Refactor media modules. (#15146)

* Removes the `v1` directory from `test.rest.media.v1`.
* Moves the non-REST code from `synapse.rest.media.v1` to `synapse.media`.
* Flatten the `v1` directory from `synapse.rest.media`,  but leave compatiblity
  with 3rd party media repositories and spam checkers.

synapse/media/storage_provider.py

@@ -0,0 +1,181 @@
+# Copyright 2018-2021 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 abc
+import logging
+import os
+import shutil
+from typing import TYPE_CHECKING, Callable, Optional
+
+from synapse.config._base import Config
+from synapse.logging.context import defer_to_thread, run_in_background
+from synapse.util.async_helpers import maybe_awaitable
+
+from ._base import FileInfo, Responder
+from .media_storage import FileResponder
+
+logger = logging.getLogger(__name__)
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+
+class StorageProvider(metaclass=abc.ABCMeta):
+    """A storage provider is a service that can store uploaded media and
+    retrieve them.
+    """
+
+    @abc.abstractmethod
+    async def store_file(self, path: str, file_info: FileInfo) -> None:
+        """Store the file described by file_info. The actual contents can be
+        retrieved by reading the file in file_info.upload_path.
+
+        Args:
+            path: Relative path of file in local cache
+            file_info: The metadata of the file.
+        """
+
+    @abc.abstractmethod
+    async def fetch(self, path: str, file_info: FileInfo) -> Optional[Responder]:
+        """Attempt to fetch the file described by file_info and stream it
+        into writer.
+
+        Args:
+            path: Relative path of file in local cache
+            file_info: The metadata of the file.
+
+        Returns:
+            Returns a Responder if the provider has the file, otherwise returns None.
+        """
+
+
+class StorageProviderWrapper(StorageProvider):
+    """Wraps a storage provider and provides various config options
+
+    Args:
+        backend: The storage provider to wrap.
+        store_local: Whether to store new local files or not.
+        store_synchronous: Whether to wait for file to be successfully
+            uploaded, or todo the upload in the background.
+        store_remote: Whether remote media should be uploaded
+    """
+
+    def __init__(
+        self,
+        backend: StorageProvider,
+        store_local: bool,
+        store_synchronous: bool,
+        store_remote: bool,
+    ):
+        self.backend = backend
+        self.store_local = store_local
+        self.store_synchronous = store_synchronous
+        self.store_remote = store_remote
+
+    def __str__(self) -> str:
+        return "StorageProviderWrapper[%s]" % (self.backend,)
+
+    async def store_file(self, path: str, file_info: FileInfo) -> None:
+        if not file_info.server_name and not self.store_local:
+            return None
+
+        if file_info.server_name and not self.store_remote:
+            return None
+
+        if file_info.url_cache:
+            # The URL preview cache is short lived and not worth offloading or
+            # backing up.
+            return None
+
+        if self.store_synchronous:
+            # store_file is supposed to return an Awaitable, but guard
+            # against improper implementations.
+            await maybe_awaitable(self.backend.store_file(path, file_info))  # type: ignore
+        else:
+            # TODO: Handle errors.
+            async def store() -> None:
+                try:
+                    return await maybe_awaitable(
+                        self.backend.store_file(path, file_info)
+                    )
+                except Exception:
+                    logger.exception("Error storing file")
+
+            run_in_background(store)
+
+    async def fetch(self, path: str, file_info: FileInfo) -> Optional[Responder]:
+        if file_info.url_cache:
+            # Files in the URL preview cache definitely aren't stored here,
+            # so avoid any potentially slow I/O or network access.
+            return None
+
+        # store_file is supposed to return an Awaitable, but guard
+        # against improper implementations.
+        return await maybe_awaitable(self.backend.fetch(path, file_info))
+
+
+class FileStorageProviderBackend(StorageProvider):
+    """A storage provider that stores files in a directory on a filesystem.
+
+    Args:
+        hs
+        config: The config returned by `parse_config`.
+    """
+
+    def __init__(self, hs: "HomeServer", config: str):
+        self.hs = hs
+        self.cache_directory = hs.config.media.media_store_path
+        self.base_directory = config
+
+    def __str__(self) -> str:
+        return "FileStorageProviderBackend[%s]" % (self.base_directory,)
+
+    async def store_file(self, path: str, file_info: FileInfo) -> None:
+        """See StorageProvider.store_file"""
+
+        primary_fname = os.path.join(self.cache_directory, path)
+        backup_fname = os.path.join(self.base_directory, path)
+
+        dirname = os.path.dirname(backup_fname)
+        os.makedirs(dirname, exist_ok=True)
+
+        # mypy needs help inferring the type of the second parameter, which is generic
+        shutil_copyfile: Callable[[str, str], str] = shutil.copyfile
+        await defer_to_thread(
+            self.hs.get_reactor(),
+            shutil_copyfile,
+            primary_fname,
+            backup_fname,
+        )
+
+    async def fetch(self, path: str, file_info: FileInfo) -> Optional[Responder]:
+        """See StorageProvider.fetch"""
+
+        backup_fname = os.path.join(self.base_directory, path)
+        if os.path.isfile(backup_fname):
+            return FileResponder(open(backup_fname, "rb"))
+
+        return None
+
+    @staticmethod
+    def parse_config(config: dict) -> str:
+        """Called on startup to parse config supplied. This should parse
+        the config and raise if there is a problem.
+
+        The returned value is passed into the constructor.
+
+        In this case we only care about a single param, the directory, so let's
+        just pull that out.
+        """
+        return Config.ensure_directory(config["directory"])