mirror of
https://git.anonymousland.org/anonymousland/synapse.git
synced 2024-10-01 11:49:51 -04:00
eb39da6782
* Splits the logic for parsing HTML from the resource handling code. * Fix a circular import in the oEmbed code (which uses the HTML parsing code). * Renames some of the HTML parsing methods to: * Make it clear which methods are "internal" to the module. * Clarify what the methods do.
398 lines
14 KiB
Python
398 lines
14 KiB
Python
# Copyright 2021 The Matrix.org Foundation C.I.C.
|
|
#
|
|
# Licensed under the Apache License, Version 2.0 (the "License");
|
|
# you may not use this file except in compliance with the License.
|
|
# You may obtain a copy of the License at
|
|
#
|
|
# http://www.apache.org/licenses/LICENSE-2.0
|
|
#
|
|
# Unless required by applicable law or agreed to in writing, software
|
|
# distributed under the License is distributed on an "AS IS" BASIS,
|
|
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
# See the License for the specific language governing permissions and
|
|
# limitations under the License.
|
|
import codecs
|
|
import itertools
|
|
import logging
|
|
import re
|
|
from typing import TYPE_CHECKING, Dict, Generator, Iterable, Optional, Set, Union
|
|
from urllib import parse as urlparse
|
|
|
|
if TYPE_CHECKING:
|
|
from lxml import etree
|
|
|
|
logger = logging.getLogger(__name__)
|
|
|
|
_charset_match = re.compile(
|
|
br'<\s*meta[^>]*charset\s*=\s*"?([a-z0-9_-]+)"?', flags=re.I
|
|
)
|
|
_xml_encoding_match = re.compile(
|
|
br'\s*<\s*\?\s*xml[^>]*encoding="([a-z0-9_-]+)"', flags=re.I
|
|
)
|
|
_content_type_match = re.compile(r'.*; *charset="?(.*?)"?(;|$)', flags=re.I)
|
|
|
|
|
|
def _normalise_encoding(encoding: str) -> Optional[str]:
|
|
"""Use the Python codec's name as the normalised entry."""
|
|
try:
|
|
return codecs.lookup(encoding).name
|
|
except LookupError:
|
|
return None
|
|
|
|
|
|
def _get_html_media_encodings(
|
|
body: bytes, content_type: Optional[str]
|
|
) -> Iterable[str]:
|
|
"""
|
|
Get potential encoding of the body based on the (presumably) HTML body or the content-type header.
|
|
|
|
The precedence used for finding a character encoding is:
|
|
|
|
1. <meta> tag with a charset declared.
|
|
2. The XML document's character encoding attribute.
|
|
3. The Content-Type header.
|
|
4. Fallback to utf-8.
|
|
5. Fallback to windows-1252.
|
|
|
|
This roughly follows the algorithm used by BeautifulSoup's bs4.dammit.EncodingDetector.
|
|
|
|
Args:
|
|
body: The HTML document, as bytes.
|
|
content_type: The Content-Type header.
|
|
|
|
Returns:
|
|
The character encoding of the body, as a string.
|
|
"""
|
|
# There's no point in returning an encoding more than once.
|
|
attempted_encodings: Set[str] = set()
|
|
|
|
# Limit searches to the first 1kb, since it ought to be at the top.
|
|
body_start = body[:1024]
|
|
|
|
# Check if it has an encoding set in a meta tag.
|
|
match = _charset_match.search(body_start)
|
|
if match:
|
|
encoding = _normalise_encoding(match.group(1).decode("ascii"))
|
|
if encoding:
|
|
attempted_encodings.add(encoding)
|
|
yield encoding
|
|
|
|
# TODO Support <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
|
|
|
|
# Check if it has an XML document with an encoding.
|
|
match = _xml_encoding_match.match(body_start)
|
|
if match:
|
|
encoding = _normalise_encoding(match.group(1).decode("ascii"))
|
|
if encoding and encoding not in attempted_encodings:
|
|
attempted_encodings.add(encoding)
|
|
yield encoding
|
|
|
|
# Check the HTTP Content-Type header for a character set.
|
|
if content_type:
|
|
content_match = _content_type_match.match(content_type)
|
|
if content_match:
|
|
encoding = _normalise_encoding(content_match.group(1))
|
|
if encoding and encoding not in attempted_encodings:
|
|
attempted_encodings.add(encoding)
|
|
yield encoding
|
|
|
|
# Finally, fallback to UTF-8, then windows-1252.
|
|
for fallback in ("utf-8", "cp1252"):
|
|
if fallback not in attempted_encodings:
|
|
yield fallback
|
|
|
|
|
|
def decode_body(
|
|
body: bytes, uri: str, content_type: Optional[str] = None
|
|
) -> Optional["etree.Element"]:
|
|
"""
|
|
This uses lxml to parse the HTML document.
|
|
|
|
Args:
|
|
body: The HTML document, as bytes.
|
|
uri: The URI used to download the body.
|
|
content_type: The Content-Type header.
|
|
|
|
Returns:
|
|
The parsed HTML body, or None if an error occurred during processed.
|
|
"""
|
|
# If there's no body, nothing useful is going to be found.
|
|
if not body:
|
|
return None
|
|
|
|
# The idea here is that multiple encodings are tried until one works.
|
|
# Unfortunately the result is never used and then LXML will decode the string
|
|
# again with the found encoding.
|
|
for encoding in _get_html_media_encodings(body, content_type):
|
|
try:
|
|
body.decode(encoding)
|
|
except Exception:
|
|
pass
|
|
else:
|
|
break
|
|
else:
|
|
logger.warning("Unable to decode HTML body for %s", uri)
|
|
return None
|
|
|
|
from lxml import etree
|
|
|
|
# Create an HTML parser.
|
|
parser = etree.HTMLParser(recover=True, encoding=encoding)
|
|
|
|
# Attempt to parse the body. Returns None if the body was successfully
|
|
# parsed, but no tree was found.
|
|
return etree.fromstring(body, parser)
|
|
|
|
|
|
def parse_html_to_open_graph(
|
|
tree: "etree.Element", media_uri: str
|
|
) -> Dict[str, Optional[str]]:
|
|
"""
|
|
Parse the HTML document into an Open Graph response.
|
|
|
|
This uses lxml to search the HTML document for Open Graph data (or
|
|
synthesizes it from the document).
|
|
|
|
Args:
|
|
tree: The parsed HTML document.
|
|
media_url: The URI used to download the body.
|
|
|
|
Returns:
|
|
The Open Graph response as a dictionary.
|
|
"""
|
|
|
|
# if we see any image URLs in the OG response, then spider them
|
|
# (although the client could choose to do this by asking for previews of those
|
|
# URLs to avoid DoSing the server)
|
|
|
|
# "og:type" : "video",
|
|
# "og:url" : "https://www.youtube.com/watch?v=LXDBoHyjmtw",
|
|
# "og:site_name" : "YouTube",
|
|
# "og:video:type" : "application/x-shockwave-flash",
|
|
# "og:description" : "Fun stuff happening here",
|
|
# "og:title" : "RemoteJam - Matrix team hack for Disrupt Europe Hackathon",
|
|
# "og:image" : "https://i.ytimg.com/vi/LXDBoHyjmtw/maxresdefault.jpg",
|
|
# "og:video:url" : "http://www.youtube.com/v/LXDBoHyjmtw?version=3&autohide=1",
|
|
# "og:video:width" : "1280"
|
|
# "og:video:height" : "720",
|
|
# "og:video:secure_url": "https://www.youtube.com/v/LXDBoHyjmtw?version=3",
|
|
|
|
og: Dict[str, Optional[str]] = {}
|
|
for tag in tree.xpath("//*/meta[starts-with(@property, 'og:')]"):
|
|
if "content" in tag.attrib:
|
|
# if we've got more than 50 tags, someone is taking the piss
|
|
if len(og) >= 50:
|
|
logger.warning("Skipping OG for page with too many 'og:' tags")
|
|
return {}
|
|
og[tag.attrib["property"]] = tag.attrib["content"]
|
|
|
|
# TODO: grab article: meta tags too, e.g.:
|
|
|
|
# "article:publisher" : "https://www.facebook.com/thethudonline" />
|
|
# "article:author" content="https://www.facebook.com/thethudonline" />
|
|
# "article:tag" content="baby" />
|
|
# "article:section" content="Breaking News" />
|
|
# "article:published_time" content="2016-03-31T19:58:24+00:00" />
|
|
# "article:modified_time" content="2016-04-01T18:31:53+00:00" />
|
|
|
|
if "og:title" not in og:
|
|
# do some basic spidering of the HTML
|
|
title = tree.xpath("(//title)[1] | (//h1)[1] | (//h2)[1] | (//h3)[1]")
|
|
if title and title[0].text is not None:
|
|
og["og:title"] = title[0].text.strip()
|
|
else:
|
|
og["og:title"] = None
|
|
|
|
if "og:image" not in og:
|
|
# TODO: extract a favicon failing all else
|
|
meta_image = tree.xpath(
|
|
"//*/meta[translate(@itemprop, 'IMAGE', 'image')='image']/@content"
|
|
)
|
|
if meta_image:
|
|
og["og:image"] = rebase_url(meta_image[0], media_uri)
|
|
else:
|
|
# TODO: consider inlined CSS styles as well as width & height attribs
|
|
images = tree.xpath("//img[@src][number(@width)>10][number(@height)>10]")
|
|
images = sorted(
|
|
images,
|
|
key=lambda i: (
|
|
-1 * float(i.attrib["width"]) * float(i.attrib["height"])
|
|
),
|
|
)
|
|
if not images:
|
|
images = tree.xpath("//img[@src]")
|
|
if images:
|
|
og["og:image"] = images[0].attrib["src"]
|
|
|
|
if "og:description" not in og:
|
|
meta_description = tree.xpath(
|
|
"//*/meta"
|
|
"[translate(@name, 'DESCRIPTION', 'description')='description']"
|
|
"/@content"
|
|
)
|
|
if meta_description:
|
|
og["og:description"] = meta_description[0]
|
|
else:
|
|
og["og:description"] = parse_html_description(tree)
|
|
elif og["og:description"]:
|
|
# This must be a non-empty string at this point.
|
|
assert isinstance(og["og:description"], str)
|
|
og["og:description"] = summarize_paragraphs([og["og:description"]])
|
|
|
|
# TODO: delete the url downloads to stop diskfilling,
|
|
# as we only ever cared about its OG
|
|
return og
|
|
|
|
|
|
def parse_html_description(tree: "etree.Element") -> Optional[str]:
|
|
"""
|
|
Calculate a text description based on an HTML document.
|
|
|
|
Grabs any text nodes which are inside the <body/> tag, unless they are within
|
|
an HTML5 semantic markup tag (<header/>, <nav/>, <aside/>, <footer/>), or
|
|
if they are within a <script/> or <style/> tag.
|
|
|
|
This is a very very very coarse approximation to a plain text render of the page.
|
|
|
|
Args:
|
|
tree: The parsed HTML document.
|
|
|
|
Returns:
|
|
The plain text description, or None if one cannot be generated.
|
|
"""
|
|
# We don't just use XPATH here as that is slow on some machines.
|
|
|
|
from lxml import etree
|
|
|
|
TAGS_TO_REMOVE = (
|
|
"header",
|
|
"nav",
|
|
"aside",
|
|
"footer",
|
|
"script",
|
|
"noscript",
|
|
"style",
|
|
etree.Comment,
|
|
)
|
|
|
|
# Split all the text nodes into paragraphs (by splitting on new
|
|
# lines)
|
|
text_nodes = (
|
|
re.sub(r"\s+", "\n", el).strip()
|
|
for el in _iterate_over_text(tree.find("body"), *TAGS_TO_REMOVE)
|
|
)
|
|
return summarize_paragraphs(text_nodes)
|
|
|
|
|
|
def _iterate_over_text(
|
|
tree: "etree.Element", *tags_to_ignore: Iterable[Union[str, "etree.Comment"]]
|
|
) -> Generator[str, None, None]:
|
|
"""Iterate over the tree returning text nodes in a depth first fashion,
|
|
skipping text nodes inside certain tags.
|
|
"""
|
|
# This is basically a stack that we extend using itertools.chain.
|
|
# This will either consist of an element to iterate over *or* a string
|
|
# to be returned.
|
|
elements = iter([tree])
|
|
while True:
|
|
el = next(elements, None)
|
|
if el is None:
|
|
return
|
|
|
|
if isinstance(el, str):
|
|
yield el
|
|
elif el.tag not in tags_to_ignore:
|
|
# el.text is the text before the first child, so we can immediately
|
|
# return it if the text exists.
|
|
if el.text:
|
|
yield el.text
|
|
|
|
# We add to the stack all the elements children, interspersed with
|
|
# each child's tail text (if it exists). The tail text of a node
|
|
# is text that comes *after* the node, so we always include it even
|
|
# if we ignore the child node.
|
|
elements = itertools.chain(
|
|
itertools.chain.from_iterable( # Basically a flatmap
|
|
[child, child.tail] if child.tail else [child]
|
|
for child in el.iterchildren()
|
|
),
|
|
elements,
|
|
)
|
|
|
|
|
|
def rebase_url(url: str, base: str) -> str:
|
|
base_parts = list(urlparse.urlparse(base))
|
|
url_parts = list(urlparse.urlparse(url))
|
|
if not url_parts[0]: # fix up schema
|
|
url_parts[0] = base_parts[0] or "http"
|
|
if not url_parts[1]: # fix up hostname
|
|
url_parts[1] = base_parts[1]
|
|
if not url_parts[2].startswith("/"):
|
|
url_parts[2] = re.sub(r"/[^/]+$", "/", base_parts[2]) + url_parts[2]
|
|
return urlparse.urlunparse(url_parts)
|
|
|
|
|
|
def summarize_paragraphs(
|
|
text_nodes: Iterable[str], min_size: int = 200, max_size: int = 500
|
|
) -> Optional[str]:
|
|
"""
|
|
Try to get a summary respecting first paragraph and then word boundaries.
|
|
|
|
Args:
|
|
text_nodes: The paragraphs to summarize.
|
|
min_size: The minimum number of words to include.
|
|
max_size: The maximum number of words to include.
|
|
|
|
Returns:
|
|
A summary of the text nodes, or None if that was not possible.
|
|
"""
|
|
|
|
# TODO: Respect sentences?
|
|
|
|
description = ""
|
|
|
|
# Keep adding paragraphs until we get to the MIN_SIZE.
|
|
for text_node in text_nodes:
|
|
if len(description) < min_size:
|
|
text_node = re.sub(r"[\t \r\n]+", " ", text_node)
|
|
description += text_node + "\n\n"
|
|
else:
|
|
break
|
|
|
|
description = description.strip()
|
|
description = re.sub(r"[\t ]+", " ", description)
|
|
description = re.sub(r"[\t \r\n]*[\r\n]+", "\n\n", description)
|
|
|
|
# If the concatenation of paragraphs to get above MIN_SIZE
|
|
# took us over MAX_SIZE, then we need to truncate mid paragraph
|
|
if len(description) > max_size:
|
|
new_desc = ""
|
|
|
|
# This splits the paragraph into words, but keeping the
|
|
# (preceding) whitespace intact so we can easily concat
|
|
# words back together.
|
|
for match in re.finditer(r"\s*\S+", description):
|
|
word = match.group()
|
|
|
|
# Keep adding words while the total length is less than
|
|
# MAX_SIZE.
|
|
if len(word) + len(new_desc) < max_size:
|
|
new_desc += word
|
|
else:
|
|
# At this point the next word *will* take us over
|
|
# MAX_SIZE, but we also want to ensure that its not
|
|
# a huge word. If it is add it anyway and we'll
|
|
# truncate later.
|
|
if len(new_desc) < min_size:
|
|
new_desc += word
|
|
break
|
|
|
|
# Double check that we're not over the limit
|
|
if len(new_desc) > max_size:
|
|
new_desc = new_desc[:max_size]
|
|
|
|
# We always add an ellipsis because at the very least
|
|
# we chopped mid paragraph.
|
|
description = new_desc.strip() + "…"
|
|
return description if description else None
|