#! /usr/bin/python


class Asset:

  def __init__(self, name, value, rate):
    self.value          = value
    self.basis          = value
    self.rate           = rate
    self.name           = name

# self.value cannot go below 0 (since financial assets, w/o debt, cannot have negative values)
# returns amount that cannot be applied.

# examples:

# A)
# init values:
#   value = 1000
#   basis = 1000

# adj_value = 500
#   value = 1500
#   basis = 1500
#   return 0

# adj_value = -500
#   value = 1000
#   basis = 1000
#   return 0

# adj_value = -2000
#   value = 0
#   basis = 0
#   return 1000  -- (2000 - 1000)

# B) 
# init values:
#   value = 1500
#   basis = 1000
#   
#   adj_value = -500
#   value = 1000
#   basis = 1000 + -500 * (1000/1500)
#   return 0

#   adj_value = -1200
#   value = 0
#   basis = 0
#   return 200

#


  def apply_return(self):
    self.value *= (1 + self.rate)


class AssetTaxable(Asset):
  def adjust_value(self, adj_value):
    self.taxable_income = 0
    diff = 0
    if adj_value > 0:
      self.value += adj_value
      self.basis += adj_value
    else: 
      # no need to calc anything and keeps us from div. by zero.
      if self.value == 0:
        return adj_value 

      # calculate taxable income.
      diff = self.value + adj_value
      usable_amount = (diff < 0 and -self.value) or adj_value
      self.taxable_income = (1.0 - float(self.basis)/self.value) * usable_amount

      if diff < 0:
        self.value = 0 
        self.basis = 0
      else: 
        self.basis = self.basis + adj_value * (self.basis/self.value)
        self.value += adj_value
        diff = 0
    
    return diff

class AssetTaxDeferred(Asset):
  def adjust_value(self, adj_value):
    self.taxable_income = 0
    diff = 0
    if adj_value > 0:
      self.value += adj_value
    else: 
      # no need to calc anything and keeps us from div. by zero.
      if self.value == 0:
        return adj_value 

      # calculate taxable income.
      diff = self.value + adj_value

      usable_amount = (diff < 0 and -self.value) or adj_value
      self.taxable_income = usable_amount

      if diff < 0:
        self.value = 0 
      else: 
        self.value += adj_value
        diff = 0
    
    return diff

class AssetTaxFree(Asset):
  def adjust_value(self, adj_value):
    self.taxable_income = 0
    diff = 0
    if adj_value > 0:
      self.value += adj_value
    else: 
      # no need to calc anything and keeps us from div. by zero.
      if self.value == 0:
        return adj_value 

      diff = self.value + adj_value

      if diff < 0:
        self.value = 0 
      else: 
        self.value += adj_value
        diff = 0
    
    return diff
  



import inspect

def lineno():
  """Returns the current line number."""
  return inspect.currentframe().f_back.f_lineno


def unit_test():
  asset = AssetTaxable("Test", 1000, 0.12)
  excess = 0
  adj_value = 0

  assert(asset.value == 1000, lineno())
  assert(asset.basis == 1000, lineno())

  adj_value = 500
  excess = asset.adjust_value(adj_value)
  assert(excess == 0, lineno())
  assert(asset.value == 1500, lineno())
  assert(asset.basis == 1500, lineno())

  adj_value = -500
  excess = asset.adjust_value(adj_value)
  assert(excess == 0, lineno())
  assert(asset.value == 1000, lineno());
  assert(asset.basis == 1000, lineno())

  adj_value = -2000
  excess = asset.adjust_value(adj_value)
  assert(excess == -1000, lineno())
  assert(asset.value == 0, lineno())
  assert(asset.basis == 0, lineno())

  asset.value = 1500
  asset.basis = 1000

  adj_value = -500
  excess = asset.adjust_value(adj_value)
  assert(excess == 0, lineno())
  assert(asset.value == 1000, lineno())
  assert(asset.basis == 1000 + (1000/1500) * -500, lineno())

  adj_value = -1200
  excess = asset.adjust_value(adj_value)
  assert(excess == -200, lineno())
  assert(asset.value == 0, lineno())
  assert(asset.basis == 0, lineno())

  # taxable income  

  asset.value = 1000
  asset.basis = 500
  adj_value = -500
  asset.adjust_value(adj_value)
  #print asset.taxable_income
  assert(asset.taxable_income == -250, lineno())

  asset.value = 1000
  asset.basis = 0
  adj_value = -500
  asset.adjust_value(adj_value)
  assert(asset.taxable_income == -500, lineno())

  asset = AssetTaxDeferred("Test", 1000, 0.12)
  asset.value = 1000
  asset.basis = 500
  adj_value = -500
  asset.adjust_value(adj_value)
  assert(asset.taxable_income == -500, lineno())

  asset = AssetTaxable("Test", 1000, 0.12)
  #print "------------------"
  asset.value = 1000
  asset.basis = 250
  adj_value = -500
  asset.adjust_value(adj_value)
  assert(asset.taxable_income == -375, lineno())


if __name__ == '__main__':
  unit_test()