from types import SliceType
import descriptor_base

class LazyCTX:
    def __init__ (self, G): 
        self.G = G
    def _is_compatible_for_ops(self, g): 
        m1,m2  = self.G.mesh, g.mesh
        return m1 is m2 or m1 == m2
    def __eq__ (self, y):
        return isinstance(y, self.__class__) and self._is_compatible_for_ops(y.G)
    def __call__ (self, x): 
        if not isinstance(x, descriptor_base.Base): return x
        tmp = self.G.copy()
        x(tmp)
        return tmp

def get_indices_in_dict( d): 
    if not ( ('indicesL' in d and 'indicesR' in d) or 'indices' in d) : return ()

    indicesL = list ( d.pop('indicesL',()) or d.pop('indices',()) )
    indicesR = list ( d.pop('indicesR',()) or indicesL  )

    # Now check the indices
    ty = set([type(x) for x in indicesL]+[type(x) for x in indicesR])
    assert len(ty) !=0, "No indices found !"
    assert len(ty)==1, " All indices must have the same type %s"%ty

    # If the indices are not string, make them string anyway
    indicesL = [ str(x) for x in indicesL ]     
    indicesR = [ str(x) for x in indicesR ]  

    return indicesL, indicesR