"""
One hot Op
"""

#from theano import tensor
from theano.tensor import as_tensor, Tensor
from theano.gof import op
from theano.gof.graph import Apply

import numpy

class OneHot(op.Op):
    """
    Construct a one-hot vector, x out of y.

    @todo: Document inputs and outputs
    @todo: Use 'bool' as output dtype? Or, at least 'int64' ? Not float64!
    @todo: Use 'bool' as output dtype, not 'int64' ?
    @todo: Allow this to operate on column vectors (Tensor)
    @todo: Describe better.
    """

    def make_node(self, x, y):
        """
        @type x: Vector L{Tensor} of integers
        @param x: The entries of the one-hot vector to be one.
        @type y: Integer scalar L{Tensor}
        @param y: The length (#columns) of the one-hot vectors.
        @return: A L{Tensor} of one-hot vectors

        @precondition: x < y for all entries of x
        @todo: Check that x and y are int types
        """
        x = as_tensor(x)
        y = as_tensor(y)
        #assert x.dtype[0:3] == "int"
        #assert y.dtype[0:3] == "int"
        inputs = [x, y]
        ##outputs = [tensor.Tensor("int64", broadcastable=[False, False])]
        #outputs = [tensor.Tensor("float64", broadcastable=[False, False])]
        #outputs = [Tensor("int64", broadcastable=[False, False])]
        outputs = [Tensor("float64", broadcastable=[False, False]).make_result()]
        node = Apply(op = self, inputs = inputs, outputs = outputs)
        return node

    def perform(self, node, (x, y), (out, )):
        assert x.dtype == "int64" or x.dtype == "int32"
        assert x.ndim == 1
        assert y.dtype == "int64" or x.dtype == "int32"
        assert y.ndim == 0
        out[0] = numpy.zeros((x.shape[0], y), dtype="float64")
        for c in range(x.shape[0]):
            assert x[c] < y
            out[0][c, x[c]] = 1

    def grad(self, (x, y), (out_gradient, )):
        return None, None
one_hot = OneHot()