"""ざっくり勝敗スコアリング（ピタゴラス期待＋ログ5法）"""
from __future__ import annotations

from dataclasses import dataclass
from typing import Iterable

PYTH_EXP = 1.83
HOME_FIELD_ADV = 0.02
MIN_GAMES = 10


@dataclass
class TeamForm:
    games: int = 0
    runs_scored: int = 0
    runs_allowed: int = 0

    @property
    def rs_per_game(self) -> float:
        if self.games == 0:
            return 4.5
        return self.runs_scored / self.games

    @property
    def ra_per_game(self) -> float:
        if self.games == 0:
            return 4.5
        return self.runs_allowed / self.games


def pythagorean_win_pct(runs_scored: float, runs_allowed: float, exp: float = PYTH_EXP) -> float:
    if runs_scored <= 0 and runs_allowed <= 0:
        return 0.5
    rs = max(runs_scored, 0.01)
    ra = max(runs_allowed, 0.01)
    num = rs**exp
    den = num + ra**exp
    return num / den if den > 0 else 0.5


def log5(home_pct: float, away_pct: float) -> float:
    """2チーム間の勝率（ホーム視点・ホーム補正なし）"""
    if home_pct <= 0 or away_pct <= 0:
        return 0.5
    if home_pct >= 1 or away_pct >= 1:
        return 0.5
    num = home_pct - home_pct * away_pct
    den = home_pct + away_pct - 2 * home_pct * away_pct
    if den == 0:
        return 0.5
    return num / den


def predict_matchup(home: TeamForm, away: TeamForm) -> dict[str, float]:
    """試合前のチーム成績からホーム勝率と目安得点を返す。"""
    home_pct = pythagorean_win_pct(home.rs_per_game, home.ra_per_game)
    away_pct = pythagorean_win_pct(away.rs_per_game, away.ra_per_game)

    if home.games < MIN_GAMES or away.games < MIN_GAMES:
        raw = 0.5 + HOME_FIELD_ADV
    else:
        raw = log5(home_pct, away_pct) + HOME_FIELD_ADV

    home_win = min(0.95, max(0.05, raw))
    away_win = 1.0 - home_win

    # 目安得点: 各チームの得点力と相手失点力の平均（参考値）
    home_runs_est = (home.rs_per_game + away.ra_per_game) / 2
    away_runs_est = (away.rs_per_game + home.ra_per_game) / 2

    return {
        "home_win_prob": round(home_win, 4),
        "away_win_prob": round(away_win, 4),
        "home_runs_est": round(home_runs_est, 2),
        "away_runs_est": round(away_runs_est, 2),
    }


def update_form(form: TeamForm, runs_scored: int, runs_allowed: int) -> None:
    form.games += 1
    form.runs_scored += runs_scored
    form.runs_allowed += runs_allowed


def reset_season_forms(team_ids: Iterable[int]) -> dict[int, TeamForm]:
    return {tid: TeamForm() for tid in team_ids}