"""Prompt template loader for GSD-OpenClaw."""
from __future__ import annotations

from pathlib import Path
from typing import Dict, Any


class PromptLoader:
    """Load and render prompt templates with {{variable}} substitution.

    Uses simple string replacement for {{variable}} syntax.
    Missing variables are left as-is (safe substitution behavior).
    """

    def __init__(self, template_dir: Path | None = None):
        """Initialize PromptLoader.

        Args:
            template_dir: Directory containing template files.
                         Defaults to src/gsd_openclaw/prompts/.
        """
        if template_dir is None:
            template_dir = Path(__file__).parent / "prompts"
        self.template_dir = Path(template_dir)
        self._cache: Dict[str, str] = {}

    def get(self, name: str) -> str:
        """Get raw template content by name (cached).

        Args:
            name: Template name without .md extension.

        Returns:
            Raw template content.

        Raises:
            FileNotFoundError: If template file doesn't exist.
        """
        if name not in self._cache:
            path = self.template_dir / f"{name}.md"
            if not path.exists():
                raise FileNotFoundError(f"Template not found: {name}")
            self._cache[name] = path.read_text(encoding='utf-8')
        return self._cache[name]

    def render(self, name: str, **variables: Any) -> str:
        """Render a template with variable substitution.

        Uses {{variable}} syntax. Missing variables are left as literal
        {{variable}} strings (safe substitution).

        Args:
            name: Template name without .md extension.
            **variables: Variable values to substitute.

        Returns:
            Rendered template content.

        Raises:
            FileNotFoundError: If template file doesn't exist.
        """
        content = self.get(name)
        for key, value in variables.items():
            content = content.replace("{{" + key + "}}", str(value))
        return content