import logging
from contextlib import contextmanager
from dataclasses import dataclass, field
from enum import Enum
from functools import partial
from typing import Any, Iterable, Optional, Tuple, Union

import torch
from einops import rearrange, repeat, unpack
from einops.layers.torch import EinMix as Mix
from hooks import add_generated_lora_hook, remove_hook_handles
from jaxtyping import Float, Integer
from model_loading import get_lora_config, get_model_and_tokenizer
from peft import LoraConfig
from pooling import POOL_FN, get_pooling_fn
from torch import Tensor, nn
from transformers import PreTrainedModel
from transformers.modeling_outputs import ModelOutput
from utils import get_lora_module_names, get_num_layers, get_peft_in_out_features

logger = logging.getLogger()


AGGREGATOR_TYPE = Enum("AGGREGATOR_TYPE", ["POOLER", "PERCEIVER"])


@dataclass
class AggregatorConfig:
    feature_size: int
    num_layers: int
    num_modules: int
    pooling_type: POOL_FN


def get_aggregator_config(
    model: PreTrainedModel,
    pooling_type: POOL_FN = POOL_FN.MEAN,
):
    lora_config = model.peft_config["default"]
    return AggregatorConfig(
        feature_size=model.config.hidden_size,
        num_layers=get_num_layers(model),
        num_modules=len(lora_config.target_modules),
        pooling_type=pooling_type,
    )


@dataclass
class HypernetConfig:
    latent_size: int
    lora_config: LoraConfig
    module_names: dict[str, list[str]]
    layer_indices: Iterable[int]
    feature_sizes: tuple[dict[str, int], dict[str, int]]
    aggregator_type: AGGREGATOR_TYPE
    aggregator_config: AggregatorConfig


def get_hypernet_config(model: PreTrainedModel, latent_size: int = 256):
    lora_config = model.peft_config["default"]
    indices = torch.arange(get_num_layers(model), device=model.device)
    return HypernetConfig(
        latent_size=latent_size,
        lora_config=lora_config,
        module_names=get_lora_module_names(model, lora_config.target_modules, indices),
        layer_indices=indices,
        feature_sizes=get_peft_in_out_features(model, peft_config=lora_config),
        aggregator_type=AGGREGATOR_TYPE.POOLER,
        aggregator_config=get_aggregator_config(model, POOL_FN.MEAN),
    )


# TODO: implement Perceiver
class Perceiver(nn.Module):
    """perceiver w/ bottleneck size = n_modules * n_layers"""

    def __init__(self, *args, **kwargs):
        super().__init__()
        pass


class Mixer(nn.Module):
    def __init__(
        self,
        input_size: int,
        intermediate_emb_size: int,
        output_size: int,
    ):
        super().__init__()
        self.gate_proj = nn.Linear(input_size, intermediate_emb_size, bias=False)
        self.up_proj = nn.Linear(input_size, intermediate_emb_size, bias=False)
        self.down_proj = nn.Linear(intermediate_emb_size, output_size, bias=False)
        self.act_fn = nn.SiLU()

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        return self.down_proj(self.act_fn(self.gate_proj(x)) * self.up_proj(x))


class MLPResidualBlock(nn.Module):
    def __init__(
        self,
        input_size: int,
        hidden_size: int,
        output_size: int,
        pre_layer_norm: bool = True,
        post_dropout: bool = True,
    ):
        super().__init__()
        layers = []
        if pre_layer_norm:
            layers.append(nn.LayerNorm(input_size))
        layers += [
            nn.Dropout(0.05),
            nn.Linear(input_size, hidden_size),
            nn.SiLU(),
            nn.Dropout(0.05),
            nn.Linear(hidden_size, output_size),
            nn.SiLU(),
        ]
        if post_dropout:
            layers.append(nn.Dropout(0.05))
        self.mlp = nn.Sequential(*layers)

    def forward(self, x):
        return x + self.mlp(x)


class Pooler(nn.Module):
    def __init__(
        self,
        feature_size: int,
        output_size: int,
        pooling_type: POOL_FN,
        num_layers: int,
        num_modules: int,
    ):
        super().__init__()
        self.num_layers = num_layers
        self.num_modules = num_modules

        # NOTE: features will be projected to size = output_size // 2
        # then cat with layer and module embeddings (each with size output_size // 4)
        # which are collectively form features with size = output_size
        self.pool_fn = get_pooling_fn(pooling_type)
        self.feature_proj = nn.Linear(feature_size, output_size // 2)
        self.ln = nn.LayerNorm(output_size // 2)
        self.layer_embs = nn.Sequential(
            nn.Embedding(num_layers, output_size // 4),
            nn.LayerNorm(output_size // 4),
        )
        self.module_embs = nn.Sequential(
            nn.Embedding(num_modules, output_size // 4),
            nn.LayerNorm(output_size // 4),
        )
        self.mixer = Mixer(output_size, output_size * 4, output_size)
        self.mlp = MLPResidualBlock(output_size, output_size * 4, output_size)

        self.register_buffer("layer_indices", torch.arange(num_layers))
        self.register_buffer("module_indices", torch.arange(num_modules))

    def forward(
        self,
        features: Float[Tensor, "bs seq_len feature_dim"],
        attn_mask: Optional[Integer[Tensor, "bs seq_len"]] = None,
    ):
        bs = features.shape[0]

        # [bs, feature_dim]
        x = self.ln(self.feature_proj(self.pool_fn(features, attn_mask).float()))
        x = repeat(
            x,
            "bs d -> bs n_layers n_modules d",
            n_modules=self.num_modules,
            n_layers=self.num_layers,
        )

        layer_embs = self.layer_embs(self.layer_indices)  # [num_layers, d]
        layer_embs = repeat(
            layer_embs,
            "n_layers d -> bs n_layers n_modules d",
            bs=bs,
            n_modules=self.num_modules,
        )

        module_embs = self.module_embs(self.module_indices)  # [num_modules, d]
        module_embs = repeat(
            module_embs,
            "n_modules d -> bs n_layers n_modules d",
            bs=bs,
            n_layers=self.num_layers,
        )

        emb = torch.cat([x, layer_embs, module_embs], dim=3)
        return self.mlp(self.mixer(emb))


AGGREGATOR_CLS = {
    AGGREGATOR_TYPE.POOLER: Pooler,
    AGGREGATOR_TYPE.PERCEIVER: Perceiver,
}


@contextmanager
def early_exit(base_model: PreTrainedModel, exit_layer: int):
    try:
        layers = base_model.layers
        base_model.layers = layers[:exit_layer]
        yield base_model
    finally:
        base_model.layers = layers


@contextmanager
def maybe_add_batch_dim(kwargs):
    try:
        batched_input = False
        batched_attn_mask = False
        if len(kwargs["input_ids"].shape) == 1:
            kwargs["input_ids"] = kwargs["input_ids"].unsqueeze(0)
            batched_input = True
        if len(kwargs["attention_mask"].shape) == 1:
            kwargs["attention_mask"] = kwargs["attention_mask"].unsqueeze(0)
            batched_attn_mask = True
        yield batched_input, batched_attn_mask
    finally:
        if batched_input:
            kwargs["input_ids"] = kwargs["input_ids"].squeeze(0)
        if batched_attn_mask:
            kwargs["attention_mask"] = kwargs["attention_mask"].squeeze(0)


class EarlyExit(nn.Module):
    def __init__(self, base_model: PreTrainedModel, exit_layer: int):
        super().__init__()
        self.base_model = base_model
        self.exit_layer = exit_layer

    def forward(self, **kwargs):
        # if len(kwargs["input_ids"].shape) == 1:
        #     kwargs["input_ids"] = kwargs["input_ids"].unsqueeze(0)
        # if len(kwargs["attention_mask"].shape) == 1:
        #     kwargs["attention_mask"] = kwargs["attention_mask"].unsqueeze(0)

        with (
            early_exit(self.base_model, self.exit_layer),
            maybe_add_batch_dim(kwargs) as (batched_input, batched_attn_mask),
        ):
            model_outputs = self.base_model(**kwargs)

        if batched_input:
            model_outputs.last_hidden_state = model_outputs.last_hidden_state.squeeze(0)

        return model_outputs.last_hidden_state


class HyperLoRA(nn.Module):
    def __init__(
        self,
        # latent_size: int,
        # lora_config: LoraConfig,
        # layer_indices: Integer[Tensor, "num_layers"],
        # in_out_features: dict,
        # aggregator_type: AGGREGATOR_TYPE,
        # aggregator_kwargs: dict,
        config: HypernetConfig,
    ):
        super().__init__()

        # NOTE: this class then only handles the output space of the hypernet
        # e.g., shared_AB_head, per_rank_gen, etc.
        # TODO: add different output spaces

        # aggregator output [bs, n_layers, n_modules, feature_dim]
        # by mixing the pooled features with layer embs and module embs (for pooling)
        # or via a perceiver w/ bottleneck size = n_modules * n_layers
        self.aggregator = AGGREGATOR_CLS[config.aggregator_type](
            **vars(config.aggregator_config),
            output_size=config.latent_size,
        )

        self.lora_config = config.lora_config

        self.target_modules = self.lora_config.target_modules
        self.layer_indices = config.layer_indices

        # TODO: add lightweight LoRA i.e., a projection layer of the input of LoRA
        # have to also change in_d and out_d accordingly
        self.in_d, self.out_d = config.feature_sizes

        # TODO: add different output spaces

        self.layers = MLPResidualBlock(
            input_size=config.latent_size,
            hidden_size=config.latent_size * 4,
            output_size=config.latent_size,
        )

        # TODO: check initialization of the head
        # default values are prob. way too big
        self.head = Mix(
            "bs n_layers n_modules d -> bs n_layers r out_d",
            weight_shape="n_modules d r out_d",
            bias_shape=None,  # no bias
            n_modules=len(self.target_modules),
            d=config.latent_size,
            r=config.lora_config.r,
            out_d=sum(self.in_d[m] + self.out_d[m] for m in self.target_modules),
        )

    def _to_lora_dict(
        self, flat_loras: Float[Tensor, "bs n_layers r _"]
    ) -> dict[str, dict[str, Float[Tensor, "bs n_layers r _"]]]:
        # list of [bs, n_layers, r, in_out_dim]
        # and in_out_dim might vary across modules
        loras = unpack(
            flat_loras,
            [[self.in_d[m] + self.out_d[m]] for m in self.target_modules],
            "bs n_layers r *",
        )

        # dict of {module:
        #   {A: [bs, n_layers, r, in_dim],
        #    B: [bs, n_layers, r, out_dim]}}
        lora_dict = dict()
        for module, lora in zip(self.target_modules, loras):
            A, B = unpack(
                lora,
                [[self.in_d[module]], [self.out_d[module]]],
                "bs n_layers r *",
            )
            # transpose B
            B = rearrange(B, "bs n_layers r d_out -> bs n_layers d_out r")
            lora_dict[module] = dict(A=A, B=B)

        return lora_dict

    def forward(
        self,
        features: Float[Tensor, "bs seq_len feature_dim"],
        attn_mask: Optional[Integer[Tensor, "bs seq_len"]] = None,
    ):

        # [bs, n_layers, n_modules, feature_dim]
        emb = self.aggregator(features, attn_mask)

        # [bs, n_layers, r, in_out_dim_mod1 + in_out_dim_mod2 + ...]
        flat_loras = self.head(self.layers(emb))

        return flat_loras

    def generate_loras(
        self,
        features: Float[Tensor, "bs seq_len feature_dim"],
        attn_mask: Optional[Integer[Tensor, "bs seq_len"]] = None,
    ):
        flat_loras = self.forward(features, attn_mask)
        return self._to_lora_dict(flat_loras)


class ModulatedPretrainedModel(nn.Module):
    def __init__(
        self,
        base_model: PreTrainedModel,  # TODO: maybe just use the name/config?
        hypernet: HyperLoRA,
        ctx_encoder: nn.Module,  # TODO: maybe just use the name/config?
    ):
        super().__init__()
        self.device = base_model.device
        # register base_model as a submodule
        self.register_module("base_model", base_model)
        self.register_module("hypernet", hypernet)
        self.register_module("ctx_encoder", ctx_encoder)

    # Delegate to base_model
    @property
    def config(self):
        return self.base_model.config

    def get_input_embeddings(self):
        return self.base_model.get_input_embeddings()

    def state_dict(self, *args, **kwargs):
        state_dict = super().state_dict(*args, **kwargs)
        # remove non-trainable and base_model's params
        for name, param in self.named_parameters():
            if not param.requires_grad:
                state_dict.pop(name, None)

        for name in list(state_dict.keys()):
            if name.startswith("base_model") or name.startswith("ctx_encoder"):
                state_dict.pop(name, None)

        return state_dict

    def load_state_dict(self, state_dict: dict, *args, **kwargs):
        # NOTE: might have to set `strict=False` as we don't save all the params
        return super().load_state_dict(state_dict, *args, **kwargs)

    @torch.no_grad()
    def get_ctx_features(
        self,
        examples: dict[str, Any],
    ):
        # TODO: truncate the ctx_ids to the max_ctx_len
        out = dict()
        input_ids = torch.tensor(examples.get("ctx_ids")).to(self.device)
        attention_mask = torch.tensor(examples.get("ctx_attn_mask")).to(self.device)

        if isinstance(self.ctx_encoder, nn.Embedding):
            features = self.ctx_encoder(input_ids[torch.where(attention_mask)])
        else:
            features = self.ctx_encoder(
                input_ids=input_ids, attention_mask=attention_mask
            )
        out["ctx_features"] = features
        return out

    def forward(
        self,
        ctx_features: Optional[Float[Tensor, "bs ctx_length feature_dim"]] = None,
        ctx_attn_mask: Optional[Integer[Tensor, "bs ctx_length"]] = None,
        **model_inputs_kwargs: dict[str, Any],
    ) -> Union[tuple, ModelOutput]:
        """Forward pass of the modulated model."""

        generated_loras = None
        if ctx_features is None:
            logger.warning(
                (
                    "*" * 100,
                    "\n\nNo ctx_features provided, using the base model for forward pass\n\n",
                    "*" * 100,
                )
            )
            # model_outputs = self.base_model(**model_inputs_kwargs)
            # model_outputs.generated_loras = None
            # return model_outputs

        else:
            generated_loras = self.hypernet.generate_loras(ctx_features, ctx_attn_mask)

        # apply lora hook to the base model
        # self.apply_generated_loras(generated_loras)
        with apply_generated_loras(
            self.base_model,
            generated_loras,
            self.hypernet.layer_indices,
            self.training,
        ):
            model_outputs = self.base_model(**model_inputs_kwargs)
        # model_outputs.generated_loras = generated_loras

        return model_outputs

    @torch.no_grad()
    def generate(
        self,
        ctx_features: Optional[Float[Tensor, "bs ctx_length feature_dim"]] = None,
        ctx_attn_mask: Optional[Integer[Tensor, "bs ctx_length"]] = None,
        **model_inputs_kwargs: dict[str, Any],
    ):
        generated_loras = None
        if ctx_features is None:
            logger.warning(
                (
                    "*" * 100,
                    "\n\nNo ctx_features provided, using the base model for generation\n\n",
                    "*" * 100,
                )
            )
            # model_outputs = self.base_model(**model_inputs_kwargs)
            # model_outputs.generated_loras = None
            # return model_outputs
        else:
            generated_loras = self.hypernet.generate_loras(ctx_features, ctx_attn_mask)

        # apply lora hook to the base model
        # self.apply_generated_loras(generated_loras)
        with apply_generated_loras(
            self.base_model,
            generated_loras,
            self.hypernet.layer_indices,
            self.training,
        ):
            model_outputs = self.base_model.generate(**model_inputs_kwargs)
        return model_outputs


@contextmanager
def apply_generated_loras(
    base_model: nn.Module,
    generated_loras: Optional[dict] = None,
    layer_indices: Optional[Iterable[int]] = None,
    training: bool = False,
):
    if generated_loras is None:
        yield base_model
        return

    try:
        hooks = []
        for module_name in generated_loras:
            for layer_idx in layer_indices:
                hooks += add_generated_lora_hook(
                    base_model,
                    module_name,
                    layer_idx,
                    A=generated_loras[module_name]["A"][:, layer_idx],
                    B=generated_loras[module_name]["B"][:, layer_idx],
                    scaling=base_model.peft_config["default"].lora_alpha,
                    input_dropout=base_model.peft_config["default"].lora_dropout,
                    training=training,
                )

        yield base_model
    finally:
        remove_hook_handles(hooks)


if __name__ == "__main__":
    # set torch randomness seed
    torch.manual_seed(42)
    model_name = "meta-llama/Llama-3.2-1B-Instruct"
    base_model, tokenizer = get_model_and_tokenizer(
        model_name,
        train=True,
        requires_grad=False,
        peft_config=get_lora_config(model_name),
    )
    print(base_model)
    # lora_config = base_model.peft_config["default"]
    # in_d, out_d = get_peft_in_out_features(base_model, peft_config=lora_config)

    # hypernet = HyperLoRA(
    #     lora_config,
    #     torch.arange(get_num_layers(base_model), device=base_model.device),
    #     in_out_features={"in": in_d, "out": out_d},
    #     aggregator_type=AGGREGATOR_TYPE.POOLER,
    #     aggregator_config=get_aggregator_config(base_model, POOL_FN.MEAN),
    # ).to(base_model.device)

    hypernet = HyperLoRA(get_hypernet_config(base_model)).to(base_model.device)

    model = ModulatedPretrainedModel(base_model, hypernet).to(base_model.device)
    print(model)

    ctx_msg = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."
    ctx_inputs = tokenizer(ctx_msg, return_tensors="pt").to(model.device)
    ctx_features = model.get_ctx_features(**ctx_inputs)
    ctx_attn_mask = ctx_inputs["attention_mask"]
    print(ctx_features.shape)

    model.eval()
    agg_features = hypernet.aggregator(ctx_features, ctx_attn_mask)
    print(agg_features)
    print(agg_features.shape)

    hnetout = hypernet(ctx_features, ctx_attn_mask)
    print(hnetout)
    print(hnetout.shape)

    prompt_msg = "hello"
    prompt_inputs = tokenizer(prompt_msg, return_tensors="pt").to(model.device)

    basemodelout = model.base_model(**prompt_inputs)
    print(basemodelout)

    modelout = model(ctx_features, ctx_attn_mask, **prompt_inputs)
    print(modelout)

    breakpoint()