551 lines
20 KiB
Python
551 lines
20 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2016 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from twisted.web.server import NOT_DONE_YET
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from twisted.internet import defer
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from twisted.web.resource import Resource
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from synapse.api.errors import (
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SynapseError, Codes,
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)
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from synapse.util.stringutils import random_string
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from synapse.util.caches.expiringcache import ExpiringCache
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from synapse.http.client import SpiderHttpClient
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from synapse.http.server import (
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request_handler, respond_with_json_bytes
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)
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from synapse.util.async import ObservableDeferred
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from synapse.util.stringutils import is_ascii
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import os
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import re
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import fnmatch
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import cgi
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import ujson as json
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import urlparse
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import itertools
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import logging
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logger = logging.getLogger(__name__)
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class PreviewUrlResource(Resource):
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isLeaf = True
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def __init__(self, hs, media_repo):
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Resource.__init__(self)
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self.auth = hs.get_auth()
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self.clock = hs.get_clock()
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self.version_string = hs.version_string
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self.filepaths = media_repo.filepaths
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self.max_spider_size = hs.config.max_spider_size
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self.server_name = hs.hostname
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self.store = hs.get_datastore()
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self.client = SpiderHttpClient(hs)
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self.media_repo = media_repo
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self.url_preview_url_blacklist = hs.config.url_preview_url_blacklist
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# simple memory cache mapping urls to OG metadata
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self.cache = ExpiringCache(
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cache_name="url_previews",
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clock=self.clock,
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# don't spider URLs more often than once an hour
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expiry_ms=60 * 60 * 1000,
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)
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self.cache.start()
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self.downloads = {}
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def render_GET(self, request):
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self._async_render_GET(request)
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return NOT_DONE_YET
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@request_handler()
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@defer.inlineCallbacks
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def _async_render_GET(self, request):
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# XXX: if get_user_by_req fails, what should we do in an async render?
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requester = yield self.auth.get_user_by_req(request)
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url = request.args.get("url")[0]
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if "ts" in request.args:
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ts = int(request.args.get("ts")[0])
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else:
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ts = self.clock.time_msec()
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url_tuple = urlparse.urlsplit(url)
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for entry in self.url_preview_url_blacklist:
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match = True
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for attrib in entry:
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pattern = entry[attrib]
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value = getattr(url_tuple, attrib)
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logger.debug((
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"Matching attrib '%s' with value '%s' against"
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" pattern '%s'"
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) % (attrib, value, pattern))
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if value is None:
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match = False
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continue
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if pattern.startswith('^'):
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if not re.match(pattern, getattr(url_tuple, attrib)):
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match = False
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continue
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else:
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if not fnmatch.fnmatch(getattr(url_tuple, attrib), pattern):
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match = False
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continue
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if match:
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logger.warn(
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"URL %s blocked by url_blacklist entry %s", url, entry
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)
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raise SynapseError(
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403, "URL blocked by url pattern blacklist entry",
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Codes.UNKNOWN
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)
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# first check the memory cache - good to handle all the clients on this
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# HS thundering away to preview the same URL at the same time.
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og = self.cache.get(url)
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if og:
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respond_with_json_bytes(request, 200, json.dumps(og), send_cors=True)
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return
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# then check the URL cache in the DB (which will also provide us with
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# historical previews, if we have any)
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cache_result = yield self.store.get_url_cache(url, ts)
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if (
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cache_result and
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cache_result["download_ts"] + cache_result["expires"] > ts and
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cache_result["response_code"] / 100 == 2
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):
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respond_with_json_bytes(
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request, 200, cache_result["og"].encode('utf-8'),
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send_cors=True
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)
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return
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# Ensure only one download for a given URL is active at a time
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download = self.downloads.get(url)
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if download is None:
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download = self._download_url(url, requester.user)
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download = ObservableDeferred(
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download,
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consumeErrors=True
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)
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self.downloads[url] = download
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@download.addBoth
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def callback(media_info):
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del self.downloads[url]
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return media_info
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media_info = yield download.observe()
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# FIXME: we should probably update our cache now anyway, so that
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# even if the OG calculation raises, we don't keep hammering on the
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# remote server. For now, leave it uncached to aid debugging OG
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# calculation problems
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logger.debug("got media_info of '%s'" % media_info)
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if _is_media(media_info['media_type']):
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dims = yield self.media_repo._generate_local_thumbnails(
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media_info['filesystem_id'], media_info
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)
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og = {
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"og:description": media_info['download_name'],
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"og:image": "mxc://%s/%s" % (
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self.server_name, media_info['filesystem_id']
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),
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"og:image:type": media_info['media_type'],
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"matrix:image:size": media_info['media_length'],
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}
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if dims:
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og["og:image:width"] = dims['width']
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og["og:image:height"] = dims['height']
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else:
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logger.warn("Couldn't get dims for %s" % url)
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# define our OG response for this media
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elif _is_html(media_info['media_type']):
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# TODO: somehow stop a big HTML tree from exploding synapse's RAM
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file = open(media_info['filename'])
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body = file.read()
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file.close()
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# clobber the encoding from the content-type, or default to utf-8
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# XXX: this overrides any <meta/> or XML charset headers in the body
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# which may pose problems, but so far seems to work okay.
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match = re.match(r'.*; *charset=(.*?)(;|$)', media_info['media_type'], re.I)
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encoding = match.group(1) if match else "utf-8"
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og = decode_and_calc_og(body, media_info['uri'], encoding)
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# pre-cache the image for posterity
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# FIXME: it might be cleaner to use the same flow as the main /preview_url
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# request itself and benefit from the same caching etc. But for now we
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# just rely on the caching on the master request to speed things up.
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if 'og:image' in og and og['og:image']:
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image_info = yield self._download_url(
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_rebase_url(og['og:image'], media_info['uri']), requester.user
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)
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if _is_media(image_info['media_type']):
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# TODO: make sure we don't choke on white-on-transparent images
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dims = yield self.media_repo._generate_local_thumbnails(
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image_info['filesystem_id'], image_info
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)
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if dims:
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og["og:image:width"] = dims['width']
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og["og:image:height"] = dims['height']
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else:
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logger.warn("Couldn't get dims for %s" % og["og:image"])
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og["og:image"] = "mxc://%s/%s" % (
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self.server_name, image_info['filesystem_id']
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)
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og["og:image:type"] = image_info['media_type']
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og["matrix:image:size"] = image_info['media_length']
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else:
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del og["og:image"]
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else:
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logger.warn("Failed to find any OG data in %s", url)
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og = {}
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logger.debug("Calculated OG for %s as %s" % (url, og))
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# store OG in ephemeral in-memory cache
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self.cache[url] = og
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# store OG in history-aware DB cache
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yield self.store.store_url_cache(
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url,
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media_info["response_code"],
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media_info["etag"],
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media_info["expires"],
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json.dumps(og),
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media_info["filesystem_id"],
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media_info["created_ts"],
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)
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respond_with_json_bytes(request, 200, json.dumps(og), send_cors=True)
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@defer.inlineCallbacks
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def _download_url(self, url, user):
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# TODO: we should probably honour robots.txt... except in practice
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# we're most likely being explicitly triggered by a human rather than a
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# bot, so are we really a robot?
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# XXX: horrible duplication with base_resource's _download_remote_file()
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file_id = random_string(24)
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fname = self.filepaths.local_media_filepath(file_id)
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self.media_repo._makedirs(fname)
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try:
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with open(fname, "wb") as f:
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logger.debug("Trying to get url '%s'" % url)
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length, headers, uri, code = yield self.client.get_file(
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url, output_stream=f, max_size=self.max_spider_size,
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)
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# FIXME: pass through 404s and other error messages nicely
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media_type = headers["Content-Type"][0]
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time_now_ms = self.clock.time_msec()
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content_disposition = headers.get("Content-Disposition", None)
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if content_disposition:
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_, params = cgi.parse_header(content_disposition[0],)
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download_name = None
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# First check if there is a valid UTF-8 filename
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download_name_utf8 = params.get("filename*", None)
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if download_name_utf8:
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if download_name_utf8.lower().startswith("utf-8''"):
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download_name = download_name_utf8[7:]
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# If there isn't check for an ascii name.
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if not download_name:
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download_name_ascii = params.get("filename", None)
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if download_name_ascii and is_ascii(download_name_ascii):
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download_name = download_name_ascii
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if download_name:
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download_name = urlparse.unquote(download_name)
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try:
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download_name = download_name.decode("utf-8")
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except UnicodeDecodeError:
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download_name = None
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else:
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download_name = None
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yield self.store.store_local_media(
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media_id=file_id,
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media_type=media_type,
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time_now_ms=self.clock.time_msec(),
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upload_name=download_name,
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media_length=length,
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user_id=user,
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)
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except Exception as e:
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os.remove(fname)
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raise SynapseError(
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500, ("Failed to download content: %s" % e),
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Codes.UNKNOWN
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)
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defer.returnValue({
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"media_type": media_type,
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"media_length": length,
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"download_name": download_name,
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"created_ts": time_now_ms,
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"filesystem_id": file_id,
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"filename": fname,
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"uri": uri,
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"response_code": code,
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# FIXME: we should calculate a proper expiration based on the
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# Cache-Control and Expire headers. But for now, assume 1 hour.
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"expires": 60 * 60 * 1000,
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"etag": headers["ETag"][0] if "ETag" in headers else None,
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})
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def decode_and_calc_og(body, media_uri, request_encoding=None):
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from lxml import etree
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try:
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parser = etree.HTMLParser(recover=True, encoding=request_encoding)
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tree = etree.fromstring(body, parser)
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og = _calc_og(tree, media_uri)
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except UnicodeDecodeError:
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# blindly try decoding the body as utf-8, which seems to fix
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# the charset mismatches on https://google.com
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parser = etree.HTMLParser(recover=True, encoding=request_encoding)
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tree = etree.fromstring(body.decode('utf-8', 'ignore'), parser)
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og = _calc_og(tree, media_uri)
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return og
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def _calc_og(tree, media_uri):
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# suck our tree into lxml and define our OG response.
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# if we see any image URLs in the OG response, then spider them
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# (although the client could choose to do this by asking for previews of those
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# URLs to avoid DoSing the server)
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# "og:type" : "video",
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# "og:url" : "https://www.youtube.com/watch?v=LXDBoHyjmtw",
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# "og:site_name" : "YouTube",
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# "og:video:type" : "application/x-shockwave-flash",
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# "og:description" : "Fun stuff happening here",
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# "og:title" : "RemoteJam - Matrix team hack for Disrupt Europe Hackathon",
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# "og:image" : "https://i.ytimg.com/vi/LXDBoHyjmtw/maxresdefault.jpg",
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# "og:video:url" : "http://www.youtube.com/v/LXDBoHyjmtw?version=3&autohide=1",
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# "og:video:width" : "1280"
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# "og:video:height" : "720",
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# "og:video:secure_url": "https://www.youtube.com/v/LXDBoHyjmtw?version=3",
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og = {}
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for tag in tree.xpath("//*/meta[starts-with(@property, 'og:')]"):
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if 'content' in tag.attrib:
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og[tag.attrib['property']] = tag.attrib['content']
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# TODO: grab article: meta tags too, e.g.:
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# "article:publisher" : "https://www.facebook.com/thethudonline" />
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# "article:author" content="https://www.facebook.com/thethudonline" />
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# "article:tag" content="baby" />
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# "article:section" content="Breaking News" />
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# "article:published_time" content="2016-03-31T19:58:24+00:00" />
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# "article:modified_time" content="2016-04-01T18:31:53+00:00" />
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if 'og:title' not in og:
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# do some basic spidering of the HTML
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title = tree.xpath("(//title)[1] | (//h1)[1] | (//h2)[1] | (//h3)[1]")
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if title and title[0].text is not None:
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og['og:title'] = title[0].text.strip()
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else:
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og['og:title'] = None
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if 'og:image' not in og:
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# TODO: extract a favicon failing all else
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meta_image = tree.xpath(
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"//*/meta[translate(@itemprop, 'IMAGE', 'image')='image']/@content"
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)
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if meta_image:
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og['og:image'] = _rebase_url(meta_image[0], media_uri)
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else:
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# TODO: consider inlined CSS styles as well as width & height attribs
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images = tree.xpath("//img[@src][number(@width)>10][number(@height)>10]")
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images = sorted(images, key=lambda i: (
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-1 * float(i.attrib['width']) * float(i.attrib['height'])
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))
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if not images:
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images = tree.xpath("//img[@src]")
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if images:
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og['og:image'] = images[0].attrib['src']
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if 'og:description' not in og:
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meta_description = tree.xpath(
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"//*/meta"
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"[translate(@name, 'DESCRIPTION', 'description')='description']"
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"/@content")
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if meta_description:
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og['og:description'] = meta_description[0]
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else:
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# grab any text nodes which are inside the <body/> tag...
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# unless they are within an HTML5 semantic markup tag...
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# <header/>, <nav/>, <aside/>, <footer/>
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# ...or if they are within a <script/> or <style/> tag.
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# This is a very very very coarse approximation to a plain text
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# render of the page.
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# We don't just use XPATH here as that is slow on some machines.
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from lxml import etree
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TAGS_TO_REMOVE = (
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"header", "nav", "aside", "footer", "script", "style", etree.Comment
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)
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# Split all the text nodes into paragraphs (by splitting on new
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# lines)
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text_nodes = (
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re.sub(r'\s+', '\n', el).strip()
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for el in _iterate_over_text(tree.find("body"), *TAGS_TO_REMOVE)
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)
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og['og:description'] = summarize_paragraphs(text_nodes)
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# TODO: delete the url downloads to stop diskfilling,
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# as we only ever cared about its OG
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return og
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def _iterate_over_text(tree, *tags_to_ignore):
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"""Iterate over the tree returning text nodes in a depth first fashion,
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skipping text nodes inside certain tags.
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"""
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# This is basically a stack that we extend using itertools.chain.
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# This will either consist of an element to iterate over *or* a string
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# to be returned.
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elements = iter([tree])
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while True:
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el = elements.next()
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if isinstance(el, basestring):
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yield el
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elif el is not None and el.tag not in tags_to_ignore:
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# el.text is the text before the first child, so we can immediately
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# return it if the text exists.
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if el.text:
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yield el.text
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# We add to the stack all the elements children, interspersed with
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# each child's tail text (if it exists). The tail text of a node
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# is text that comes *after* the node, so we always include it even
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# if we ignore the child node.
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elements = itertools.chain(
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itertools.chain.from_iterable( # Basically a flatmap
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[child, child.tail] if child.tail else [child]
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for child in el.iterchildren()
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),
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elements
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)
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def _rebase_url(url, base):
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base = list(urlparse.urlparse(base))
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url = list(urlparse.urlparse(url))
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if not url[0]: # fix up schema
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url[0] = base[0] or "http"
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if not url[1]: # fix up hostname
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url[1] = base[1]
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if not url[2].startswith('/'):
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url[2] = re.sub(r'/[^/]+$', '/', base[2]) + url[2]
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return urlparse.urlunparse(url)
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def _is_media(content_type):
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if content_type.lower().startswith("image/"):
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return True
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def _is_html(content_type):
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content_type = content_type.lower()
|
|
if (
|
|
content_type.startswith("text/html") or
|
|
content_type.startswith("application/xhtml")
|
|
):
|
|
return True
|
|
|
|
|
|
def summarize_paragraphs(text_nodes, min_size=200, max_size=500):
|
|
# Try to get a summary of between 200 and 500 words, respecting
|
|
# first paragraph and then word boundaries.
|
|
# 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
|
|
# (preceeding) whitespace intact so we can easily concat
|
|
# words back together.
|
|
for match in re.finditer("\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() + u"…"
|
|
return description if description else None
|