# ------------------------------------------------------------------------
# Modified from OFA (https://github.com/OFA-Sys/OFA)
# Copyright 2022 The OFA-Sys Team. 
# All rights reserved.
# This source code is licensed under the Apache 2.0 license 
# found in the LICENSE file in the root directory.
# ------------------------------------------------------------------------
# Modifications Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
# SPDX-License-Identifier: Apache-2.0

from typing import Dict, List, Optional

import torch
import torch.nn as nn
from fairseq import utils
from fairseq.modules import LayerNorm
from fairseq.modules.fairseq_dropout import FairseqDropout
from fairseq.modules.quant_noise import quant_noise
from torch import Tensor

from .unify_multihead_attention import MultiheadAttention


def drop_path(x, drop_prob: float = 0.0, training: bool = False):
    """
    Drop paths (Stochastic Depth) per sample (when applied in main path of residual blocks).
    Comment by Ross Wightman: This is the same as the DropConnect impl I created for EfficientNet, etc networks,
    however, the original name is misleading as 'Drop Connect' is a different form of dropout in a separate paper...
    See discussion: https://github.com/tensorflow/tpu/issues/494#issuecomment-532968956 ... I've opted for changing the
    layer and argument names to 'drop path' rather than mix DropConnect as a layer name and use 'survival rate' as the
    argument.
    """
    if drop_prob == 0.0 or not training:
        return x
    keep_prob = 1 - drop_prob
    shape = (1, x.shape[1], 1)
    random_tensor = keep_prob + torch.rand(shape, dtype=x.dtype, device=x.device)
    random_tensor.floor_()  # binarize
    output = x.div(keep_prob) * random_tensor
    return output


class DropPath(nn.Module):
    """Drop paths (Stochastic Depth) per sample (when applied in main path of residual blocks)."""

    def __init__(self, drop_prob=None):
        super().__init__()
        self.drop_prob = drop_prob

    def forward(self, x):
        return drop_path(x, self.drop_prob, self.training)

    def extra_repr(self) -> str:
        return "p={}".format(self.drop_prob)


class TransformerEncoderLayer(nn.Module):
    """Encoder layer block.

    In the original paper each operation (multi-head attention or FFN) is
    postprocessed with: `dropout -> add residual -> layernorm`. In the
    tensor2tensor code they suggest that learning is more robust when
    preprocessing each layer with layernorm and postprocessing with:
    `dropout -> add residual`. We default to the approach in the paper, but the
    tensor2tensor approach can be enabled by setting
    *args.encoder_normalize_before* to ``True``.

    Args:
        args (argparse.Namespace): parsed command-line arguments
    """

    def __init__(self, args, drop_path_rate=0.0):
        super().__init__()
        self.args = args
        self.embed_dim = args.encoder_embed_dim
        self.quant_noise = getattr(args, 'quant_noise_pq', 0)
        self.quant_noise_block_size = getattr(args, 'quant_noise_pq_block_size', 8) or 8
        self.self_attn = self.build_self_attention(self.embed_dim, args)
        self.self_attn_layer_norm = LayerNorm(self.embed_dim)
        self.dropout_module = FairseqDropout(
            args.dropout, module_name=self.__class__.__name__
        )
        self.activation_fn = utils.get_activation_fn(
            activation=getattr(args, 'activation_fn', 'relu') or "relu"
        )
        activation_dropout_p = getattr(args, "activation_dropout", 0) or 0
        if activation_dropout_p == 0:
            # for backwards compatibility with models that use args.relu_dropout
            activation_dropout_p = getattr(args, "relu_dropout", 0) or 0
        self.activation_dropout_module = FairseqDropout(
            float(activation_dropout_p), module_name=self.__class__.__name__
        )
        self.normalize_before = args.encoder_normalize_before
        self.fc1 = self.build_fc1(
            self.embed_dim,
            args.encoder_ffn_embed_dim,
            self.quant_noise,
            self.quant_noise_block_size,
        )
        self.fc2 = self.build_fc2(
            args.encoder_ffn_embed_dim,
            self.embed_dim,
            self.quant_noise,
            self.quant_noise_block_size,
        )

        self.attn_ln = LayerNorm(self.embed_dim) if getattr(args, 'scale_attn', False) else None
        self.nh = self.self_attn.num_heads
        self.head_dim = self.self_attn.head_dim

        self.ffn_layernorm = LayerNorm(args.encoder_ffn_embed_dim) if getattr(args, 'scale_fc', False) else None
        self.w_resid = nn.Parameter(torch.ones(self.embed_dim, ), requires_grad=True) if getattr(args, 'scale_resids', False) else None

        self.final_layer_norm = LayerNorm(self.embed_dim)

        self.drop_path = DropPath(drop_path_rate) if drop_path_rate > 0.0 else nn.Identity()

    def build_fc1(self, input_dim, output_dim, q_noise, qn_block_size):
        return quant_noise(
            nn.Linear(input_dim, output_dim), p=q_noise, block_size=qn_block_size
        )

    def build_fc2(self, input_dim, output_dim, q_noise, qn_block_size):
        return quant_noise(
            nn.Linear(input_dim, output_dim), p=q_noise, block_size=qn_block_size
        )

    def build_self_attention(self, embed_dim, args):
        return MultiheadAttention(
            embed_dim,
            args.encoder_attention_heads,
            dropout=args.attention_dropout,
            self_attention=True,
            q_noise=self.quant_noise,
            qn_block_size=self.quant_noise_block_size,
            scale_factor=args.attn_scale_factor,
            scale_heads=getattr(args, 'scale_heads', False)
        )

    def residual_connection(self, x, residual):
        return residual + self.drop_path(x)

    def upgrade_state_dict_named(self, state_dict, name):
        """
        Rename layer norm states from `...layer_norms.0.weight` to
        `...self_attn_layer_norm.weight` and `...layer_norms.1.weight` to
        `...final_layer_norm.weight`
        """
        layer_norm_map = {"0": "self_attn_layer_norm", "1": "final_layer_norm"}
        for old, new in layer_norm_map.items():
            for m in ("weight", "bias"):
                k = "{}.layer_norms.{}.{}".format(name, old, m)
                if k in state_dict:
                    state_dict["{}.{}.{}".format(name, new, m)] = state_dict[k]
                    del state_dict[k]
                if "{}.{}.{}".format(name, new, m) not in state_dict and "{}.{}".format(new, m) in self.state_dict():
                    state_dict[
                        "{}.{}.{}".format(name, new, m)
                    ] = self.state_dict()["{}.{}".format(new, m)]

        prefix = name + "." if name != "" else ""
        for param_name, param_tensor in self.state_dict().items():
            if (prefix + param_name) not in state_dict:
                state_dict[prefix + param_name] = self.state_dict()[param_name]

    def forward(
        self,
        x,
        encoder_padding_mask: Optional[Tensor],
        attn_mask: Optional[Tensor] = None,
        self_attn_bias: Optional[Tensor] = None
    ):
        """
        Args:
            x (Tensor): input to the layer of shape `(seq_len, batch, embed_dim)`
            encoder_padding_mask (ByteTensor): binary ByteTensor of shape
                `(batch, seq_len)` where padding elements are indicated by ``1``.
            attn_mask (ByteTensor): binary tensor of shape `(tgt_len, src_len)`,
                where `tgt_len` is the length of output and `src_len` is the
                length of input, though here both are equal to `seq_len`.
                `attn_mask[tgt_i, src_j] = 1` means that when calculating the
                embedding for `tgt_i`, we exclude (mask out) `src_j`. This is
                useful for strided self-attention.

        Returns:
            encoded output of shape `(seq_len, batch, embed_dim)`
        """
        # anything in original attn_mask = 1, becomes -1e8
        # anything in original attn_mask = 0, becomes 0
        # Note that we cannot use -inf here, because at some edge cases,
        # the attention weight (before softmax) for some padded element in query
        # will become -inf, which results in NaN in model parameters
        if attn_mask is not None:
            attn_mask = attn_mask.masked_fill(
                attn_mask.to(torch.bool),
                -1e8 if x.dtype == torch.float32 else -1e4
            )

        residual = x
        if self.normalize_before:
            x = self.self_attn_layer_norm(x)
        x, _ = self.self_attn(
            query=x,
            key=x,
            value=x,
            key_padding_mask=encoder_padding_mask,
            need_weights=False,
            attn_mask=attn_mask,
            attn_bias=self_attn_bias
        )
        if self.attn_ln is not None:
            x = self.attn_ln(x)
        x = self.dropout_module(x)
        x = self.residual_connection(x, residual)
        if not self.normalize_before:
            x = self.self_attn_layer_norm(x)

        residual = x
        if self.normalize_before:
            x = self.final_layer_norm(x)
        x = self.activation_fn(self.fc1(x))
        x = self.activation_dropout_module(x)
        if self.ffn_layernorm is not None:
            x = self.ffn_layernorm(x)
        x = self.fc2(x)
        x = self.dropout_module(x)
        if self.w_resid is not None:
            residual = torch.mul(self.w_resid, residual)
        x = self.residual_connection(x, residual)
        if not self.normalize_before:
            x = self.final_layer_norm(x)
        return x


class TransformerDecoderLayer(nn.Module):
    """Decoder layer block.

    In the original paper each operation (multi-head attention, encoder
    attention or FFN) is postprocessed with: `dropout -> add residual ->
    layernorm`. In the tensor2tensor code they suggest that learning is more
    robust when preprocessing each layer with layernorm and postprocessing with:
    `dropout -> add residual`. We default to the approach in the paper, but the
    tensor2tensor approach can be enabled by setting
    *args.decoder_normalize_before* to ``True``.

    Args:
        args (argparse.Namespace): parsed command-line arguments
        no_encoder_attn (bool, optional): whether to attend to encoder outputs
            (default: False).
    """

    def __init__(
        self, args, no_encoder_attn=False, add_bias_kv=False, add_zero_attn=False, drop_path_rate=0.0
    ):
        super().__init__()
        self.embed_dim = args.decoder_embed_dim
        self.dropout_module = FairseqDropout(
            args.dropout, module_name=self.__class__.__name__
        )
        self.quant_noise = getattr(args, "quant_noise_pq", 0)
        self.quant_noise_block_size = getattr(args, "quant_noise_pq_block_size", 8)

        self.cross_self_attention = getattr(args, "cross_self_attention", False)

        self.self_attn = self.build_self_attention(
            self.embed_dim,
            args,
            add_bias_kv=add_bias_kv,
            add_zero_attn=add_zero_attn,
        )
        self.self_attn_ln = LayerNorm(self.embed_dim) if getattr(args, 'scale_attn', False) else None
        self.cross_attn_ln = LayerNorm(self.embed_dim) if getattr(args, 'scale_attn', False) else None
        self.nh = self.self_attn.num_heads
        self.head_dim = self.self_attn.head_dim

        self.activation_fn = utils.get_activation_fn(
            activation=str(args.activation_fn)
            if getattr(args, "activation_fn", None) is not None
            else "relu"
        )
        activation_dropout_p = getattr(args, "activation_dropout", 0) or 0
        if activation_dropout_p == 0:
            # for backwards compatibility with models that use args.relu_dropout
            activation_dropout_p = getattr(args, "relu_dropout", 0) or 0
        self.activation_dropout_module = FairseqDropout(
            float(activation_dropout_p), module_name=self.__class__.__name__
        )
        self.normalize_before = args.decoder_normalize_before

        # use layerNorm rather than FusedLayerNorm for exporting.
        # char_inputs can be used to determint this.
        # TODO  remove this once we update apex with the fix
        export = getattr(args, "char_inputs", False)
        self.self_attn_layer_norm = LayerNorm(self.embed_dim, export=export)

        if no_encoder_attn:
            self.encoder_attn = None
            self.encoder_attn_layer_norm = None
        else:
            self.encoder_attn = self.build_encoder_attention(self.embed_dim, args)
            self.encoder_attn_layer_norm = LayerNorm(self.embed_dim, export=export)

        self.ffn_layernorm = LayerNorm(args.decoder_ffn_embed_dim) if getattr(args, 'scale_fc', False) else None
        self.w_resid = nn.Parameter(torch.ones(self.embed_dim, ), requires_grad=True) if getattr(args, 'scale_resids', False) else None

        self.fc1 = self.build_fc1(
            self.embed_dim,
            args.decoder_ffn_embed_dim,
            self.quant_noise,
            self.quant_noise_block_size,
        )
        self.fc2 = self.build_fc2(
            args.decoder_ffn_embed_dim,
            self.embed_dim,
            self.quant_noise,
            self.quant_noise_block_size,
        )

        self.final_layer_norm = LayerNorm(self.embed_dim, export=export)
        self.need_attn = True

        self.onnx_trace = False

        self.drop_path = DropPath(drop_path_rate) if drop_path_rate > 0.0 else nn.Identity()

    def build_fc1(self, input_dim, output_dim, q_noise, qn_block_size):
        return quant_noise(nn.Linear(input_dim, output_dim), q_noise, qn_block_size)

    def build_fc2(self, input_dim, output_dim, q_noise, qn_block_size):
        return quant_noise(nn.Linear(input_dim, output_dim), q_noise, qn_block_size)

    def build_self_attention(
        self, embed_dim, args, add_bias_kv=False, add_zero_attn=False
    ):
        return MultiheadAttention(
            embed_dim,
            args.decoder_attention_heads,
            dropout=args.attention_dropout,
            add_bias_kv=add_bias_kv,
            add_zero_attn=add_zero_attn,
            self_attention=not getattr(args, "cross_self_attention", False),
            q_noise=self.quant_noise,
            qn_block_size=self.quant_noise_block_size,
            scale_factor=args.attn_scale_factor,
            scale_heads=getattr(args, 'scale_heads', False)
        )

    def build_encoder_attention(self, embed_dim, args):
        return MultiheadAttention(
            embed_dim,
            args.decoder_attention_heads,
            kdim=getattr(args, "encoder_embed_dim", None),
            vdim=getattr(args, "encoder_embed_dim", None),
            dropout=args.attention_dropout,
            encoder_decoder_attention=True,
            q_noise=self.quant_noise,
            qn_block_size=self.quant_noise_block_size,
            scale_factor=args.attn_scale_factor,
            scale_heads=getattr(args, 'scale_heads', False)
        )

    def prepare_for_onnx_export_(self):
        self.onnx_trace = True

    def residual_connection(self, x, residual):
        return residual + self.drop_path(x)

    def forward(
        self,
        x,
        encoder_out: Optional[torch.Tensor] = None,
        encoder_padding_mask: Optional[torch.Tensor] = None,
        incremental_state: Optional[Dict[str, Dict[str, Optional[Tensor]]]] = None,
        prev_self_attn_state: Optional[List[torch.Tensor]] = None,
        prev_attn_state: Optional[List[torch.Tensor]] = None,
        self_attn_mask: Optional[torch.Tensor] = None,
        self_attn_padding_mask: Optional[torch.Tensor] = None,
        need_attn: bool = False,
        need_head_weights: bool = False,
        self_attn_bias: Optional[Tensor] = None,
        cross_attn_bias: Optional[Tensor] = None
    ):
        """
        Args:
            x (Tensor): input to the layer of shape `(seq_len, batch, embed_dim)`
            encoder_padding_mask (ByteTensor, optional): binary
                ByteTensor of shape `(batch, src_len)` where padding
                elements are indicated by ``1``.
            need_attn (bool, optional): return attention weights
            need_head_weights (bool, optional): return attention weights
                for each head (default: return average over heads).

        Returns:
            encoded output of shape `(seq_len, batch, embed_dim)`
        """
        if need_head_weights:
            need_attn = True

        residual = x
        if self.normalize_before:
            x = self.self_attn_layer_norm(x)
        if prev_self_attn_state is not None:
            prev_key, prev_value = prev_self_attn_state[:2]
            saved_state: Dict[str, Optional[Tensor]] = {
                "prev_key": prev_key,
                "prev_value": prev_value,
            }
            if len(prev_self_attn_state) >= 3:
                saved_state["prev_key_padding_mask"] = prev_self_attn_state[2]
            assert incremental_state is not None
            self.self_attn._set_input_buffer(incremental_state, saved_state)
        _self_attn_input_buffer = self.self_attn._get_input_buffer(incremental_state)
        if self.cross_self_attention and not (
            incremental_state is not None
            and _self_attn_input_buffer is not None
            and "prev_key" in _self_attn_input_buffer
        ):
            if self_attn_mask is not None:
                assert encoder_out is not None
                self_attn_mask = torch.cat(
                    (x.new_zeros(x.size(0), encoder_out.size(0)), self_attn_mask), dim=1
                )
            if self_attn_padding_mask is not None:
                if encoder_padding_mask is None:
                    assert encoder_out is not None
                    encoder_padding_mask = self_attn_padding_mask.new_zeros(
                        encoder_out.size(1), encoder_out.size(0)
                    )
                self_attn_padding_mask = torch.cat(
                    (encoder_padding_mask, self_attn_padding_mask), dim=1
                )
            assert encoder_out is not None
            y = torch.cat((encoder_out, x), dim=0)
        else:
            y = x

        x, attn = self.self_attn(
            query=x,
            key=y,
            value=y,
            key_padding_mask=self_attn_padding_mask,
            incremental_state=incremental_state,
            need_weights=False,
            attn_mask=self_attn_mask,
            attn_bias=self_attn_bias
        )
        if self.self_attn_ln is not None:
            x = self.self_attn_ln(x)
        x = self.dropout_module(x)
        x = self.residual_connection(x, residual)
        if not self.normalize_before:
            x = self.self_attn_layer_norm(x)

        if self.encoder_attn is not None and encoder_out is not None:
            residual = x
            if self.normalize_before:
                x = self.encoder_attn_layer_norm(x)
            if prev_attn_state is not None:
                prev_key, prev_value = prev_attn_state[:2]
                saved_state: Dict[str, Optional[Tensor]] = {
                    "prev_key": prev_key,
                    "prev_value": prev_value,
                }
                if len(prev_attn_state) >= 3:
                    saved_state["prev_key_padding_mask"] = prev_attn_state[2]
                assert incremental_state is not None
                self.encoder_attn._set_input_buffer(incremental_state, saved_state)

            x, attn = self.encoder_attn(
                query=x,
                key=encoder_out,
                value=encoder_out,
                key_padding_mask=encoder_padding_mask,
                incremental_state=incremental_state,
                static_kv=True,
                need_weights=need_attn or (not self.training and self.need_attn),
                need_head_weights=need_head_weights,
                attn_bias=cross_attn_bias
            )
            if self.cross_attn_ln is not None:
                x = self.cross_attn_ln(x)
            x = self.dropout_module(x)
            x = self.residual_connection(x, residual)
            if not self.normalize_before:
                x = self.encoder_attn_layer_norm(x)

        residual = x
        if self.normalize_before:
            x = self.final_layer_norm(x)

        x = self.activation_fn(self.fc1(x))
        x = self.activation_dropout_module(x)
        if self.ffn_layernorm is not None:
            x = self.ffn_layernorm(x)
        x = self.fc2(x)
        x = self.dropout_module(x)
        if self.w_resid is not None:
            residual = torch.mul(self.w_resid, residual)
        x = self.residual_connection(x, residual)
        if not self.normalize_before:
            x = self.final_layer_norm(x)
        if self.onnx_trace and incremental_state is not None:
            saved_state = self.self_attn._get_input_buffer(incremental_state)
            assert saved_state is not None
            if self_attn_padding_mask is not None:
                self_attn_state = [
                    saved_state["prev_key"],
                    saved_state["prev_value"],
                    saved_state["prev_key_padding_mask"],
                ]
            else:
                self_attn_state = [saved_state["prev_key"], saved_state["prev_value"]]
            return x, attn, self_attn_state
        return x, attn, None

    def make_generation_fast_(self, need_attn: bool = False, **kwargs):
        self.need_attn = need_attn

    def upgrade_state_dict_named(self, state_dict, name):
        """
        Rename layer norm states from `...layer_norms.0.weight` to
        `...self_attn_layer_norm.weight` and `...layer_norms.1.weight` to
        `...final_layer_norm.weight`
        """
        # update layer norms
        layer_norm_map = {
            "0": "self_attn_layer_norm",
            "1": "encoder_attn_layer_norm",
            "2": "final_layer_norm",
        }
        for old, new in layer_norm_map.items():
            for m in ("weight", "bias"):
                k = "{}.layer_norms.{}.{}".format(name, old, m)
                if k in state_dict:
                    state_dict[
                        "{}.{}.{}".format(name, new, m)
                    ] = state_dict[k]
                    del state_dict[k]
                if "{}.{}.{}".format(name, new, m) not in state_dict and "{}.{}".format(new, m) in self.state_dict():
                    state_dict[
                        "{}.{}.{}".format(name, new, m)
                    ] = self.state_dict()["{}.{}".format(new, m)]

        prefix = name + "." if name != "" else ""
        for param_name, param_tensor in self.state_dict().items():
            if (prefix + param_name) not in state_dict:
                state_dict[prefix + param_name] = self.state_dict()[param_name]