"""Option symbol parsing utilities."""
import re
from datetime import datetime
from typing import Optional, NamedTuple
from decimal import Decimal


class OptionInfo(NamedTuple):
    """
    Parsed option information.

    Attributes:
        underlying_symbol: Base ticker symbol (e.g., "AAPL")
        expiration_date: Option expiration date
        option_type: "CALL" or "PUT"
        strike_price: Strike price
    """
    underlying_symbol: str
    expiration_date: datetime
    option_type: str
    strike_price: Decimal


def parse_option_symbol(option_symbol: str) -> Optional[OptionInfo]:
    """
    Parse Fidelity option symbol format into components.

    Fidelity format: -SYMBOL + YYMMDD + C/P + STRIKE
    Example: -AAPL260116C150 = AAPL Call expiring Jan 16, 2026 at $150 strike

    Args:
        option_symbol: Fidelity option symbol string

    Returns:
        OptionInfo object if parsing successful, None otherwise

    Examples:
        >>> parse_option_symbol("-AAPL260116C150")
        OptionInfo(
            underlying_symbol='AAPL',
            expiration_date=datetime(2026, 1, 16),
            option_type='CALL',
            strike_price=Decimal('150')
        )

        >>> parse_option_symbol("-TSLA251219P500")
        OptionInfo(
            underlying_symbol='TSLA',
            expiration_date=datetime(2025, 12, 19),
            option_type='PUT',
            strike_price=Decimal('500')
        )
    """
    # Regex pattern: -SYMBOL + YYMMDD + C/P + STRIKE
    # Symbol: one or more uppercase letters
    # Date: 6 digits (YYMMDD)
    # Type: C (call) or P (put)
    # Strike: digits with optional decimal point
    pattern = r"^-([A-Z]+)(\d{6})([CP])(\d+\.?\d*)$"

    match = re.match(pattern, option_symbol)
    if not match:
        return None

    symbol, date_str, option_type, strike_str = match.groups()

    # Parse date (YYMMDD format)
    try:
        # Assume 20XX for years (works until 2100)
        year = 2000 + int(date_str[:2])
        month = int(date_str[2:4])
        day = int(date_str[4:6])
        expiration_date = datetime(year, month, day)
    except (ValueError, IndexError):
        return None

    # Parse option type
    option_type_full = "CALL" if option_type == "C" else "PUT"

    # Parse strike price
    try:
        strike_price = Decimal(strike_str)
    except (ValueError, ArithmeticError):
        return None

    return OptionInfo(
        underlying_symbol=symbol,
        expiration_date=expiration_date,
        option_type=option_type_full,
        strike_price=strike_price,
    )