"""Unit tests for DB pool configuration (SEC-14-04, phase 106, task 01).

Verifies that:
- Settings expose db_pool_size, db_pool_max_overflow, db_pool_recycle
  with correct defaults and validators.
- create_engine() receives the pool kwargs from settings.
"""
from __future__ import annotations

import contextlib

import pytest

from app.config import Settings


class TestSettingsDefaults:
    """Pool config defaults match SQLAlchemy implicit defaults."""

    def test_pool_size_default(self):
        assert Settings().db_pool_size == 5

    def test_pool_max_overflow_default(self):
        assert Settings().db_pool_max_overflow == 10

    def test_pool_recycle_default(self):
        assert Settings().db_pool_recycle == 3600


class TestSettingsCustomValues:
    """Custom values round-trip correctly."""

    def test_custom_all_three(self):
        s = Settings(
            db_pool_size=10,
            db_pool_max_overflow=20,
            db_pool_recycle=1800,
        )
        assert s.db_pool_size == 10
        assert s.db_pool_max_overflow == 20
        assert s.db_pool_recycle == 1800

    def test_custom_pool_size_only(self):
        s = Settings(db_pool_size=8)
        assert s.db_pool_size == 8
        assert s.db_pool_max_overflow == 10
        assert s.db_pool_recycle == 3600


class TestValidators:
    """Pool config validators reject invalid values."""

    def test_pool_size_zero_raises(self):
        with pytest.raises(ValueError, match="db_pool_size must be >= 1"):
            Settings(db_pool_size=0)

    def test_pool_size_negative_raises(self):
        with pytest.raises(ValueError, match="db_pool_size must be >= 1"):
            Settings(db_pool_size=-5)

    def test_pool_max_overflow_negative_raises(self):
        with pytest.raises(ValueError, match="db_pool_max_overflow must be >= 0"):
            Settings(db_pool_max_overflow=-1)

    def test_pool_max_overflow_zero_is_legal(self):
        s = Settings(db_pool_max_overflow=0)
        assert s.db_pool_max_overflow == 0

    def test_pool_recycle_zero_is_legal(self):
        """pool_recycle=0 means never recycle — legal, just aggressive."""
        s = Settings(db_pool_recycle=0)
        assert s.db_pool_recycle == 0


class TestEngineKwargs:
    """create_engine() receives the correct pool parameters from settings."""

    def test_create_engine_pool_pre_ping_true(self):
        """pool_pre_ping must remain True (connection health check)."""
        from app import db  # noqa: F811

        # The engine's pool options include pool_pre_ping=True.
        # We verify by checking the pool's _pre_ping attribute.
        assert db.engine.pool._pre_ping is True

    def test_create_engine_pool_recycle(self):
        """pool_recycle defaults to 3600 seconds."""
        from app import db  # noqa: F811

        assert db.engine.pool._recycle == 3600

    def test_sessionlocal_still_callable(self):
        """SessionLocal remains a valid session factory."""
        from app import db  # noqa: F811

        assert callable(db.SessionLocal)

    def test_get_db_still_yields_session(self):
        """get_db() dependency still yields a Session (contract preserved)."""
        from app import db  # noqa: F811

        gen = db.get_db()
        session = next(gen)
        assert isinstance(session, db.Session)
        session.close()
        # Generator cleanup
        with contextlib.suppress(StopIteration):
            next(gen)