from __future__ import annotations

from dataclasses import dataclass
from functools import lru_cache

import torch
from transformers import AutoModelForCausalLM, AutoTokenizer, PreTrainedModel, PreTrainedTokenizerBase

from app.core.model_support import ModelSupport, describe_model_support


@dataclass(slots=True)
class ModelBundle:
    model_name: str
    model: PreTrainedModel
    tokenizer: PreTrainedTokenizerBase
    device: torch.device
    dtype: torch.dtype
    capability: ModelSupport


def resolve_dtype(preference: str, device: torch.device) -> torch.dtype:
    if preference == "float32":
        return torch.float32
    if preference == "float16":
        return torch.float16
    if preference == "bfloat16":
        return torch.bfloat16
    if device.type == "cuda":
        return torch.bfloat16 if torch.cuda.is_bf16_supported() else torch.float16
    if device.type == "mps":
        return torch.float16
    return torch.float32


def resolve_device(preference: str = "auto") -> torch.device:
    if preference == "cuda":
        if not torch.cuda.is_available():
            raise RuntimeError("CUDA requested but not available.")
        return torch.device("cuda")
    if preference == "mps":
        if not torch.backends.mps.is_available():
            raise RuntimeError("MPS requested but not available.")
        return torch.device("mps")
    if preference == "cpu":
        return torch.device("cpu")
    if torch.cuda.is_available():
        return torch.device("cuda")
    if torch.backends.mps.is_available():
        return torch.device("mps")
    return torch.device("cpu")


@lru_cache(maxsize=2)
def load_model_bundle(
    model_name: str,
    device_preference: str = "auto",
    dtype_preference: str = "auto",
    attn_implementation: str = "eager",
    trust_remote_code: bool = True,
    low_cpu_mem_usage: bool = True,
) -> ModelBundle:
    device = resolve_device(device_preference)
    dtype = resolve_dtype(dtype_preference, device)
    tokenizer = AutoTokenizer.from_pretrained(model_name, trust_remote_code=trust_remote_code)
    if tokenizer.pad_token is None:
        tokenizer.pad_token = tokenizer.eos_token

    model = AutoModelForCausalLM.from_pretrained(
        model_name,
        trust_remote_code=trust_remote_code,
        attn_implementation=attn_implementation,
        torch_dtype=dtype,
        low_cpu_mem_usage=low_cpu_mem_usage,
    )
    model.to(device)
    model.eval()
    capability = describe_model_support(model)

    return ModelBundle(
        model_name=model_name,
        model=model,
        tokenizer=tokenizer,
        device=device,
        dtype=dtype,
        capability=capability,
    )


def compute_attribution_analysis(**kwargs):
    from app.core.runtime_pipeline import compute_attribution_analysis as _compute_attribution_analysis

    return _compute_attribution_analysis(**kwargs)