from pathlib import Path

import pytest
from alembic.config import Config
from alembic.script import ScriptDirectory

from ai_platform.bootstrap.app import _current_migration_heads, validate_migration_heads


def test_startup_migration_heads_come_from_alembic_metadata():
    project_root = Path(__file__).resolve().parents[1]
    config = Config(str(project_root / "alembic.ini"))
    config.set_main_option("path_separator", "os")
    config.set_main_option("script_location", str(project_root / "migrations"))
    expected_heads = frozenset(ScriptDirectory.from_config(config).get_heads())

    assert _current_migration_heads() == expected_heads
    validate_migration_heads(expected_heads)


def test_startup_rejects_missing_applied_migration_heads():
    with pytest.raises(RuntimeError, match="migrations are missing or not at head"):
        validate_migration_heads(frozenset())


def test_startup_rejects_stale_applied_migration_heads():
    with pytest.raises(RuntimeError, match="migrations are missing or not at head"):
        validate_migration_heads({"stale-head"})