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

from .generic import Stack, flatten_list, expand_list, isNumber, isOperator
from .render import txt, tex
from .str2tokens import str2tokens
from .operator import op

__all__ = ['Expression']

class Expression(object):
    """A calculus expression. Today it can andle only expression with numbers later it will be able to manipulate unknown"""

    STR_RENDER = tex
    DEFAULT_RENDER = tex

    @classmethod
    def set_render(cls, render):
        cls.STR_RENDER = render

    @classmethod
    def set_default_render(cls):
        cls.set_render(cls.DEFAULT_RENDER)

    def __init__(self, exp):
        """ Initiate the expression

        :param exp: the expression. It can be a string or a list of postfix tokens.
        """
        if type(exp) == str:
            #self._exp = exp
            self.postfix_tokens = str2tokens(exp) # les tokens seront alors stockés dans self.tokens temporairement
        elif type(exp) == list:
            self.postfix_tokens = flatten_list([tok.postfix_tokens if self.isExpression(tok) else tok for tok in exp])

        self._isExpression = 1

    def __str__(self):
        """
        Overload str
        If you want to changer render set Expression.RENDER
        """
        return self.STR_RENDER(self.postfix_tokens)

    def __repr__(self):
        return "< Expression " + str(self.postfix_tokens) + ">"

    def render(self, render = lambda  x:str(x)):
        """ Same as __str__ but accept render as argument
        :param render: function which render the list of token (postfix form) to string

        """
        # TODO: I don't like the name of this method |ven. janv. 17 12:48:14 CET 2014
        return render(self.postfix_tokens)

    ## ---------------------
    ## Mechanism functions

    def simplify(self):
        """ Generator which return steps for computing the expression  """
        if not self.can_go_further():
            yield self.STR_RENDER(self.postfix_tokens) 
        else:
            self.compute_exp() 
            old_s = ''
            for s in self.steps:
                new_s = self.STR_RENDER(s)
                # Astuce pour éviter d'avoir deux fois la même étape (par exemple pour la transfo d'une division en fraction)
                if new_s != old_s:
                    old_s = new_s
                    yield new_s
            for s in self.child.simplify():
                if old_s != s:
                    yield s
    def simplified(self):
        """ Get the simplified version of the expression """
        if not self.can_go_further():
            return self.postfix_tokens[0]
        else:
            return self.child.simplified()

    def can_go_further(self):
        """Check whether it's a last step or not. If not create self.child the next expression.
        :returns: 1 if it's not the last step, 0 otherwise
        """
        if len(self.postfix_tokens) == 1:
            return 0
        else:
            return 1

    def compute_exp(self):
        """ Create self.child with self.steps to go up to it """
        self.steps = [self.postfix_tokens]

        tokenList = self.postfix_tokens.copy()
        tmpTokenList = []

        while len(tokenList) > 2: 
            # on va chercher les motifs du genre A B +, quand l'operateur est d'arité 2, pour les calculer 
            if isNumber(tokenList[0]) and isNumber(tokenList[1]) \
                    and isOperator(tokenList[2]) and tokenList[2].arity == 2 :
                
                # S'il y a une opération à faire
                op1 = tokenList[0]
                op2 = tokenList[1]
                operator = tokenList[2]
                
                res = operator(op1, op2)

                tmpTokenList.append(res)

                # Comme on vient de faire le calcul, on peut détruire aussi les deux prochains termes
                del tokenList[0:3]

            # Et les motifs du gens A -, quand l'operateur est d'arité 1
            elif isNumber(tokenList[0]) \
                    and isOperator(tokenList[1]) and tokenList[1].arity == 1:
                
                # S'il y a une opération à faire
                op1 = tokenList[0]
                operator = tokenList[1]

                res = operator(op1)

                tmpTokenList.append(res)

                # Comme on vient de faire le calcul, on peut détruire aussi les deux prochains termes
                del tokenList[0:2]

            else:
                tmpTokenList.append(tokenList[0])

                del tokenList[0]
        tmpTokenList += tokenList

        steps = expand_list(tmpTokenList)

        if len(steps[:-1]) > 0:
            self.steps += [flatten_list(s) for s in steps[:-1]]

        self.child = Expression(steps[-1])

    def isExpression(self, other):
        try:
            other._isExpression
        except AttributeError:
                return 0
        return  1

    # -----------
    # Expression act as container from self.postfix_tokens

    def __getitem__(self, index):
        return self.postfix_tokens[index]

    def __setitem__(self, index, value):
        self.postfix_tokens[index] = value

    # -----------
    # Some math manipulations

    def operate(self, other, operator):
        if type(other) == Expression:
            return Expression(self.postfix_tokens + other.postfix_tokens + [operator])
        elif type(other) == list:
            return Expression(self.postfix_tokens + other + [operator])
        else:
            return Expression(self.postfix_tokens + [other] + [operator])
    
    def roperate(self, other, operator):
        if type(other) == Expression:
            return Expression(other.postfix_tokens + self.postfix_tokens + [operator])
        elif type(other) == list:
            return Expression(other + self.postfix_tokens + [operator])
        else:
            return Expression([other] + self.postfix_tokens + [operator])

    def __add__(self, other):
        return self.operate(other, op.add)

    def __radd__(self, other):
        return self.roperate(other, op.add)

    def __sub__(self, other):
        return self.operate(other, op.sub)

    def __rsub__(self, other):
        return self.roperate(other, op.sub)

    def __mul__(self, other):
        return self.operate(other, op.mul)

    def __rmul__(self, other):
        return self.roperate(other, op.mul)

    def __div__(self, other):
        return self.operate(other, op.div)

    def __rdiv__(self, other):
        return self.roperate(other, op.div)

    def __pow__(self, other):
        return self.operate(other, op.pow)

    def __neg__(self):
        return Expression(self.postfix_tokens + [op.sub1])
    

def test(exp):
    a = Expression(exp)
    print(a)
    for i in a.simplify():
        print(i)

    print(type(a.simplified()), ":", a.simplified())

    print("\n")

if __name__ == '__main__':
    Expression.set_render(txt)
    exp1 = "2 ^ 3 * 5"
    test(exp1)

    Expression.set_render(tex)

    test(exp1)

    from pymath.operator import op
    exp = [2, 3, op.pw, 5, op.mul]
    test(exp)

    Expression.set_render(txt)

    test([Expression(exp1), Expression(exp), op.add])

    exp = "1 + 3 * 5"
    e = Expression(exp)
    f = -e
    print(f)

    #exp = "2 * 3 * 3 * 5"
    #test(exp)

    #exp = "2 * 3 + 3 * 5"
    #test(exp)

    #exp = "2 * ( 3 + 4 ) + 3 * 5"
    #test(exp)

    #exp = "2 * ( 3 + 4 ) + ( 3 - 4 ) * 5"
    #test(exp)
    #
    #exp = "2 * ( 2 - ( 3 + 4 ) ) + ( 3 - 4 ) * 5"
    #test(exp)
    #
    #exp = "2 * ( 2 - ( 3 + 4 ) ) + 5 * ( 3 - 4 )"
    #test(exp)
    #
    #exp = "2 + 5 * ( 3 - 4 )"
    #test(exp)

    #exp = "( 2 + 5 ) * ( 3 - 4 )^4"
    #test(exp)

    #exp = "( 2 + 5 ) * ( 3 * 4 )"
    #test(exp)

    #exp = "( 2 + 5 - 1 ) / ( 3 * 4 )"
    #test(exp)

    #exp = "( 2 + 5 ) / ( 3 * 4 ) + 1 / 12"
    #test(exp)

    #exp = "( 2+ 5 )/( 3 * 4 ) + 1 / 2"
    #test(exp)

    #exp="(-2+5)/(3*4)+1/12+5*5"
    #test(exp)

    #exp="-2*4(12 + 1)(3-12)"
    #test(exp)


    #exp="(-2+5)/(3*4)+1/12+5*5"
    #test(exp)

    # TODO: The next one doesn't work  |ven. janv. 17 14:56:58 CET 2014
    #exp="-2*(-a)(12 + 1)(3-12)"
    #e = Expression(exp)
    #print(e)

    ## Can't handle it yet!!
    #exp="-(-2)"
    #test(exp)

    #import doctest
    #doctest.testmod()

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