from transformers import AutoTokenizer, AutoModelForCausalLM
from sentence_transformers import SentenceTransformer
import torch
import logging
from config.config import settings

logger = logging.getLogger(__name__)

class ModelService:
    _instance = None

    def __new__(cls):
        if cls._instance is None:
            cls._instance = super().__new__(cls)
            cls._instance._initialized = False
        return cls._instance

    def __init__(self):
        if not self._initialized:
            self._initialized = True
            self.tokenizer = None
            self.model = None
            self.embedder = None
            self._load_models()

    def _load_models(self):
        try:
            logger.info("Loading models...")

            # Load tokenizer
            #self.tokenizer = AutoTokenizer.from_pretrained(settings.MODEL_NAME)
            self.tokenizer = AutoTokenizer.from_pretrained(settings.MODEL_NAME, use_fast=False)
            self.tokenizer.pad_token = self.tokenizer.eos_token

            logger.info(f"Tokenizer for {settings.MODEL_NAME} loaded successfully.")

            # Load language model
            quantization_device = settings.DEVICE
            quantization_bits = settings.QUANTIZATION_BITS

            self.model = AutoModelForCausalLM.from_pretrained(
                settings.MODEL_NAME,
                torch_dtype=torch.float16 if quantization_device == "cuda" else torch.float32,
                device_map="auto" if quantization_device == "cuda" else None,
           #     load_in_8bit=(quantization_bits == 8),
                trust_remote_code=True
            )
            logger.info(f"Model {settings.MODEL_NAME} loaded successfully on {quantization_device}.")

            # Load sentence embedder
            self.embedder = SentenceTransformer(settings.EMBEDDER_MODEL, device='cuda' if torch.cuda.is_available() else 'cpu')

            #self.embedder = SentenceTransformer(settings.EMBEDDER_MODEL)
            logger.info(f"Embedder {settings.EMBEDDER_MODEL} loaded successfully.")

        except Exception as e:
            logger.error(f"Error loading models: {e}")
            raise RuntimeError(f"Failed to initialize ModelService: {str(e)}")

    def get_models(self):
        """
        Returns the tokenizer, language model, and sentence embedder instances.
        """
        if not self.tokenizer or not self.model or not self.embedder:
            raise RuntimeError("Models are not fully loaded.")
        return self.tokenizer, self.model, self.embedder