"""Recurrent layers backed by cuDNN.
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

from .. import backend as K
from .. import initializers
from .. import regularizers
from .. import constraints
from .recurrent import RNN
from ..layers import InputSpec

from collections import namedtuple


class _CuDNNRNN(RNN):
    """Private base class for CuDNNGRU and CuDNNLSTM.

    # Arguments
        return_sequences: Boolean. Whether to return the last output.
            in the output sequence, or the full sequence.
        return_state: Boolean. Whether to return the last state
            in addition to the output.
        stateful: Boolean (default False). If True, the last state
            for each sample at index i in a batch will be used as initial
            state for the sample of index i in the following batch.
    """

    def __init__(self,
                 return_sequences=False,
                 return_state=False,
                 go_backwards=False,
                 stateful=False,
                 **kwargs):
        if K.backend() != 'tensorflow':
            raise RuntimeError('CuDNN RNNs are only available '
                               'with the TensorFlow backend.')
        super(RNN, self).__init__(**kwargs)
        self.return_sequences = return_sequences
        self.return_state = return_state
        self.go_backwards = go_backwards
        self.stateful = stateful
        self.supports_masking = False
        self.input_spec = [InputSpec(ndim=3)]
        if hasattr(self.cell.state_size, '__len__'):
            state_size = self.cell.state_size
        else:
            state_size = [self.cell.state_size]
        self.state_spec = [InputSpec(shape=(None, dim))
                           for dim in state_size]
        self.constants_spec = None
        self._states = None
        self._num_constants = None

    def _canonical_to_params(self, weights, biases):
        import tensorflow as tf
        weights = [tf.reshape(x, (-1,)) for x in weights]
        biases = [tf.reshape(x, (-1,)) for x in biases]
        return tf.concat(weights + biases, 0)

    def call(self, inputs, mask=None, training=None, initial_state=None):
        if isinstance(mask, list):
            mask = mask[0]
        if mask is not None:
            raise ValueError('Masking is not supported for CuDNN RNNs.')

        # input shape: `(samples, time (padded with zeros), input_dim)`
        # note that the .build() method of subclasses MUST define
        # self.input_spec and self.state_spec with complete input shapes.
        if isinstance(inputs, list):
            initial_state = inputs[1:]
            inputs = inputs[0]
        elif initial_state is not None:
            pass
        elif self.stateful:
            initial_state = self.states
        else:
            initial_state = self.get_initial_state(inputs)

        if len(initial_state) != len(self.states):
            raise ValueError('Layer has ' + str(len(self.states)) +
                             ' states but was passed ' +
                             str(len(initial_state)) +
                             ' initial states.')

        if self.go_backwards:
            # Reverse time axis.
            inputs = K.reverse(inputs, 1)
        output, states = self._process_batch(inputs, initial_state)

        if self.stateful:
            updates = []
            for i in range(len(states)):
                updates.append((self.states[i], states[i]))
            self.add_update(updates, inputs)

        if self.return_state:
            return [output] + states
        else:
            return output

    def get_config(self):
        config = {'return_sequences': self.return_sequences,
                  'return_state': self.return_state,
                  'go_backwards': self.go_backwards,
                  'stateful': self.stateful}
        base_config = super(RNN, self).get_config()
        return dict(list(base_config.items()) + list(config.items()))

    @classmethod
    def from_config(cls, config):
        return cls(**config)

    @property
    def trainable_weights(self):
        if self.trainable and self.built:
            return [self.kernel, self.recurrent_kernel, self.bias]
        return []

    @property
    def non_trainable_weights(self):
        if not self.trainable and self.built:
            return [self.kernel, self.recurrent_kernel, self.bias]
        return []

    @property
    def losses(self):
        return super(RNN, self).losses

    def get_losses_for(self, inputs=None):
        return super(RNN, self).get_losses_for(inputs=inputs)


class CuDNNGRU(_CuDNNRNN):
    """Fast GRU implementation backed by [CuDNN](https://developer.nvidia.com/cudnn).

    Can only be run on GPU, with the TensorFlow backend.

    # Arguments
        units: Positive integer, dimensionality of the output space.
        kernel_initializer: Initializer for the `kernel` weights matrix,
            used for the linear transformation of the inputs.
            (see [initializers](../initializers.md)).
        recurrent_initializer: Initializer for the `recurrent_kernel`
            weights matrix,
            used for the linear transformation of the recurrent state.
            (see [initializers](../initializers.md)).
        bias_initializer: Initializer for the bias vector
            (see [initializers](../initializers.md)).
        kernel_regularizer: Regularizer function applied to
            the `kernel` weights matrix
            (see [regularizer](../regularizers.md)).
        recurrent_regularizer: Regularizer function applied to
            the `recurrent_kernel` weights matrix
            (see [regularizer](../regularizers.md)).
        bias_regularizer: Regularizer function applied to the bias vector
            (see [regularizer](../regularizers.md)).
        activity_regularizer: Regularizer function applied to
            the output of the layer (its "activation").
            (see [regularizer](../regularizers.md)).
        kernel_constraint: Constraint function applied to
            the `kernel` weights matrix
            (see [constraints](../constraints.md)).
        recurrent_constraint: Constraint function applied to
            the `recurrent_kernel` weights matrix
            (see [constraints](../constraints.md)).
        bias_constraint: Constraint function applied to the bias vector
            (see [constraints](../constraints.md)).
        return_sequences: Boolean. Whether to return the last output.
            in the output sequence, or the full sequence.
        return_state: Boolean. Whether to return the last state
            in addition to the output.
        stateful: Boolean (default False). If True, the last state
            for each sample at index i in a batch will be used as initial
            state for the sample of index i in the following batch.
    """

    def __init__(self, units,
                 kernel_initializer='glorot_uniform',
                 recurrent_initializer='orthogonal',
                 bias_initializer='zeros',
                 kernel_regularizer=None,
                 recurrent_regularizer=None,
                 bias_regularizer=None,
                 activity_regularizer=None,
                 kernel_constraint=None,
                 recurrent_constraint=None,
                 bias_constraint=None,
                 return_sequences=False,
                 return_state=False,
                 stateful=False,
                 **kwargs):
        self.units = units
        super(CuDNNGRU, self).__init__(
            return_sequences=return_sequences,
            return_state=return_state,
            stateful=stateful,
            **kwargs)

        self.kernel_initializer = initializers.get(kernel_initializer)
        self.recurrent_initializer = initializers.get(recurrent_initializer)
        self.bias_initializer = initializers.get(bias_initializer)

        self.kernel_regularizer = regularizers.get(kernel_regularizer)
        self.recurrent_regularizer = regularizers.get(recurrent_regularizer)
        self.bias_regularizer = regularizers.get(bias_regularizer)
        self.activity_regularizer = regularizers.get(activity_regularizer)

        self.kernel_constraint = constraints.get(kernel_constraint)
        self.recurrent_constraint = constraints.get(recurrent_constraint)
        self.bias_constraint = constraints.get(bias_constraint)

    @property
    def cell(self):
        Cell = namedtuple('cell', 'state_size')
        cell = Cell(state_size=self.units)
        return cell

    def build(self, input_shape):
        super(CuDNNGRU, self).build(input_shape)
        if isinstance(input_shape, list):
            input_shape = input_shape[0]
        input_dim = input_shape[-1]

        from tensorflow.contrib.cudnn_rnn.python.ops import cudnn_rnn_ops
        self._cudnn_gru = cudnn_rnn_ops.CudnnGRU(
            num_layers=1,
            num_units=self.units,
            input_size=input_dim,
            input_mode='linear_input')

        self.kernel = self.add_weight(shape=(input_dim, self.units * 3),
                                      name='kernel',
                                      initializer=self.kernel_initializer,
                                      regularizer=self.kernel_regularizer,
                                      constraint=self.kernel_constraint)
        self.recurrent_kernel = self.add_weight(
            shape=(self.units, self.units * 3),
            name='recurrent_kernel',
            initializer=self.recurrent_initializer,
            regularizer=self.recurrent_regularizer,
            constraint=self.recurrent_constraint)

        self.bias = self.add_weight(shape=(self.units * 6,),
                                    name='bias',
                                    initializer=self.bias_initializer,
                                    regularizer=self.bias_regularizer,
                                    constraint=self.bias_constraint)

        self.kernel_z = self.kernel[:, :self.units]
        self.recurrent_kernel_z = self.recurrent_kernel[:, :self.units]
        self.kernel_r = self.kernel[:, self.units: self.units * 2]
        self.recurrent_kernel_r = self.recurrent_kernel[:,
                                                        self.units:
                                                        self.units * 2]
        self.kernel_h = self.kernel[:, self.units * 2:]
        self.recurrent_kernel_h = self.recurrent_kernel[:, self.units * 2:]

        self.bias_z_i = self.bias[:self.units]
        self.bias_r_i = self.bias[self.units: self.units * 2]
        self.bias_h_i = self.bias[self.units * 2: self.units * 3]
        self.bias_z = self.bias[self.units * 3: self.units * 4]
        self.bias_r = self.bias[self.units * 4: self.units * 5]
        self.bias_h = self.bias[self.units * 5:]

        self.built = True

    def _process_batch(self, inputs, initial_state):
        import tensorflow as tf
        inputs = tf.transpose(inputs, (1, 0, 2))
        input_h = initial_state[0]
        input_h = tf.expand_dims(input_h, axis=0)

        params = self._canonical_to_params(
            weights=[
                self.kernel_r,
                self.kernel_z,
                self.kernel_h,
                self.recurrent_kernel_r,
                self.recurrent_kernel_z,
                self.recurrent_kernel_h,
            ],
            biases=[
                self.bias_r_i,
                self.bias_z_i,
                self.bias_h_i,
                self.bias_r,
                self.bias_z,
                self.bias_h,
            ],
        )
        outputs, h = self._cudnn_gru(
            inputs,
            input_h=input_h,
            params=params,
            is_training=True)

        if self.stateful or self.return_state:
            h = h[0]
        if self.return_sequences:
            output = tf.transpose(outputs, (1, 0, 2))
        else:
            output = outputs[-1]
        return output, [h]

    def get_config(self):
        config = {
            'units': self.units,
            'kernel_initializer': initializers.serialize(self.kernel_initializer),
            'recurrent_initializer':
                initializers.serialize(self.recurrent_initializer),
            'bias_initializer': initializers.serialize(self.bias_initializer),
            'kernel_regularizer': regularizers.serialize(self.kernel_regularizer),
            'recurrent_regularizer':
                regularizers.serialize(self.recurrent_regularizer),
            'bias_regularizer': regularizers.serialize(self.bias_regularizer),
            'activity_regularizer':
                regularizers.serialize(self.activity_regularizer),
            'kernel_constraint': constraints.serialize(self.kernel_constraint),
            'recurrent_constraint':
                constraints.serialize(self.recurrent_constraint),
            'bias_constraint': constraints.serialize(self.bias_constraint)}
        base_config = super(CuDNNGRU, self).get_config()
        return dict(list(base_config.items()) + list(config.items()))


class CuDNNLSTM(_CuDNNRNN):
    """Fast LSTM implementation with [CuDNN](https://developer.nvidia.com/cudnn).

    Can only be run on GPU, with the TensorFlow backend.

    # Arguments
        units: Positive integer, dimensionality of the output space.
        kernel_initializer: Initializer for the `kernel` weights matrix,
            used for the linear transformation of the inputs.
            (see [initializers](../initializers.md)).
        recurrent_initializer: Initializer for the `recurrent_kernel`
            weights matrix,
            used for the linear transformation of the recurrent state.
            (see [initializers](../initializers.md)).
        bias_initializer: Initializer for the bias vector
            (see [initializers](../initializers.md)).
        unit_forget_bias: Boolean.
            If True, add 1 to the bias of the forget gate at initialization.
            Setting it to true will also force `bias_initializer="zeros"`.
            This is recommended in [Jozefowicz et al. (2015)](
            http://www.jmlr.org/proceedings/papers/v37/jozefowicz15.pdf).
        kernel_regularizer: Regularizer function applied to
            the `kernel` weights matrix
            (see [regularizer](../regularizers.md)).
        recurrent_regularizer: Regularizer function applied to
            the `recurrent_kernel` weights matrix
            (see [regularizer](../regularizers.md)).
        bias_regularizer: Regularizer function applied to the bias vector
            (see [regularizer](../regularizers.md)).
        activity_regularizer: Regularizer function applied to
            the output of the layer (its "activation").
            (see [regularizer](../regularizers.md)).
        kernel_constraint: Constraint function applied to
            the `kernel` weights matrix
            (see [constraints](../constraints.md)).
        recurrent_constraint: Constraint function applied to
            the `recurrent_kernel` weights matrix
            (see [constraints](../constraints.md)).
        bias_constraint: Constraint function applied to the bias vector
            (see [constraints](../constraints.md)).
        return_sequences: Boolean. Whether to return the last output.
            in the output sequence, or the full sequence.
        return_state: Boolean. Whether to return the last state
            in addition to the output.
        stateful: Boolean (default False). If True, the last state
            for each sample at index i in a batch will be used as initial
            state for the sample of index i in the following batch.
    """
    def __init__(self, units,
                 kernel_initializer='glorot_uniform',
                 recurrent_initializer='orthogonal',
                 bias_initializer='zeros',
                 unit_forget_bias=True,
                 kernel_regularizer=None,
                 recurrent_regularizer=None,
                 bias_regularizer=None,
                 activity_regularizer=None,
                 kernel_constraint=None,
                 recurrent_constraint=None,
                 bias_constraint=None,
                 return_sequences=False,
                 return_state=False,
                 stateful=False,
                 **kwargs):
        self.units = units
        super(CuDNNLSTM, self).__init__(
            return_sequences=return_sequences,
            return_state=return_state,
            stateful=stateful,
            **kwargs)

        self.kernel_initializer = initializers.get(kernel_initializer)
        self.recurrent_initializer = initializers.get(recurrent_initializer)
        self.bias_initializer = initializers.get(bias_initializer)
        self.unit_forget_bias = unit_forget_bias

        self.kernel_regularizer = regularizers.get(kernel_regularizer)
        self.recurrent_regularizer = regularizers.get(recurrent_regularizer)
        self.bias_regularizer = regularizers.get(bias_regularizer)
        self.activity_regularizer = regularizers.get(activity_regularizer)

        self.kernel_constraint = constraints.get(kernel_constraint)
        self.recurrent_constraint = constraints.get(recurrent_constraint)
        self.bias_constraint = constraints.get(bias_constraint)

    @property
    def cell(self):
        Cell = namedtuple('cell', 'state_size')
        cell = Cell(state_size=(self.units, self.units))
        return cell

    def build(self, input_shape):
        super(CuDNNLSTM, self).build(input_shape)
        if isinstance(input_shape, list):
            input_shape = input_shape[0]
        input_dim = input_shape[-1]

        from tensorflow.contrib.cudnn_rnn.python.ops import cudnn_rnn_ops
        self._cudnn_lstm = cudnn_rnn_ops.CudnnLSTM(
            num_layers=1,
            num_units=self.units,
            input_size=input_dim,
            input_mode='linear_input')

        self.kernel = self.add_weight(shape=(input_dim, self.units * 4),
                                      name='kernel',
                                      initializer=self.kernel_initializer,
                                      regularizer=self.kernel_regularizer,
                                      constraint=self.kernel_constraint)
        self.recurrent_kernel = self.add_weight(
            shape=(self.units, self.units * 4),
            name='recurrent_kernel',
            initializer=self.recurrent_initializer,
            regularizer=self.recurrent_regularizer,
            constraint=self.recurrent_constraint)

        if self.unit_forget_bias:
            def bias_initializer(shape, *args, **kwargs):
                return K.concatenate([
                    self.bias_initializer((self.units * 5,), *args, **kwargs),
                    initializers.Ones()((self.units,), *args, **kwargs),
                    self.bias_initializer((self.units * 2,), *args, **kwargs),
                ])
        else:
            bias_initializer = self.bias_initializer
        self.bias = self.add_weight(shape=(self.units * 8,),
                                    name='bias',
                                    initializer=bias_initializer,
                                    regularizer=self.bias_regularizer,
                                    constraint=self.bias_constraint)

        self.kernel_i = self.kernel[:, :self.units]
        self.kernel_f = self.kernel[:, self.units: self.units * 2]
        self.kernel_c = self.kernel[:, self.units * 2: self.units * 3]
        self.kernel_o = self.kernel[:, self.units * 3:]

        self.recurrent_kernel_i = self.recurrent_kernel[:, :self.units]
        self.recurrent_kernel_f = (
            self.recurrent_kernel[:, self.units: self.units * 2])
        self.recurrent_kernel_c = (
            self.recurrent_kernel[:, self.units * 2: self.units * 3])
        self.recurrent_kernel_o = self.recurrent_kernel[:, self.units * 3:]

        self.bias_i_i = self.bias[:self.units]
        self.bias_f_i = self.bias[self.units: self.units * 2]
        self.bias_c_i = self.bias[self.units * 2: self.units * 3]
        self.bias_o_i = self.bias[self.units * 3: self.units * 4]
        self.bias_i = self.bias[self.units * 4: self.units * 5]
        self.bias_f = self.bias[self.units * 5: self.units * 6]
        self.bias_c = self.bias[self.units * 6: self.units * 7]
        self.bias_o = self.bias[self.units * 7:]

        self.built = True

    def _process_batch(self, inputs, initial_state):
        import tensorflow as tf
        inputs = tf.transpose(inputs, (1, 0, 2))
        input_h = initial_state[0]
        input_c = initial_state[1]
        input_h = tf.expand_dims(input_h, axis=0)
        input_c = tf.expand_dims(input_c, axis=0)

        params = self._canonical_to_params(
            weights=[
                self.kernel_i,
                self.kernel_f,
                self.kernel_c,
                self.kernel_o,
                self.recurrent_kernel_i,
                self.recurrent_kernel_f,
                self.recurrent_kernel_c,
                self.recurrent_kernel_o,
            ],
            biases=[
                self.bias_i_i,
                self.bias_f_i,
                self.bias_c_i,
                self.bias_o_i,
                self.bias_i,
                self.bias_f,
                self.bias_c,
                self.bias_o,
            ],
        )
        outputs, h, c = self._cudnn_lstm(
            inputs,
            input_h=input_h,
            input_c=input_c,
            params=params,
            is_training=True)

        if self.stateful or self.return_state:
            h = h[0]
            c = c[0]
        if self.return_sequences:
            output = tf.transpose(outputs, (1, 0, 2))
        else:
            output = outputs[-1]
        return output, [h, c]

    def get_config(self):
        config = {
            'units': self.units,
            'kernel_initializer': initializers.serialize(self.kernel_initializer),
            'recurrent_initializer':
                initializers.serialize(self.recurrent_initializer),
            'bias_initializer': initializers.serialize(self.bias_initializer),
            'unit_forget_bias': self.unit_forget_bias,
            'kernel_regularizer': regularizers.serialize(self.kernel_regularizer),
            'recurrent_regularizer':
                regularizers.serialize(self.recurrent_regularizer),
            'bias_regularizer': regularizers.serialize(self.bias_regularizer),
            'activity_regularizer':
                regularizers.serialize(self.activity_regularizer),
            'kernel_constraint': constraints.serialize(self.kernel_constraint),
            'recurrent_constraint': constraints.serialize(self.recurrent_constraint),
            'bias_constraint': constraints.serialize(self.bias_constraint)}
        base_config = super(CuDNNLSTM, self).get_config()
        return dict(list(base_config.items()) + list(config.items()))
