"""Tests for app.config module."""

from __future__ import annotations

import pytest

from app.config import Settings


def _isolated_settings(**kwargs: object) -> Settings:
    """Create a Settings instance that ignores .env files and process env vars.

    pydantic-settings reads from env_file and environment by default, which
    causes test results to depend on the machine they run on.  We override
    model_config at the class level temporarily so that every test gets
    deterministic results.
    """
    # Build a throwaway subclass that disables env-file and env-var loading.
    class _IsolatedSettings(Settings):
        model_config = Settings.model_config.copy()
        model_config["env_file"] = None  # type: ignore[assignment]
        model_config["env_ignore_empty"] = True

    # _env_parse_none_str makes pydantic-settings treat missing env vars as
    # absent rather than empty-string, so required fields will raise.
    import os

    env_backup = os.environ.copy()
    # Strip all env vars that Settings knows about so they can't leak in.
    settings_fields = set(Settings.model_fields)
    for key in list(os.environ):
        if key.lower() in settings_fields:
            del os.environ[key]
    try:
        return _IsolatedSettings(**kwargs)  # type: ignore[return-value]
    finally:
        os.environ.clear()
        os.environ.update(env_backup)


@pytest.mark.unit
class TestSettings:
    def test_default_values(self) -> None:
        settings = _isolated_settings(
            database_url="postgresql://x:x@localhost/db",
            anthropic_api_key="key",
        )
        assert settings.llm_provider == "anthropic"
        assert settings.llm_model == "claude-sonnet-4-6"
        assert settings.session_ttl_minutes == 30
        assert settings.interrupt_ttl_minutes == 30

    def test_custom_values(self) -> None:
        settings = _isolated_settings(
            database_url="postgresql://x:x@localhost/db",
            llm_provider="openai",
            llm_model="gpt-4o",
            session_ttl_minutes=15,
            openai_api_key="sk-test",
        )
        assert settings.llm_provider == "openai"
        assert settings.llm_model == "gpt-4o"
        assert settings.session_ttl_minutes == 15

    def test_invalid_provider_rejected(self) -> None:
        with pytest.raises(Exception):
            _isolated_settings(
                database_url="postgresql://x:x@localhost/db",
                llm_provider="invalid",
            )

    def test_missing_database_url_rejected(self) -> None:
        with pytest.raises(Exception):
            _isolated_settings(anthropic_api_key="key")

    def test_empty_api_key_for_provider_rejected(self) -> None:
        with pytest.raises(ValueError, match="API key"):
            _isolated_settings(
                database_url="postgresql://x:x@localhost/db",
                llm_provider="anthropic",
                anthropic_api_key="",
            )

    def test_wrong_provider_key_rejected(self) -> None:
        with pytest.raises(ValueError, match="API key"):
            _isolated_settings(
                database_url="postgresql://x:x@localhost/db",
                llm_provider="openai",
                anthropic_api_key="key",
                openai_api_key="",
            )