################################################################################
# Copyright (c) 2021 ContinualAI.                                              #
# Copyrights licensed under the MIT License.                                   #
# See the accompanying LICENSE file for terms.                                 #
#                                                                              #
# Date: 1-05-2020                                                              #
# Author(s): Vincenzo Lomonaco, Antonio Carta                                  #
# E-mail: contact@continualai.org                                              #
# Website: avalanche.continualai.org                                           #
################################################################################

import torch.nn as nn

from avalanche.models.dynamic_modules import MultiTaskModule, \
    MultiHeadClassifier
from avalanche.models.base_model import BaseModel


class SimpleMLP(nn.Module, BaseModel):
    """
    Multi-Layer Perceptron with custom parameters.
    It can be configured to have multiple layers and dropout.
    """
    def __init__(self, num_classes=10, input_size=28 * 28,
                 hidden_size=512, hidden_layers=1, drop_rate=0.5):
        """
        :param num_classes: output size
        :param input_size: input size
        :param hidden_size: hidden layer size
        :param hidden_layers: number of hidden layers
        :param drop_rate: dropout rate. 0 to disable
        """
        super().__init__()

        layers = nn.Sequential(*(nn.Linear(input_size, hidden_size),
                                 nn.ReLU(inplace=True),
                                 nn.Dropout(p=drop_rate)))
        for layer_idx in range(hidden_layers - 1):
            layers.add_module(
                f"fc{layer_idx + 1}", nn.Sequential(
                    *(nn.Linear(hidden_size, hidden_size),
                      nn.ReLU(inplace=True),
                      nn.Dropout())))

        self.features = nn.Sequential(*layers)
        self.classifier = nn.Linear(hidden_size, num_classes)
        self._input_size = input_size

    def forward(self, x):
        x = x.contiguous()
        x = x.view(x.size(0), self._input_size)
        x = self.features(x)
        x = self.classifier(x)
        return x

    def get_features(self, x):
        x = x.contiguous()
        x = x.view(x.size(0), self._input_size)
        x = self.features(x)
        return x


class MTSimpleMLP(MultiTaskModule):
    """Multi-layer perceptron with multi-head classifier"""
    def __init__(self, input_size=28 * 28, hidden_size=512):
        super().__init__()

        self.features = nn.Sequential(
            nn.Linear(input_size, hidden_size),
            nn.ReLU(inplace=True),
            nn.Dropout(),
        )
        self.classifier = MultiHeadClassifier(hidden_size)
        self._input_size = input_size

    def forward(self, x, task_labels):
        x = x.contiguous()
        x = x.view(x.size(0), self._input_size)
        x = self.features(x)
        x = self.classifier(x, task_labels)
        return x


__all__ = [
    'SimpleMLP',
    'MTSimpleMLP'
]
