import numpy as np
import tensorflow as tf  # pylint: ignore-module
import builtins
import functools
import copy
import os
import collections


# ================================================================
# Make consistent with numpy
# ================================================================

clip = tf.clip_by_value


def sum(x, axis=None, keepdims=False):
    axis = None if axis is None else [axis]
    return tf.reduce_sum(x, axis=axis, keep_dims=keepdims)


def mean(x, axis=None, keepdims=False):
    axis = None if axis is None else [axis]
    return tf.reduce_mean(x, axis=axis, keep_dims=keepdims)


def var(x, axis=None, keepdims=False):
    meanx = mean(x, axis=axis, keepdims=keepdims)
    return mean(tf.square(x - meanx), axis=axis, keepdims=keepdims)


def std(x, axis=None, keepdims=False):
    return tf.sqrt(var(x, axis=axis, keepdims=keepdims))


def max(x, axis=None, keepdims=False):
    axis = None if axis is None else [axis]
    return tf.reduce_max(x, axis=axis, keep_dims=keepdims)


def min(x, axis=None, keepdims=False):
    axis = None if axis is None else [axis]
    return tf.reduce_min(x, axis=axis, keep_dims=keepdims)


def concatenate(arrs, axis=0):
    return tf.concat(axis=axis, values=arrs)


def argmax(x, axis=None):
    return tf.argmax(x, axis=axis)


def switch(condition, then_expression, else_expression):
    '''Switches between two operations depending on a scalar value (int or bool).
    Note that both `then_expression` and `else_expression`
    should be symbolic tensors of the *same shape*.

    # Arguments
        condition: scalar tensor.
        then_expression: TensorFlow operation.
        else_expression: TensorFlow operation.
    '''
    x_shape = copy.copy(then_expression.get_shape())
    x = tf.cond(tf.cast(condition, 'bool'),
                lambda: then_expression,
                lambda: else_expression)
    x.set_shape(x_shape)
    return x

# ================================================================
# Extras
# ================================================================


def l2loss(params):
    if len(params) == 0:
        return tf.constant(0.0)
    else:
        return tf.add_n([sum(tf.square(p)) for p in params])


def lrelu(x, leak=0.2):
    f1 = 0.5 * (1 + leak)
    f2 = 0.5 * (1 - leak)
    return f1 * x + f2 * abs(x)


def categorical_sample_logits(X):
    # https://github.com/tensorflow/tensorflow/issues/456
    U = tf.random_uniform(tf.shape(X))
    return argmax(X - tf.log(-tf.log(U)), axis=1)


# ================================================================
# Inputs
# ================================================================


def is_placeholder(x):
    return type(x) is tf.Tensor and len(x.op.inputs) == 0


class TfInput(object):
    def __init__(self, name="(unnamed)"):
        """Generalized Tensorflow placeholder. The main differences are:
            - possibly uses multiple placeholders internally and returns multiple values
            - can apply light postprocessing to the value feed to placeholder.
        """
        self.name = name

    def get(self):
        """Return the tf variable(s) representing the possibly postprocessed value
        of placeholder(s).
        """
        raise NotImplemented()

    def make_feed_dict(data):
        """Given data input it to the placeholder(s)."""
        raise NotImplemented()


class PlacholderTfInput(TfInput):
    def __init__(self, placeholder):
        """Wrapper for regular tensorflow placeholder."""
        super().__init__(placeholder.name)
        self._placeholder = placeholder

    def get(self):
        return self._placeholder

    def make_feed_dict(self, data):
        return {self._placeholder: data}


class BatchInput(PlacholderTfInput):
    def __init__(self, shape, dtype=tf.float32, name=None):
        """Creates a placeholder for a batch of tensors of a given shape and dtype

        Parameters
        ----------
        shape: [int]
            shape of a single elemenet of the batch
        dtype: tf.dtype
            number representation used for tensor contents
        name: str
            name of the underlying placeholder
        """
        super().__init__(tf.placeholder(dtype, [None] + list(shape), name=name))


class Uint8Input(PlacholderTfInput):
    def __init__(self, shape, name=None):
        """Takes input in uint8 format which is cast to float32 and divided by 255
        before passing it to the model.

        On GPU this ensures lower data transfer times.

        Parameters
        ----------
        shape: [int]
            shape of the tensor.
        name: str
            name of the underlying placeholder
        """

        super().__init__(tf.placeholder(tf.uint8, [None] + list(shape), name=name))
        self._shape = shape
        self._output = tf.cast(super().get(), tf.float32) / 255.0

    def get(self):
        return self._output


def ensure_tf_input(thing):
    """Takes either tf.placeholder of TfInput and outputs equivalent TfInput"""
    if isinstance(thing, TfInput):
        return thing
    elif is_placeholder(thing):
        return PlacholderTfInput(thing)
    else:
        raise ValueError("Must be a placeholder or TfInput")

# ================================================================
# Mathematical utils
# ================================================================


def huber_loss(x, delta=1.0):
    """Reference: https://en.wikipedia.org/wiki/Huber_loss"""
    return tf.where(
        tf.abs(x) < delta,
        tf.square(x) * 0.5,
        delta * (tf.abs(x) - 0.5 * delta)
    )

# ================================================================
# Optimizer utils
# ================================================================


def minimize_and_clip(optimizer, objective, var_list, clip_val=10):
    """Minimized `objective` using `optimizer` w.r.t. variables in
    `var_list` while ensure the norm of the gradients for each
    variable is clipped to `clip_val`
    """
    gradients = optimizer.compute_gradients(objective, var_list=var_list)
    for i, (grad, var) in enumerate(gradients):
        if grad is not None:
            gradients[i] = (tf.clip_by_norm(grad, clip_val), var)
    return optimizer.apply_gradients(gradients)


# ================================================================
# Global session
# ================================================================

def get_session():
    """Returns recently made Tensorflow session"""
    return tf.get_default_session()


def make_session(num_cpu):
    """Returns a session that will use <num_cpu> CPU's only"""
    tf_config = tf.ConfigProto(
        inter_op_parallelism_threads=num_cpu,
        intra_op_parallelism_threads=num_cpu)
    return tf.Session(config=tf_config)


def single_threaded_session():
    """Returns a session which will only use a single CPU"""
    return make_session(1)


ALREADY_INITIALIZED = set()


def initialize():
    """Initialize all the uninitialized variables in the global scope."""
    new_variables = set(tf.global_variables()) - ALREADY_INITIALIZED
    get_session().run(tf.variables_initializer(new_variables))
    ALREADY_INITIALIZED.update(new_variables)


def eval(expr, feed_dict=None):
    if feed_dict is None:
        feed_dict = {}
    return get_session().run(expr, feed_dict=feed_dict)


VALUE_SETTERS = collections.OrderedDict()


def set_value(v, val):
    global VALUE_SETTERS
    if v in VALUE_SETTERS:
        set_op, set_endpoint = VALUE_SETTERS[v]
    else:
        set_endpoint = tf.placeholder(v.dtype)
        set_op = v.assign(set_endpoint)
        VALUE_SETTERS[v] = (set_op, set_endpoint)
    get_session().run(set_op, feed_dict={set_endpoint: val})


# ================================================================
# Saving variables
# ================================================================


def load_state(fname, varlist=None):
    if varlist != None:
        saver = tf.train.Saver(var_list=varlist)
    else:
        saver = tf.train.Saver()
    saver.restore(get_session(), fname)


def save_state(fname):
    os.makedirs(os.path.dirname(fname), exist_ok=True)
    saver = tf.train.Saver()
    saver.save(get_session(), fname)

# ================================================================
# Model components
# ================================================================


def normc_initializer(std=1.0):
    def _initializer(shape, dtype=None, partition_info=None):  # pylint: disable=W0613
        out = np.random.randn(*shape).astype(np.float32)
        out *= std / np.sqrt(np.square(out).sum(axis=0, keepdims=True))
        return tf.constant(out)
    return _initializer


def conv2d(x, num_filters, name, filter_size=(3, 3), stride=(1, 1), pad="SAME", dtype=tf.float32, collections=None,
           summary_tag=None):
    with tf.variable_scope(name):
        stride_shape = [1, stride[0], stride[1], 1]
        filter_shape = [filter_size[0], filter_size[1], int(x.get_shape()[3]), num_filters]

        # there are "num input feature maps * filter height * filter width"
        # inputs to each hidden unit
        fan_in = intprod(filter_shape[:3])
        # each unit in the lower layer receives a gradient from:
        # "num output feature maps * filter height * filter width" /
        #   pooling size
        fan_out = intprod(filter_shape[:2]) * num_filters
        # initialize weights with random weights
        w_bound = np.sqrt(6. / (fan_in + fan_out))

        w = tf.get_variable("W", filter_shape, dtype, tf.random_uniform_initializer(-w_bound, w_bound),
                            collections=collections)
        b = tf.get_variable("b", [1, 1, 1, num_filters], initializer=tf.zeros_initializer(),
                            collections=collections)

        if summary_tag is not None:
            tf.summary.image(summary_tag,
                             tf.transpose(tf.reshape(w, [filter_size[0], filter_size[1], -1, 1]),
                                          [2, 0, 1, 3]),
                             max_images=10)

        return tf.nn.conv2d(x, w, stride_shape, pad) + b


def dense(x, size, name, weight_init=None, bias=True):
    w = tf.get_variable(name + "/w", [x.get_shape()[1], size], initializer=weight_init)
    ret = tf.matmul(x, w)
    if bias:
        b = tf.get_variable(name + "/b", [size], initializer=tf.zeros_initializer())
        return ret + b
    else:
        return ret


def wndense(x, size, name, init_scale=1.0):
    v = tf.get_variable(name + "/V", [int(x.get_shape()[1]), size],
                        initializer=tf.random_normal_initializer(0, 0.05))
    g = tf.get_variable(name + "/g", [size], initializer=tf.constant_initializer(init_scale))
    b = tf.get_variable(name + "/b", [size], initializer=tf.constant_initializer(0.0))

    # use weight normalization (Salimans & Kingma, 2016)
    x = tf.matmul(x, v)
    scaler = g / tf.sqrt(sum(tf.square(v), axis=0, keepdims=True))
    return tf.reshape(scaler, [1, size]) * x + tf.reshape(b, [1, size])


def densenobias(x, size, name, weight_init=None):
    return dense(x, size, name, weight_init=weight_init, bias=False)


def dropout(x, pkeep, phase=None, mask=None):
    mask = tf.floor(pkeep + tf.random_uniform(tf.shape(x))) if mask is None else mask
    if phase is None:
        return mask * x
    else:
        return switch(phase, mask * x, pkeep * x)


# ================================================================
# Theano-like Function
# ================================================================



def function(inputs, outputs, updates=None, givens=None):
    """Just like Theano function. Take a bunch of tensorflow placeholders and expersions
    computed based on those placeholders and produces f(inputs) -> outputs. Function f takes
    values to be feed to the inputs placeholders and produces the values of the experessions
    in outputs.

    Input values can be passed in the same order as inputs or can be provided as kwargs based
    on placeholder name (passed to constructor or accessible via placeholder.op.name).

    Example:
        x = tf.placeholder(tf.int32, (), name="x")
        y = tf.placeholder(tf.int32, (), name="y")
        z = 3 * x + 2 * y
        lin = function([x, y], z, givens={y: 0})

        with single_threaded_session():
            initialize()

            assert lin(2) == 6
            assert lin(x=3) == 9
            assert lin(2, 2) == 10
            assert lin(x=2, y=3) == 12

    Parameters
    ----------
    inputs: [tf.placeholder or TfInput]
        list of input arguments
    outputs: [tf.Variable] or tf.Variable
        list of outputs or a single output to be returned from function. Returned
        value will also have the same shape.
    """
    if isinstance(outputs, list):
        return _Function(inputs, outputs, updates, givens=givens)
    elif isinstance(outputs, (dict, collections.OrderedDict)):
        f = _Function(inputs, outputs.values(), updates, givens=givens)
        return lambda *args, **kwargs: type(outputs)(zip(outputs.keys(), f(*args, **kwargs)))
    else:
        f = _Function(inputs, [outputs], updates, givens=givens)
        return lambda *args, **kwargs: f(*args, **kwargs)[0]


class _Function(object):
    def __init__(self, inputs, outputs, updates, givens, check_nan=False):
        # for inpt in inputs:
            # if not issubclass(type(inpt), TfInput):
                # assert len(inpt.op.inputs) == 0, "inputs should all be placeholders of rl_algs.common.TfInput"
        self.inputs = inputs
        updates = updates or []
        self.update_group = tf.group(*updates)
        self.outputs_update = list(outputs) + [self.update_group]
        self.givens = {} if givens is None else givens
        self.check_nan = check_nan

    def _feed_input(self, feed_dict, inpt, value):
        if issubclass(type(inpt), TfInput):
            feed_dict.update(inpt.make_feed_dict(value))
        elif is_placeholder(inpt):
            feed_dict[inpt] = value

    def __call__(self, *args, **kwargs):
        assert len(args) <= len(self.inputs), "Too many arguments provided"
        feed_dict = {}
        # Update the args
        for inpt, value in zip(self.inputs, args):
            self._feed_input(feed_dict, inpt, value)
        # Update the kwargs
        kwargs_passed_inpt_names = set()
        for inpt in self.inputs[len(args):]:
            inpt_name = inpt.name.split(':')[0]
            inpt_name = inpt_name.split('/')[-1]
            assert inpt_name not in kwargs_passed_inpt_names, \
                "this function has two arguments with the same name \"{}\", so kwargs cannot be used.".format(inpt_name)
            if inpt_name in kwargs:
                kwargs_passed_inpt_names.add(inpt_name)
                self._feed_input(feed_dict, inpt, kwargs.pop(inpt_name))
            else:
                assert inpt in self.givens, "Missing argument " + inpt_name
        assert len(kwargs) == 0, "Function got extra arguments " + str(list(kwargs.keys()))
        # Update feed dict with givens.
        for inpt in self.givens:
            feed_dict[inpt] = feed_dict.get(inpt, self.givens[inpt])
        results = get_session().run(self.outputs_update, feed_dict=feed_dict)[:-1]
        if self.check_nan:
            if any(np.isnan(r).any() for r in results):
                raise RuntimeError("Nan detected")
        return results


def mem_friendly_function(nondata_inputs, data_inputs, outputs, batch_size):
    if isinstance(outputs, list):
        return _MemFriendlyFunction(nondata_inputs, data_inputs, outputs, batch_size)
    else:
        f = _MemFriendlyFunction(nondata_inputs, data_inputs, [outputs], batch_size)
        return lambda *inputs: f(*inputs)[0]


class _MemFriendlyFunction(object):
    def __init__(self, nondata_inputs, data_inputs, outputs, batch_size):
        self.nondata_inputs = nondata_inputs
        self.data_inputs = data_inputs
        self.outputs = list(outputs)
        self.batch_size = batch_size

    def __call__(self, *inputvals):
        assert len(inputvals) == len(self.nondata_inputs) + len(self.data_inputs)
        nondata_vals = inputvals[0:len(self.nondata_inputs)]
        data_vals = inputvals[len(self.nondata_inputs):]
        feed_dict = dict(zip(self.nondata_inputs, nondata_vals))
        n = data_vals[0].shape[0]
        for v in data_vals[1:]:
            assert v.shape[0] == n
        for i_start in range(0, n, self.batch_size):
            slice_vals = [v[i_start:builtins.min(i_start + self.batch_size, n)] for v in data_vals]
            for (var, val) in zip(self.data_inputs, slice_vals):
                feed_dict[var] = val
            results = tf.get_default_session().run(self.outputs, feed_dict=feed_dict)
            if i_start == 0:
                sum_results = results
            else:
                for i in range(len(results)):
                    sum_results[i] = sum_results[i] + results[i]
        for i in range(len(results)):
            sum_results[i] = sum_results[i] / n
        return sum_results

# ================================================================
# Modules
# ================================================================


class Module(object):
    def __init__(self, name):
        self.name = name
        self.first_time = True
        self.scope = None
        self.cache = {}

    def __call__(self, *args):
        if args in self.cache:
            print("(%s) retrieving value from cache" % (self.name,))
            return self.cache[args]
        with tf.variable_scope(self.name, reuse=not self.first_time):
            scope = tf.get_variable_scope().name
            if self.first_time:
                self.scope = scope
                print("(%s) running function for the first time" % (self.name,))
            else:
                assert self.scope == scope, "Tried calling function with a different scope"
                print("(%s) running function on new inputs" % (self.name,))
            self.first_time = False
            out = self._call(*args)
        self.cache[args] = out
        return out

    def _call(self, *args):
        raise NotImplementedError

    @property
    def trainable_variables(self):
        assert self.scope is not None, "need to call module once before getting variables"
        return tf.get_collection(tf.GraphKeys.TRAINABLE_VARIABLES, self.scope)

    @property
    def variables(self):
        assert self.scope is not None, "need to call module once before getting variables"
        return tf.get_collection(tf.GraphKeys.VARIABLES, self.scope)


def module(name):
    @functools.wraps
    def wrapper(f):
        class WrapperModule(Module):
            def _call(self, *args):
                return f(*args)
        return WrapperModule(name)
    return wrapper

# ================================================================
# Graph traversal
# ================================================================


VARIABLES = {}


def get_parents(node):
    return node.op.inputs


def topsorted(outputs):
    """
    Topological sort via non-recursive depth-first search
    """
    assert isinstance(outputs, (list, tuple))
    marks = {}
    out = []
    stack = []  # pylint: disable=W0621
    # i: node
    # jidx = number of children visited so far from that node
    # marks: state of each node, which is one of
    #   0: haven't visited
    #   1: have visited, but not done visiting children
    #   2: done visiting children
    for x in outputs:
        stack.append((x, 0))
        while stack:
            (i, jidx) = stack.pop()
            if jidx == 0:
                m = marks.get(i, 0)
                if m == 0:
                    marks[i] = 1
                elif m == 1:
                    raise ValueError("not a dag")
                else:
                    continue
            ps = get_parents(i)
            if jidx == len(ps):
                marks[i] = 2
                out.append(i)
            else:
                stack.append((i, jidx + 1))
                j = ps[jidx]
                stack.append((j, 0))
    return out


# ================================================================
# Flat vectors
# ================================================================

def var_shape(x):
    out = x.get_shape().as_list()
    assert all(isinstance(a, int) for a in out), \
        "shape function assumes that shape is fully known"
    return out


def numel(x):
    return intprod(var_shape(x))


def intprod(x):
    return int(np.prod(x))


def flatgrad(loss, var_list, clip_norm=None):
    grads = tf.gradients(loss, var_list)
    if clip_norm is not None:
        grads = [tf.clip_by_norm(grad, clip_norm=clip_norm) for grad in grads]
    return tf.concat(axis=0, values=[
        tf.reshape(grad if grad is not None else tf.zeros_like(v), [numel(v)])
        for (v, grad) in zip(var_list, grads)
    ])


class SetFromFlat(object):
    def __init__(self, var_list, dtype=tf.float32):
        assigns = []
        shapes = list(map(var_shape, var_list))
        total_size = np.sum([intprod(shape) for shape in shapes])

        self.theta = theta = tf.placeholder(dtype, [total_size])
        start = 0
        assigns = []
        for (shape, v) in zip(shapes, var_list):
            size = intprod(shape)
            assigns.append(tf.assign(v, tf.reshape(theta[start:start + size], shape)))
            start += size
        self.op = tf.group(*assigns)

    def __call__(self, theta):
        get_session().run(self.op, feed_dict={self.theta: theta})


class GetFlat(object):
    def __init__(self, var_list):
        self.op = tf.concat(axis=0, values=[tf.reshape(v, [numel(v)]) for v in var_list])

    def __call__(self):
        return get_session().run(self.op)

# ================================================================
# Misc
# ================================================================


def fancy_slice_2d(X, inds0, inds1):
    """
    like numpy X[inds0, inds1]
    XXX this implementation is bad
    """
    inds0 = tf.cast(inds0, tf.int64)
    inds1 = tf.cast(inds1, tf.int64)
    shape = tf.cast(tf.shape(X), tf.int64)
    ncols = shape[1]
    Xflat = tf.reshape(X, [-1])
    return tf.gather(Xflat, inds0 * ncols + inds1)


# ================================================================
# Scopes
# ================================================================


def scope_vars(scope, trainable_only=False):
    """
    Get variables inside a scope
    The scope can be specified as a string

    Parameters
    ----------
    scope: str or VariableScope
        scope in which the variables reside.
    trainable_only: bool
        whether or not to return only the variables that were marked as trainable.

    Returns
    -------
    vars: [tf.Variable]
        list of variables in `scope`.
    """
    return tf.get_collection(
        tf.GraphKeys.TRAINABLE_VARIABLES if trainable_only else tf.GraphKeys.VARIABLES,
        scope=scope if isinstance(scope, str) else scope.name
    )


def scope_name():
    """Returns the name of current scope as a string, e.g. deepq/q_func"""
    return tf.get_variable_scope().name


def absolute_scope_name(relative_scope_name):
    """Appends parent scope name to `relative_scope_name`"""
    return scope_name() + "/" + relative_scope_name


def lengths_to_mask(lengths_b, max_length):
    """
    Turns a vector of lengths into a boolean mask

    Args:
        lengths_b: an integer vector of lengths
        max_length: maximum length to fill the mask

    Returns:
        a boolean array of shape (batch_size, max_length)
        row[i] consists of True repeated lengths_b[i] times, followed by False
    """
    lengths_b = tf.convert_to_tensor(lengths_b)
    assert lengths_b.get_shape().ndims == 1
    mask_bt = tf.expand_dims(tf.range(max_length), 0) < tf.expand_dims(lengths_b, 1)
    return mask_bt


def in_session(f):
    @functools.wraps(f)
    def newfunc(*args, **kwargs):
        with tf.Session():
            f(*args, **kwargs)
    return newfunc


_PLACEHOLDER_CACHE = {}  # name -> (placeholder, dtype, shape)


def get_placeholder(name, dtype, shape):
    if name in _PLACEHOLDER_CACHE:
        out, dtype1, shape1 = _PLACEHOLDER_CACHE[name]
        assert dtype1 == dtype and shape1 == shape
        return out
    else:
        out = tf.placeholder(dtype=dtype, shape=shape, name=name)
        _PLACEHOLDER_CACHE[name] = (out, dtype, shape)
        return out


def get_placeholder_cached(name):
    return _PLACEHOLDER_CACHE[name][0]


def flattenallbut0(x):
    return tf.reshape(x, [-1, intprod(x.get_shape().as_list()[1:])])


def reset():
    global _PLACEHOLDER_CACHE
    global VARIABLES
    _PLACEHOLDER_CACHE = {}
    VARIABLES = {}
    tf.reset_default_graph()