#   pyRCV2: Preferential vote counting
#   Copyright © 2020–2021  Lee Yingtong Li (RunasSudo)
#
#   This program is free software: you can redistribute it and/or modify
#   it under the terms of the GNU Affero General Public License as published by
#   the Free Software Foundation, either version 3 of the License, or
#   (at your option) any later version.
#
#   This program is distributed in the hope that it will be useful,
#   but WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#   GNU Affero General Public License for more details.
#
#   You should have received a copy of the GNU Affero General Public License
#   along with this program.  If not, see <https://www.gnu.org/licenses/>.

from pyRCV2.numbers.base import BaseNum, compatible_types

Big.DP = 12
_pos_epsilon = Big('10').pow(-6).div('2')
_neg_epsilon = _pos_epsilon.times('-1')

def _gfixed_set_dps(dps):
	global _pos_epsilon, _neg_epsilon
	Big.DP = 2 * dps
	_pos_epsilon = Big('10').pow(-dps).div('2')
	_neg_epsilon = _pos_epsilon.times('-1')

class FixedGuarded(BaseNum):
	"""
	Wrapper for big.js (fixed-point arithmetic)
	Implements guarded (quasi-exact) fixed-point
	"""
	
	@classmethod
	def _to_impl(cls, value):
		"""Implements BaseNum._to_impl"""
		return Big(value).round(Big.DP)
	
	def pp(self, dp):
		"""Implements BaseNum.pp"""
		return self.impl.toFixed(dp)
	
	@classmethod
	def _add_impl(cls, i1, i2):
		"""Implements BaseNum._add_impl"""
		return i1.plus(i2)
	@classmethod
	def _sub_impl(cls, i1, i2):
		"""Implements BaseNum._sub_impl"""
		return i1.minus(i2)
	@classmethod
	def _mul_impl(cls, i1, i2):
		"""Implements BaseNum._mul_impl"""
		return i1.times(i2)
	@classmethod
	def _truediv_impl(cls, i1, i2):
		"""Implements BaseNum._truediv_impl"""
		return i1.div(i2)
	
	@compatible_types
	def __eq__(self, other):
		"""Implements BaseNum.__eq__"""
		diff = self.impl.minus(other.impl)
		return diff.lt(_pos_epsilon) and diff.gt(_neg_epsilon)
	@compatible_types
	def __gt__(self, other):
		"""Implements BaseNum.__gt__"""
		diff = self.impl.minus(other.impl)
		return diff.gt(_pos_epsilon)
	@compatible_types
	def __ge__(self, other):
		"""Implements BaseNum.__ge__"""
		diff = self.impl.minus(other.impl)
		return diff.gt(_neg_epsilon)
	@compatible_types
	def __lt__(self, other):
		"""Implements BaseNum.__lt__"""
		diff = self.impl.minus(other.impl)
		return diff.lt(_neg_epsilon)
	@compatible_types
	def __le__(self, other):
		"""Implements BaseNum.__le__"""
		diff = self.impl.minus(other.impl)
		return diff.lt(_pos_epsilon)
	
	def __pow__(self, power):
		"""Implements BaseNum.__pow__"""
		return FixedGuarded._from_impl(self.impl.pow(power))
	
	def round(self, dps, mode):
		"""Implements BaseNum.round"""
		return FixedGuarded._from_impl(self.impl.round(dps, mode))