"""Tests for DuckDB initialization and schema."""
import asyncio
import pytest
import duckdb

from backend.app import db as db_module


@pytest.fixture(autouse=True)
def fresh_db():
    """Use an in-memory DB for each test and reset global state."""
    db_module._conn = None
    yield
    db_module.close_db()
    db_module._conn = None


# ---------------------------------------------------------------------------
# Lifecycle
# ---------------------------------------------------------------------------

def test_init_creates_users_table():
    conn = db_module.init_db(":memory:")
    result = conn.execute(
        "SELECT table_name FROM information_schema.tables WHERE table_name = 'users'"
    ).fetchone()
    assert result is not None


def test_init_creates_refresh_tokens_table():
    conn = db_module.init_db(":memory:")
    result = conn.execute(
        "SELECT table_name FROM information_schema.tables WHERE table_name = 'refresh_tokens'"
    ).fetchone()
    assert result is not None


def test_init_is_idempotent():
    conn1 = db_module.init_db(":memory:")
    conn2 = db_module.init_db(":memory:")
    assert conn1 is conn2


def test_get_conn_raises_before_init():
    with pytest.raises(RuntimeError, match="not initialised"):
        db_module.get_conn()


def test_get_conn_returns_connection_after_init():
    db_module.init_db(":memory:")
    conn = db_module.get_conn()
    assert conn is not None


def test_close_db_resets_connection():
    db_module.init_db(":memory:")
    db_module.close_db()
    with pytest.raises(RuntimeError):
        db_module.get_conn()


# ---------------------------------------------------------------------------
# Schema: users table columns and defaults
# ---------------------------------------------------------------------------

def test_users_columns():
    conn = db_module.init_db(":memory:")
    cols = {
        row[0]
        for row in conn.execute(
            "SELECT column_name FROM information_schema.columns WHERE table_name = 'users'"
        ).fetchall()
    }
    assert {"id", "email", "password_hash",
            "role", "created_at", "updated_at"} <= cols


def test_users_default_role_is_user():
    conn = db_module.init_db(":memory:")
    conn.execute(
        "INSERT INTO users (email, password_hash) VALUES ('a@example.com', 'hash')"
    )
    row = conn.execute(
        "SELECT role FROM users WHERE email = 'a@example.com'").fetchone()
    assert row[0] == "user"


def test_users_id_auto_generated():
    conn = db_module.init_db(":memory:")
    conn.execute(
        "INSERT INTO users (email, password_hash) VALUES ('b@example.com', 'hash')"
    )
    row = conn.execute(
        "SELECT id FROM users WHERE email = 'b@example.com'").fetchone()
    assert row[0] is not None


def test_users_email_unique_constraint():
    conn = db_module.init_db(":memory:")
    conn.execute(
        "INSERT INTO users (email, password_hash) VALUES ('c@example.com', 'h')")
    with pytest.raises(Exception):
        conn.execute(
            "INSERT INTO users (email, password_hash) VALUES ('c@example.com', 'h2')")


def test_users_timestamps_auto_set():
    conn = db_module.init_db(":memory:")
    conn.execute(
        "INSERT INTO users (email, password_hash) VALUES ('d@example.com', 'hash')"
    )
    row = conn.execute(
        "SELECT created_at, updated_at FROM users WHERE email = 'd@example.com'"
    ).fetchone()
    assert row[0] is not None
    assert row[1] is not None


# ---------------------------------------------------------------------------
# Schema: refresh_tokens table columns and defaults
# ---------------------------------------------------------------------------

def test_refresh_tokens_columns():
    conn = db_module.init_db(":memory:")
    cols = {
        row[0]
        for row in conn.execute(
            "SELECT column_name FROM information_schema.columns WHERE table_name = 'refresh_tokens'"
        ).fetchall()
    }
    assert {"jti", "user_id", "issued_at", "expires_at", "revoked"} <= cols


def test_refresh_tokens_default_revoked_false():
    conn = db_module.init_db(":memory:")
    conn.execute(
        "INSERT INTO users (email, password_hash) VALUES ('e@example.com', 'h')")
    user_id = conn.execute(
        "SELECT id FROM users WHERE email = 'e@example.com'").fetchone()[0]
    conn.execute(
        "INSERT INTO refresh_tokens (user_id, expires_at) VALUES (?, now() + INTERVAL 7 DAY)",
        [user_id],
    )
    row = conn.execute("SELECT revoked FROM refresh_tokens WHERE user_id = ?", [
                       user_id]).fetchone()
    assert row[0] is False


def test_refresh_tokens_jti_auto_generated():
    conn = db_module.init_db(":memory:")
    conn.execute(
        "INSERT INTO users (email, password_hash) VALUES ('f@example.com', 'h')")
    user_id = conn.execute(
        "SELECT id FROM users WHERE email = 'f@example.com'").fetchone()[0]
    conn.execute(
        "INSERT INTO refresh_tokens (user_id, expires_at) VALUES (?, now() + INTERVAL 7 DAY)",
        [user_id],
    )
    row = conn.execute("SELECT jti FROM refresh_tokens WHERE user_id = ?", [
                       user_id]).fetchone()
    assert row[0] is not None


# ---------------------------------------------------------------------------
# Write lock
# ---------------------------------------------------------------------------

def test_get_write_lock_returns_asyncio_lock():
    lock = db_module.get_write_lock()
    assert isinstance(lock, asyncio.Lock)


def test_get_write_lock_returns_same_instance():
    lock1 = db_module.get_write_lock()
    lock2 = db_module.get_write_lock()
    assert lock1 is lock2


async def test_write_lock_serialises_concurrent_writes():
    """Two coroutines acquiring the lock must not overlap."""
    conn = db_module.init_db(":memory:")
    lock = db_module.get_write_lock()
    order = []

    async def writer(label: str):
        async with lock:
            order.append(f"{label}-start")
            await asyncio.sleep(0)   # yield to event loop
            order.append(f"{label}-end")

    await asyncio.gather(writer("A"), writer("B"))
    # Each writer's start and end must be adjacent (no interleaving)
    assert order.index("A-start") + 1 == order.index("A-end") or \
        order.index("B-start") + 1 == order.index("B-end")