from dataclasses import dataclass
from typing import Dict, List, Optional
from datetime import datetime

@dataclass
class NavErosionConfig:
    max_erosion_level: int = 9
    max_monthly_erosion: float = 1 - (0.1)**(1/12)  # ~17.54% monthly for 90% annual erosion
    use_per_ticker: bool = False
    global_nav_rate: float = 0
    per_ticker_rates: Dict[str, float] = None

@dataclass
class NavErosionResult:
    ticker: str
    nav_erosion_rate: float
    monthly_erosion_rate: float
    annual_erosion_rate: float
    risk_level: int  # 0-9 scale
    risk_explanation: str
    max_drawdown: float
    volatility: float
    is_new_etf: bool
    etf_age_years: Optional[float]

@dataclass
class NavErosionAnalysis:
    results: List[NavErosionResult]
    portfolio_nav_risk: float  # Average risk level
    portfolio_erosion_rate: float  # Weighted average erosion rate
    risk_summary: str