"""Configuration management for the MCP server."""

import argparse
import os
import sys

from pydantic_settings import (
    BaseSettings,
    PydanticBaseSettingsSource,
    YamlConfigSettingsSource,
)


def _parse_args() -> argparse.Namespace:
    """Parse command-line arguments.

    Returns a namespace with default values if running under pytest.
    """
    # Don't parse args if running under pytest
    if "pytest" in sys.modules:
        parser = argparse.ArgumentParser()
        return argparse.Namespace(
            transport="stdio",
            host="0.0.0.0",  # noqa: S104
            port=8080,
            config=os.environ.get("CONFIG_FILE", "config.yaml"),
        )

    parser = argparse.ArgumentParser()
    parser.add_argument(
        "--transport",
        choices=["stdio", "sse", "streamable-http"],
        default="stdio",
    )
    parser.add_argument("--host", default="0.0.0.0")  # noqa: S104
    parser.add_argument("--port", type=int, default=8080)
    parser.add_argument(
        "--config",
        default=os.environ.get("CONFIG_FILE", "config.yaml"),
    )
    return parser.parse_args()


_args = _parse_args()


class Settings(BaseSettings):
    """Server configuration populated from env vars and a YAML config file."""

    model_config = {"env_file": ".env", "yaml_file": _args.config}

    project_id: str
    location: str
    bucket: str
    index_name: str
    deployed_index_id: str
    endpoint_name: str
    endpoint_domain: str
    embedding_model: str = "gemini-embedding-001"
    search_limit: int = 10
    log_name: str = "va_agent_evaluation_logs"
    log_level: str = "INFO"
    cloud_logging_enabled: bool = False

    @classmethod
    def settings_customise_sources(
        cls,
        settings_cls: type[BaseSettings],
        init_settings: PydanticBaseSettingsSource,
        env_settings: PydanticBaseSettingsSource,
        dotenv_settings: PydanticBaseSettingsSource,
        file_secret_settings: PydanticBaseSettingsSource,
    ) -> tuple[PydanticBaseSettingsSource, ...]:
        """Customize the order of settings sources to include YAML config."""
        return (
            init_settings,
            env_settings,
            dotenv_settings,
            YamlConfigSettingsSource(settings_cls),
            file_secret_settings,
        )


# Lazy singleton instance of Settings
_cfg: Settings | None = None


def get_config() -> Settings:
    """Get or create the singleton Settings instance."""
    global _cfg  # noqa: PLW0603
    if _cfg is None:
        _cfg = Settings.model_validate({})
    return _cfg


# For backwards compatibility, provide cfg as a property-like accessor
class _ConfigProxy:
    """Proxy object that lazily loads config on attribute access."""

    def __getattr__(self, name: str) -> object:
        return getattr(get_config(), name)


cfg = _ConfigProxy()