import numpy as np

from ray.rllib.models.modelv2 import ModelV2
from ray.rllib.models.preprocessors import get_preprocessor
from ray.rllib.models.tf.recurrent_net import RecurrentNetwork
from ray.rllib.models.torch.recurrent_net import RecurrentNetwork as TorchRNN
from ray.rllib.utils.annotations import override
from ray.rllib.utils.framework import try_import_tf, try_import_torch

tf1, tf, tfv = try_import_tf()
torch, nn = try_import_torch()


class RNNModel(RecurrentNetwork):
    """Example of using the Keras functional API to define a RNN model."""

    def __init__(self,
                 obs_space,
                 action_space,
                 num_outputs,
                 model_config,
                 name,
                 hiddens_size=256,
                 cell_size=64):
        super(RNNModel, self).__init__(obs_space, action_space, num_outputs,
                                       model_config, name)
        self.cell_size = cell_size

        # Define input layers
        input_layer = tf.keras.layers.Input(
            shape=(None, obs_space.shape[0]), name="inputs")
        state_in_h = tf.keras.layers.Input(shape=(cell_size, ), name="h")
        state_in_c = tf.keras.layers.Input(shape=(cell_size, ), name="c")
        seq_in = tf.keras.layers.Input(shape=(), name="seq_in", dtype=tf.int32)

        # Preprocess observation with a hidden layer and send to LSTM cell
        dense1 = tf.keras.layers.Dense(
            hiddens_size, activation=tf.nn.relu, name="dense1")(input_layer)
        lstm_out, state_h, state_c = tf.keras.layers.LSTM(
            cell_size, return_sequences=True, return_state=True, name="lstm")(
                inputs=dense1,
                mask=tf.sequence_mask(seq_in),
                initial_state=[state_in_h, state_in_c])

        # Postprocess LSTM output with another hidden layer and compute values
        logits = tf.keras.layers.Dense(
            self.num_outputs,
            activation=tf.keras.activations.linear,
            name="logits")(lstm_out)
        values = tf.keras.layers.Dense(
            1, activation=None, name="values")(lstm_out)

        # Create the RNN model
        self.rnn_model = tf.keras.Model(
            inputs=[input_layer, seq_in, state_in_h, state_in_c],
            outputs=[logits, values, state_h, state_c])
        self.rnn_model.summary()

    @override(RecurrentNetwork)
    def forward_rnn(self, inputs, state, seq_lens):
        model_out, self._value_out, h, c = self.rnn_model([inputs, seq_lens] +
                                                          state)
        return model_out, [h, c]

    @override(ModelV2)
    def get_initial_state(self):
        return [
            np.zeros(self.cell_size, np.float32),
            np.zeros(self.cell_size, np.float32),
        ]

    @override(ModelV2)
    def value_function(self):
        return tf.reshape(self._value_out, [-1])


class TorchRNNModel(TorchRNN, nn.Module):
    def __init__(self,
                 obs_space,
                 action_space,
                 num_outputs,
                 model_config,
                 name,
                 fc_size=64,
                 lstm_state_size=256):
        nn.Module.__init__(self)
        super().__init__(obs_space, action_space, num_outputs, model_config,
                         name)

        self.obs_size = get_preprocessor(obs_space)(obs_space).size
        self.fc_size = fc_size
        self.lstm_state_size = lstm_state_size

        # Build the Module from fc + LSTM + 2xfc (action + value outs).
        self.fc1 = nn.Linear(self.obs_size, self.fc_size)
        self.lstm = nn.LSTM(
            self.fc_size, self.lstm_state_size, batch_first=True)
        self.action_branch = nn.Linear(self.lstm_state_size, num_outputs)
        self.value_branch = nn.Linear(self.lstm_state_size, 1)
        # Holds the current "base" output (before logits layer).
        self._features = None

    @override(ModelV2)
    def get_initial_state(self):
        # TODO: (sven): Get rid of `get_initial_state` once Trajectory
        #  View API is supported across all of RLlib.
        # Place hidden states on same device as model.
        h = [
            self.fc1.weight.new(1, self.lstm_state_size).zero_().squeeze(0),
            self.fc1.weight.new(1, self.lstm_state_size).zero_().squeeze(0)
        ]
        return h

    @override(ModelV2)
    def value_function(self):
        assert self._features is not None, "must call forward() first"
        return torch.reshape(self.value_branch(self._features), [-1])

    @override(TorchRNN)
    def forward_rnn(self, inputs, state, seq_lens):
        """Feeds `inputs` (B x T x ..) through the Gru Unit.

        Returns the resulting outputs as a sequence (B x T x ...).
        Values are stored in self._cur_value in simple (B) shape (where B
        contains both the B and T dims!).

        Returns:
            NN Outputs (B x T x ...) as sequence.
            The state batches as a List of two items (c- and h-states).
        """
        x = nn.functional.relu(self.fc1(inputs))
        self._features, [h, c] = self.lstm(
            x, [torch.unsqueeze(state[0], 0),
                torch.unsqueeze(state[1], 0)])
        action_out = self.action_branch(self._features)
        return action_out, [torch.squeeze(h, 0), torch.squeeze(c, 0)]
