"""账本（T-P0：DDL 初始化 + 连接纪律；CRUD/预扣在 T-P1 落地）。

工程纪律：
- D-P10：sqlite3 是同步库，所有 DB 调用必须经 asyncio.to_thread（由调用方
  routes 层包装；本模块保持同步实现，可测试性好）。连接 check_same_thread=False
  + threading.Lock 串行化（沿用 ReviewQueue 模式：每操作新连接 + 全局锁）。
- WAL 模式（§3）。
- D-P11：预扣用原子 UPDATE，见 try_hold（T-P1 实现）。
"""
from __future__ import annotations

import sqlite3
import threading
from pathlib import Path
from typing import Any, Dict, List, Optional

# 四表 + 两索引（§3，一字不改）
_SCHEMA = """
CREATE TABLE IF NOT EXISTS students(
  id INTEGER PRIMARY KEY, name TEXT NOT NULL, class TEXT DEFAULT '',
  status TEXT NOT NULL DEFAULT 'active',
  balance_milli INTEGER NOT NULL DEFAULT 0,
  daily_cap_milli INTEGER NOT NULL DEFAULT 5000,
  spent_today_milli INTEGER NOT NULL DEFAULT 0, spent_date TEXT DEFAULT '');

CREATE TABLE IF NOT EXISTS proxy_keys(
  id INTEGER PRIMARY KEY, key_hash TEXT UNIQUE NOT NULL, key_prefix TEXT NOT NULL,
  student_id INTEGER NOT NULL REFERENCES students(id),
  created_ts INTEGER NOT NULL, revoked INTEGER NOT NULL DEFAULT 0,
  rpm_cap INTEGER NOT NULL DEFAULT 10, day_cap_req INTEGER NOT NULL DEFAULT 200,
  req_today INTEGER NOT NULL DEFAULT 0, req_date TEXT DEFAULT '');

CREATE TABLE IF NOT EXISTS usage_ledger(
  request_id TEXT PRIMARY KEY, ts INTEGER NOT NULL, key_id INTEGER NOT NULL,
  model TEXT NOT NULL, bucket TEXT NOT NULL DEFAULT 'default',
  in_miss_tok INTEGER NOT NULL DEFAULT 0, in_hit_tok INTEGER NOT NULL DEFAULT 0,
  out_tok INTEGER NOT NULL DEFAULT 0, gateway_cached INTEGER NOT NULL DEFAULT 0,
  upstream_cost_milli INTEGER NOT NULL DEFAULT 0, charged_milli INTEGER NOT NULL DEFAULT 0,
  margin_milli INTEGER NOT NULL DEFAULT 0, ttfb_ms INTEGER, total_ms INTEGER,
  status TEXT NOT NULL);

CREATE TABLE IF NOT EXISTS semcache(
  cache_key TEXT PRIMARY KEY,
  bucket TEXT NOT NULL, q_norm TEXT NOT NULL, answer TEXT NOT NULL, model TEXT NOT NULL,
  created_ts INTEGER NOT NULL, ttl_ts INTEGER NOT NULL,
  doc_version INTEGER NOT NULL DEFAULT 1, hits INTEGER NOT NULL DEFAULT 0);
CREATE INDEX IF NOT EXISTS idx_semcache_bucket ON semcache(bucket, ttl_ts);
CREATE INDEX IF NOT EXISTS idx_ledger_ts ON usage_ledger(ts);
"""

_TABLES = ("students", "proxy_keys", "usage_ledger", "semcache")


class Ledger:
    """代理层账本（sqlite WAL；同步实现，调用方负责 to_thread）。"""

    def __init__(self, db_path: str | Path):
        self.db_path = Path(db_path)
        self.db_path.parent.mkdir(parents=True, exist_ok=True)
        self._lock = threading.Lock()
        self._init_db()

    # ---------- 初始化 ----------
    @classmethod
    def init_db(cls, db_path: str | Path) -> "Ledger":
        """工厂（§6 签名）：建库建表（幂等）。"""
        return cls(db_path)

    def _connect(self) -> sqlite3.Connection:
        conn = sqlite3.connect(self.db_path, check_same_thread=False)
        conn.row_factory = sqlite3.Row
        conn.execute("PRAGMA journal_mode=WAL")
        return conn

    def _init_db(self) -> None:
        with self._lock, self._connect() as conn:
            conn.executescript(_SCHEMA)

    # ---------- 自省（T-P0 验收用） ----------
    def table_names(self) -> List[str]:
        """列出已建表名（测试验收）。"""
        with self._lock, self._connect() as conn:
            rows = conn.execute(
                "SELECT name FROM sqlite_master WHERE type='table'").fetchall()
        return [r["name"] for r in rows]

    def index_names(self) -> List[str]:
        with self._lock, self._connect() as conn:
            rows = conn.execute(
                "SELECT name FROM sqlite_master WHERE type='index' AND name LIKE 'idx_%'"
            ).fetchall()
        return [r["name"] for r in rows]