"""Readers beside an agent open its files without writing to them (X6)."""

import sqlite3
from pathlib import Path

import pytest

from nisse_core.state import readonly


def wal_db(path: Path) -> sqlite3.Connection:
    conn = sqlite3.connect(path, isolation_level=None)
    conn.execute("PRAGMA journal_mode=WAL")
    conn.execute("CREATE TABLE t (v TEXT)")
    conn.execute("INSERT INTO t VALUES ('one')")
    return conn


def test_a_closed_database_is_read_without_creating_any_file(tmp_path: Path) -> None:
    wal_db(tmp_path / "a.db").close()
    assert sorted(p.name for p in tmp_path.iterdir()) == ["a.db"]
    conn = readonly.connect(tmp_path / "a.db")
    assert conn.execute("SELECT v FROM t").fetchall()[0]["v"] == "one"
    conn.close()
    assert sorted(p.name for p in tmp_path.iterdir()) == ["a.db"]


def test_a_live_database_is_read_as_its_writer_commits(tmp_path: Path) -> None:
    writer = wal_db(tmp_path / "a.db")
    conn = readonly.connect(tmp_path / "a.db")
    writer.execute("INSERT INTO t VALUES ('two')")
    assert [r["v"] for r in conn.execute("SELECT v FROM t")] == ["one", "two"]
    with pytest.raises(sqlite3.OperationalError):
        conn.execute("INSERT INTO t VALUES ('three')")
    conn.close()
    writer.execute("INSERT INTO t VALUES ('four')")  # no lock left behind
    writer.close()


def test_a_missing_file_is_an_error_not_a_new_database(tmp_path: Path) -> None:
    with pytest.raises(sqlite3.OperationalError):
        readonly.connect(tmp_path / "none.db")
    assert not (tmp_path / "none.db").exists()