from __future__ import annotations

import inspect
import logging
import os
from collections.abc import Callable
from pathlib import Path
from typing import TYPE_CHECKING, Any

from sentence_transformers.backend import load_onnx_model, load_openvino_model

try:
    from typing import Self
except ImportError:
    from typing_extensions import Self

import torch
from transformers import AutoConfig, AutoModel, AutoTokenizer, MT5Config, PretrainedConfig, T5Config
from transformers.utils.import_utils import is_peft_available
from transformers.utils.peft_utils import find_adapter_config_file

from sentence_transformers.models.InputModule import InputModule

logger = logging.getLogger(__name__)

if TYPE_CHECKING and is_peft_available():
    from peft import PeftConfig


def _save_pretrained_wrapper(_save_pretrained_fn: Callable, subfolder: str) -> Callable[..., None]:
    def wrapper(save_directory: str | Path, **kwargs) -> None:
        os.makedirs(Path(save_directory) / subfolder, exist_ok=True)
        return _save_pretrained_fn(Path(save_directory) / subfolder, **kwargs)

    return wrapper


class Transformer(InputModule):
    """Hugging Face AutoModel to generate token embeddings.
    Loads the correct class, e.g. BERT / RoBERTa etc.

    Args:
        model_name_or_path: Hugging Face models name
            (https://huggingface.co/models)
        max_seq_length: Truncate any inputs longer than max_seq_length
        model_args: Keyword arguments passed to the Hugging Face
            Transformers model
        tokenizer_args: Keyword arguments passed to the Hugging Face
            Transformers tokenizer
        config_args: Keyword arguments passed to the Hugging Face
            Transformers config
        cache_dir: Cache dir for Hugging Face Transformers to store/load
            models
        do_lower_case: If true, lowercases the input (independent if the
            model is cased or not)
        tokenizer_name_or_path: Name or path of the tokenizer. When
            None, then model_name_or_path is used
        backend: Backend used for model inference. Can be `torch`, `onnx`,
            or `openvino`. Default is `torch`.
    """

    config_file_name: str = "sentence_bert_config.json"
    config_keys: list[str] = ["max_seq_length", "do_lower_case"]
    save_in_root: bool = True

    def __init__(
        self,
        model_name_or_path: str,
        max_seq_length: int | None = None,
        model_args: dict[str, Any] | None = None,
        tokenizer_args: dict[str, Any] | None = None,
        config_args: dict[str, Any] | None = None,
        cache_dir: str | None = None,
        do_lower_case: bool = False,
        tokenizer_name_or_path: str | None = None,
        backend: str = "torch",
    ) -> None:
        super().__init__()
        self.do_lower_case = do_lower_case
        self.backend = backend
        if model_args is None:
            model_args = {}
        if tokenizer_args is None:
            tokenizer_args = {}
        if config_args is None:
            config_args = {}

        config, is_peft_model = self._load_config(model_name_or_path, cache_dir, backend, config_args)
        self._load_model(model_name_or_path, config, cache_dir, backend, is_peft_model, **model_args)

        # Get the signature of the auto_model's forward method to pass only the expected arguments from `features`,
        # plus some common values like "input_ids", "attention_mask", etc.
        model_forward_params = list(inspect.signature(self.auto_model.forward).parameters)
        self.model_forward_params = set(model_forward_params) | {
            "input_ids",
            "attention_mask",
            "token_type_ids",
            "inputs_embeds",
        }

        if max_seq_length is not None and "model_max_length" not in tokenizer_args:
            tokenizer_args["model_max_length"] = max_seq_length
        self.tokenizer = AutoTokenizer.from_pretrained(
            tokenizer_name_or_path if tokenizer_name_or_path is not None else model_name_or_path,
            cache_dir=cache_dir,
            **tokenizer_args,
        )

        # No max_seq_length set. Try to infer from model
        if max_seq_length is None:
            if (
                hasattr(self.auto_model, "config")
                and hasattr(self.auto_model.config, "max_position_embeddings")
                and hasattr(self.tokenizer, "model_max_length")
            ):
                max_seq_length = min(self.auto_model.config.max_position_embeddings, self.tokenizer.model_max_length)

        self.max_seq_length = max_seq_length

        if tokenizer_name_or_path is not None:
            self.auto_model.config.tokenizer_class = self.tokenizer.__class__.__name__

    def _load_config(
        self, model_name_or_path: str, cache_dir: str | None, backend: str, config_args: dict[str, Any]
    ) -> tuple[PeftConfig | PretrainedConfig, bool]:
        """Loads the transformers or PEFT configuration

        Args:
            model_name_or_path (str): The model name on Hugging Face (e.g. 'sentence-transformers/all-MiniLM-L6-v2')
                or the path to a local model directory.
            cache_dir (str | None): The cache directory to store the model configuration.
            backend (str): The backend used for model inference. Can be `torch`, `onnx`, or `openvino`.
            config_args (dict[str, Any]): Keyword arguments passed to the Hugging Face Transformers config.

        Returns:
            tuple[PretrainedConfig, bool]: The model configuration and a boolean indicating whether the model is a PEFT model.
        """
        if (
            find_adapter_config_file(
                model_name_or_path,
                cache_dir=cache_dir,
                token=config_args.get("token"),
                revision=config_args.get("revision"),
                local_files_only=config_args.get("local_files_only", False),
            )
            is not None
        ):
            if not is_peft_available():
                raise Exception(
                    "Loading a PEFT model requires installing the `peft` package. You can install it via `pip install peft`."
                )
            if backend != "torch":
                # TODO: Consider following these steps automatically so we can load PEFT models with other backends
                raise ValueError(
                    "PEFT models can currently only be loaded with the `torch` backend. "
                    'To use other backends, load the model with `backend="torch"`, call `model.transformers_model.merge_and_unload()`, '
                    "save that model with `model.save_pretrained()` and then load the model with the desired backend."
                )
            from peft import PeftConfig

            return PeftConfig.from_pretrained(model_name_or_path, **config_args, cache_dir=cache_dir), True

        return AutoConfig.from_pretrained(model_name_or_path, **config_args, cache_dir=cache_dir), False

    def _load_model(
        self,
        model_name_or_path: str,
        config: PeftConfig | PretrainedConfig,
        cache_dir: str,
        backend: str,
        is_peft_model: bool,
        **model_args,
    ) -> None:
        """Loads the transformers or PEFT model into the `auto_model` attribute

        Args:
            model_name_or_path (str): The model name on Hugging Face (e.g. 'sentence-transformers/all-MiniLM-L6-v2')
                or the path to a local model directory.
            config ("PeftConfig" | PretrainedConfig): The model configuration.
            cache_dir (str | None): The cache directory to store the model configuration.
            backend (str): The backend used for model inference. Can be `torch`, `onnx`, or `openvino`.
            is_peft_model (bool): Whether the model is a PEFT model.
            model_args (dict[str, Any]): Keyword arguments passed to the Hugging Face Transformers model.
        """
        if backend == "torch":
            # When loading a PEFT model, we need to load the base model first,
            # but some model_args are only for the adapter
            if is_peft_model:
                for adapter_only_kwarg in ["revision"]:
                    model_args.pop(adapter_only_kwarg, None)

            if isinstance(config, T5Config):
                self._load_t5_model(model_name_or_path, config, cache_dir, **model_args)
            elif isinstance(config, MT5Config):
                self._load_mt5_model(model_name_or_path, config, cache_dir, **model_args)
            else:
                self.auto_model = AutoModel.from_pretrained(
                    model_name_or_path, config=config, cache_dir=cache_dir, **model_args
                )
        elif backend == "onnx":
            self.auto_model = load_onnx_model(
                model_name_or_path=model_name_or_path,
                config=config,
                task_name="feature-extraction",
                **model_args,
            )
        elif backend == "openvino":
            self.auto_model = load_openvino_model(
                model_name_or_path=model_name_or_path,
                config=config,
                task_name="feature-extraction",
                **model_args,
            )
        else:
            raise ValueError(f"Unsupported backend '{backend}'. `backend` should be `torch`, `onnx`, or `openvino`.")

    def _load_t5_model(self, model_name_or_path: str, config: PretrainedConfig, cache_dir: str, **model_args) -> None:
        """Loads the encoder model from T5"""
        from transformers import T5EncoderModel

        T5EncoderModel._keys_to_ignore_on_load_unexpected = ["decoder.*"]
        self.auto_model = T5EncoderModel.from_pretrained(
            model_name_or_path, config=config, cache_dir=cache_dir, **model_args
        )

    def _load_mt5_model(self, model_name_or_path: str, config: PretrainedConfig, cache_dir: str, **model_args) -> None:
        """Loads the encoder model from T5"""
        from transformers import MT5EncoderModel

        MT5EncoderModel._keys_to_ignore_on_load_unexpected = ["decoder.*"]
        self.auto_model = MT5EncoderModel.from_pretrained(
            model_name_or_path, config=config, cache_dir=cache_dir, **model_args
        )

    def __repr__(self) -> str:
        return f"Transformer({dict(self.get_config_dict(), architecture=self.auto_model.__class__.__name__)})"

    def forward(self, features: dict[str, torch.Tensor], **kwargs) -> dict[str, torch.Tensor]:
        """
        Forward pass through the transformer model.

        This method processes the input features through the underlying transformers model
        and returns the token embeddings along with any other relevant outputs.

        Notes:
            - Only passes arguments that are expected by the underlying transformer model

        Args:
            features (dict[str, torch.Tensor]): Input features dictionary containing at least
                'input_ids' and 'attention_mask'. May also contain other tensors required by
                the underlying transformer model.
            **kwargs: Additional keyword arguments to pass to the underlying transformer model.

        Returns:
            dict[str, torch.Tensor]: Updated features dictionary containing the input features, plus:
                - 'token_embeddings': Token-level embeddings from the transformer model
                - 'attention_mask': Possibly modified attention mask if using PeftModel with prompt learning
                - 'all_layer_embeddings': If the model outputs hidden states, contains embeddings from all layers
        """
        trans_features = {key: value for key, value in features.items() if key in self.model_forward_params}

        outputs = self.auto_model(**trans_features, **kwargs, return_dict=True)
        token_embeddings = outputs[0]
        features["token_embeddings"] = token_embeddings

        # If the AutoModel is wrapped with a PeftModelForFeatureExtraction, then it may have added virtual tokens
        # We need to extend the attention mask to include these virtual tokens, or the pooling will fail
        if is_peft_available():
            from peft import PeftModelForFeatureExtraction

            if (
                isinstance(self.auto_model, PeftModelForFeatureExtraction)
                and self.auto_model.active_peft_config.is_prompt_learning
            ):
                batch_size = token_embeddings.size(0)
                attention_mask = features["attention_mask"]
                prefix_attention_mask = torch.ones(
                    batch_size, self.auto_model.active_peft_config.num_virtual_tokens, device=attention_mask.device
                )
                features["attention_mask"] = torch.cat((prefix_attention_mask, attention_mask), dim=1)

        if self.auto_model.config.output_hidden_states and "hidden_states" in outputs:
            features["all_layer_embeddings"] = outputs["hidden_states"]

        return features

    def get_word_embedding_dimension(self) -> int:
        return self.auto_model.config.hidden_size

    def tokenize(
        self, texts: list[str] | list[dict] | list[tuple[str, str]], padding: str | bool = True
    ) -> dict[str, torch.Tensor]:
        """Tokenizes a text and maps tokens to token-ids"""
        output = {}
        if isinstance(texts[0], str):
            to_tokenize = [texts]
        elif isinstance(texts[0], dict):
            to_tokenize = []
            output["text_keys"] = []
            for lookup in texts:
                text_key, text = next(iter(lookup.items()))
                to_tokenize.append(text)
                output["text_keys"].append(text_key)
            to_tokenize = [to_tokenize]
        else:
            batch1, batch2 = [], []
            for text_tuple in texts:
                batch1.append(text_tuple[0])
                batch2.append(text_tuple[1])
            to_tokenize = [batch1, batch2]

        # strip
        to_tokenize = [[str(s).strip() for s in col] for col in to_tokenize]

        # Lowercase
        if self.do_lower_case:
            to_tokenize = [[s.lower() for s in col] for col in to_tokenize]

        output.update(
            self.tokenizer(
                *to_tokenize,
                padding=padding,
                truncation="longest_first",
                return_tensors="pt",
                max_length=self.max_seq_length,
            )
        )
        return output

    def save(self, output_path: str, safe_serialization: bool = True, **kwargs) -> None:
        self.auto_model.save_pretrained(output_path, safe_serialization=safe_serialization)
        self.tokenizer.save_pretrained(output_path)
        self.save_config(output_path)

    @classmethod
    def load(
        cls,
        model_name_or_path: str,
        # Loading arguments
        subfolder: str = "",
        token: bool | str | None = None,
        cache_folder: str | None = None,
        revision: str | None = None,
        local_files_only: bool = False,
        # Module-specific arguments
        trust_remote_code: bool = False,
        model_kwargs: dict[str, Any] | None = None,
        tokenizer_kwargs: dict[str, Any] | None = None,
        config_kwargs: dict[str, Any] | None = None,
        backend: str = "torch",
        **kwargs,
    ) -> Self:
        init_kwargs = cls._load_init_kwargs(
            model_name_or_path=model_name_or_path,
            subfolder=subfolder,
            token=token,
            cache_folder=cache_folder,
            revision=revision,
            local_files_only=local_files_only,
            trust_remote_code=trust_remote_code,
            model_kwargs=model_kwargs,
            tokenizer_kwargs=tokenizer_kwargs,
            config_kwargs=config_kwargs,
            backend=backend,
        )
        return cls(model_name_or_path=model_name_or_path, **init_kwargs)

    @classmethod
    def _load_init_kwargs(
        cls,
        model_name_or_path: str,
        # Loading arguments
        subfolder: str = "",
        token: bool | str | None = None,
        cache_folder: str | None = None,
        revision: str | None = None,
        local_files_only: bool = False,
        # Module-specific arguments
        trust_remote_code: bool = False,
        model_kwargs: dict[str, Any] | None = None,
        tokenizer_kwargs: dict[str, Any] | None = None,
        config_kwargs: dict[str, Any] | None = None,
        backend: str = "torch",
        **kwargs,
    ) -> dict[str, Any]:
        config = cls.load_config(
            model_name_or_path=model_name_or_path,
            subfolder=subfolder,
            token=token,
            cache_folder=cache_folder,
            revision=revision,
            local_files_only=local_files_only,
        )

        hub_kwargs = {
            "subfolder": subfolder,
            "token": token,
            "revision": revision,
            "local_files_only": local_files_only,
            "trust_remote_code": trust_remote_code,
        }

        # 3rd priority: config file
        if "model_args" not in config:
            config["model_args"] = {}
        if "tokenizer_args" not in config:
            config["tokenizer_args"] = {}
        if "config_args" not in config:
            config["config_args"] = {}

        # 2nd priority: hub_kwargs
        config["model_args"].update(hub_kwargs)
        config["tokenizer_args"].update(hub_kwargs)
        config["config_args"].update(hub_kwargs)

        # 1st priority: kwargs passed to SentenceTransformer
        if model_kwargs:
            config["model_args"].update(model_kwargs)
        if tokenizer_kwargs:
            config["tokenizer_args"].update(tokenizer_kwargs)
        if config_kwargs:
            config["config_args"].update(config_kwargs)

        return {**config, "cache_dir": cache_folder, "backend": backend}

    @classmethod
    def load_config(
        cls,
        model_name_or_path: str,
        subfolder: str = "",
        config_filename: str | None = None,
        token: bool | str | None = None,
        cache_folder: str | None = None,
        revision: str | None = None,
        local_files_only: bool = False,
    ) -> dict[str, Any]:
        config_filenames = (
            [config_filename]
            if config_filename
            else [
                "sentence_bert_config.json",
                "sentence_roberta_config.json",
                "sentence_distilbert_config.json",
                "sentence_camembert_config.json",
                "sentence_albert_config.json",
                "sentence_xlm-roberta_config.json",
                "sentence_xlnet_config.json",
            ]
        )
        for config_filename in config_filenames:
            config = super().load_config(
                model_name_or_path=model_name_or_path,
                subfolder=subfolder,
                config_filename=config_filename,
                token=token,
                cache_folder=cache_folder,
                revision=revision,
                local_files_only=local_files_only,
            )
            if config:
                break

        # Don't allow configs to set trust_remote_code
        if "model_args" in config and "trust_remote_code" in config["model_args"]:
            config["model_args"].pop("trust_remote_code")
        if "tokenizer_args" in config and "trust_remote_code" in config["tokenizer_args"]:
            config["tokenizer_args"].pop("trust_remote_code")
        if "config_args" in config and "trust_remote_code" in config["config_args"]:
            config["config_args"].pop("trust_remote_code")
        return config