takahe/core/html.py
2022-12-20 13:55:14 +00:00

193 lines
6.4 KiB
Python

import re
from functools import partial
import bleach
from bleach.linkifier import LinkifyFilter
from django.utils.safestring import mark_safe
url_regex = re.compile(
r"""\(* # Match any opening parentheses.
\b(?<![@.])(?:https?://(?:(?:\w+:)?\w+@)?) # http://
([\w-]+\.)+(?:[\w-]+)(?:\:[0-9]+)?(?!\.\w)\b # xx.yy.tld(:##)?
(?:[/?][^\s\{{\}}\|\\\^\[\]`<>"]*)?
# /path/zz (excluding "unsafe" chars from RFC 1738,
# except for # and ~, which happen in practice)
""",
re.IGNORECASE | re.VERBOSE | re.UNICODE,
)
def allow_a(tag: str, name: str, value: str):
if name in ["href", "title", "class"]:
return True
elif name == "rel":
# Only allow rel attributes with a small subset of values
# (we're defending against, for example, rel=me)
rel_values = value.split()
if all(v in ["nofollow", "noopener", "noreferrer", "tag"] for v in rel_values):
return True
return False
def sanitize_html(post_html: str) -> str:
"""
Only allows a, br, p and span tags, and class attributes.
"""
cleaner = bleach.Cleaner(
tags=["br", "p", "a"],
attributes={ # type:ignore
"a": allow_a,
"p": ["class"],
},
filters=[partial(LinkifyFilter, url_re=url_regex)],
strip=True,
)
return mark_safe(cleaner.clean(post_html))
def strip_html(post_html: str) -> str:
"""
Strips all tags from the text, then linkifies it.
"""
cleaner = bleach.Cleaner(
tags=[],
strip=True,
filters=[partial(LinkifyFilter, url_re=url_regex)],
)
return mark_safe(cleaner.clean(post_html))
def html_to_plaintext(post_html: str) -> str:
"""
Tries to do the inverse of the linebreaks filter.
"""
# TODO: Handle HTML entities
# Remove all newlines, then replace br with a newline and /p with two (one comes from bleach)
post_html = post_html.replace("\n", "").replace("<br>", "\n").replace("</p>", "\n")
# Remove all other HTML and return
cleaner = bleach.Cleaner(tags=[], strip=True, filters=[])
return cleaner.clean(post_html).strip()
class ContentRenderer:
"""
Renders HTML for posts, identity fields, and more.
The `local` parameter affects whether links are absolute (False) or relative (True)
"""
def __init__(self, local: bool):
self.local = local
def render_post(self, html: str, post) -> str:
"""
Given post HTML, normalises it and renders it for presentation.
"""
if not html:
return ""
html = sanitize_html(html)
html = self.linkify_mentions(html, post=post)
html = self.linkify_hashtags(html, identity=post.author)
if self.local:
html = self.imageify_emojis(html, identity=post.author)
return mark_safe(html)
def render_identity(self, html: str, identity, strip: bool = False) -> str:
"""
Given identity field HTML, normalises it and renders it for presentation.
"""
if not html:
return ""
if strip:
html = strip_html(html)
else:
html = sanitize_html(html)
html = self.linkify_hashtags(html, identity=identity)
if self.local:
html = self.imageify_emojis(html, identity=identity)
return mark_safe(html)
def linkify_mentions(self, html: str, post) -> str:
"""
Links mentions _in the context of the post_ - as in, using the mentions
property as the only source (as we might be doing this without other
DB access allowed)
"""
from activities.models import Post
possible_matches = {}
for mention in post.mentions.all():
if self.local:
url = str(mention.urls.view)
else:
url = mention.absolute_profile_uri()
possible_matches[mention.username] = url
possible_matches[f"{mention.username}@{mention.domain_id}"] = url
collapse_name: dict[str, str] = {}
def replacer(match):
precursor = match.group(1)
handle = match.group(2).lower()
if "@" in handle:
short_handle = handle.split("@", 1)[0]
else:
short_handle = handle
if handle in possible_matches:
if short_handle not in collapse_name:
collapse_name[short_handle] = handle
elif collapse_name.get(short_handle) != handle:
short_handle = handle
return f'{precursor}<a href="{possible_matches[handle]}">@{short_handle}</a>'
else:
return match.group()
return Post.mention_regex.sub(replacer, html)
def linkify_hashtags(self, html, identity) -> str:
from activities.models import Hashtag
def replacer(attrs, new=False):
# See if the text in this link looks like a hashtag
if not Hashtag.hashtag_regex.match(attrs.get("_text", "")):
return attrs
hashtag = attrs["_text"].strip().lstrip("#")
attrs[None, "class"] = "hashtag"
if (None, "rel") in attrs:
del attrs[None, "rel"]
if self.local:
attrs[None, "href"] = f"/tags/{hashtag.lower()}/"
else:
attrs[
None, "href"
] = f"https://{identity.domain.uri_domain}/tags/{hashtag.lower()}/"
return attrs
linker = bleach.linkifier.Linker(
url_re=Hashtag.hashtag_regex, callbacks=[replacer]
)
return linker.linkify(html)
def imageify_emojis(self, html: str, identity, include_local: bool = True):
"""
Find :emoji: in content and convert to <img>. If include_local is True,
the local emoji will be used as a fallback for any shortcodes not defined
by emojis.
"""
from activities.models import Emoji
emoji_set = Emoji.for_domain(identity.domain)
if include_local:
emoji_set.extend(Emoji.for_domain(None))
possible_matches = {
emoji.shortcode: emoji.as_html() for emoji in emoji_set if emoji.is_usable
}
def replacer(match):
fullcode = match.group(1).lower()
if fullcode in possible_matches:
return possible_matches[fullcode]
return match.group()
return Emoji.emoji_regex.sub(replacer, html)