# Copyright (c) 2025
# SPDX-License-Identifier: MIT
"""YAML frontmatter parsing utilities.
This module provides a simple YAML frontmatter parser that doesn't
require external dependencies like PyYAML.
"""
from __future__ import annotations
import re
from typing import Any
# Pattern to match YAML frontmatter delimited by ---
FRONTMATTER_PATTERN = re.compile(
r"^---\s*\n(.*?)\n---\s*\n(.*)$",
re.DOTALL
)
def parse_frontmatter(content: str) -> tuple[dict[str, Any], str]:
"""Parse YAML frontmatter from markdown content.
This is a simple implementation that handles basic key: value pairs
without requiring external YAML libraries.
Supported formats:
- Simple key: value pairs
- Quoted values (single or double quotes)
- Comments (lines starting with #)
Args:
content: Full markdown content with optional frontmatter.
Returns:
Tuple of (frontmatter dict, remaining markdown content).
If no frontmatter is found, returns ({}, original content).
Example:
>>> content = '''---
... name: my-skill
... description: "A great skill"
... ---
... # My Skill
... Content here...
... '''
>>> meta, body = parse_frontmatter(content)
>>> meta['name']
'my-skill'
"""
match = FRONTMATTER_PATTERN.match(content)
if not match:
return {}, content
yaml_content = match.group(1)
markdown_content = match.group(2)
frontmatter = _parse_yaml_simple(yaml_content)
return frontmatter, markdown_content
def _parse_yaml_simple(yaml_content: str) -> dict[str, Any]:
"""Parse simple YAML key-value pairs.
Args:
yaml_content: YAML content string.
Returns:
Dictionary of parsed key-value pairs.
"""
result: dict[str, Any] = {}
for line in yaml_content.split("\n"):
line = line.strip()
# Skip empty lines and comments
if not line or line.startswith("#"):
continue
# Parse key: value
if ":" in line:
key, value = line.split(":", 1)
key = key.strip()
value = value.strip()
# Remove quotes if present
value = _unquote(value)
result[key] = value
return result
def _unquote(value: str) -> str:
"""Remove surrounding quotes from a string.
Args:
value: String that may be quoted.
Returns:
String with quotes removed.
"""
if len(value) >= 2:
if (value.startswith('"') and value.endswith('"')) or \
(value.startswith("'") and value.endswith("'")):
return value[1:-1]
return value
def has_frontmatter(content: str) -> bool:
"""Check if content has YAML frontmatter.
Args:
content: Markdown content to check.
Returns:
True if frontmatter is present, False otherwise.
"""
return FRONTMATTER_PATTERN.match(content) is not None
