#!/usr/bin/env python
# -*- encoding: utf-8 -*-

import math

import torch
from torch import Tensor
from torch import nn as nn

from colossalai import kernel
from colossalai import nn as col_nn
from colossalai.core import global_context as gpc
from colossalai.kernel.cuda_native.scaled_softmax import AttnMaskType
from colossalai.nn.layer import Linear1D_Col, Linear1D_Row
from colossalai.nn.layer.base_layer import ParallelLayer
from colossalai.nn.layer.utils import ACT2FN, divide
from colossalai.utils import checkpoint
from colossalai.utils.activation_checkpoint import checkpoint

__all__ = [
    'GPTMLP1D', 'GPTSelfAttention1D', 'GPTTransformerLayer1D', 'FusedGPTSelfAttention1D', 'FusedGPTTransformerLayer1D'
]


class GPTMLP1D(ParallelLayer):

    def __init__(
        self,
        in_features: int,
        mlp_ratio: int,
        act_func: str = 'gelu',
        dropout_prob: float = 0.,
        dtype=None,
        checkpoint: bool = False,
        skip_bias_add: bool = False,
    ):
        super().__init__()

        self.in_features = in_features
        self.mlp_ratio = mlp_ratio
        self.checkpoint = checkpoint
        self.skip_bias_add = skip_bias_add

        self.act = ACT2FN[act_func]
        skip_dense_1_add_bias = False

        # Project to mlp_ratio * h.
        self.dense_1 = Linear1D_Col(
            self.in_features,
            int(self.mlp_ratio * self.in_features),
            dtype=dtype,
            gather_output=False,
            skip_bias_add=skip_dense_1_add_bias,
        )

        # Project back to h.
        self.dense_2 = Linear1D_Row(
            int(self.mlp_ratio * self.in_features),
            self.in_features,
            dtype=dtype,
            parallel_input=True,
        )

        self.dropout = col_nn.Dropout(dropout_prob)

    def _forward(self, hidden_states: Tensor) -> Tensor:
        intermediate_output = self.dense_1(hidden_states)
        intermediate_output = self.act(intermediate_output)

        output = self.dense_2(intermediate_output)
        output = self.dropout(output)
        return output

    def _checkpoint_forward(self, hidden_states: Tensor) -> Tensor:
        return checkpoint(self._forward, False, hidden_states)

    def forward(self, hidden_states: Tensor) -> Tensor:
        if self.checkpoint:
            return self._checkpoint_forward(hidden_states)
        else:
            return self._forward(hidden_states)


class GenericGPTSelfAttention1D(ParallelLayer):

    def __init__(
        self,
        hidden_size: int,
        num_attention_heads: int,
        attention_dropout_prob: float,
        hidden_dropout_prob: float,
        dtype=None,
        checkpoint: bool = False,
        max_position_embeddings=1024,
    ):
        super().__init__()
        self.hidden_size = hidden_size
        self.attention_head_size = divide(hidden_size, num_attention_heads)
        self.num_attention_heads_per_partition = divide(num_attention_heads, gpc.tensor_parallel_size)
        self.hidden_size_per_partition = divide(hidden_size, gpc.tensor_parallel_size)
        self.checkpoint = checkpoint
        self.query_key_value = Linear1D_Col(
            hidden_size,
            3 * hidden_size,
            dtype=dtype,
        )
        self.attention_dropout = col_nn.Dropout(attention_dropout_prob)
        self.dense = Linear1D_Row(
            hidden_size,
            hidden_size,
            dtype=dtype,
            parallel_input=True,
        )
        self.dropout = col_nn.Dropout(hidden_dropout_prob)

    def softmax_forward(self, attention_scores, attention_mask, query_layer, key_layer):
        raise NotImplementedError

    def _forward(self, hidden_states: Tensor, attention_mask=None) -> Tensor:
        query_key_value = self.query_key_value(hidden_states)
        new_qkv_shape = query_key_value.shape[:-1] + \
            (self.num_attention_heads_per_partition, 3 * self.attention_head_size)
        query_key_value = query_key_value.view(new_qkv_shape)
        query_key_value = query_key_value.permute((0, 2, 1, 3))
        query_layer, key_layer, value_layer = torch.chunk(query_key_value, 3, dim=-1)

        attention_scores = torch.matmul(query_layer, key_layer.transpose(-1, -2))

        attention_scores = self.softmax_forward(attention_scores, attention_mask, query_layer, key_layer)

        attention_scores = attention_scores.type(value_layer.dtype)

        attention_probs = self.attention_dropout(attention_scores)

        context_layer = torch.matmul(attention_probs, value_layer)
        context_layer = context_layer.transpose(1, 2)
        new_context_layer_shape = context_layer.size()[:-2] + (self.hidden_size_per_partition,)
        context_layer = context_layer.reshape(new_context_layer_shape)
        output = self.dense(context_layer)
        output = self.dropout(output)

        return output

    def _checkpoint_forward(self, hidden_states: Tensor, attention_mask=None) -> Tensor:
        return checkpoint(self._forward, False, hidden_states, attention_mask)

    def forward(self, hidden_states: Tensor, attention_mask=None) -> Tensor:
        if self.checkpoint:
            return self._checkpoint_forward(hidden_states, attention_mask)
        else:
            return self._forward(hidden_states, attention_mask)


class GPTSelfAttention1D(GenericGPTSelfAttention1D):

    def __init__(self,
                 hidden_size: int,
                 num_attention_heads: int,
                 attention_dropout_prob: float,
                 hidden_dropout_prob: float,
                 dtype=None,
                 checkpoint: bool = False,
                 max_position_embeddings=1024):
        super().__init__(hidden_size,
                         num_attention_heads,
                         attention_dropout_prob,
                         hidden_dropout_prob,
                         dtype=dtype,
                         checkpoint=checkpoint,
                         max_position_embeddings=max_position_embeddings)
        self.softmax = nn.Softmax(dim=-1)
        max_positions = max_position_embeddings
        self.register_buffer(
            "bias",
            torch.tril(torch.ones((max_positions, max_positions),
                                  dtype=torch.uint8)).view(1, 1, max_positions, max_positions),
        )
        self.register_buffer("masked_bias", torch.tensor(-1e4))

    def softmax_forward(self, attention_scores, attention_mask, query_layer, key_layer):
        attention_scores = attention_scores / math.sqrt(self.attention_head_size)
        # causal mask
        query_length, key_length = query_layer.size(-2), key_layer.size(-2)
        causal_mask = self.bias[:, :, key_length - query_length:key_length, :key_length].bool()
        attention_scores = torch.where(causal_mask, attention_scores, self.masked_bias.to(attention_scores))
        if attention_mask is not None:
            # Apply the attention mask
            attention_scores = attention_scores + attention_mask
        attention_scores = self.softmax(attention_scores)
        return attention_scores


class FusedGPTSelfAttention1D(GenericGPTSelfAttention1D):

    def __init__(self,
                 hidden_size: int,
                 num_attention_heads: int,
                 attention_dropout_prob: float,
                 hidden_dropout_prob: float,
                 dtype=None,
                 checkpoint: bool = False,
                 max_position_embeddings=1024):
        super().__init__(hidden_size,
                         num_attention_heads,
                         attention_dropout_prob,
                         hidden_dropout_prob,
                         dtype=dtype,
                         checkpoint=checkpoint,
                         max_position_embeddings=max_position_embeddings)
        self.softmax = kernel.FusedScaleMaskSoftmax(input_in_fp16=True,
                                                    input_in_bf16=False,
                                                    attn_mask_type=AttnMaskType.causal,
                                                    scaled_masked_softmax_fusion=True,
                                                    mask_func=None,
                                                    softmax_in_fp32=True,
                                                    scale=math.sqrt(self.attention_head_size))

    def softmax_forward(self, attention_scores, attention_mask, query_layer, key_layer):
        return self.softmax(attention_scores, attention_mask)


class GenericGPTTransformerLayer1D(ParallelLayer):

    def __init__(self,
                 hidden_size: int,
                 num_attention_heads: int,
                 act_func: str = 'gelu',
                 mlp_ratio: float = 4.0,
                 attention_dropout_prob: float = 0.,
                 hidden_dropout_prob: float = 0.,
                 dtype=None,
                 checkpoint: bool = False,
                 max_position_embeddings: int = 1024,
                 layer_norm_epsilon: float = 1e-5,
                 apply_post_layer_norm: bool = False,
                 attention=None,
                 layer_norm=None):
        super().__init__()
        self.checkpoint = checkpoint
        self.dtype = dtype
        self.norm1 = layer_norm(hidden_size, eps=layer_norm_epsilon)
        self.apply_post_layer_norm = apply_post_layer_norm
        self.attention = attention(
            hidden_size=hidden_size,
            num_attention_heads=num_attention_heads,
            attention_dropout_prob=attention_dropout_prob,
            hidden_dropout_prob=hidden_dropout_prob,
            dtype=dtype,
            max_position_embeddings=max_position_embeddings,
            checkpoint=False,
        )

        self.norm2 = layer_norm(hidden_size, eps=layer_norm_epsilon)
        self.mlp = GPTMLP1D(
            in_features=hidden_size,
            dropout_prob=hidden_dropout_prob,
            act_func=act_func,
            mlp_ratio=mlp_ratio,
            dtype=dtype,
            checkpoint=False,
        )

    def _forward(self, hidden_states, attention_mask) -> Tensor:
        if not self.apply_post_layer_norm:
            residual = hidden_states
        hidden_states = self.norm1(hidden_states)
        if self.apply_post_layer_norm:
            residual = hidden_states
        attention_output = self.attention(hidden_states, attention_mask)
        hidden_states = residual + attention_output

        if not self.apply_post_layer_norm:
            residual = hidden_states
        hidden_states = self.norm2(hidden_states)
        if self.apply_post_layer_norm:
            residual = hidden_states
        feed_forward_hidden_states = self.mlp(hidden_states)
        hidden_states = residual + feed_forward_hidden_states

        output = (hidden_states, attention_mask)
        return output

    def forward(self, hidden_states, attention_mask):
        if self.checkpoint:
            return checkpoint(self._forward, False, hidden_states, attention_mask)
        else:
            return self._forward(hidden_states, attention_mask)


class GPTTransformerLayer1D(GenericGPTTransformerLayer1D):

    def __init__(self,
                 hidden_size: int,
                 num_attention_heads: int,
                 act_func: str = 'gelu',
                 mlp_ratio: float = 4,
                 attention_dropout_prob: float = 0,
                 hidden_dropout_prob: float = 0,
                 dtype=None,
                 checkpoint: bool = False,
                 max_position_embeddings: int = 1024,
                 layer_norm_epsilon: float = 0.00001,
                 apply_post_layer_norm: bool = False):
        attention = GPTSelfAttention1D
        layer_norm = nn.LayerNorm
        super().__init__(hidden_size,
                         num_attention_heads,
                         act_func=act_func,
                         mlp_ratio=mlp_ratio,
                         attention_dropout_prob=attention_dropout_prob,
                         hidden_dropout_prob=hidden_dropout_prob,
                         dtype=dtype,
                         checkpoint=checkpoint,
                         max_position_embeddings=max_position_embeddings,
                         layer_norm_epsilon=layer_norm_epsilon,
                         apply_post_layer_norm=apply_post_layer_norm,
                         attention=attention,
                         layer_norm=layer_norm)


class FusedGPTTransformerLayer1D(GenericGPTTransformerLayer1D):

    def __init__(self,
                 hidden_size: int,
                 num_attention_heads: int,
                 act_func: str = 'gelu',
                 mlp_ratio: float = 4,
                 attention_dropout_prob: float = 0,
                 hidden_dropout_prob: float = 0,
                 dtype=None,
                 checkpoint: bool = False,
                 max_position_embeddings: int = 1024,
                 layer_norm_epsilon: float = 0.00001,
                 apply_post_layer_norm: bool = False):
        attention = FusedGPTSelfAttention1D
        layer_norm = kernel.LayerNorm
        super().__init__(hidden_size,
                         num_attention_heads,
                         act_func=act_func,
                         mlp_ratio=mlp_ratio,
                         attention_dropout_prob=attention_dropout_prob,
                         hidden_dropout_prob=hidden_dropout_prob,
                         dtype=dtype,
                         checkpoint=checkpoint,
                         max_position_embeddings=max_position_embeddings,
                         layer_norm_epsilon=layer_norm_epsilon,
                         apply_post_layer_norm=apply_post_layer_norm,
                         attention=attention,
                         layer_norm=layer_norm)
