"""
Frontmatter parsing and serialization
"""
import re
import yaml
from typing import Optional, Tuple


class FrontmatterParser:
    FRONTMATTER_PATTERN = re.compile(r'^---\s*\n(.*?\n)---\s*\n', re.DOTALL)
    
    @staticmethod
    def parse(content: str) -> Tuple[Optional[dict], str]:
        """Parse frontmatter from markdown content"""
        match = FrontmatterParser.FRONTMATTER_PATTERN.match(content)
        
        if match:
            yaml_content = match.group(1)
            body = content[match.end():]
            
            try:
                frontmatter = yaml.safe_load(yaml_content) or {}
                return frontmatter, body
            except yaml.YAMLError:
                return None, content
        
        return None, content
    
    @staticmethod
    def serialize(frontmatter: dict, body: str) -> str:
        """Serialize frontmatter and body to markdown"""
        yaml_str = yaml.dump(frontmatter, default_flow_style=False, allow_unicode=True, sort_keys=False)
        return f"---\n{yaml_str}---\n{body}"
    
    @staticmethod
    def extract_title(body: str) -> Optional[str]:
        """Extract title from markdown body"""
        match = re.search(r'^#\s+(.+)$', body, re.MULTILINE)
        return match.group(1).strip() if match else None