"""MkDocs hook: make directory-style links work on a static site.

The documents sometimes link to a directory the way Gitea renders it, e.g.
infrastructure.md contains [`incidents/`](incidents/). On a static site with
directory URLs, that href resolves relative to the *page* (giving
/infrastructure/incidents/ and a 404). This hook rewrites such links to the
generated landing page for that directory (build.sh creates
<dir>/index.md for documented directories that lack one). It never edits the
documents themselves.
"""

import posixpath
import re

from mkdocs.utils import get_relative_url

_HREF = re.compile(r'(href=)("([^"]+)/")')


def on_page_content(html, page, config, files):
    index_urls = {}
    for f in files:
        src = f.src_path
        if src.endswith("/index.md"):
            index_urls[posixpath.dirname(src)] = f.url

    page_dir = posixpath.dirname(page.file.src_path)

    def fix(match):
        href = match.group(3)
        if href.startswith(("http://", "https://", "/", "#")):
            return match.group(0)
        target = posixpath.normpath(posixpath.join(page_dir, href))
        if target in (".", "..") or target not in index_urls:
            return match.group(0)
        return f'{match.group(1)}"{get_relative_url(index_urls[target], page.file.url)}"'

    return _HREF.sub(fix, html)