contentdb/app/markdown.py

from functools import partial

import bleach
from bleach import Cleaner
from bleach.linkifier import LinkifyFilter
from markdown import Markdown
from flask import Markup

# 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",
]

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 = {
	"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)

def init_app(app):
	global md

	md = Markdown(extensions=app.config["FLATPAGES_MARKDOWN_EXTENSIONS"], output_format="html5")

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