import httpx2
import subprocess
import re
from typing import Dict, Union
from dataclasses import dataclass


@dataclass
class FetchSuccess:
    """Successful fetch result containing the markdown content."""

    content: str


@dataclass
class FetchError:
    """Failed fetch result containing the error message."""

    error: str


FetchResult = Union[FetchSuccess, FetchError]

# Memoization cache for web pages
_cache: Dict[str, FetchResult] = {}


def html_to_markdown(html: str) -> str:
    """Converts HTML to markdown using pandoc with GFM format."""
    try:
        # Use gfm (GitHub Flavored Markdown) for better compatibility and robust conversion
        process = subprocess.run(
            ["pandoc", "-f", "html", "-t", "gfm", "-o", "-"],
            input=html,
            capture_output=True,
            text=True,
            check=True,
            encoding="utf-8",
        )
        return process.stdout.strip()
    except subprocess.CalledProcessError as e:
        raise RuntimeError(f"Pandoc error: {e}")
    except Exception as e:
        raise RuntimeError(f"Unexpected error during markdown conversion: {e}")


def fetch_and_markdownify(url: str) -> FetchResult:
    """Fetches a web page and transforms it to markdown, with memoization."""
    if url in _cache:
        return _cache[url]

    try:
        with httpx2.Client(headers={"User-Agent": "Mozilla/5.0"}, timeout=10.0) as client:
            response = client.get(url)
            response.raise_for_status()
            html = response.text
            markdown = html_to_markdown(html)
            res = FetchSuccess(content=markdown)
            _cache[url] = res
            return res
    except Exception as e:
        return FetchError(error=str(e))