"""Tests for the scheduler lock mechanism.

These tests verify that the database-backed scheduler lock correctly enforces
single-executor safety across multiple startup attempts, including stale lock
cleanup, heartbeat updates, and multi-process race condition prevention.
"""

from __future__ import annotations

import os
import time
from typing import Any

import aiosqlite
import pytest

from app.utils.scheduler_lock import (
    SCHEDULER_LOCK_HEARTBEAT_INTERVAL_SECONDS,
    SCHEDULER_LOCK_TTL_SECONDS,
    acquire_scheduler_lock,
    get_scheduler_lock_info,
    release_scheduler_lock,
    update_scheduler_lock_heartbeat,
)


@pytest.fixture
async def lock_db(tmp_path: Any) -> aiosqlite.Connection:
    """Create a temporary database with scheduler_lock table."""
    db_path = tmp_path / "test.db"
    db = await aiosqlite.connect(str(db_path))
    await db.execute(
        """
        CREATE TABLE scheduler_lock (
            id INTEGER PRIMARY KEY CHECK (id = 1),
            pid INTEGER NOT NULL,
            hostname TEXT NOT NULL,
            created_at REAL NOT NULL,
            heartbeat_at REAL NOT NULL
        );
        """
    )
    await db.commit()
    yield db
    await db.close()


@pytest.mark.asyncio
async def test_acquire_scheduler_lock_success(lock_db: aiosqlite.Connection) -> None:
    """Test successful lock acquisition."""
    result = await acquire_scheduler_lock(lock_db)
    assert result is True

    # Verify the lock is in the database
    cursor = await lock_db.execute("SELECT COUNT(*) FROM scheduler_lock")
    count = await cursor.fetchone()
    assert count[0] == 1


@pytest.mark.asyncio
async def test_acquire_scheduler_lock_fails_when_held(
    lock_db: aiosqlite.Connection,
) -> None:
    """Test that lock acquisition fails if already held."""
    # First instance acquires the lock
    result1 = await acquire_scheduler_lock(lock_db)
    assert result1 is True

    # Second instance tries to acquire, should fail
    result2 = await acquire_scheduler_lock(lock_db)
    assert result2 is False


@pytest.mark.asyncio
async def test_acquire_scheduler_lock_cleans_stale_locks(
    lock_db: aiosqlite.Connection,
) -> None:
    """Test that stale locks are automatically cleaned up."""
    # Insert a stale lock manually (old heartbeat)
    now = time.time()
    stale_heartbeat = now - SCHEDULER_LOCK_TTL_SECONDS - 10
    await lock_db.execute(
        """
        INSERT INTO scheduler_lock (id, pid, hostname, created_at, heartbeat_at)
        VALUES (1, 9999, 'stale-host', ?, ?)
        """,
        (now - 100, stale_heartbeat),
    )
    await lock_db.commit()

    # New instance should clean up the stale lock and acquire
    result = await acquire_scheduler_lock(lock_db)
    assert result is True

    # Verify the old lock is gone and new one is in place
    cursor = await lock_db.execute(
        "SELECT pid, hostname FROM scheduler_lock WHERE id = 1"
    )
    row = await cursor.fetchone()
    assert row is not None
    pid, hostname = row
    assert pid == os.getpid()
    assert hostname is not None


@pytest.mark.asyncio
async def test_release_scheduler_lock_success(
    lock_db: aiosqlite.Connection,
) -> None:
    """Test successful lock release."""
    # Acquire the lock
    await acquire_scheduler_lock(lock_db)

    # Release it
    await release_scheduler_lock(lock_db)

    # Verify the lock is gone
    cursor = await lock_db.execute("SELECT COUNT(*) FROM scheduler_lock")
    count = await cursor.fetchone()
    assert count[0] == 0


@pytest.mark.asyncio
async def test_release_scheduler_lock_not_held(
    lock_db: aiosqlite.Connection,
) -> None:
    """Test that releasing a lock we don't hold is safe."""
    # Try to release without acquiring — should not crash
    await release_scheduler_lock(lock_db)

    # Verify the lock is still empty
    cursor = await lock_db.execute("SELECT COUNT(*) FROM scheduler_lock")
    count = await cursor.fetchone()
    assert count[0] == 0


@pytest.mark.asyncio
async def test_update_scheduler_lock_heartbeat_success(
    lock_db: aiosqlite.Connection,
) -> None:
    """Test successful heartbeat update."""
    # Acquire the lock
    await acquire_scheduler_lock(lock_db)

    # Get the original heartbeat
    cursor = await lock_db.execute("SELECT heartbeat_at FROM scheduler_lock WHERE id = 1")
    original_row = await cursor.fetchone()
    original_heartbeat = original_row[0]

    # Wait a moment and update the heartbeat
    time.sleep(0.01)
    result = await update_scheduler_lock_heartbeat(lock_db)
    assert result is True

    # Verify the heartbeat was updated
    cursor = await lock_db.execute("SELECT heartbeat_at FROM scheduler_lock WHERE id = 1")
    new_row = await cursor.fetchone()
    new_heartbeat = new_row[0]
    assert new_heartbeat > original_heartbeat


@pytest.mark.asyncio
async def test_update_scheduler_lock_heartbeat_fails_if_not_held(
    lock_db: aiosqlite.Connection,
) -> None:
    """Test that heartbeat update fails if we don't hold the lock."""
    result = await update_scheduler_lock_heartbeat(lock_db)
    assert result is False


@pytest.mark.asyncio
async def test_get_scheduler_lock_info_returns_details(
    lock_db: aiosqlite.Connection,
) -> None:
    """Test that lock info includes all relevant fields."""
    await acquire_scheduler_lock(lock_db)

    info = await get_scheduler_lock_info(lock_db)
    assert info is not None
    assert "pid" in info
    assert "hostname" in info
    assert "created_at" in info
    assert "heartbeat_at" in info
    assert info["pid"] == os.getpid()


@pytest.mark.asyncio
async def test_get_scheduler_lock_info_returns_none_when_empty(
    lock_db: aiosqlite.Connection,
) -> None:
    """Test that lock info returns None when no lock is held."""
    info = await get_scheduler_lock_info(lock_db)
    assert info is None


@pytest.mark.asyncio
async def test_scheduler_lock_full_lifecycle(
    lock_db: aiosqlite.Connection,
) -> None:
    """Test the full lifecycle: acquire, update heartbeat, release."""
    # Initially no lock
    info = await get_scheduler_lock_info(lock_db)
    assert info is None

    # Acquire the lock
    result = await acquire_scheduler_lock(lock_db)
    assert result is True
    info = await get_scheduler_lock_info(lock_db)
    assert info is not None
    initial_heartbeat = info["heartbeat_at"]

    # Update heartbeat multiple times
    time.sleep(0.01)
    result = await update_scheduler_lock_heartbeat(lock_db)
    assert result is True
    info = await get_scheduler_lock_info(lock_db)
    updated_heartbeat = info["heartbeat_at"]
    assert updated_heartbeat > initial_heartbeat

    # Release the lock
    await release_scheduler_lock(lock_db)
    info = await get_scheduler_lock_info(lock_db)
    assert info is None


@pytest.mark.asyncio
async def test_scheduler_lock_heartbeat_interval_sanity(
    lock_db: aiosqlite.Connection,
) -> None:
    """Verify heartbeat interval is less than TTL to prevent premature expiry.

    With a 5-second heartbeat interval and 60-second TTL, the lock can survive
    ~12 missed heartbeats before expiring. This provides robust protection against
    temporary delays or high load that could cause a single missed heartbeat.
    """
    # Verify the configuration ratio is safe (interval < TTL)
    assert SCHEDULER_LOCK_HEARTBEAT_INTERVAL_SECONDS < SCHEDULER_LOCK_TTL_SECONDS

    # With this ratio, the lock can survive at least 12 missed heartbeats
    # (60s TTL / 5s interval = 12 intervals between heartbeats before expiry)
    safe_ratio = SCHEDULER_LOCK_TTL_SECONDS / SCHEDULER_LOCK_HEARTBEAT_INTERVAL_SECONDS
    assert safe_ratio >= 12, (
        f"Heartbeat interval too long: lock can only survive {safe_ratio:.1f} missed heartbeats. "
        f"Should be at least 12 for safety."
    )


@pytest.mark.asyncio
async def test_scheduler_lock_race_condition_prevention(
    lock_db: aiosqlite.Connection,
) -> None:
    """Test that the lock prevents concurrent execution (race condition).

    Scenario: Process A acquires the lock and starts working. Process B starts
    up and tries to acquire the lock. Even if Process A's heartbeat fails
    momentarily, Process B should not acquire the lock immediately.

    This test verifies:
    1. Only one process can hold the lock at a time
    2. The lock cannot be stolen while being actively maintained (via heartbeat)
    3. Stale locks are only cleaned after TTL expires
    """
    # Process A acquires the lock
    result_a = await acquire_scheduler_lock(lock_db)
    assert result_a is True

    # Get the lock info
    info_a = await get_scheduler_lock_info(lock_db)
    assert info_a is not None
    lock_heartbeat_a = info_a["heartbeat_at"]

    # Process B tries to acquire — should fail
    result_b = await acquire_scheduler_lock(lock_db)
    assert result_b is False

    # Process A updates its heartbeat (simulating ongoing work)
    time.sleep(0.01)
    result_heartbeat = await update_scheduler_lock_heartbeat(lock_db)
    assert result_heartbeat is True

    # Verify heartbeat was updated
    info_a_updated = await get_scheduler_lock_info(lock_db)
    assert info_a_updated is not None
    assert info_a_updated["heartbeat_at"] > lock_heartbeat_a

    # Process B still cannot acquire the lock (it's active and well-maintained)
    result_b_retry = await acquire_scheduler_lock(lock_db)
    assert result_b_retry is False

    # Process A releases the lock
    await release_scheduler_lock(lock_db)

    # Now Process B can acquire it
    result_b_final = await acquire_scheduler_lock(lock_db)
    assert result_b_final is True