"""Lambda handler unit tests."""

import pytest
from src import app
from src.models.preference_change import InvalidPreferenceMessage


class TestHandler:
    """Unit tests for the Lambda handler function."""

    def test_returns_ok_on_success(self, handler_event, handler_success_mocks, sample_invalid_messages):
        """Handler should run the whole flow and return OK."""
        result = app.handler(handler_event, None)

        assert result == {'status': 'OK'}
        handler_success_mocks.parse.assert_called_once_with(handler_event)
        handler_success_mocks.flatten.assert_called_once_with(handler_success_mocks.parse.return_value[0])
        handler_success_mocks.prepare.assert_called_once_with(handler_success_mocks.flatten.return_value)
        handler_success_mocks.send.assert_called_once_with(handler_success_mocks.prepare.return_value)
        handler_success_mocks.dlq_send.assert_called_once_with(sample_invalid_messages)

    def test_logs_and_reraises_on_failure(self, handler_event, handler_error_mocks):
        """Handler should log and re-raise unexpected errors."""
        with pytest.raises(RuntimeError):
            app.handler(handler_event, None)

        handler_error_mocks.parse.assert_called_once_with(handler_event)
        handler_error_mocks.flatten.assert_not_called()
        handler_error_mocks.prepare.assert_not_called()
        handler_error_mocks.send.assert_not_called()
        handler_error_mocks.dlq_send.assert_called_once()
        sent_messages = handler_error_mocks.dlq_send.call_args.args[0]
        assert len(sent_messages) == 1
        dlq_message = sent_messages[0]
        assert isinstance(dlq_message, InvalidPreferenceMessage)
        assert dlq_message.message_key is None
        assert dlq_message.message_value == str(handler_event)
        assert dlq_message.error_type == 'RuntimeError'
        assert dlq_message.error_message == 'source parsing failed'