# Python Markdown

# A Python implementation of John Gruber's Markdown.

# Documentation: https://python-markdown.github.io/
# GitHub: https://github.com/Python-Markdown/markdown/
# PyPI: https://pypi.org/project/Markdown/

# Started by Manfred Stienstra (http://www.dwerg.net/).
# Maintained for a few years by Yuri Takhteyev (http://www.freewisdom.org).
# Currently maintained by Waylan Limberg (https://github.com/waylan),
# Dmitry Shachnev (https://github.com/mitya57) and Isaac Muse (https://github.com/facelessuser).

# Copyright 2007-2023 The Python Markdown Project (v. 1.7 and later)
# Copyright 2004, 2005, 2006 Yuri Takhteyev (v. 0.2-1.6b)
# Copyright 2004 Manfred Stienstra (the original version)

# License: BSD (see LICENSE.md for details).

"""
An extension to Python Markdown which implements legacy attributes.

Prior to Python-Markdown version 3.0, the Markdown class had an `enable_attributes`
keyword which was on by default and provided for attributes to be defined for elements
using the format `{@key=value}`. This extension is provided as a replacement for
backward compatibility. New documents should be authored using `attr_lists`. However,
numerous documents exist which have been using the old attribute format for many
years. This extension can be used to continue to render those documents correctly.
"""

from __future__ import annotations

import re
from markdown.treeprocessors import Treeprocessor, isString
from markdown.extensions import Extension


ATTR_RE = re.compile(r'\{@([^\}]*)=([^\}]*)}')  # {@id=123}


class LegacyAttrs(Treeprocessor):
    def run(self, doc):
        """Find and set values of attributes ({@key=value}). """
        for el in doc.iter():
            alt = el.get('alt', None)
            if alt is not None:
                el.set('alt', self.handleAttributes(el, alt))
            if el.text and isString(el.text):
                el.text = self.handleAttributes(el, el.text)
            if el.tail and isString(el.tail):
                el.tail = self.handleAttributes(el, el.tail)

    def handleAttributes(self, el, txt):
        """ Set attributes and return text without definitions. """
        def attributeCallback(match):
            el.set(match.group(1), match.group(2).replace('\n', ' '))
        return ATTR_RE.sub(attributeCallback, txt)


class LegacyAttrExtension(Extension):
    def extendMarkdown(self, md):
        """ Add `LegacyAttrs` to Markdown instance. """
        md.treeprocessors.register(LegacyAttrs(md), 'legacyattrs', 15)


def makeExtension(**kwargs):  # pragma: no cover
    return LegacyAttrExtension(**kwargs)
