"""
Extract expression value from NX .prt file
Used for extracting computed values like mass, volume, etc.

This extractor reads expressions using the .exp export method for accuracy.
"""

from pathlib import Path
from typing import Dict, Any
from optimization_engine.nx_updater import NXParameterUpdater


def extract_expression(prt_file: Path, expression_name: str):
    """
    Extract an expression value from NX .prt file.

    Args:
        prt_file: Path to .prt file
        expression_name: Name of expression to extract (e.g., 'p173' for mass)

    Returns:
        Dict with expression value and units
    """
    updater = NXParameterUpdater(prt_file, backup=False)
    expressions = updater.get_all_expressions(use_exp_export=True)

    if expression_name not in expressions:
        raise ValueError(f"Expression '{expression_name}' not found in {prt_file}")

    expr_info = expressions[expression_name]

    # If expression is a formula (value is None), we need to evaluate it
    # For now, we'll raise an error if it's a formula - user should use the computed value
    if expr_info['value'] is None and expr_info['formula'] is not None:
        raise ValueError(
            f"Expression '{expression_name}' is a formula: {expr_info['formula']}. "
            f"This extractor requires a computed value, not a formula reference."
        )

    return {
        expression_name: expr_info['value'],
        f'{expression_name}_units': expr_info['units']
    }


if __name__ == '__main__':
    # Example usage
    import sys
    if len(sys.argv) > 2:
        prt_file = Path(sys.argv[1])
        expression_name = sys.argv[2]
        result = extract_expression(prt_file, expression_name)
        print(f"Extraction result: {result}")
    else:
        print(f"Usage: python {sys.argv[0]} <prt_file> <expression_name>")