"""夜间 true_tier 推导（T-G3，§4 四条规则，确定性）+ 留存清理。

规则（对每条 true_tier 为空的观察，按序判定）：
0. human_override 非空 -> 以人工为准（规则 4，优先级最高）。
1. features.plan_multi（consumer=pipeline 发出 brief 的多步信号）-> true=T3。
2. outcome∈{escalated,failed,user_retry,timeout} -> true = executed 的下一档
   （T1→T2→T3，T3 保持 T3）。
3. outcome∈{ok,verified} -> true = executed（T1 成功即 T1；T2/T3 同理）。
4. 其余（outcome 为空等）-> 跳过，等下一轮。
"""
from __future__ import annotations

import json
import time
from typing import Any, Dict, Optional

NEXT_TIER = {"T1": "T2", "T2": "T3", "T3": "T3"}
SUCCESS = ("ok", "verified")
FAILURE = ("escalated", "failed", "user_retry", "timeout")


def _features(row: Dict[str, Any]) -> Dict[str, Any]:
    try:
        obj = json.loads(row.get("features") or "{}")
        return obj if isinstance(obj, dict) else {}
    except json.JSONDecodeError:
        return {}


def derive_true_tier(row: Dict[str, Any]) -> Optional[str]:
    """单行推导（纯函数，测试友好）。返回 None = 暂不判定。"""
    if row.get("human_override"):
        return str(row["human_override"])
    outcome = row.get("outcome") or ""
    executed = row.get("executed_tier") or "T2"
    feats = _features(row)
    if feats.get("plan_multi"):
        return "T3"                                       # 规则 1（pipeline brief 信号）
    if outcome in FAILURE:                                # 规则 2
        return NEXT_TIER.get(executed, "T3")
    if outcome in SUCCESS:                                # 规则 3
        return executed
    return None                                           # 规则 4：等待结果


def derive_true_tiers(store, now: Optional[float] = None,
                      retention_days: int = 180) -> int:
    """批量推导（§7 签名）：返回回填条数；顺带 180d 留存清理。"""
    now = time.time() if now is None else now
    rows = store.all_observations()
    count = 0
    for row in rows:
        if row.get("true_tier"):
            continue
        true_tier = derive_true_tier(row)
        if true_tier:
            store.set_true_tier(row["request_id"], true_tier)
            count += 1
    store.purge_older_than(now - retention_days * 86400)
    return count