import tensorflow as tf

from gym.spaces import Discrete, Box

def observation_input(ob_space, batch_size=None, name='Ob'):

    '''

    Build observation input with encoding depending on the 

    observation space type

    Params:

    ob_space: observation space (should be one of gym.spaces)

    batch_size: batch size for input (default is None, so that resulting input placeholder can take tensors with any batch size)

    name: tensorflow variable name for input placeholder

    returns: tuple (input_placeholder, processed_input_tensor)

    '''

    if isinstance(ob_space, Discrete):

        input_x  = tf.placeholder(shape=(batch_size,), dtype=tf.int32, name=name)

        processed_x = tf.to_float(tf.one_hot(input_x, ob_space.n))

        return input_x, processed_x

    elif isinstance(ob_space, Box):

        input_shape = (batch_size,) + ob_space.shape

        input_x = tf.placeholder(shape=input_shape, dtype=ob_space.dtype, name=name)

        processed_x = tf.to_float(input_x)

        return input_x, processed_x

    else:

        raise NotImplementedError