import warnings
from functools import partial
from typing import Callable, Dict, List

import torch.nn as nn
from torch import Tensor, nn

from colossalai.shardformer.layer import FusedLayerNorm, Linear1D_Col, Linear1D_Row, VocabParallelEmbedding1D

from .._utils import getattr_
from ..modeling.jit import get_jit_fused_dropout_add_func
from ..modeling.opt import OPTPipelineForwards, get_jit_fused_opt_decoder_layer_forward, get_opt_flash_attention_forward
from .base_policy import ModulePolicyDescription, Policy, SubModuleReplacementDescription

__all__ = [
    'OPTPolicy', 'OPTModelPolicy', 'OPTForCausalLMPolicy', 'OPTForSequenceClassificationPolicy',
    'OPTForQuestionAnsweringPolicy'
]


class OPTPolicy(Policy):

    def config_sanity_check(self):
        pass

    def preprocess(self):
        # reshape the embedding layer
        r"""
        Reshape the Embedding layer to make the embedding dimension divisible by world_size
        """
        if self.shard_config.enable_tensor_parallelism:
            vocab_size = self.model.config.vocab_size
            world_size = self.shard_config.tensor_parallel_size
            if vocab_size % world_size != 0:
                new_vocab_size = vocab_size + world_size - vocab_size % world_size
                self.model.resize_token_embeddings(new_vocab_size)
        return self.model

    def module_policy(self):
        from transformers.models.opt.modeling_opt import OPTAttention, OPTDecoder, OPTDecoderLayer

        policy = {}
        if self.shard_config.enable_sequence_parallelism:
            self.shard_config.enable_sequence_parallelism = False
            warnings.warn("OPT dosen't support sequence parallelism now, will ignore the sequence parallelism flag.")

        if self.shard_config.enable_tensor_parallelism:
            policy[OPTDecoder] = ModulePolicyDescription(sub_module_replacement=[
                SubModuleReplacementDescription(
                    suffix="embed_tokens",
                    target_module=VocabParallelEmbedding1D,
                )
            ])
            policy[OPTDecoderLayer] = ModulePolicyDescription(sub_module_replacement=[
                SubModuleReplacementDescription(
                    suffix="fc1",
                    target_module=Linear1D_Col,
                ),
                SubModuleReplacementDescription(
                    suffix="fc2",
                    target_module=Linear1D_Row,
                )
            ])

            policy[OPTAttention] = ModulePolicyDescription(attribute_replacement={
                "embed_dim": self.model.config.hidden_size // self.shard_config.tensor_parallel_size,
                "num_heads": self.model.config.num_attention_heads // self.shard_config.tensor_parallel_size
            },
                                                           sub_module_replacement=[
                                                               SubModuleReplacementDescription(
                                                                   suffix="q_proj",
                                                                   target_module=Linear1D_Col,
                                                               ),
                                                               SubModuleReplacementDescription(
                                                                   suffix="k_proj",
                                                                   target_module=Linear1D_Col,
                                                               ),
                                                               SubModuleReplacementDescription(
                                                                   suffix="v_proj",
                                                                   target_module=Linear1D_Col,
                                                               ),
                                                               SubModuleReplacementDescription(
                                                                   suffix="out_proj",
                                                                   target_module=Linear1D_Row,
                                                               ),
                                                           ])

        # optimization configuration
        if self.shard_config.enable_fused_normalization:
            self.append_or_create_submodule_replacement(description=SubModuleReplacementDescription(
                suffix="final_layer_norm", target_module=FusedLayerNorm, ignore_if_not_exist=True),
                                                        policy=policy,
                                                        target_key=OPTDecoder)
            self.append_or_create_submodule_replacement(description=[
                SubModuleReplacementDescription(suffix="self_attn_layer_norm",
                                                target_module=FusedLayerNorm,
                                                ignore_if_not_exist=True),
                SubModuleReplacementDescription(suffix="final_layer_norm",
                                                target_module=FusedLayerNorm,
                                                ignore_if_not_exist=True)
            ],
                                                        policy=policy,
                                                        target_key=OPTDecoderLayer)

        # use flash attention
        if self.shard_config.enable_flash_attention:
            self.append_or_create_method_replacement(description={
                'forward': get_opt_flash_attention_forward(),
            },
                                                     policy=policy,
                                                     target_key=OPTAttention)

        # use jit fused operator
        if self.shard_config.enable_jit_fused:
            self.append_or_create_method_replacement(description={
                'forward': get_jit_fused_opt_decoder_layer_forward(),
                'dropout_add': get_jit_fused_dropout_add_func(),
            },
                                                     policy=policy,
                                                     target_key=OPTDecoderLayer)

        return policy

    def postprocess(self):
        return self.model

    def get_held_layers(self) -> List[nn.Module]:
        """Get pipeline layers for current stage."""
        assert self.pipeline_stage_manager is not None

        if self.model.__class__.__name__ == 'OPTModel':
            module = self.model.decoder
        else:
            module = self.model.model.decoder
        stage_manager = self.pipeline_stage_manager

        held_layers = []
        layers_per_stage = self.distribute_layers(len(module.layers), stage_manager.num_stages)
        if stage_manager.is_first_stage():
            held_layers.append(module.embed_tokens)
            held_layers.append(module.embed_positions)
            held_layers.append(module.project_in)
        start_idx, end_idx = self.get_stage_index(layers_per_stage, stage_manager.stage)
        held_layers.extend(module.layers[start_idx:end_idx])
        if stage_manager.is_last_stage():
            held_layers.append(module.final_layer_norm)
            held_layers.append(module.project_out)
        return held_layers

    def set_pipeline_forward(self, model_cls: nn.Module, new_forward: Callable, policy: Dict) -> None:
        """If under pipeline parallel setting, replacing the original forward method of huggingface
           to customized forward method, and add this changing to policy."""
        if self.pipeline_stage_manager:
            stage_manager = self.pipeline_stage_manager
            if self.model.__class__.__name__ == 'OPTModel':
                module = self.model.decoder
            else:
                module = self.model.model.decoder

            layers_per_stage = Policy.distribute_layers(len(module.layers), stage_manager.num_stages)
            stage_index = Policy.get_stage_index(layers_per_stage, stage_manager.stage)
            method_replacement = {'forward': partial(new_forward, stage_manager=stage_manager, stage_index=stage_index)}
            self.append_or_create_method_replacement(description=method_replacement,
                                                     policy=policy,
                                                     target_key=model_cls)


class OPTModelPolicy(OPTPolicy):

    def __init__(self) -> None:
        super().__init__()

    def module_policy(self):
        from transformers.models.opt.modeling_opt import OPTModel

        policy = super().module_policy()
        if self.pipeline_stage_manager:
            self.set_pipeline_forward(model_cls=OPTModel,
                                      new_forward=OPTPipelineForwards.opt_model_forward,
                                      policy=policy)
        return policy

    def get_held_layers(self) -> List[nn.Module]:
        return super().get_held_layers()

    def get_shared_params(self) -> List[Dict[int, Tensor]]:
        """No shared params in OPTModel."""
        return []


class OPTForCausalLMPolicy(OPTPolicy):

    def module_policy(self):
        from transformers.models.opt.modeling_opt import OPTForCausalLM

        policy = super().module_policy()
        if self.shard_config.enable_tensor_parallelism:
            self.append_or_create_submodule_replacement(description=SubModuleReplacementDescription(
                suffix="lm_head", target_module=Linear1D_Col, kwargs=dict(gather_output=True)),
                                                        policy=policy,
                                                        target_key=OPTForCausalLM)
        if self.pipeline_stage_manager:
            self.set_pipeline_forward(model_cls=OPTForCausalLM,
                                      new_forward=OPTPipelineForwards.opt_for_causal_lm_forward,
                                      policy=policy)

        return policy

    def get_held_layers(self) -> List[nn.Module]:
        held_layers = super().get_held_layers()
        if self.pipeline_stage_manager.is_last_stage():
            held_layers.append(self.model.lm_head)
        return held_layers

    def get_shared_params(self) -> List[Dict[int, Tensor]]:
        opt_model = self.model
        if self.pipeline_stage_manager and self.pipeline_stage_manager.num_stages > 1:
            num_stages = self.pipeline_stage_manager.num_stages
            if id(opt_model.model.decoder.embed_tokens.weight) == id(opt_model.lm_head.weight):
                return [{0: opt_model.model.decoder.embed_tokens.weight, num_stages - 1: opt_model.lm_head.weight}]
        return []

    def postprocess(self):
        if self.shard_config.enable_tensor_parallelism and self.pipeline_stage_manager is None:
            binding_map = {
                'model.decoder.embed_tokens': 'lm_head',
            }

            for k, v in binding_map.items():
                src_mod = getattr_(self.model, k)
                dst_mod = getattr_(self.model, v)
                dst_mod.weight = src_mod.weight

        return self.model


class OPTForSequenceClassificationPolicy(OPTPolicy):

    def __init__(self) -> None:
        super().__init__()

    def module_policy(self):
        from transformers.models.opt.modeling_opt import OPTForSequenceClassification

        policy = super().module_policy()
        if self.pipeline_stage_manager:
            self.set_pipeline_forward(model_cls=OPTForSequenceClassification,
                                      new_forward=OPTPipelineForwards.opt_for_sequence_classification_forward,
                                      policy=policy)

        return policy

    def get_held_layers(self) -> List[nn.Module]:
        held_layers = super().get_held_layers()
        if self.pipeline_stage_manager.is_last_stage():
            held_layers.append(self.model.score)
        return held_layers

    def get_shared_params(self) -> List[Dict[int, Tensor]]:
        "no shared params in OPTForSequenceClassification"
        return []


class OPTForQuestionAnsweringPolicy(OPTPolicy):

    def __init__(self) -> None:
        super().__init__()

    def module_policy(self):
        from transformers.models.opt.modeling_opt import OPTForQuestionAnswering

        policy = super().module_policy()
        if self.pipeline_stage_manager:
            self.set_pipeline_forward(model_cls=OPTForQuestionAnswering,
                                      new_forward=OPTPipelineForwards.opt_for_question_answering_forward,
                                      policy=policy)

        return policy

    def get_held_layers(self) -> List[nn.Module]:
        held_layers = super().get_held_layers()
        if self.pipeline_stage_manager.is_last_stage():
            held_layers.append(self.model.qa_outputs)
        return held_layers

    def get_shared_params(self) -> List[Dict[int, Tensor]]:
        "no shared params in OPTForSequenceClassification"
        return []
