import os
import json
import joblib

_MODEL_CACHE = {}

def load_store_model(store_id: str, base_dir: str = "models"):
    """Load and cache best model + metadata for a given store_id.
    Looks under {base_dir}/store_{store_id}/
    Returns (model, metadata) or raises FileNotFoundError.
    """
    key = (base_dir, str(store_id))
    if key in _MODEL_CACHE:
        return _MODEL_CACHE[key]

    store_dir = os.path.join(base_dir, f"store_{store_id}")
    meta_path = os.path.join(store_dir, "metadata.json")
    if not os.path.exists(meta_path):
        raise FileNotFoundError(f"metadata.json not found for store {store_id} in {store_dir}")

    with open(meta_path, "r") as f:
        metadata = json.load(f)

    model_name = metadata.get("model")
    if not model_name:
        raise FileNotFoundError(f"'model' not defined in metadata.json for store {store_id}")

    model_path = os.path.join(store_dir, f"{model_name}.joblib")
    if not os.path.exists(model_path):
        raise FileNotFoundError(f"Model file missing: {model_path}")

    model = joblib.load(model_path)
    _MODEL_CACHE[key] = (model, metadata)
    return model, metadata