"""get_conn 连接策略契约：WAL 首连设置一次 + 目录自动创建。

背景：get_conn 原实现每个连接都执行 mkdir + PRAGMA journal_mode=WAL，
实测每次多付 ~1.2ms（mkdir 190us + 新连接上 PRAGMA ~1ms）。WAL 模式
持久化在库文件头里，与 core/db.py 的 _WAL_READY_FOR 同款，按路径设一次即可。
"""

import sqlite3
from pathlib import Path

from auth_system import db


def _point_db_to(monkeypatch, tmp_path: Path, conn_counter: list[int] | None = None):
    """把 DB_PATH 指到临时库，并清空 WAL 已就绪缓存。"""
    new_path = tmp_path / 'site.db'
    monkeypatch.setattr(db, 'DB_PATH', new_path)
    monkeypatch.setattr(db, '_WAL_READY', set())
    if conn_counter is not None:
        real_connect = sqlite3.connect

        def counting_connect(*a, **k):
            conn_counter[0] += 1
            return real_connect(*a, **k)

        monkeypatch.setattr(db.sqlite3, 'connect', counting_connect)
    return new_path


def test_wal_mode_active_on_fresh_db(monkeypatch, tmp_path):
    """新路径首连：WAL 生效。"""
    _point_db_to(monkeypatch, tmp_path)
    conn = db.get_conn()
    try:
        mode = conn.execute('PRAGMA journal_mode').fetchone()[0]
        assert mode.lower() == 'wal'
    finally:
        conn.close()


def test_wal_pragma_only_once_per_path(monkeypatch, tmp_path):
    """同一路径第二次起不再执行 PRAGMA journal_mode=WAL（用 SQL 追踪器实证）。"""
    _point_db_to(monkeypatch, tmp_path)

    conn1 = db.get_conn()
    conn1.close()
    conn2 = db.get_conn()
    conn2.close()

    # 用 sqlite3 的 set_trace_callback 记录第三条连接上的语句（2 连接已建立缓存）
    statements: list[str] = []
    conn3 = db.get_conn()
    conn3.set_trace_callback(statements.append)
    conn3.execute('SELECT 1').fetchall()
    conn3.close()
    assert statements == ['SELECT 1'], f'第三条连接不应再跑 PRAGMA，实际: {statements}'


def test_new_path_resets_wal_cache(monkeypatch, tmp_path):
    """换库路径（测试隔离场景）：新路径重新设置 WAL。"""
    _point_db_to(monkeypatch, tmp_path / 'a')
    c = db.get_conn()
    c.close()

    monkeypatch.setattr(db, 'DB_PATH', tmp_path / 'b' / 'site.db')
    c = db.get_conn()
    try:
        mode = c.execute('PRAGMA journal_mode').fetchone()[0]
        assert mode.lower() == 'wal'
    finally:
        c.close()


def test_missing_dir_auto_created(monkeypatch, tmp_path):
    """目录不存在：connect 失败兜底 mkdir 重试，不经 init_db 也能用。"""
    deep = tmp_path / 'x' / 'y'
    _point_db_to(monkeypatch, deep)
    assert not deep.exists()

    conn = db.get_conn()
    try:
        conn.execute('CREATE TABLE t (v)').close()
        conn.commit()
    finally:
        conn.close()
    assert (deep / 'site.db').exists()


def test_deleted_db_file_recovers(monkeypatch, tmp_path):
    """库文件被删（目录还在）：重连自动重建且恢复 WAL 模式，不崩。"""
    _point_db_to(monkeypatch, tmp_path)
    c = db.get_conn()
    c.close()

    (tmp_path / 'site.db').unlink()
    conn = db.get_conn()
    try:
        conn.execute('SELECT 1').fetchall()
        mode = conn.execute('PRAGMA journal_mode').fetchone()[0]
        assert mode.lower() == 'wal', '重建的库文件必须恢复 WAL（journal_mode 不持久于新文件）'
    finally:
        conn.close()


def test_concurrent_first_connect_no_lease_conflict(monkeypatch, tmp_path):
    """多线程同时首连（读路径不持 _DB_LOCK）：WAL 设置正确、无连接报错。

    core/db.py 记录过并发 PRAGMA 争排他锁报 database is locked 的实测坑，
    同步层用专用锁 + 二次复查同款防护。
    """
    import threading

    _point_db_to(monkeypatch, tmp_path)
    errors: list[Exception] = []

    def worker():
        try:
            for _ in range(5):
                c = db.get_conn()
                c.execute('SELECT 1').fetchall()
                c.close()
        except Exception as e:  # 收集全部失败供断言
            errors.append(e)

    threads = [threading.Thread(target=worker) for _ in range(8)]
    for t in threads:
        t.start()
    for t in threads:
        t.join()

    assert errors == []