import math
import warnings
from typing import Dict, List, Optional, Tuple, Union

import torch
import torch.distributed
import torch.utils.checkpoint
from torch import nn
from torch.nn import BCEWithLogitsLoss, CrossEntropyLoss, MSELoss
from transformers.cache_utils import Cache, DynamicCache
from transformers.modeling_outputs import (
    BaseModelOutputWithPast,
    CausalLMOutputWithPast,
    SequenceClassifierOutputWithPast,
)
from transformers.models.llama.modeling_llama import (
    LlamaForCausalLM,
    LlamaForSequenceClassification,
    LlamaModel,
    StaticCache,
    apply_rotary_pos_emb,
    repeat_kv,
)
from transformers.utils import logging

from colossalai.pipeline.stage_manager import PipelineStageManager
from colossalai.shardformer.layer._operation import all_to_all_comm, gather_sp_output, split_forward_gather_backward
from colossalai.shardformer.layer.utils import is_share_sp_tp, split_batch_zigzag
from colossalai.shardformer.shard import ShardConfig

from ..layer import ColoAttention, RingAttention, dist_cross_entropy

_SUPPORTED_SP_MODE = ["all_to_all", "split_gather", "ring", "ring_attn"]


class LlamaPipelineForwards:
    """
    This class serves as a micro library for forward function substitution of Llama models
    under pipeline setting.
    """

    @staticmethod
    def llama_model_forward(
        self: LlamaModel,
        input_ids: torch.LongTensor = None,
        attention_mask: Optional[torch.Tensor] = None,
        position_ids: Optional[torch.LongTensor] = None,
        past_key_values: Optional[List[torch.FloatTensor]] = None,
        inputs_embeds: Optional[torch.FloatTensor] = None,
        use_cache: Optional[bool] = None,
        output_attentions: Optional[bool] = None,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
        cache_position: Optional[torch.LongTensor] = None,
        stage_manager: Optional[PipelineStageManager] = None,
        hidden_states: Optional[torch.FloatTensor] = None,
        stage_index: Optional[List[int]] = None,
        shard_config: ShardConfig = None,
        force_sp_gather: bool = True,  # Set to false only when computing cross entropy
    ):
        logger = logging.get_logger(__name__)

        output_attentions = output_attentions if output_attentions is not None else self.config.output_attentions
        output_hidden_states = (
            output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
        )
        use_cache = use_cache if use_cache is not None else self.config.use_cache
        if use_cache:
            logger.warning_once(
                "`use_cache=True` is incompatible with pipeline parallelism. Setting `use_cache=False`..."
            )
            use_cache = False

        return_dict = return_dict if return_dict is not None else self.config.use_return_dict

        disable_pp = stage_manager is None
        # retrieve input_ids and inputs_embeds
        if disable_pp or stage_manager.is_first_stage():
            if input_ids is not None and inputs_embeds is not None:
                raise ValueError("You cannot specify both input_ids and inputs_embeds at the same time")
            elif input_ids is not None:
                batch_size, seq_length = input_ids.shape[:2]
            elif inputs_embeds is not None:
                batch_size, seq_length = inputs_embeds.shape[:2]
            else:
                raise ValueError("You have to specify either input_ids or inputs_embeds")
            if inputs_embeds is None:
                inputs_embeds = self.embed_tokens(input_ids)
            hidden_states = inputs_embeds
            device = hidden_states.device
        else:
            input_shape = hidden_states.shape[:-1]
            batch_size, seq_length = input_shape
            device = hidden_states.device

        # Support SP + PP
        sp_mode = shard_config.sequence_parallelism_mode
        sp_group = shard_config.sequence_parallel_process_group
        sp_size = shard_config.sequence_parallel_size
        # Generating full positions ids for modes that gather sequence before attn
        if stage_manager and (sp_mode != "ring_attn" and not stage_manager.is_first_stage()):
            seq_length *= sp_size

        past_seen_tokens = 0
        if use_cache:  # kept for BC (cache positions)
            if not isinstance(past_key_values, StaticCache):
                past_key_values = DynamicCache.from_legacy_cache(past_key_values)
                past_seen_tokens = past_key_values.get_seq_length()
        if cache_position is None:
            if isinstance(past_key_values, StaticCache):
                raise ValueError("cache_position is a required argument when using StaticCache.")
            cache_position = torch.arange(past_seen_tokens, past_seen_tokens + seq_length, device=device)

        seq_length_with_past = seq_length + past_seen_tokens

        if output_attentions:
            logger.warning_once("output_attentions=True is not supported for pipeline models at the moment.")
            output_attentions = False
        if output_hidden_states:
            logger.warning_once("output_hidden_states=True is not supported for pipeline models at the moment.")
            output_hidden_states = False
        if use_cache:
            logger.warning_once("use_cache=True is not supported for pipeline models at the moment.")
            use_cache = False

        if position_ids is None:
            position_ids = cache_position.unsqueeze(0)

        no_split_input = disable_pp or not stage_manager.is_first_stage()
        if no_split_input and sp_mode == "ring_attn":
            _, attn_kwargs, _ = RingAttention.prepare_varlen_batch(attention_mask, sp_group)
        elif shard_config.enable_flash_attention:
            mask_shape = (batch_size, 1, seq_length_with_past, seq_length_with_past)
            attn_kwargs: dict = ColoAttention.prepare_attn_kwargs(
                mask_shape,
                hidden_states.dtype,
                hidden_states.device,
                q_padding_mask=attention_mask,
                is_causal=True,
                invert=(sp_mode != "ring_attn"),
            )
        else:
            attn_kwargs: torch.Tensor = self._update_causal_mask(
                attention_mask, hidden_states, cache_position, past_key_values
            )

        # Support SP + PP. Later stages have already received the split input.
        split_input = disable_pp or stage_manager.is_first_stage()
        if split_input:
            # Ring Attention zigzag batch processing
            if sp_mode == "ring_attn":
                assert shard_config.enable_flash_attention, "Ring Attention inherently requires Flash Attention."
                if not attention_mask.bool().all():
                    hidden_states, attn_kwargs, position_ids = RingAttention.prepare_varlen_batch(
                        attention_mask, sp_group, hidden_states, position_ids
                    )
                else:
                    hidden_states, position_ids = split_batch_zigzag([hidden_states, position_ids], sp_group)

            elif is_share_sp_tp(sp_mode):
                hidden_states = split_forward_gather_backward(
                    hidden_states, 1, sp_group, fp8_communication=shard_config.fp8_communication
                )
            elif sp_mode == "all_to_all":
                hidden_states = split_forward_gather_backward(
                    hidden_states, 1, sp_group, 1 / sp_size, fp8_communication=shard_config.fp8_communication
                )

        if self.gradient_checkpointing and self.training and use_cache:
            if use_cache:
                logger.warning_once(
                    "`use_cache=True` is incompatible with gradient checkpointing. Setting `use_cache=False`..."
                )
                use_cache = False

        # decoder layers
        all_hidden_states = () if output_hidden_states else None
        all_self_attns = () if output_attentions else None
        next_decoder_cache = None
        start_idx, end_idx = (0, len(self.layers)) if disable_pp else (stage_index[0], stage_index[1])
        position_embeddings = self.rotary_emb(hidden_states, position_ids)

        num_ckpt_layers = 0
        if self.gradient_checkpointing and self.training:
            num_ckpt_layers = end_idx - start_idx
            # TODO: We can replace `gradient_checkpointing_enable` fn and initialize a gradient_checkpointing (List[bool]) for each layer
            if shard_config.gradient_checkpoint_config is not None:
                num_ckpt_layers = shard_config.gradient_checkpoint_config.get_num_ckpt_layers(
                    stage=stage_manager.stage,
                    num_stages=stage_manager.num_stages,
                    num_layers=end_idx - start_idx,
                    model_chunk_id=(stage_manager.model_chunk_id if stage_manager.is_interleave else 0),
                    num_model_chunks=stage_manager.num_model_chunks,
                )
            assert num_ckpt_layers <= end_idx - start_idx
        for idx, decoder_layer in enumerate(self.layers[start_idx:end_idx], start=start_idx):
            if output_hidden_states:
                all_hidden_states += (hidden_states,)
            if idx - start_idx < num_ckpt_layers:
                layer_outputs = self._gradient_checkpointing_func(
                    decoder_layer.__call__,
                    hidden_states,
                    attn_kwargs,
                    position_ids,
                    past_key_values,
                    output_attentions,
                    use_cache,
                    cache_position,
                    position_embeddings,
                )
            else:
                layer_outputs = decoder_layer(
                    hidden_states,
                    attention_mask=attn_kwargs,
                    position_ids=position_ids,
                    past_key_value=past_key_values,
                    output_attentions=output_attentions,
                    use_cache=use_cache,
                    cache_position=cache_position,
                    position_embeddings=position_embeddings,
                )
            hidden_states = layer_outputs[0]

            if use_cache:
                next_decoder_cache = layer_outputs[2 if output_attentions else 1]
            if output_attentions:
                all_self_attns += (layer_outputs[1],)

        if disable_pp or stage_manager.is_last_stage():
            hidden_states = self.norm(hidden_states)
            if (not shard_config.parallel_output) or force_sp_gather or is_share_sp_tp(sp_mode):  # noqa
                hidden_states = gather_sp_output(hidden_states, shard_config)

        # add hidden states from the last decoder layer
        if output_hidden_states:
            all_hidden_states += (hidden_states,)
        next_cache = next_decoder_cache if use_cache else None
        if disable_pp or stage_manager.is_last_stage():
            if not return_dict:
                return tuple(
                    v
                    for v in [
                        hidden_states,
                        next_cache,
                        all_hidden_states,
                        all_self_attns,
                    ]
                    if v is not None
                )
            return BaseModelOutputWithPast(
                last_hidden_state=hidden_states,
                past_key_values=next_cache,
                hidden_states=all_hidden_states,
                attentions=all_self_attns,
            )
        # always return dict for intermediate stage
        return {"hidden_states": hidden_states}

    @staticmethod
    def llama_for_causal_lm_forward(
        self: LlamaForCausalLM,
        input_ids: torch.LongTensor = None,
        attention_mask: Optional[torch.Tensor] = None,
        position_ids: Optional[torch.LongTensor] = None,
        past_key_values: Optional[List[torch.FloatTensor]] = None,
        inputs_embeds: Optional[torch.FloatTensor] = None,
        labels: Optional[torch.LongTensor] = None,
        use_cache: Optional[bool] = None,
        output_attentions: Optional[bool] = None,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
        cache_position: Optional[torch.LongTensor] = None,
        stage_manager: Optional[PipelineStageManager] = None,
        hidden_states: Optional[torch.FloatTensor] = None,
        stage_index: Optional[List[int]] = None,
        shard_config: ShardConfig = None,
        **kwargs,
    ):
        r"""
        Args:
            labels (`torch.LongTensor` of shape `(batch_size, sequence_length)`, *optional*):
                Labels for computing the masked language modeling loss. Indices should either be in `[0, ...,
                config.vocab_size]` or -100 (see `input_ids` docstring). Tokens with indices set to `-100` are ignored
                (masked), the loss is only computed for the tokens with labels in `[0, ..., config.vocab_size]`.

        Returns:

        Example:

        ```python
        >>> from transformers import AutoTokenizer, LlamaForCausalLM

        >>> model = LlamaForCausalLM.from_pretrained(PATH_TO_CONVERTED_WEIGHTS)
        >>> tokenizer = AutoTokenizer.from_pretrained(PATH_TO_CONVERTED_TOKENIZER)

        >>> prompt = "Hey, are you conscious? Can you talk to me?"
        >>> inputs = tokenizer(prompt, return_tensors="pt")

        >>> # Generate
        >>> generate_ids = model.generate(inputs.input_ids, max_length=30)
        >>> tokenizer.batch_decode(generate_ids, skip_special_tokens=True, clean_up_tokenization_spaces=False)[0]
        "Hey, are you conscious? Can you talk to me?\nI'm not conscious, but I can talk to you."
        ```"""
        logger = logging.get_logger(__name__)
        output_attentions = output_attentions if output_attentions is not None else self.config.output_attentions
        output_hidden_states = (
            output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
        )
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict

        # TODO(jianghai): left the recording kv-value tensors as () or None type, this feature may be added in the future.
        if output_attentions:
            logger.warning_once("output_attentions=True is not supported for pipeline models at the moment.")
            output_attentions = False
        if output_hidden_states:
            logger.warning_once("output_hidden_states=True is not supported for pipeline models at the moment.")
            output_hidden_states = False

        if shard_config.sequence_parallelism_mode == "ring_attn" and shard_config.parallel_output:
            # Split labels in a zigzag fashion too
            sp_group = shard_config.sequence_parallel_process_group
            if attention_mask.bool().all():
                labels = split_batch_zigzag(labels, sp_group, seq_dim=1, is_label=True)
            else:
                # [B, max_seqlen // sp_size]
                labels, _, _ = RingAttention.prepare_varlen_batch(attention_mask, sp_group, labels, is_label=True)

        # decoder outputs consists of (dec_features, layer_state, dec_hidden, dec_attn)
        outputs = LlamaPipelineForwards.llama_model_forward(
            self.model,
            input_ids=input_ids,
            attention_mask=attention_mask,
            position_ids=position_ids,
            past_key_values=past_key_values,
            inputs_embeds=inputs_embeds,
            use_cache=use_cache,
            output_attentions=output_attentions,
            output_hidden_states=output_hidden_states,
            return_dict=return_dict,
            cache_position=cache_position,
            stage_manager=stage_manager,
            hidden_states=hidden_states,
            stage_index=stage_index,
            shard_config=shard_config,
            force_sp_gather=False,
        )
        past_key_values = None

        disable_pp = stage_manager is None
        if disable_pp or stage_manager.is_last_stage():
            hidden_states = outputs[0]
            logits = self.lm_head(hidden_states)
            loss = None
            if labels is not None:
                loss = dist_cross_entropy(labels, logits, shard_config, self.lm_head.out_features, self.model.dtype)

            if not return_dict:
                output = (logits,) + outputs[1:]
                return (loss,) + output if loss is not None else output

            return CausalLMOutputWithPast(
                loss=loss,
                logits=logits,
                past_key_values=outputs.past_key_values,
                hidden_states=outputs.hidden_states,
                attentions=outputs.attentions,
            )
        else:
            hidden_states = outputs.get("hidden_states")
            return {"hidden_states": hidden_states}

    @staticmethod
    def llama_for_sequence_classification_forward(
        self: LlamaForSequenceClassification,
        input_ids: torch.LongTensor = None,
        attention_mask: Optional[torch.Tensor] = None,
        position_ids: Optional[torch.LongTensor] = None,
        past_key_values: Optional[List[torch.FloatTensor]] = None,
        inputs_embeds: Optional[torch.FloatTensor] = None,
        labels: Optional[torch.LongTensor] = None,
        use_cache: Optional[bool] = None,
        output_attentions: Optional[bool] = None,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
        cache_position: Optional[torch.LongTensor] = None,
        stage_manager: Optional[PipelineStageManager] = None,
        hidden_states: Optional[torch.FloatTensor] = None,
        stage_index: Optional[List[int]] = None,
        shard_config: ShardConfig = None,
    ):
        r"""
        labels (`torch.LongTensor` of shape `(batch_size,)`, *optional*):
            Labels for computing the sequence classification/regression loss. Indices should be in `[0, ...,
            config.num_labels - 1]`. If `config.num_labels == 1` a regression loss is computed (Mean-Square loss), If
            `config.num_labels > 1` a classification loss is computed (Cross-Entropy).
        """
        logger = logging.get_logger(__name__)

        return_dict = return_dict if return_dict is not None else self.config.use_return_dict
        # TODO(jianghai): left the recording kv-value tensors as () or None type, this feature may be added in the future.
        if output_attentions:
            logger.warning_once("output_attentions=True is not supported for pipeline models at the moment.")
            output_attentions = False
        if output_hidden_states:
            logger.warning_once("output_hidden_states=True is not supported for pipeline models at the moment.")
            output_hidden_states = False

        transformer_outputs = LlamaPipelineForwards.llama_model_forward(
            self.model,
            input_ids,
            attention_mask=attention_mask,
            position_ids=position_ids,
            past_key_values=past_key_values,
            inputs_embeds=inputs_embeds,
            use_cache=use_cache,
            output_attentions=output_attentions,
            output_hidden_states=output_hidden_states,
            return_dict=return_dict,
            cache_position=cache_position,
            stage_manager=stage_manager,
            hidden_states=hidden_states,
            stage_index=stage_index,
            shard_config=shard_config,
        )

        if input_ids is not None:
            batch_size = input_ids.shape[0]
        elif inputs_embeds is not None:
            batch_size = inputs_embeds.shape[0]
        else:
            batch_size = hidden_states.shape[0]

        if stage_manager.is_last_stage():
            hidden_states = transformer_outputs[0]
            logits = self.score(hidden_states)

            if self.config.pad_token_id is None and batch_size != 1:
                raise ValueError("Cannot handle batch sizes > 1 if no padding token is defined.")
            if self.config.pad_token_id is None:
                sequence_lengths = -1
            else:
                if input_ids is not None:
                    sequence_lengths = (torch.ne(input_ids, self.config.pad_token_id).sum(-1) - 1).to(logits.device)
                else:
                    sequence_lengths = -1

            pooled_logits = logits[torch.arange(batch_size, device=logits.device), sequence_lengths]

            loss = None
            if labels is not None:
                labels = labels.to(logits.device)
                if self.config.problem_type is None:
                    if self.num_labels == 1:
                        self.config.problem_type = "regression"
                    elif self.num_labels > 1 and (labels.dtype == torch.long or labels.dtype == torch.int):
                        self.config.problem_type = "single_label_classification"
                    else:
                        self.config.problem_type = "multi_label_classification"

                if self.config.problem_type == "regression":
                    loss_fct = MSELoss()
                    if self.num_labels == 1:
                        loss = loss_fct(pooled_logits.squeeze(), labels.squeeze())
                    else:
                        loss = loss_fct(pooled_logits, labels)
                elif self.config.problem_type == "single_label_classification":
                    loss_fct = CrossEntropyLoss()
                    loss = loss_fct(pooled_logits.view(-1, self.num_labels), labels.view(-1))
                elif self.config.problem_type == "multi_label_classification":
                    loss_fct = BCEWithLogitsLoss()
                    loss = loss_fct(pooled_logits, labels)
            if not return_dict:
                output = (pooled_logits,) + transformer_outputs[1:]
                return ((loss,) + output) if loss is not None else output

            return SequenceClassifierOutputWithPast(
                loss=loss,
                logits=pooled_logits,
                past_key_values=transformer_outputs.past_key_values,
                hidden_states=transformer_outputs.hidden_states,
                attentions=transformer_outputs.attentions,
            )

        else:
            hidden_states = transformer_outputs.get("hidden_states")
            return {"hidden_states": hidden_states}


def get_llama_flash_attention_forward(shard_config: ShardConfig, sp_mode=None, sp_size=None, sp_group=None):
    def forward(
        self,
        hidden_states: torch.Tensor,
        position_embeddings: Tuple[torch.Tensor, torch.Tensor],
        attention_mask: Optional[Union[torch.Tensor, Dict]] = None,
        past_key_value: Optional[Cache] = None,
        output_attentions: bool = False,
        use_cache: bool = False,
        cache_position: Optional[torch.LongTensor] = None,
        **kwargs,
    ) -> Tuple[torch.Tensor, Optional[torch.Tensor], Optional[Cache]]:
        if sp_mode is not None:
            assert sp_mode in _SUPPORTED_SP_MODE, f"SP mode {sp_mode} is not supported by {type(self)} yet"
            assert (sp_size is not None) and (
                sp_group is not None
            ), "Must specify sp_size and sp_group for sequence parallel"
        if "padding_mask" in kwargs:
            warnings.warn(
                "Passing `padding_mask` is deprecated and will be removed in v4.37. Please make sure use `attention_mask` instead.`"
            )

        bsz, q_len, _ = hidden_states.size()
        input_shape = hidden_states.shape[:-1]
        # sp: modify sp_len when sequence parallel mode is ring
        if is_share_sp_tp(sp_mode):
            q_len *= sp_size

        query_states = self.q_proj(hidden_states)
        key_states = self.k_proj(hidden_states)
        value_states = self.v_proj(hidden_states)

        # sp: all-to-all comminucation when introducing sequence parallel
        if sp_mode == "all_to_all":
            query_states = all_to_all_comm(query_states, sp_group, fp8_communication=shard_config.fp8_communication)
            key_states = all_to_all_comm(key_states, sp_group, fp8_communication=shard_config.fp8_communication)
            value_states = all_to_all_comm(value_states, sp_group, fp8_communication=shard_config.fp8_communication)
            bsz, q_len, _ = query_states.size()

        query_states = query_states.view(bsz, q_len, -1, self.head_dim).transpose(1, 2)
        key_states = key_states.view(bsz, q_len, -1, self.head_dim).transpose(1, 2)
        value_states = value_states.view(bsz, q_len, -1, self.head_dim).transpose(1, 2)

        kv_seq_len = key_states.shape[-2]
        if past_key_value is not None:
            if self.layer_idx is None:
                raise ValueError(
                    f"The cache structure has changed since version v4.36. If you are using {self.__class__.__name__} "
                    "for auto-regressive decoding with k/v caching, please make sure to initialize the attention class "
                    "with a layer index."
                )

            kv_seq_len += past_key_value.get_usable_length(kv_seq_len, self.layer_idx)

        cos, sin = position_embeddings
        query_states, key_states = apply_rotary_pos_emb(query_states, key_states, cos, sin)

        if past_key_value is not None:
            cache_kwargs = {"sin": sin, "cos": cos, "cache_position": cache_position}
            key_states, value_states = past_key_value.update(key_states, value_states, self.layer_idx, cache_kwargs)

        # repeat k/v heads if n_kv_heads < n_heads
        key_states = repeat_kv(key_states, self.num_key_value_groups)
        value_states = repeat_kv(value_states, self.num_key_value_groups)

        if sp_mode == "ring_attn":
            attn_output = RingAttention.attention(
                query_states,
                key_states,
                value_states,
                sp_axis=shard_config.sp_axis,
                **attention_mask,
                inner_ring_size=shard_config.inner_ring_size,
                pg_mesh=shard_config.pg_mesh,
            )

        elif shard_config.enable_flash_attention:
            assert isinstance(attention_mask, dict), "Flash Attention Error: attention_mask should be a dict."
            attn_output = ColoAttention.attention(query_states, key_states, value_states, **attention_mask)
        else:
            attn_weights = torch.matmul(query_states, key_states.transpose(2, 3)) / math.sqrt(self.head_dim)
            if attn_weights.size() != (bsz, self.num_heads, q_len, kv_seq_len):
                raise ValueError(
                    f"Attention weights should be of size {(bsz, self.num_heads, q_len, kv_seq_len)}, but is"
                    f" {attn_weights.size()}"
                )

            if attention_mask is not None:
                if attention_mask.size() != (bsz, 1, q_len, kv_seq_len):
                    raise ValueError(
                        f"Attention mask should be of size {(bsz, 1, q_len, kv_seq_len)}, but is {attention_mask.size()}"
                    )
                attn_weights = attn_weights + attention_mask

            # upcast attention to fp32
            attn_weights = nn.functional.softmax(attn_weights, dim=-1, dtype=torch.float32).to(query_states.dtype)
            attn_output = torch.matmul(attn_weights, value_states)

            if attn_output.size() != (bsz, self.num_heads, q_len, self.head_dim):
                raise ValueError(
                    f"`attn_output` should be of size {(bsz, self.num_heads, q_len, self.head_dim)}, but is"
                    f" {attn_output.size()}"
                )

        attn_output = attn_output.transpose(1, 2).contiguous()
        # sp: all-to-all comminucation when introducing sequence parallel
        if sp_mode == "all_to_all":
            attn_output = attn_output.reshape(bsz, q_len, self.num_heads * self.head_dim)
            attn_output = all_to_all_comm(
                attn_output, sp_group, scatter_dim=1, gather_dim=2, fp8_communication=shard_config.fp8_communication
            )
        else:
            attn_output = attn_output.reshape(bsz, q_len, -1).contiguous()

        attn_output = self.o_proj(attn_output)

        if not output_attentions:
            attn_weights = None
        return attn_output, attn_weights

    return forward
