"""Focused source-level contracts for legacy Agent migrations."""

import importlib.util
import unittest
from pathlib import Path
from unittest.mock import patch


VERSIONS = Path(__file__).parents[1] / "alembic" / "versions"


def load_migration(filename):
    path = VERSIONS / filename
    spec = importlib.util.spec_from_file_location(filename.removesuffix(".py"), path)
    module = importlib.util.module_from_spec(spec)
    spec.loader.exec_module(module)
    return module


class EmptyResult:
    def all(self):
        return []


class RecordingConnection:
    def __init__(self):
        self.statements = []

    def execute(self, statement, parameters=None):
        del parameters
        self.statements.append(str(statement))
        return EmptyResult()


class LegacyRoutingMigrationTests(unittest.TestCase):
    def test_0018_locks_every_preflight_and_update_table_before_reads(self):
        migration = load_migration("0018_legacy_agent_routing.py")
        connection = RecordingConnection()
        with patch.object(migration.op, "get_bind", return_value=connection):
            migration.upgrade()

        first = " ".join(connection.statements[0].split()).lower()
        self.assertTrue(first.startswith("lock table"))
        self.assertIn("in share row exclusive mode", first)
        for table in (
            "agent_zones", "minerops_agent_discoveries",
            "minerops_agent_snapshots", "minerops_site_agents", "sites",
        ):
            with self.subTest(table=table):
                self.assertIn(table, first)

        first_update = next(
            index for index, statement in enumerate(connection.statements)
            if "UPDATE " in statement
        )
        self.assertEqual(first_update, 4)

    def test_0019_is_the_direct_forward_only_successor(self):
        migration = load_migration("0019_agent_legacy_auth_retire.py")
        self.assertEqual(migration.revision, "0019_agent_legacy_auth_retire")
        self.assertEqual(migration.down_revision, "0018_legacy_agent_routing")

    def test_0020_adds_only_existing_identity_transition_binding(self):
        migration = load_migration(
            "0020_existing_agent_credential_transition.py"
        )
        self.assertEqual(migration.revision, "0020_existing_agent_transition")
        self.assertEqual(
            migration.down_revision,
            "0019_agent_legacy_auth_retire",
        )


if __name__ == "__main__":
    unittest.main()