#!/usr/bin/env python
# encoding: utf-8

from .render import Renderable
from decimal import Decimal
from .generic import transpose_fill


class Explicable(Renderable):

    """ An Explicable object is an object which can be explicable!

    It's a parent class of a more classical Expression, Fraction and Polynom (and later square root)
    Child class will have the following method
        * explain: Generator which return steps which leed to himself

    """

    def __init__(self, *args, **kwargs):
        super(Explicable, self).__init__()
        self.steps = []

    def explain(self, noself=True):
        r""" Generate and render steps  which leed to itself

        :param noself: does explain return self

        >>> action = Explicable()
        >>> from .expression import Expression
        >>> action.postfix_tokens = Expression('42')
        >>> action.this_append_before([Expression('2+10*4'), Expression('2+40')])
        >>> for i in action.explain():
        ...    print(i)
        2 + 10 \times 4
        2 + 40
        42

        """
        old_s = ''
        # les étapes pour l'atteindre
        try:
            for s in self.steps:
                try:
                    new_s = self.STR_RENDER(s.postfix_tokens)
                except AttributeError:
                    new_s = self.STR_RENDER(s)

                if not self.is_same_step(new_s, old_s):
                    old_s = new_s
                    yield new_s

        except AttributeError:
            pass

        if noself:
            # Lui même
            new_s = self.STR_RENDER(self.postfix_tokens)
            if not self.is_same_step(new_s, old_s):
                yield new_s

    def is_same_step(self, new, old):
        """Return whether the new step is the same than old step
        """
        try:
            if new.replace(" ", "") == old.replace(" ", ""):
                return True
            else:
                return False
        except AttributeError:
            if new == old:
                return True
            else:
                return False

    def this_append_before(self, steps):
        """ Add steps at the beginning of self.steps

        :param steps: list of steps that append before

        >>> e = Explicable()
        >>> s = ['eat', 'sleep']
        >>> e.this_append_before(s)
        >>> print(e.steps)
        ['eat', 'sleep']
        >>> s0 = ['cook']
        >>> e.this_append_before(s0)
        >>> print(e.steps)
        ['cook', 'eat', 'sleep']
        """
        self.steps = steps + self.steps

    @staticmethod
    def merge_history(expl1, expl2, operation):
        """ Take two Explicable objects, explain where they are from and merge their history

        /!\ Using this method make the two objects amnesiac

        :param expl1: fist explicable
        :param expl2: second explicable
        :param operation: the operation that link them
        :returns: the list of steps

        >>> from .expression import Expression
        >>> from .operator import op
        >>> action1 = Explicable()
        >>> action1.postfix_tokens = Expression('42')
        >>> action1.this_append_before([Expression('2+10*4'), Expression('2+40')])
        >>> action2 = Explicable()
        >>> action2.postfix_tokens = Expression('24')
        >>> action2.this_append_before([Expression('2*12')])
        >>> m_history = Explicable().merge_history(action1, action2, op.add)
        >>> m_history
        <generator object transpose_fill ...>
        >>> for i in m_history:
        ...    print(i)
        ['2 + 10 \\times 4', '2 \\times 12', +]
        ['2 + 40', '24', +]
        ['42', '24', +]

        """
        steps1 = list(expl1.explain())
        steps2 = list(expl2.explain())

        return transpose_fill([steps1, steps2, [operation]])


class Explicable_int(int, Explicable):

    """ An Explicable_int is an int which can be explain """

    isNumber = True

    def __init__(self, val):
        super(Explicable_int, self).__init__(val)
        self._val = val
        self.postfix_tokens = [self]
        self.steps = []

    def simplify(self):
        return Explicable_int(self._val)

    def __txt__(self):
        return str(self._val)

    def __tex__(self):
        return str(self._val)


class Explicable_Decimal(Decimal, Explicable):

    """ An Explicable_Decimal is an decimal which can be explain """

    isNumber = True

    def __init__(self, val):
        super(Explicable_Decimal, self).__init__(val)
        self._val = val
        self.postfix_tokens = [self]
        self.steps = []

    def simplify(self):
        return Explicable_Decimal(self._val)

    def __txt__(self):
        return str(self._val)

    def __tex__(self):
        return str(self._val)


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