"""Unit tests for agent_team.db.schema (§3.3.1, §6.7)."""

from __future__ import annotations

import sqlite3
import threading
from pathlib import Path

import pytest

from agent_team.db.schema import (
    BUDGET_LEDGER_DDL,
    PENDING_QUESTIONS_DDL,
    QUESTION_STATES,
    SCHEMA_VERSION,
    answer_question,
    connect,
    expire_question,
    init_db,
    migrate,
    reopen_question,
    supersede_question,
)


def _insert_open_question(conn: sqlite3.Connection, qid: str, turn: int = 0) -> None:
    conn.execute(
        "INSERT INTO pending_questions "
        "(question_id, thread_id, turn, status, transport) "
        "VALUES (?, 'thread-1', ?, 'open', 'slack')",
        (qid, turn),
    )


def test_ddl_constants_are_nonempty_strings() -> None:
    assert isinstance(PENDING_QUESTIONS_DDL, str) and PENDING_QUESTIONS_DDL
    assert isinstance(BUDGET_LEDGER_DDL, str) and BUDGET_LEDGER_DDL
    assert "pending_questions" in PENDING_QUESTIONS_DDL
    assert "budget_ledger" in BUDGET_LEDGER_DDL


def test_schema_version_is_int() -> None:
    assert isinstance(SCHEMA_VERSION, int)


def test_question_states_match_ddl_check() -> None:
    assert QUESTION_STATES == ("open", "answered", "expired", "superseded")
    for state in QUESTION_STATES:
        assert f"'{state}'" in PENDING_QUESTIONS_DDL


def test_connect_sets_pragmas(tmp_path: Path) -> None:
    conn = connect(tmp_path / "db.sqlite")
    try:
        assert conn.execute("PRAGMA journal_mode").fetchone()[0].lower() == "wal"
        assert conn.execute("PRAGMA foreign_keys").fetchone()[0] == 1
        assert conn.execute("PRAGMA busy_timeout").fetchone()[0] >= 1
    finally:
        conn.close()


def test_init_db_creates_tables(tmp_path: Path) -> None:
    db = tmp_path / "db.sqlite"
    init_db(db)
    conn = connect(db)
    try:
        names = {
            r[0]
            for r in conn.execute(
                "SELECT name FROM sqlite_master WHERE type='table'"
            ).fetchall()
        }
    finally:
        conn.close()
    assert {"pending_questions", "budget_ledger", "schema_meta"} <= names


def test_init_db_is_idempotent(tmp_path: Path) -> None:
    db = tmp_path / "db.sqlite"
    init_db(db)
    init_db(db)  # must not raise
    conn = connect(db)
    try:
        version = conn.execute(
            "SELECT schema_version FROM schema_meta WHERE id=1"
        ).fetchone()[0]
    finally:
        conn.close()
    assert version == SCHEMA_VERSION


def test_pending_questions_status_check_constraint(tmp_path: Path) -> None:
    db = tmp_path / "db.sqlite"
    init_db(db)
    conn = connect(db)
    try:
        with pytest.raises(sqlite3.IntegrityError):
            conn.execute(
                "INSERT INTO pending_questions "
                "(question_id, thread_id, turn, status, transport) "
                "VALUES ('q', 't', 0, 'bogus', 'slack')"
            )
    finally:
        conn.close()


def test_migrate_stamps_version(tmp_path: Path) -> None:
    db = tmp_path / "db.sqlite"
    conn = connect(db)
    try:
        migrate(conn)
        version = conn.execute(
            "SELECT schema_version FROM schema_meta WHERE id=1"
        ).fetchone()[0]
        # Tables exist after migrate.
        conn.execute("SELECT 1 FROM pending_questions LIMIT 1")
        conn.execute("SELECT 1 FROM budget_ledger LIMIT 1")
    finally:
        conn.close()
    assert version == SCHEMA_VERSION


def test_answer_question_first_wins(tmp_path: Path) -> None:
    db = tmp_path / "db.sqlite"
    init_db(db)
    conn = connect(db)
    try:
        _insert_open_question(conn, "q1")
        first = answer_question(
            conn, question_id="q1", answer_json='{"a":1}', answered_via="slack"
        )
        second = answer_question(
            conn, question_id="q1", answer_json='{"a":2}', answered_via="github"
        )
        assert first is True
        assert second is False  # duplicate/late loses the compare-and-set
        row = conn.execute(
            "SELECT status, answer_json, answered_via, answered_at "
            "FROM pending_questions WHERE question_id='q1'"
        ).fetchone()
    finally:
        conn.close()
    assert row["status"] == "answered"
    assert row["answer_json"] == '{"a":1}'  # first answer retained
    assert row["answered_via"] == "slack"
    assert row["answered_at"]


def test_answer_after_expire_loses(tmp_path: Path) -> None:
    db = tmp_path / "db.sqlite"
    init_db(db)
    conn = connect(db)
    try:
        _insert_open_question(conn, "q2")
        assert expire_question(conn, question_id="q2") is True
        assert (
            answer_question(
                conn, question_id="q2", answer_json="{}", answered_via="slack"
            )
            is False
        )
        status = conn.execute(
            "SELECT status FROM pending_questions WHERE question_id='q2'"
        ).fetchone()["status"]
    finally:
        conn.close()
    assert status == "expired"


def test_expire_only_open(tmp_path: Path) -> None:
    db = tmp_path / "db.sqlite"
    init_db(db)
    conn = connect(db)
    try:
        _insert_open_question(conn, "q3")
        answer_question(conn, question_id="q3", answer_json="{}", answered_via="slack")
        # already answered -> cannot expire
        assert expire_question(conn, question_id="q3") is False
    finally:
        conn.close()


def test_supersede_open_or_answered(tmp_path: Path) -> None:
    db = tmp_path / "db.sqlite"
    init_db(db)
    conn = connect(db)
    try:
        _insert_open_question(conn, "q4")
        answer_question(conn, question_id="q4", answer_json="{}", answered_via="slack")
        assert supersede_question(conn, question_id="q4") is True
        # already superseded -> no-op
        assert supersede_question(conn, question_id="q4") is False
    finally:
        conn.close()


def test_reopen_question_unparks_expired_only(tmp_path: Path) -> None:
    db = tmp_path / "db.sqlite"
    init_db(db)
    conn = connect(db)
    try:
        _insert_open_question(conn, "exp")
        _insert_open_question(conn, "ans")
        assert expire_question(conn, question_id="exp") is True
        assert answer_question(
            conn, question_id="ans", answer_json="{}", answered_via="t"
        )
        # Expired -> reopened.
        assert reopen_question(conn, question_id="exp") is True
        row = conn.execute(
            "SELECT status, deadline_at FROM pending_questions WHERE question_id='exp'"
        ).fetchone()
        assert row["status"] == "open"
        assert row["deadline_at"] is None  # no deadline until one is set
        # Answered row is NOT reopenable (only expired rows are).
        assert reopen_question(conn, question_id="ans") is False
        assert (
            conn.execute(
                "SELECT status FROM pending_questions WHERE question_id='ans'"
            ).fetchone()["status"]
            == "answered"
        )
    finally:
        conn.close()


def test_concurrent_answers_single_winner(tmp_path: Path) -> None:
    """Two threads racing to answer the same open question: exactly one wins."""
    db = tmp_path / "db.sqlite"
    init_db(db)
    seed = connect(db)
    try:
        _insert_open_question(seed, "race")
    finally:
        seed.close()

    results: list[bool] = []
    barrier = threading.Barrier(2)
    lock = threading.Lock()

    def worker(via: str) -> None:
        conn = connect(db)
        try:
            barrier.wait()
            won = answer_question(
                conn, question_id="race", answer_json='{"v":1}', answered_via=via
            )
            with lock:
                results.append(won)
        finally:
            conn.close()

    threads = [threading.Thread(target=worker, args=(f"c{i}",)) for i in range(2)]
    for t in threads:
        t.start()
    for t in threads:
        t.join()

    assert sorted(results) == [False, True]


def test_shared_connection_concurrent_distinct_questions(tmp_path: Path) -> None:
    """Regression: many threads share ONE connection, answering DISTINCT questions.

    The responder and resume worker hold a single connection and call the CAS
    helpers from different threads concurrently (``connect()`` sets
    ``check_same_thread=False``). A single connection cannot hold two explicit
    ``BEGIN IMMEDIATE`` transactions at once, so the previous implementation
    raised "cannot start a transaction within a transaction" for all but one
    thread. The CAS now runs each write on its own private connection, so every
    distinct question is answered with no error.
    """
    db = tmp_path / "db.sqlite"
    init_db(db)
    shared = connect(db)
    n = 8
    try:
        for i in range(n):
            _insert_open_question(shared, f"q{i}")

        barrier = threading.Barrier(n)
        lock = threading.Lock()
        wins: list[bool] = []
        errors: list[BaseException] = []

        def worker(qid: str) -> None:
            try:
                barrier.wait()
                won = answer_question(
                    shared, question_id=qid, answer_json='{"v":1}', answered_via="t"
                )
                with lock:
                    wins.append(won)
            except BaseException as exc:  # noqa: BLE001 - record for assertion
                with lock:
                    errors.append(exc)

        threads = [threading.Thread(target=worker, args=(f"q{i}",)) for i in range(n)]
        for t in threads:
            t.start()
        for t in threads:
            t.join()
    finally:
        shared.close()

    assert errors == [], f"shared-connection CAS raised: {errors!r}"
    assert wins == [True] * n


def test_shared_connection_concurrent_same_question_single_winner(
    tmp_path: Path,
) -> None:
    """Regression: shared connection, many threads racing the SAME question.

    Exactly one first-answer-wins, the rest no-op (rowcount 0), and no thread
    raises a transaction-nesting or lock error.
    """
    db = tmp_path / "db.sqlite"
    init_db(db)
    shared = connect(db)
    n = 8
    try:
        _insert_open_question(shared, "race")

        barrier = threading.Barrier(n)
        lock = threading.Lock()
        wins: list[bool] = []
        errors: list[BaseException] = []

        def worker(via: str) -> None:
            try:
                barrier.wait()
                won = answer_question(
                    shared, question_id="race", answer_json='{"v":1}', answered_via=via
                )
                with lock:
                    wins.append(won)
            except BaseException as exc:  # noqa: BLE001 - record for assertion
                with lock:
                    errors.append(exc)

        threads = [threading.Thread(target=worker, args=(f"c{i}",)) for i in range(n)]
        for t in threads:
            t.start()
        for t in threads:
            t.join()
    finally:
        shared.close()

    assert errors == [], f"shared-connection CAS raised: {errors!r}"
    assert sum(wins) == 1
    assert wins.count(False) == n - 1