import argparse
import pathlib
import re
from typing import Optional


def preprocess_github_markdown_file(source_path: str, dest_path: Optional[str] = None):
    """
    Preprocesses GitHub Markdown files by:
        - Uncommenting all ``<!-- -->`` comments in which opening tag is immediately
          succeded by ``$UNCOMMENT``(eg. ``<!--$UNCOMMENTthis will be uncommented-->``)
        - Removing text between ``<!--$REMOVE-->`` and ``<!--$END_REMOVE-->``

    This is to enable translation between GitHub Markdown and MyST Markdown used
    in docs. For more details, see ``doc/README.md``.

    Args:
        source_path: The path to the locally saved markdown file to preprocess.
        dest_path: The destination path to save the preprocessed markdown file.
            If not provided, save to the same location as source_path.
    """
    dest_path = dest_path if dest_path else source_path
    with open(source_path, "r") as f:
        text = f.read()
    # $UNCOMMENT
    text = re.sub(r"<!--\s*\$UNCOMMENT(.*?)(-->)", r"\1", text, flags=re.DOTALL)
    # $REMOVE
    text = re.sub(
        r"(<!--\s*\$REMOVE\s*-->)(.*?)(<!--\s*\$END_REMOVE\s*-->)",
        r"",
        text,
        flags=re.DOTALL,
    )
    with open(dest_path, "w") as f:
        f.write(text)


if __name__ == "__main__":
    parser = argparse.ArgumentParser(
        description="Preprocess github markdown file to Ray Docs MyST markdown"
    )
    parser.add_argument(
        "source_path",
        type=pathlib.Path,
        help="Path to github markdown file to " "preprocess",
    )
    parser.add_argument(
        "dest_path", type=pathlib.Path, help="Path to save preprocessed markdown file."
    )
    args, _ = parser.parse_known_args()

    preprocess_github_markdown_file(
        args.source_path.expanduser(), args.dest_path.expanduser()
    )