# File lib/financial_maths.rb, line 171
def efective_given_nominal_anticipated(nominal_rate, term)
  (((1/((1-((nominal_rate.to_f/100)/term))**term))-1)*100).round(4)
end

# File lib/financial_maths.rb, line 164
def efective_given_nominal_due(nominal_rate, term)
  ((((1+((nominal_rate.to_f/100)/term))**term)-1).round(6))*100
end

# File lib/financial_maths.rb, line 155
def future_given_annuity(annuity, interest, term)
  (annuity * (((1 + interest.to_f) ** term) -1) / interest.to_f ).round(4)
end

# File lib/financial_maths.rb, line 129
def future_given_present(present_value, interest, term)
  (present_value.to_f * (1 + interest.to_f) ** term).round(4)
end

# File lib/financial_maths.rb, line 181
def nominal_anticipated_given_efective(effective_rate, periods)
  nominalRate = (1+(effective_rate.to_f/100))**(1/periods.to_f)-1
  toAnticipated = nominalRate / (1+nominalRate)
  (toAnticipated * periods.to_f * 100).round(4)
end

# File lib/financial_maths.rb, line 190
def nominal_due_given_efective(effective_rate, periods)
                    ((((1 + (effective_rate.to_f/100))**(1/periods.to_f)-1)*periods.to_f)*100).round(4)
end

# File lib/financial_maths.rb, line 150
def present_given_annuity(annuity, interest, term)
  (annuity.to_f * (((1 + interest.to_f) ** term) -1) / (interest.to_f * (1 + interest.to_f) ** term )).round(4)
end

# File lib/financial_maths.rb, line 134
def present_given_future(future_value, interest, term)
  (future_value.to_f / (1 +interest.to_f) ** term).round(4)
end

# File lib/financial_maths.rb, line 114
def unique_payment_amortization(periods, amount, rate)
  result = []
  result << {:period=> 0, :monthly_payment => nil, :interest => nil, :payment => nil, :balance => amount}
  
  interest = (amount * rate) * periods
  
  for i in 1..(periods - 1) do  
    result << {:period=> i, :monthly_payment => 0, :interest => 0, :payment => 0, :balance => amount}
  end 
  
  result << {:period=> periods, :monthly_payment => amount, :interest => interest, :payment => amount + interest , :balance => 0}
end

# File lib/financial_maths.rb, line 208
def variable_payment(amount, periods)
  amount.to_f / periods
end