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# 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 logging
from typing import TYPE_CHECKING, Optional
import attr
from synapse.http.client import SimpleHttpClient
if TYPE_CHECKING:
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
@attr.s(slots=True, auto_attribs=True)
class OEmbedResult:
# Either HTML content or URL must be provided.
html: Optional[str]
url: Optional[str]
title: Optional[str]
# Number of seconds to cache the content.
cache_age: int
class OEmbedError(Exception):
"""An error occurred processing the oEmbed object."""
class OEmbedProvider:
"""
A helper for accessing oEmbed content.
It can be used to check if a URL should be accessed via oEmbed and for
requesting/parsing oEmbed content.
"""
def __init__(self, hs: "HomeServer", client: SimpleHttpClient):
self._oembed_patterns = {}
for oembed_endpoint in hs.config.oembed.oembed_patterns:
api_endpoint = oembed_endpoint.api_endpoint
# Only JSON is supported at the moment. This could be declared in
# the formats field. Otherwise, if the endpoint ends in .xml assume
# it doesn't support JSON.
if (
oembed_endpoint.formats is not None
and "json" not in oembed_endpoint.formats
) or api_endpoint.endswith(".xml"):
logger.info(
"Ignoring oEmbed endpoint due to not supporting JSON: %s",
api_endpoint,
)
continue
# Iterate through each URL pattern and point it to the endpoint.
for pattern in oembed_endpoint.url_patterns:
self._oembed_patterns[pattern] = api_endpoint
self._client = client
def get_oembed_url(self, url: str) -> Optional[str]:
"""
Check whether the URL should be downloaded as oEmbed content instead.
Args:
url: The URL to check.
Returns:
A URL to use instead or None if the original URL should be used.
"""
for url_pattern, endpoint in self._oembed_patterns.items():
if url_pattern.fullmatch(url):
return endpoint
# No match.
return None
async def get_oembed_content(self, endpoint: str, url: str) -> OEmbedResult:
"""
Request content from an oEmbed endpoint.
Args:
endpoint: The oEmbed API endpoint.
url: The URL to pass to the API.
Returns:
An object representing the metadata returned.
Raises:
OEmbedError if fetching or parsing of the oEmbed information fails.
"""
try:
logger.debug("Trying to get oEmbed content for url '%s'", url)
# Note that only the JSON format is supported, some endpoints want
# this in the URL, others want it as an argument.
endpoint = endpoint.replace("{format}", "json")
result = await self._client.get_json(
endpoint,
# TODO Specify max height / width.
args={"url": url, "format": "json"},
)
# Ensure there's a version of 1.0.
if result.get("version") != "1.0":
raise OEmbedError("Invalid version: %s" % (result.get("version"),))
oembed_type = result.get("type")
# Ensure the cache age is None or an int.
cache_age = result.get("cache_age")
if cache_age:
cache_age = int(cache_age)
oembed_result = OEmbedResult(None, None, result.get("title"), cache_age)
# HTML content.
if oembed_type == "rich":
oembed_result.html = result.get("html")
return oembed_result
if oembed_type == "photo":
oembed_result.url = result.get("url")
return oembed_result
# TODO Handle link and video types.
if "thumbnail_url" in result:
oembed_result.url = result.get("thumbnail_url")
return oembed_result
raise OEmbedError("Incompatible oEmbed information.")
except OEmbedError as e:
# Trap OEmbedErrors first so we can directly re-raise them.
logger.warning("Error parsing oEmbed metadata from %s: %r", url, e)
raise
except Exception as e:
# Trap any exception and let the code follow as usual.
# FIXME: pass through 404s and other error messages nicely
logger.warning("Error downloading oEmbed metadata from %s: %r", url, e)
raise OEmbedError() from e
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