from rdkit import Chem


MAX_HEAVY_ATOMS = 50


def validate_smiles(smiles: str) -> bool:
    """Return True if the SMILES is parseable, non-empty, and within size limits."""
    if not smiles or not smiles.strip():
        return False
    mol = Chem.MolFromSmiles(smiles.strip())
    if mol is None:
        return False
    if mol.GetNumHeavyAtoms() > MAX_HEAVY_ATOMS:
        return False
    return True