contentdb/app/markdown.py

from functools import partial

import bleach
from bleach import Cleaner
from bleach.linkifier import LinkifyFilter
from bs4 import BeautifulSoup
from markdown import Markdown
from flask import Markup
from markdown.extensions import Extension
from markdown.inlinepatterns import SimpleTagInlineProcessor


# Based on
# https://github.com/Wenzil/mdx_bleach/blob/master/mdx_bleach/whitelist.py
#
# License: MIT

ALLOWED_TAGS = [
	"h1", "h2", "h3", "h4", "h5", "h6", "hr",
	"ul", "ol", "li",
	"p",
	"br",
	"pre",
	"code",
	"blockquote",
	"strong",
	"em",
	"a",
	"img",
	"table", "thead", "tbody", "tr", "th", "td",
	"div", "span", "del", "s",
]

ALLOWED_CSS = [
	"highlight", "codehilite",
	"hll", "c", "err", "g", "k", "l", "n", "o", "x", "p", "ch", "cm", "cp", "cpf", "c1", "cs",
	"gd", "ge", "gr", "gh", "gi", "go", "gp", "gs", "gu", "gt", "kc", "kd", "kn", "kp", "kr",
	"kt", "ld", "m", "s", "na", "nb", "nc", "no", "nd", "ni", "ne", "nf", "nl", "nn", "nx",
	"py", "nt", "nv", "ow", "w", "mb", "mf", "mh", "mi", "mo", "sa", "sb", "sc", "dl", "sd",
	"s2", "se", "sh", "si", "sx", "sr", "s1", "ss", "bp", "fm", "vc", "vg", "vi", "vm", "il",
]

def allow_class(_tag, name, value):
	return name == "class" and value in ALLOWED_CSS

ALLOWED_ATTRIBUTES = {
	"h1": ["id"],
	"h2": ["id"],
	"h3": ["id"],
	"h4": ["id"],
	"a": ["href", "title"],
	"img": ["src", "title", "alt"],
	"code": allow_class,
	"div": allow_class,
	"span": allow_class,
}

ALLOWED_PROTOCOLS = ["http", "https", "mailto"]

md = None


def render_markdown(source):
	html = md.convert(source)

	cleaner = Cleaner(
			tags=ALLOWED_TAGS,
			attributes=ALLOWED_ATTRIBUTES,
			protocols=ALLOWED_PROTOCOLS,
			filters=[partial(LinkifyFilter, callbacks=bleach.linkifier.DEFAULT_CALLBACKS)])
	return cleaner.clean(html)


class DelInsExtension(Extension):
	def extendMarkdown(self, md):
		del_proc = SimpleTagInlineProcessor(r'(\~\~)(.+?)(\~\~)', 'del')
		md.inlinePatterns.register(del_proc, 'del', 200)

		ins_proc = SimpleTagInlineProcessor(r'(\+\+)(.+?)(\+\+)', 'ins')
		md.inlinePatterns.register(ins_proc, 'ins', 200)


MARKDOWN_EXTENSIONS = ["fenced_code", "tables", "codehilite", "toc", DelInsExtension()]
MARKDOWN_EXTENSION_CONFIG = {
	"fenced_code": {},
	"tables": {},
	"codehilite": {
		"guess_lang": False,
	}
}


def init_markdown(app):
	global md

	md = Markdown(extensions=MARKDOWN_EXTENSIONS,
			extension_configs=MARKDOWN_EXTENSION_CONFIG,
			output_format="html5")

	@app.template_filter()
	def markdown(source):
		return Markup(render_markdown(source))


def get_headings(html: str):
	soup = BeautifulSoup(html, "html.parser")
	headings = soup.find_all(["h1", "h2", "h3"])

	root = []
	stack = []
	for heading in headings:
		this = { "link": heading.get("id") or "", "text": heading.text, "children": [] }
		this_level = int(heading.name[1:]) - 1

		while this_level <= len(stack):
			stack.pop()

		if len(stack) > 0:
			stack[-1]["children"].append(this)
		else:
			root.append(this)

		stack.append(this)

	return root