"""Environment variable loader for .env files and os.environ."""

import os
from pathlib import Path
from typing import Optional

from dotenv import dotenv_values


class EnvLoader:
    """Load environment variables from .env files or os.environ."""

    def __init__(self, file_path: Optional[str] = None, use_environment: bool = True):
        """Initialize the loader.

        Args:
            file_path: Path to .env file. If None, only uses os.environ.
            use_environment: Whether to include os.environ as fallback.
        """
        self.file_path = file_path
        self.use_environment = use_environment
        self._env_vars: dict[str, str] = {}

    def load(self) -> dict[str, str]:
        """Load environment variables.

        Returns:
            Dictionary of environment variable names to values.
        """
        self._env_vars = {}

        if self.file_path:
            path = Path(self.file_path)
            if path.exists():
                file_values = dotenv_values(str(path))
                for key, value in file_values.items():
                    if value is not None:
                        self._env_vars[key] = value

        if self.use_environment:
            for key, value in os.environ.items():
                if key not in self._env_vars:
                    self._env_vars[key] = value

        return self._env_vars

    def get(self, key: str, default: Optional[str] = None) -> Optional[str]:
        """Get an environment variable value.

        Args:
            key: Variable name.
            default: Default value if not found.

        Returns:
            Variable value or default.
        """
        if not self._env_vars:
            self.load()
        return self._env_vars.get(key, default)

    def get_raw(self) -> dict[str, str]:
        """Get all loaded variables as a raw dictionary.

        Returns:
            Dictionary of all loaded environment variables.
        """
        if not self._env_vars:
            self.load()
        return self._env_vars.copy()

    def set(self, key: str, value: str) -> None:
        """Set an environment variable value in memory.

        Args:
            key: Variable name.
            value: Variable value.
        """
        self._env_vars[key] = value


def load_env_file(file_path: str) -> dict[str, str]:
    """Convenience function to load environment from a file.

    Args:
        file_path: Path to .env file.

    Returns:
        Dictionary of environment variables.
    """
    loader = EnvLoader(file_path=file_path, use_environment=False)
    return loader.load()