"""Trinity 4% Safe Withdrawal Rate.

Bengen's seminal 1994 paper + the Trinity Study (Cooley/Hubbard/Walz,
1998) — withdraw 4% of the starting balance in year 1, then keep the
real withdrawal constant for the rest of retirement. In our real-GBP
internal frame this is just "the same number every year".
"""
from __future__ import annotations

from fire_planner.strategies.base import StrategyState, WithdrawalStrategy

DEFAULT_INITIAL_RATE = 0.04


class TrinityStrategy(WithdrawalStrategy):
    name = "trinity"

    def __init__(self, initial_rate: float = DEFAULT_INITIAL_RATE) -> None:
        self.initial_rate = initial_rate

    def propose_withdrawal(self, state: StrategyState) -> float:
        if state.year_idx == 0:
            return state.initial_portfolio * self.initial_rate
        return state.last_withdrawal