"""
Template utilities for Jinja2 template rendering with LangChain
"""
import logging
from typing import Dict, Any
from jinja2 import Environment, BaseLoader, TemplateError

logger = logging.getLogger(__name__)


class TemplateRenderer:
    """Jinja2 template renderer for LLM prompts"""
    
    def __init__(self):
        self.env = Environment(
            loader=BaseLoader(),
            # Enable safe variable substitution
            autoescape=False,
            # Custom delimiters to avoid conflicts with common markdown syntax
            variable_start_string='{{',
            variable_end_string='}}',
            block_start_string='{%',
            block_end_string='%}',
            comment_start_string='{#',
            comment_end_string='#}',
            # Keep linebreaks
            keep_trailing_newline=True,
            # Remove unnecessary whitespace
            trim_blocks=True,
            lstrip_blocks=True
        )
    
    def render_template(self, template_string: str, variables: Dict[str, Any]) -> str:
        """
        Render a Jinja2 template string with provided variables
        
        Args:
            template_string: The template string with Jinja2 syntax
            variables: Dictionary of variables to substitute
            
        Returns:
            Rendered template string
            
        Raises:
            TemplateError: If template rendering fails
        """
        try:
            template = self.env.from_string(template_string)
            rendered = template.render(**variables)
            logger.debug(f"Template rendered successfully with variables: {list(variables.keys())}")
            return rendered
        except TemplateError as e:
            logger.error(f"Template rendering failed: {e}")
            logger.error(f"Template: {template_string[:200]}...")
            logger.error(f"Variables: {variables}")
            raise
        except Exception as e:
            logger.error(f"Unexpected error during template rendering: {e}")
            raise TemplateError(f"Template rendering failed: {e}")
    
    def render_system_prompt(self, template_string: str, variables: Dict[str, Any]) -> str:
        """
        Render system prompt template
        
        Args:
            template_string: System prompt template
            variables: Variables for substitution
            
        Returns:
            Rendered system prompt
        """
        return self.render_template(template_string, variables)
    
    def render_user_prompt(self, template_string: str, variables: Dict[str, Any]) -> str:
        """
        Render user prompt template
        
        Args:
            template_string: User prompt template  
            variables: Variables for substitution
            
        Returns:
            Rendered user prompt
        """
        return self.render_template(template_string, variables)


# Global template renderer instance
template_renderer = TemplateRenderer()


def render_prompt_template(template_string: str, variables: Dict[str, Any]) -> str:
    """
    Convenience function to render prompt templates
    
    Args:
        template_string: Template string with Jinja2 syntax
        variables: Dictionary of variables to substitute
        
    Returns:
        Rendered template string
    """
    return template_renderer.render_template(template_string, variables)