backend/app/model.py

import torch
from transformers import AutoTokenizer, AutoModelForSequenceClassification
import os

MODEL_NAME = "distilbert-base-uncased"
SAVE_PATH = "./data/best_model"
LABEL_MAP = {0: "low risk", 1: "medium risk", 2: "high risk"}

# Load tokenizer from saved fine-tuned model if available
tokenizer = AutoTokenizer.from_pretrained(SAVE_PATH if os.path.isdir(SAVE_PATH) else MODEL_NAME)

_model = None  # ← this stores the model in memory

def load_model():
    global _model
    if _model is not None:
        return _model  # ✅ already loaded

    model_path = os.path.join(SAVE_PATH, "pytorch_model.bin")
    if os.path.exists(model_path):
        print("✅ Loading fine-tuned model...")
        _model = AutoModelForSequenceClassification.from_pretrained(SAVE_PATH)
    else:
        print("⚠️ Fine-tuned model not found. Falling back to base model:", MODEL_NAME)
        _model = AutoModelForSequenceClassification.from_pretrained(MODEL_NAME, num_labels=3)

    _model.eval()
    return _model

def predict(input_data: str):
    model = load_model()
    with torch.no_grad():
        inputs = tokenizer(input_data, return_tensors="pt", truncation=True, padding=True, max_length=256)
        outputs = model(**inputs)
        predicted_class = torch.argmax(outputs.logits, dim=1).item()
        return LABEL_MAP.get(predicted_class, "unknown")



# import torch
# from transformers import AutoTokenizer, AutoModelForSequenceClassification
# import os

# MODEL_NAME = "google/gemma-1.1-2b-it"
# SAVE_PATH = "./data/best_model"
# LABEL_MAP = {0: "low risk", 1: "medium risk", 2: "high risk"}

# # Load tokenizer from saved model if available
# if os.path.exists(SAVE_PATH):
#     tokenizer = AutoTokenizer.from_pretrained(SAVE_PATH)
# else:
#     tokenizer = AutoTokenizer.from_pretrained(MODEL_NAME)

# def load_model():
#     model_path = os.path.join(SAVE_PATH, "best_model")
#     if os.path.exists(model_path):
#         print("✅ Loading fine-tuned model from:", model_path)
#         model = AutoModelForSequenceClassification.from_pretrained(model_path)
#     else:
#         print("🔁 Loading base model (not yet fine-tuned):", MODEL_NAME)
#         model = AutoModelForSequenceClassification.from_pretrained(MODEL_NAME, num_labels=3)
#     return model

# def predict(input_data: str):
#     model = load_model()
#     model.eval()
#     with torch.no_grad():
#         inputs = tokenizer(input_data, return_tensors="pt", truncation=True, padding=True, max_length=256)
#         outputs = model(**inputs)
#         predicted_class = torch.argmax(outputs.logits, dim=1).item()
#         return LABEL_MAP.get(predicted_class, "unknown")