"""Markdown file parsing with frontmatter extraction."""

import re
from dataclasses import dataclass, field
from pathlib import Path

import frontmatter


@dataclass
class ParsedDocument:
    file_path: str
    title: str
    body: str
    tags: list[str] = field(default_factory=list)
    frontmatter: dict = field(default_factory=dict)
    headings: list[tuple[int, str]] = field(default_factory=list)


def parse_markdown(file_path: Path, text: str | None = None) -> ParsedDocument:
    """Parse a markdown file, extracting frontmatter and structure."""
    raw_text = text if text is not None else file_path.read_text(encoding="utf-8")
    post = frontmatter.loads(raw_text)

    meta = dict(post.metadata) if post.metadata else {}
    body = post.content.strip()

    # Extract title: first H1, or filename
    title = _extract_title(body, file_path)

    # Extract tags from frontmatter
    tags = meta.get("tags", [])
    if isinstance(tags, str):
        tags = [t.strip() for t in tags.split(",") if t.strip()]
    tags = tags or []

    # Extract heading structure
    headings = _extract_headings(body)

    return ParsedDocument(
        file_path=str(file_path.resolve()),
        title=title,
        body=body,
        tags=tags,
        frontmatter=meta,
        headings=headings,
    )


def _extract_title(body: str, file_path: Path) -> str:
    """Get title from first H1 or fallback to filename."""
    match = re.search(r"^#\s+(.+)$", body, re.MULTILINE)
    if match:
        return match.group(1).strip()
    return file_path.stem.replace("_", " ").replace("-", " ").title()


def _extract_headings(body: str) -> list[tuple[int, str]]:
    """Extract all headings with their level."""
    headings = []
    for match in re.finditer(r"^(#{1,4})\s+(.+)$", body, re.MULTILINE):
        level = len(match.group(1))
        text = match.group(2).strip()
        headings.append((level, text))
    return headings