"""Variable substitution for $VAR/${VAR} and {{var}} templates."""

import os
import re
from pathlib import Path
from typing import Dict


def substitute(text: str, variables: Dict[str, str]) -> str:
    """Replace $VAR and ${VAR} with values from variables dict or env."""
    if not isinstance(text, str):
        return text

    pattern = re.compile(r"\$(\w+)|\$\{([^}]+)\}")

    def _replace(match: re.Match[str]) -> str:
        key = match.group(1) or match.group(2) or ""
        if key in variables:
            return str(variables[key])
        if key == "HOME":
            return str(Path.home())
        if key in os.environ:
            return os.environ[key]
        return match.group(0)

    return pattern.sub(_replace, text)


def substitute_template(text: str, context: Dict[str, str]) -> str:
    """Replace {{key}} placeholders with values from context dict."""
    if not isinstance(text, str):
        return text

    def _replace(match: re.Match[str]) -> str:
        key = match.group(1).strip()
        return context.get(key, match.group(0))

    return re.sub(r"\{\{(\w+)\}\}", _replace, text)