import math

import torch
from torch import nn


class Activation_Function_Class(nn.Module):
    """
    Implementation of various activation function.
    """

    def __init__(self, hidden_act):

        if hidden_act.lower() == "relu":
            self.f = nn.functional.relu
        elif hidden_act.lower() == "tanh":
            self.f = torch.tanh
        elif hidden_act.lower() == "swish":

            def swish(x):
                return x * torch.sigmoid(x)

            self.f = swish
        elif hidden_act.lower() == "gelu":

            def gelu_new(x):
                """
                Implementation of the gelu activation function currently in Google Bert repo (identical to OpenAI GPT).
                Also see https://arxiv.org/abs/1606.08415
                """
                return 0.5 * x * (1 + torch.tanh(math.sqrt(2 / math.pi) * (x + 0.044715 * torch.pow(x, 3))))

            self.f = gelu_new
        elif hidden_act.lower() == "leakyrelu":
            self.f = nn.functional.leaky_relu

        super().__init__()

    def forward(self, x):
        return self.f(x)


# Single Adapter


class Adapter(nn.Module):
    """
    Implementation of a single Adapter block.
    """

    def __init__(
            self,
            input_size,
            down_sample=None,
            non_linearity="relu",
            init_bert_weights=True,
            add_layer_norm_before=True,
            add_layer_norm_after=False,
            residual_before_ln=True,
            add_gate=False,
    ):
        super().__init__()

        self.input_size = input_size
        self.add_layer_norm_before = add_layer_norm_before
        self.add_layer_norm_after = add_layer_norm_after
        self.residual_before_ln = residual_before_ln
        self.add_gate = add_gate

        # list for all modules of the adapter, passed into nn.Sequential()
        seq_list = []

        # If we want to have a layer norm on input, we add it to seq_list
        if self.add_layer_norm_before:
            self.adapter_norm_before = nn.LayerNorm(self.input_size)
            seq_list.append(self.adapter_norm_before)

        # if a downsample size is not passed, we just half the size of the original input
        self.down_sample = down_sample
        if down_sample is None:
            self.down_sample = self.input_size // 2

        # Linear down projection of the input
        seq_list.append(nn.Linear(self.input_size, self.down_sample))

        # select non-linearity
        self.non_linearity = Activation_Function_Class(non_linearity.lower())

        seq_list.append(self.non_linearity)

        # sequential adapter, first downproject, then non-linearity then upsample. In the forward pass we include the
        # residual connection
        self.adapter_down = nn.Sequential(*seq_list)

        # Up projection to input size
        self.adapter_up = nn.Linear(self.down_sample, self.input_size)

        # If we want to have a layer norm on output, we apply it later after a separate residual connection
        # This means that we learn a new output layer norm, which replaces another layer norm learned in the bert layer
        if self.add_layer_norm_after:
            self.adapter_norm_after = nn.LayerNorm(self.input_size)

        if add_gate:
            self.gate = nn.Linear(self.input_size, 1)

        # if we want to initialize with the bert strategy then this function is called for all the linear layers
        if init_bert_weights:
            self.adapter_down.apply(self.init_bert_weights)
            self.adapter_up.apply(self.init_bert_weights)
            if add_gate:
                self.gate.apply(self.init_bert_weights)

    def forward(self, x, residual_input, return_gate_output=False, central_gate=None):  # , residual_input=None):
        # residual_input is after FFN and before layer_norm.
        # if up is 0, then adapter is effectively skipped
        down = self.adapter_down(x)
        up = self.adapter_up(down)
        output = up

        if self.add_gate or central_gate is not None:
            # x is (bsz, seq_len, hid_dim)
            if central_gate is None:
                gate = torch.sigmoid(self.gate(x))
                gate = torch.mean(gate, dim=1).unsqueeze(-1)
            else:
                gate = central_gate
            output = output * gate

        # apply residual connection before layer norm if configured in this way
        if self.residual_before_ln:
            output = output + residual_input

        # apply layer norm if available
        if self.add_layer_norm_after:
            output = self.adapter_norm_after(output)

        # if residual should be applied after layer norm, apply it here
        if not self.residual_before_ln:
            output = output + residual_input

        if self.add_gate and return_gate_output:
            return output, down, up, gate
        return output, down, up

    # This is copied from the BertPreTrainedModel class to make this a self containing class.
    @staticmethod
    def init_bert_weights(module):
        """Initialize the weights."""
        if isinstance(module, (nn.Linear, nn.Embedding)):
            # std defaults to 0.02, this might need to be changed
            module.weight.data.normal_(mean=0.0, std=0.02)
        elif isinstance(module, nn.LayerNorm):
            module.bias.data.zero_()
            module.weight.data.fill_(1.0)
        if isinstance(module, nn.Linear) and module.bias is not None:
            module.bias.data.zero_()


# Adapter Fusion


class BertFusion(nn.Module):
    """
    Implementation of an AdapterFusion block.
    """

    def __init__(self, config):
        super(BertFusion, self).__init__()
        # if config.hidden_size % config.num_attention_heads != 0:
        #     raise ValueError(
        #         "The hidden size (%d) is not a multiple of the number of attention "
        #         "heads (%d)" % (config.hidden_size, config.num_attention_heads))
        self.config = config
        self.output_attentions = config.output_attentions

        self.dense_size = int(config.hidden_size)
        self.dropout = nn.Dropout(config.attention_probs_dropout_prob)

        if (
                not self.config.adapter_fusion["query"]
                and not self.config.adapter_fusion["key"]
                and not self.config.adapter_fusion["value"]
        ):
            self.dense = nn.Linear(self.dense_size, 1)

        if self.config.adapter_fusion["query"]:
            self.query = nn.Linear(int(config.hidden_size), self.dense_size)
            self.query.apply(Adapter.init_bert_weights)

        if self.config.adapter_fusion["key"]:
            self.key = nn.Linear(self.dense_size, self.dense_size)
            self.key.apply(Adapter.init_bert_weights)

        if self.config.adapter_fusion["value"]:
            self.value = nn.Linear(int(config.hidden_size), int(config.hidden_size), bias=False)
            self.value.apply(Adapter.init_bert_weights)
            if self.config.adapter_fusion["value_initialized"]:
                self.value.weight.data = (
                        torch.zeros(int(config.hidden_size), int(config.hidden_size)) + 0.000001
                ).fill_diagonal_(1.0)

        if self.config.adapter_fusion["temperature"]:
            self.T = 50.0
        else:
            self.T = 1.0
        self.reduction = self.T / 1000.0

    def forward(self, query, key, value, residual):

        if self.config.adapter_fusion["residual_before"]:
            value += residual[:, :, None, :].repeat(1, 1, value.size(2), 1)

        if self.config.adapter_fusion["query"]:
            query_layer = self.query(query)
        else:
            query_layer = query

        if self.config.adapter_fusion["key"]:
            key_layer = self.key(key)
        else:
            key_layer = key

        if self.config.adapter_fusion["value"] and self.config.adapter_fusion["value_before_softmax"]:
            # key/value have dims => batch, toks, number-of-adapters, feats
            value_layer = self.value(value)
        else:
            value_layer = value

        # Take the dot product between "query" and "key" to get the raw attention scores.
        attention_scores = torch.squeeze(torch.matmul(query_layer.unsqueeze(2), key_layer.transpose(-2, -1)), dim=2)

        attention_scores = self.dropout(attention_scores)

        # Normalize the attention scores to probabilities.
        attention_probs = nn.Softmax(dim=-1)(attention_scores / self.T)
        self.T = max(self.T - self.reduction, 1.0)

        if not self.training:
            self.recent_attention = attention_probs.detach().cpu().numpy()

        context_layer = torch.squeeze(torch.matmul(attention_probs.unsqueeze(2), value_layer), dim=2)

        if self.config.adapter_fusion["value"] and not self.config.adapter_fusion["value_before_softmax"]:
            # key/value have dims => batch, toks, number-of-adapters, feats
            context_layer = self.value(context_layer)
        else:
            context_layer = context_layer

        if not self.config.adapter_fusion["residual_before"]:
            context_layer += residual

        return context_layer


# Invertible Adapters


def get_subnet_constructor(non_linearity, reduction_factor):
    def subnet(dims_in, dims_out):
        return nn.Sequential(
            nn.Linear(dims_in, dims_in // reduction_factor),
            Activation_Function_Class(non_linearity),
            nn.Linear(dims_in // reduction_factor, dims_out),
        )

    return subnet


class NICECouplingBlock(nn.Module):
    """Coupling Block following the NICE design."""

    def __init__(self, dims_in, dims_c=[], non_linearity="relu", reduction_factor=2):
        super().__init__()

        channels = dims_in[0][0]
        self.split_len1 = channels // 2
        self.split_len2 = channels - channels // 2

        assert all(
            [dims_c[i][1:] == dims_in[0][1:] for i in range(len(dims_c))]
        ), "Dimensions of input and one or more conditions don't agree."
        self.conditional = len(dims_c) > 0
        condition_length = sum([dims_c[i][0] for i in range(len(dims_c))])

        subnet_constructor = get_subnet_constructor(non_linearity, reduction_factor)
        self.F = subnet_constructor(self.split_len2 + condition_length, self.split_len1)
        self.G = subnet_constructor(self.split_len1 + condition_length, self.split_len2)

    def forward(self, x, c=[], rev=False):
        x1, x2 = (x[:, :, : self.split_len1], x[:, :, self.split_len1:])
        if not rev:
            x2_c = torch.cat([x2, *c], 1) if self.conditional else x2
            y1 = x1 + self.F(x2_c)
            y1_c = torch.cat([y1, *c], 1) if self.conditional else y1
            y2 = x2 + self.G(y1_c)
        else:
            x1_c = torch.cat([x1, *c], 1) if self.conditional else x1
            y2 = x2 - self.G(x1_c)
            y2_c = torch.cat([y2, *c], 1) if self.conditional else y2
            y1 = x1 - self.F(y2_c)

        return torch.cat((y1, y2), -1)

    def jacobian(self, x, rev=False):
        return 0

    def output_dims(self, input_dims):
        assert len(input_dims) == 1, "Can only use 1 input"
        return input_dims


class GLOWCouplingBlock(nn.Module):
    """
    Coupling Block following the GLOW design. The only difference to the RealNVP coupling blocks, is the fact that it
    uses a single subnetwork to jointly predict [s_i, t_i], instead of two separate subnetworks. This reduces
    computational cost and speeds up learning. clamp: Soft clamping for the multiplicative component. The amplification
    or attenuation of each input dimension can be at most ±exp(clamp).
    """

    def __init__(self, dims_in, dims_c=[], non_linearity="relu", reduction_factor=2, clamp=5.0):
        super().__init__()

        channels = dims_in[0][0]
        self.ndims = len(dims_in[0])
        self.split_len1 = channels // 2
        self.split_len2 = channels - channels // 2

        self.clamp = clamp
        self.max_s = math.exp(clamp)
        self.min_s = math.exp(-clamp)

        assert all(
            [tuple(dims_c[i][1:]) == tuple(dims_in[0][1:]) for i in range(len(dims_c))]
        ), f"Dimensions of input and one or more conditions don't agree: {dims_c} vs {dims_in}."
        self.conditional = len(dims_c) > 0
        condition_length = sum([dims_c[i][0] for i in range(len(dims_c))])

        subnet_constructor = get_subnet_constructor(non_linearity, reduction_factor)
        self.s1 = subnet_constructor(self.split_len1 + condition_length, self.split_len2 * 2)
        self.s2 = subnet_constructor(self.split_len2 + condition_length, self.split_len1 * 2)

    def e(self, s):
        return torch.exp(self.clamp * 0.636 * torch.atan(s / self.clamp))

    def log_e(self, s):
        return self.clamp * 0.636 * torch.atan(s / self.clamp)

    def forward(self, x, c=[], rev=False):
        x1, x2 = (x[:, :, : self.split_len1], x[:, :, self.split_len1:])

        if not rev:
            s2, t2 = x1.clone(), x2.clone()
            y1 = self.e(s2) * x1 + t2

            r1 = self.s1(torch.cat([y1, *c], 1) if self.conditional else y1)
            s1, t1 = r1[:, : self.split_len2], r1[:, self.split_len2:]
            y2 = self.e(s1) * x2 + t1
            self.last_jac = torch.sum(self.log_e(s1), dim=tuple(range(1, self.ndims + 1))) + torch.sum(
                self.log_e(s2), dim=tuple(range(1, self.ndims + 1))
            )

        else:  # names of x and y are swapped!
            r1 = self.s1(torch.cat([x1, *c], 1) if self.conditional else x1)
            s1, t1 = r1[:, : self.split_len2], r1[:, self.split_len2:]
            y2 = (x2 - t1) / self.e(s1)

            r2 = self.s2(torch.cat([y2, *c], 1) if self.conditional else y2)
            s2, t2 = r2[:, : self.split_len1], r2[:, self.split_len1:]
            y1 = (x1 - t2) / self.e(s2)
            self.last_jac = -torch.sum(self.log_e(s1), dim=tuple(range(1, self.ndims + 1))) - torch.sum(
                self.log_e(s2), dim=tuple(range(1, self.ndims + 1))
            )

        return [torch.cat((y1, y2), 1)]

    def jacobian(self, x, c=[], rev=False):
        return self.last_jac

    def output_dims(self, input_dims):
        return input_dims
