# -*- coding: utf-8 -*-
from __future__ import absolute_import

from .. import backend as K
from .. import activations
from .. import initializers
from .. import regularizers
from .. import constraints
from .recurrent import Recurrent

import numpy as np
from ..engine import InputSpec
from ..utils import conv_utils


class ConvRecurrent2D(Recurrent):
    """Abstract base class for convolutional recurrent layers.

    Do not use in a model -- it's not a functional layer!

    # Arguments
        filters: Integer, the dimensionality of the output space
            (i.e. the number output of filters in the convolution).
        kernel_size: An integer or tuple/list of n integers, specifying the
            dimensions of the convolution window.
        strides: An integer or tuple/list of n integers,
            specifying the strides of the convolution.
            Specifying any stride value != 1 is incompatible with specifying
            any `dilation_rate` value != 1.
        padding: One of `"valid"` or `"same"` (case-insensitive).
        data_format: A string,
            one of `channels_last` (default) or `channels_first`.
            The ordering of the dimensions in the inputs.
            `channels_last` corresponds to inputs with shape
            `(batch, time, ..., channels)`
            while `channels_first` corresponds to
            inputs with shape `(batch, time, channels, ...)`.
            It defaults to the `image_data_format` value found in your
            Keras config file at `~/.keras/keras.json`.
            If you never set it, then it will be "channels_last".
        dilation_rate: An integer or tuple/list of n integers, specifying
            the dilation rate to use for dilated convolution.
            Currently, specifying any `dilation_rate` value != 1 is
            incompatible with specifying any `strides` value != 1.
        return_sequences: Boolean. Whether to return the last output
            in the output sequence, or the full sequence.
        go_backwards: Boolean (default False).
            If True, rocess the input sequence backwards.
        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.

    # Input shape
        5D tensor with shape `(num_samples, timesteps, channels, rows, cols)`.

    # Output shape
        - if `return_sequences`: 5D tensor with shape
            `(num_samples, timesteps, channels, rows, cols)`.
        - else, 4D tensor with shape `(num_samples, channels, rows, cols)`.

    # Masking
        This layer supports masking for input data with a variable number
        of timesteps. To introduce masks to your data,
        use an [Embedding](embeddings.md) layer with the `mask_zero` parameter
        set to `True`.
        **Note:** for the time being, masking is only supported with Theano.

    # Note on using statefulness in RNNs
        You can set RNN layers to be 'stateful', which means that the states
        computed for the samples in one batch will be reused as initial states
        for the samples in the next batch.
        This assumes a one-to-one mapping between
        samples in different successive batches.

        To enable statefulness:
            - specify `stateful=True` in the layer constructor.
            - specify a fixed batch size for your model, by passing
                a `batch_input_size=(...)` to the first layer in your model.
                This is the expected shape of your inputs *including the batch
                size*.
                It should be a tuple of integers, e.g. `(32, 10, 100)`.

        To reset the states of your model, call `.reset_states()` on either
        a specific layer, or on your entire model.
    """

    def __init__(self, filters,
                 kernel_size,
                 strides=(1, 1),
                 padding='valid',
                 data_format=None,
                 dilation_rate=(1, 1),
                 return_sequences=False,
                 go_backwards=False,
                 stateful=False,
                 **kwargs):
        super(ConvRecurrent2D, self).__init__(**kwargs)
        self.filters = filters
        self.kernel_size = conv_utils.normalize_tuple(kernel_size, 2, 'kernel_size')
        self.strides = conv_utils.normalize_tuple(strides, 2, 'strides')
        self.padding = conv_utils.normalize_padding(padding)
        self.data_format = conv_utils.normalize_data_format(data_format)
        self.dilation_rate = conv_utils.normalize_tuple(dilation_rate, 2, 'dilation_rate')
        self.return_sequences = return_sequences
        self.go_backwards = go_backwards
        self.stateful = stateful
        self.input_spec = InputSpec(ndim=5)

    def compute_output_shape(self, input_shape):
        if self.data_format == 'channels_first':
            rows = input_shape[3]
            cols = input_shape[4]
        elif self.data_format == 'channels_last':
            rows = input_shape[2]
            cols = input_shape[3]
        rows = conv_utils.conv_output_length(rows,
                                             self.kernel_size[0],
                                             padding=self.padding,
                                             stride=self.strides[0],
                                             dilation=self.dilation_rate[0])
        cols = conv_utils.conv_output_length(cols,
                                             self.kernel_size[1],
                                             padding=self.padding,
                                             stride=self.strides[1],
                                             dilation=self.dilation_rate[1])
        if self.return_sequences:
            if self.data_format == 'channels_first':
                return (input_shape[0], input_shape[1],
                        self.filters, rows, cols)
            elif self.data_format == 'channels_last':
                return (input_shape[0], input_shape[1],
                        rows, cols, self.filters)
        else:
            if self.data_format == 'channels_first':
                return (input_shape[0], self.filters, rows, cols)
            elif self.data_format == 'channels_last':
                return (input_shape[0], rows, cols, self.filters)

    def get_config(self):
        config = {'filters': self.filters,
                  'kernel_size': self.kernel_size,
                  'strides': self.strides,
                  'padding': self.padding,
                  'data_format': self.data_format,
                  'dilation_rate': self.dilation_rate,
                  'return_sequences': self.return_sequences,
                  'go_backwards': self.go_backwards,
                  'stateful': self.stateful}
        base_config = super(ConvRecurrent2D, self).get_config()
        return dict(list(base_config.items()) + list(config.items()))


class ConvLSTM2D(ConvRecurrent2D):
    """Convolutional LSTM.

    It is similar to an LSTM layer, but the input transformations
    and recurrent transformations are both convolutional.

    # Arguments
        filters: Integer, the dimensionality of the output space
            (i.e. the number output of filters in the convolution).
        kernel_size: An integer or tuple/list of n integers, specifying the
            dimensions of the convolution window.
        strides: An integer or tuple/list of n integers,
            specifying the strides of the convolution.
            Specifying any stride value != 1 is incompatible with specifying
            any `dilation_rate` value != 1.
        padding: One of `"valid"` or `"same"` (case-insensitive).
        data_format: A string,
            one of `channels_last` (default) or `channels_first`.
            The ordering of the dimensions in the inputs.
            `channels_last` corresponds to inputs with shape
            `(batch, time, ..., channels)`
            while `channels_first` corresponds to
            inputs with shape `(batch, time, channels, ...)`.
            It defaults to the `image_data_format` value found in your
            Keras config file at `~/.keras/keras.json`.
            If you never set it, then it will be "channels_last".
        dilation_rate: An integer or tuple/list of n integers, specifying
            the dilation rate to use for dilated convolution.
            Currently, specifying any `dilation_rate` value != 1 is
            incompatible with specifying any `strides` value != 1.
        activation: Activation function to use
            (see [activations](../activations.md)).
            If you don't specify anything, no activation is applied
            (ie. "linear" activation: `a(x) = x`).
        recurrent_activation: Activation function to use
            for the recurrent step
            (see [activations](../activations.md)).
        use_bias: Boolean, whether the layer uses a bias vector.
        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.
            Use in combination with `bias_initializer="zeros"`.
            This is recommended in [Jozefowicz et al.](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.
        go_backwards: Boolean (default False).
            If True, rocess the input sequence backwards.
        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.
        dropout: Float between 0 and 1.
            Fraction of the units to drop for
            the linear transformation of the inputs.
        recurrent_dropout: Float between 0 and 1.
            Fraction of the units to drop for
            the linear transformation of the recurrent state.

    # Input shape
        - if data_format='channels_first'
            5D tensor with shape:
            `(samples,time, channels, rows, cols)`
        - if data_format='channels_last'
            5D tensor with shape:
            `(samples,time, rows, cols, channels)`

     # Output shape
        - if `return_sequences`
             - if data_format='channels_first'
                5D tensor with shape:
                `(samples, time, filters, output_row, output_col)`
             - if data_format='channels_last'
                5D tensor with shape:
                `(samples, time, output_row, output_col, filters)`
        - else
            - if data_format ='channels_first'
                4D tensor with shape:
                `(samples, filters, output_row, output_col)`
            - if data_format='channels_last'
                4D tensor with shape:
                `(samples, output_row, output_col, filters)`
            where o_row and o_col depend on the shape of the filter and
            the padding

    # Raises
        ValueError: in case of invalid constructor arguments.

    # References
        - [Convolutional LSTM Network: A Machine Learning Approach for
        Precipitation Nowcasting](http://arxiv.org/abs/1506.04214v1)
        The current implementation does not include the feedback loop on the
        cells output
    """

    def __init__(self, filters,
                 kernel_size,
                 strides=(1, 1),
                 padding='valid',
                 data_format=None,
                 dilation_rate=(1, 1),
                 activation='tanh',
                 recurrent_activation='hard_sigmoid',
                 use_bias=True,
                 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,
                 go_backwards=False,
                 stateful=False,
                 dropout=0.,
                 recurrent_dropout=0.,
                 **kwargs):
        super(ConvLSTM2D, self).__init__(filters,
                                         kernel_size,
                                         strides=strides,
                                         padding=padding,
                                         data_format=data_format,
                                         dilation_rate=dilation_rate,
                                         return_sequences=return_sequences,
                                         go_backwards=go_backwards,
                                         stateful=stateful,
                                         **kwargs)
        self.activation = activations.get(activation)
        self.recurrent_activation = activations.get(recurrent_activation)
        self.use_bias = use_bias

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

        self.dropout = min(1., max(0., dropout))
        self.recurrent_dropout = min(1., max(0., recurrent_dropout))

    def build(self, input_shape):
        # TODO: better handling of input spec
        self.input_spec = InputSpec(shape=input_shape)

        if self.stateful:
            self.reset_states()
        else:
            # initial states: 2 all-zero tensor of shape (filters)
            self.states = [None, None, None, None]

        if self.data_format == 'channels_first':
            channel_axis = 1
        else:
            channel_axis = -1
        if input_shape[channel_axis] is None:
            raise ValueError('The channel dimension of the inputs '
                             'should be defined. Found `None`.')
        input_dim = input_shape[channel_axis]
        kernel_shape = self.kernel_size + (input_dim, self.filters * 4)
        self.kernel_shape = kernel_shape
        recurrent_kernel_shape = self.kernel_size + (self.filters, self.filters * 4)

        self.kernel = self.add_weight(kernel_shape,
                                      initializer=self.kernel_initializer,
                                      name='kernel',
                                      regularizer=self.kernel_regularizer,
                                      constraint=self.kernel_constraint)
        self.recurrent_kernel = self.add_weight(
            recurrent_kernel_shape,
            initializer=self.recurrent_initializer,
            name='recurrent_kernel',
            regularizer=self.recurrent_regularizer,
            constraint=self.recurrent_constraint)
        if self.use_bias:
            self.bias = self.add_weight((self.filters * 4,),
                                        initializer=self.bias_initializer,
                                        name='bias',
                                        regularizer=self.bias_regularizer,
                                        constraint=self.bias_constraint)
            if self.unit_forget_bias:
                self.bias += K.concatenate([K.zeros((self.filters,)),
                                           K.ones((self.filters,)),
                                           K.zeros((self.filters * 2,))])
        else:
            self.bias = None

        self.kernel_i = self.kernel[:, :, :, :self.filters]
        self.recurrent_kernel_i = self.recurrent_kernel[:, :, :, :self.filters]
        self.kernel_f = self.kernel[:, :, :, self.filters: self.filters * 2]
        self.recurrent_kernel_f = self.recurrent_kernel[:, :, :, self.filters: self.filters * 2]
        self.kernel_c = self.kernel[:, :, :, self.filters * 2: self.filters * 3]
        self.recurrent_kernel_c = self.recurrent_kernel[:, :, :, self.filters * 2: self.filters * 3]
        self.kernel_o = self.kernel[:, :, :, self.filters * 3:]
        self.recurrent_kernel_o = self.recurrent_kernel[:, :, :, self.filters * 3:]

        if self.use_bias:
            self.bias_i = self.bias[:self.filters]
            self.bias_f = self.bias[self.filters: self.filters * 2]
            self.bias_c = self.bias[self.filters * 2: self.filters * 3]
            self.bias_o = self.bias[self.filters * 3:]
        else:
            self.bias_i = None
            self.bias_f = None
            self.bias_c = None
            self.bias_o = None
        self.built = True

    def get_initial_states(self, inputs):
        # (samples, timesteps, rows, cols, filters)
        initial_state = K.zeros_like(inputs)
        # (samples, rows, cols, filters)
        initial_state = K.sum(initial_state, axis=1)
        shape = list(self.kernel_shape)
        shape[-1] = self.filters
        initial_state = self.input_conv(initial_state,
                                        K.zeros(tuple(shape)),
                                        padding=self.padding)

        initial_states = [initial_state for _ in range(2)]
        return initial_states

    def reset_states(self):
        if not self.stateful:
            raise RuntimeError('Layer must be stateful.')
        input_shape = self.input_spec.shape
        output_shape = self.compute_output_shape(input_shape)
        if not input_shape[0]:
            raise ValueError('If a RNN is stateful, a complete '
                             'input_shape must be provided '
                             '(including batch size). '
                             'Got input shape: ' + str(input_shape))

        if self.return_sequences:
            out_row, out_col, out_filter = output_shape[2:]
        else:
            out_row, out_col, out_filter = output_shape[1:]

        if hasattr(self, 'states'):
            K.set_value(self.states[0],
                        np.zeros((input_shape[0],
                                  out_row, out_col, out_filter)))
            K.set_value(self.states[1],
                        np.zeros((input_shape[0],
                                  out_row, out_col, out_filter)))
        else:
            self.states = [K.zeros((input_shape[0],
                                    out_row, out_col, out_filter)),
                           K.zeros((input_shape[0],
                                    out_row, out_col, out_filter))]

    def get_constants(self, inputs, training=None):
        constants = []
        if self.implementation == 0 and 0 < self.dropout < 1:
            ones = K.zeros_like(inputs)
            ones = K.sum(ones, axis=1)
            ones += 1

            def dropped_inputs():
                return K.dropout(ones, self.dropout)

            dp_mask = [K.in_train_phase(dropped_inputs,
                                        ones,
                                        training=training) for _ in range(4)]
            constants.append(dp_mask)
        else:
            constants.append([K.cast_to_floatx(1.) for _ in range(4)])

        if 0 < self.recurrent_dropout < 1:
            shape = list(self.kernel_shape)
            shape[-1] = self.filters
            ones = K.zeros_like(inputs)
            ones = K.sum(ones, axis=1)
            ones = self.input_conv(ones, K.zeros(shape),
                                   padding=self.padding)
            ones += 1.

            def dropped_inputs():
                return K.dropout(ones, self.recurrent_dropout)
            rec_dp_mask = [K.in_train_phase(dropped_inputs,
                                            ones,
                                            training=training) for _ in range(4)]
            constants.append(rec_dp_mask)
        else:
            constants.append([K.cast_to_floatx(1.) for _ in range(4)])
        return constants

    def input_conv(self, x, w, b=None, padding='valid'):
        conv_out = K.conv2d(x, w, strides=self.strides,
                            padding=padding,
                            data_format=self.data_format,
                            dilation_rate=self.dilation_rate)
        if b is not None:
            conv_out = K.bias_add(conv_out, b,
                                  data_format=self.data_format)
        return conv_out

    def reccurent_conv(self, x, w):
        conv_out = K.conv2d(x, w, strides=(1, 1),
                            padding='same',
                            data_format=self.data_format)
        return conv_out

    def step(self, inputs, states):
        assert len(states) == 4
        h_tm1 = states[0]
        c_tm1 = states[1]
        dp_mask = states[2]
        rec_dp_mask = states[3]

        x_i = self.input_conv(inputs * dp_mask[0], self.kernel_i, self.bias_i,
                              padding=self.padding)
        x_f = self.input_conv(inputs * dp_mask[1], self.kernel_f, self.bias_f,
                              padding=self.padding)
        x_c = self.input_conv(inputs * dp_mask[2], self.kernel_c, self.bias_c,
                              padding=self.padding)
        x_o = self.input_conv(inputs * dp_mask[3], self.kernel_o, self.bias_o,
                              padding=self.padding)
        h_i = self.reccurent_conv(h_tm1 * rec_dp_mask[0],
                                  self.recurrent_kernel_i)
        h_f = self.reccurent_conv(h_tm1 * rec_dp_mask[1],
                                  self.recurrent_kernel_f)
        h_c = self.reccurent_conv(h_tm1 * rec_dp_mask[2],
                                  self.recurrent_kernel_c)
        h_o = self.reccurent_conv(h_tm1 * rec_dp_mask[3],
                                  self.recurrent_kernel_o)

        i = self.recurrent_activation(x_i + h_i)
        f = self.recurrent_activation(x_f + h_f)
        c = f * c_tm1 + i * self.activation(x_c + h_c)
        o = self.recurrent_activation(x_o + h_o)
        h = o * self.activation(c)
        return h, [h, c]

    def get_config(self):
        config = {'activation': activations.serialize(self.activation),
                  'recurrent_activation': activations.serialize(self.recurrent_activation),
                  'use_bias': self.use_bias,
                  '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),
                  'kernel_constraint': constraints.serialize(self.kernel_constraint),
                  'recurrent_constraint': constraints.serialize(self.recurrent_constraint),
                  'bias_constraint': constraints.serialize(self.bias_constraint),
                  'dropout': self.dropout,
                  'recurrent_dropout': self.recurrent_dropout}
        base_config = super(ConvLSTM2D, self).get_config()
        return dict(list(base_config.items()) + list(config.items()))
