import yaml
import getpass
import os
import string
from typing import Tuple, Type, TypeVar

from tml.core.config import base_config

import fsspec

C = TypeVar("C", bound=base_config.BaseConfig)


def _read_file(f):
  """
    Read the contents of a file using fsspec.

    Args:
        f: File path or URL.

    Returns:
        The contents of the file.
    """
  with fsspec.open(f) as f:
    return f.read()


def setup_configuration(
  config_type: Type[C],
  yaml_path: str,
  substitute_env_variable: bool = False,
) -> Tuple[C, str]:
  """
    Load a Pydantic config object from a YAML file and optionally substitute environment variables.

    Args:
        config_type: Pydantic config class to load.
        yaml_path: YAML path of the config file.
        substitute_env_variable: If True, substitute strings in the format $VAR or ${VAR}
            with their environment variable values whenever possible.
            If an environment variable doesn't exist, the string is left unchanged.

    Returns:
        A tuple containing the Pydantic config object and the resolved YAML content.

    Example:
        ```python
        config, resolved_yaml = setup_configuration(MyConfig, "config.yaml", substitute_env_variable=True)
        ```
    """

  def _substitute(s):
    if substitute_env_variable:
      return string.Template(s).safe_substitute(os.environ, USER=getpass.getuser())
    return s

  assert config_type is not None, "can't use all_config without config_type"
  content = _substitute(yaml.safe_load(_read_file(yaml_path)))
  return config_type.parse_obj(content)