Added file uploading support, v0.5.2

- Added example `file_bot.py`
- Added *.tmp to .gitignore
- Added CTX_FILE_SIZE, CTX_FILE_MIME and CTX_FILE_NAME
- Added MessageHasFile filter
- Added `send_file` and `send_file_bytes` for ClientSender and Bot

.gitignore

@@ -5,4 +5,5 @@ session_storage/
 dist/
 *.egg-info/
 *.swp
-*.swo
+*.swo
+*.tmp

README.md

@@ -9,6 +9,7 @@ there, but it aims to be convenient and usable for relatively serious projects.
 The library supports the following features:
 - **Completely `asyncio` based**
 - **Filter-based callback system**
+- **Downloading and transparently decrypting files**
 - **Sending images**
 - **Sending videos with automatic thumbnail generation (requires `ffmpeg`)**
 
@@ -21,13 +22,13 @@ install the latest version of the library:
 
 ```bash
 apt install libmagic1-dev libolm-dev
-python -m pip install git+https://git.tyukalov.su/nikita/mab@v0.5.0
+python -m pip install git+https://git.tyukalov.su/nikita/mab@v0.5.1
 ```
 
 `libmagic1-dev` is needed for automatic file MIME type detection, `libolm-dev`
 is needed for E2EE to work.
 
-Please inspect [`examples/image_gen_bot.py`](examples/image_gen_bot.py),
+Please inspect [`examples/image_bot.py`](examples/image_bot.py),
 [`examples/echo_bot.py`](examples/echo_bot.py) or open [`examples/`](examples/)
 directory to find usage examples. Examples require that you set
 `MATRIX_HOMESERVER` and `MATRIX_USERNAME` environment variables. Examples create

examples/file_bot.py

@@ -0,0 +1,97 @@
+"""
+This example implements Matrix bot that calculates SHA256 for a file sent by
+user.
+
+It uses environment variables to specify authorization data. Use Ctrl+C to stop
+the bot.
+"""
+
+import asyncio
+import aiofiles
+import os
+import logging
+import hashlib
+
+from mab import *
+
+from _environment import check_environment
+
+async def on_text_message(ctx: EventContext) -> None:
+    """This callback is called when a text message arrives."""
+    await ctx.bot.send_text(ctx.room, "Please send a file/image/video")
+
+async def on_file_message(ctx: EventContext) -> None:
+    """This callback is called when a file arrives."""
+    sha = hashlib.sha256()
+    does_temp_exist = False
+    if ctx[CTX_FILE_SIZE] > 1_000_000:
+        await ctx.bot.send_text(
+            ctx.room,
+            "The file is larger than 1 MB, downloading to filesystem"
+        )
+        await ctx.bot.download_file(ctx, path="temp.tmp")
+        async with aiofiles.open("temp.tmp", "rb") as f:
+            while True:
+                data = await f.read(64 * 1024)
+                if not data:
+                    break
+                sha.update(data)
+        does_temp_exist = True
+    else:
+        await ctx.bot.send_text(
+            ctx.room,
+            "The file is smaller than 1 MB, downloading to RAM"
+        )
+        content = await ctx.bot.download_file(ctx, path=None)
+        sha.update(content)
+    # result
+    response = f"SHA256 for file `{ctx[CTX_FILE_NAME]}`"
+    response += f" ({ctx[CTX_FILE_SIZE]} bytes, {ctx[CTX_FILE_MIME]})"
+    await ctx.bot.send_file_bytes(
+        room=ctx.room,
+        data=sha.hexdigest().encode("utf-8"),
+        filename="hash of the file.txt",
+        mime_type="text/plain",
+        text=response
+    )
+    # resend the file to test uploading
+    if does_temp_exist:
+        await ctx.bot.send_file(
+            room=ctx.room,
+            path="temp.tmp",
+            filename=ctx[CTX_FILE_NAME],
+            text="This is the file you have sent, but it was reuploaded"
+        )
+        try:
+            os.unlink("temp.tmp")
+        except:
+            pass
+        
+
+async def main() -> None:
+    """Application entry point"""
+    logging.basicConfig(level=logging.INFO)
+    logging.getLogger("nio").setLevel(logging.CRITICAL+1)
+    check_environment()
+
+    config = MatrixBotConfig(
+        matrix_homeserver_url=os.environ["MATRIX_HOMESERVER"],
+        matrix_username_localpart=os.environ["MATRIX_USERNAME"],
+        storage_directory="session_storage"
+    )
+    bot = MatrixBot(config)
+    bot.add_callback(
+        ~SenderIsBotFilter() & BodyExistsFilter() & MessageTypeFilter(MessageType.TEXT),
+        on_text_message)
+    bot.add_callback(
+        ~SenderIsBotFilter() & MessageHasFile() & NewMessageFilter(),
+        on_file_message)
+
+    # run until Ctrl+C
+    try:
+        await bot.run()
+    except asyncio.CancelledError:
+        pass
+
+if __name__ == "__main__":
+    asyncio.run(main())

examples/image_bot.py

@@ -9,9 +9,10 @@ the bot.
 import asyncio
 from io import BytesIO
 import os
+import time
 import logging
 import random
-from PIL import Image
+from PIL import Image, ImageFilter
 
 from mab import *
 
@@ -45,11 +46,38 @@ async def on_gen_command(data: EventContext) -> None:
     # send
     await data.bot.send_image_bytes(data.room, buf, "noise.png")
 
+async def on_image(ctx: EventContext) -> None:
+    """This callback is called when an image is received."""
+    # download
+    s = time.time()
+    data = await ctx.bot.download_file(ctx)
+    took_time = time.time() - s
+    # convert to Image
+    with BytesIO(data) as buf:
+        img = Image.open(buf)
+        # apply effects
+        blur = ImageFilter.GaussianBlur(
+            radius=min(img.size[0] // 10, 5)
+        )
+        img = img.filter(blur)
+    # save to buffer
+    buf = BytesIO()
+    img.save(buf, format="PNG")
+    buf.seek(0)
+    buf = buf.read()
+    # send
+    await ctx.bot.send_image_bytes(
+        ctx.room,
+        buf,
+        "blurred.png",
+        text="Download and decryption took %.4f seconds" % took_time
+    )
+
 async def on_wrong_message(data: EventContext) -> None:
     """This callback is called when a wrong message is received."""
     await data.bot.send_text(
         data.room,
-        "Text me something like <code>!gen 0.1 0.7 1.0</code>"
+        "Text me something like <code>!gen 0.1 0.7 1.0</code> or send an image to blur"
     )
 
 async def main() -> None:
@@ -76,12 +104,18 @@ async def main() -> None:
     bot.add_callback(
         ~SenderIsBotFilter() & command_filter,
         on_gen_command)
+
+    # callback for new image message
+    bot.add_callback(
+        ~SenderIsBotFilter() & MessageTypeFilter(MessageType.IMAGE) & NewMessageFilter(),
+        on_image
+    )
     
     # callback for message that
     # 1. are sent not by this bot
-    # 2. do NOT match the command filter
+    # 2. are new messages (not edits)
     bot.add_callback(
-        ~SenderIsBotFilter() & ~command_filter,
+        ~SenderIsBotFilter() & BodyExistsFilter() & NewMessageFilter(),
         on_wrong_message
     )
 

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "mab"
-version = "0.5.0"
+version = "0.5.2"
 authors = [
     { name = "Tyukalov Nikita", email = "nikita@tyukalov.su" }
 ]

src/mab/__init__.py

@@ -27,6 +27,9 @@ __all__ = [
     "CTX_CMD_PREFIX",
     "CTX_CMD_VERB",
     "CTX_CMD_ARGS",
+    "CTX_FILE_SIZE",
+    "CTX_FILE_MIME",
+    "CTX_FILE_NAME",
 
     # .bot
     "MatrixBot",
@@ -50,4 +53,5 @@ __all__ = [
     "RedactedMessageFilter",
     "SenderIsFilter",
     "SenderIsBotFilter",
+    "MessageHasFile",
 ]

src/mab/bot/_client_downloader.py

@@ -0,0 +1,237 @@
+import asyncio
+import aiofiles
+import logging
+import os
+import threading
+from uuid import uuid4
+from pathlib import Path
+
+import hashlib
+import hmac
+import unpaddedbase64
+from Crypto.Cipher import AES
+from Crypto.Util import Counter
+
+from nio import (
+    AsyncClient,
+    Event,
+    DiskDownloadResponse,
+    MemoryDownloadResponse
+)
+
+from ..types import MatrixBotConfig
+from ..context import EventContext
+
+class ClientDownloader:
+    """This class downloads files"""
+
+    def __init__(self):
+        self._logger = logging.getLogger("ClientSender")
+        self._config: MatrixBotConfig | None = None
+        self._client: AsyncClient | None = None
+
+    async def setup(self,
+                    config: MatrixBotConfig,
+                    client: AsyncClient) -> None:
+        """
+        Setup the downloader.
+
+        Args:
+            - config - config to use
+            - client - client to use
+        """
+        self._config = config
+        self._client = client
+
+    async def _decrypt_file(self,
+                            src: Path,
+                            dst: Path,
+                            key: str,
+                            iv: str,
+                            sha256: str) -> None:
+        """
+        Decrypts `src` and saves it as `dst` asynchronously.
+        
+        Args:
+            - src - path to the source (encrypted) file
+            - dst - path where the resulting (decrypted) file will be saved
+            - key - key, from event["content"]["file"]["key"]["k"]
+            - iv - initialization vector, from event["content"]["file"]["iv"]
+            - sha256 - SHA-256 digest, from
+                       event["content"]["file"]["hashes"]["sha256"]
+        
+        Returns:
+            - Returns nothing on success
+            - Raises an exception on error
+        """
+        async with aiofiles.open(src, "rb") as reader:
+            # check file hash
+            expected = unpaddedbase64.decode_base64(sha256)
+            digest = hashlib.sha256()
+            while chunk := await reader.read(16 * 1024):
+                digest.update(chunk)
+            if not hmac.compare_digest(digest.digest(), expected):
+                raise RuntimeError("SHA256 mismatch")
+            await reader.seek(0)
+            # decrypt
+            decoded_key = unpaddedbase64.decode_base64(key)
+            decoded_iv = unpaddedbase64.decode_base64(iv)
+            cipher = AES.new(
+                decoded_key,
+                AES.MODE_CTR,
+                counter=Counter.new(
+                    nbits=64,
+                    prefix=decoded_iv[:8],
+                    initial_value=int.from_bytes(decoded_iv[8:], "big")
+                )
+            )
+            async with aiofiles.open(dst, "wb") as writer:
+                while chunk := await reader.read(16 * 1024):
+                    await writer.write(cipher.decrypt(chunk))
+
+    async def _decrypt_bytes(self,
+                             data: bytes,
+                             key: str,
+                             iv: str,
+                             sha256: str) -> bytes:
+        """
+        Decrypts `data`. It starts subthread that performs decryption.
+        
+        Args:
+            - data - data that needs to be decrypted
+            - key - key, from event["content"]["file"]["key"]["k"]
+            - iv - initialization vector, from event["content"]["file"]["iv"]
+            - sha265 - SHA-256 digest, from
+                       event["content"]["file"]["hashes"]["sha256"]
+        
+        Returns:
+            - Returns decrypted data on success
+            - Raises an exception on error
+        """
+        cancel = threading.Event()
+        # subfunction that will run in another thread
+        def decrypt() -> bytes:
+            chunk_size = 64 * 1024
+            view = memoryview(data)
+            expected = unpaddedbase64.decode_base64(sha256)
+            digest = hashlib.sha256()
+            for offset in range(0, len(view), chunk_size):
+                if cancel.is_set():
+                    return b""
+                digest.update(view[offset:offset + chunk_size])
+            if not hmac.compare_digest(digest.digest(), expected):
+                raise RuntimeError("SHA-256 mismatch")
+            # prepare AES-CTR
+            decoded_key = unpaddedbase64.decode_base64(key)
+            decoded_iv = unpaddedbase64.decode_base64(iv)
+            cipher = AES.new(
+                decoded_key,
+                AES.MODE_CTR,
+                counter=Counter.new(
+                    nbits=64,
+                    prefix=decoded_iv[:8],
+                    initial_value=int.from_bytes(decoded_iv[8:], "big"),
+                ),
+            )
+            # decrypt
+            result = bytearray()
+            for offset in range(0, len(view), chunk_size):
+                if cancel.is_set():
+                    return b""
+                result.extend(
+                    cipher.decrypt(view[offset:offset + chunk_size])
+                )
+            return bytes(result)
+        # decrypt in thread
+        try:
+            return await asyncio.to_thread(decrypt)
+        except asyncio.CancelledError:
+            cancel.set()
+            raise
+
+    async def download_file(self,
+                            source: EventContext | Event,
+                            *,
+                            path: str | Path | None = None) -> Path | bytes:
+        """
+        Download the file from the event. Automatically deciphers encrypted
+        media.
+
+        Args:
+            - source - event that has a file in its `content`
+            - path - where to save the file to. Use `None` to store the file in
+                     memory. Use path to specify file download path.
+        
+        Returns:
+            - Returns `Path` to the file on success (if `path` isn't `None`)
+            - Returns `bytes` of the file on success (if `path` is `None`)
+            - Raises an exception on error
+        """
+        if self._client is None:
+            raise RuntimeError("ClientDownloader is not set up")
+        # prepare the args
+        if isinstance(source, EventContext):
+            source = source.event
+        content: dict = source.source["content"]
+        f = content.get("file")
+        # encypted
+        if f:
+            if not isinstance(f["url"], str):
+                raise RuntimeError("`source` does not contain file URL")
+            mxc = f["url"]
+            if f["key"]["alg"].upper() != "A256CTR":
+                raise NotImplementedError(
+                    f"Unsupported encryption algorithm `{f['key']['alg']}`"
+                )
+            key: str | None = f["key"]["k"]
+            iv: str | None = f["iv"]
+            sha256: str | None = f["hashes"]["sha256"]
+        # not encrypted
+        else:
+            mxc = content["url"]
+            key = None
+            iv = None
+            sha256 = None
+        # prepare path
+        if isinstance(path, str):
+            path = Path(path)
+        filename: str | None = \
+            os.path.basename(path) if isinstance(path, Path) else None
+        # download
+        result = await self._client.download(
+            mxc,
+            filename=filename,
+            save_to=path
+        )
+        # check the response
+        if isinstance(result, DiskDownloadResponse):
+            result = Path(result.body)
+        elif isinstance(result, MemoryDownloadResponse):
+            result = result.body
+        else:
+            raise RuntimeError(result)
+        # decrypt if needed
+        temp_path: Path | None = None
+        try:
+            if key is not None and iv is not None and sha256 is not None:
+                # on disk
+                if isinstance(result, Path):
+                    temp_path = result.with_name(
+                        f".{result.name}.{uuid4().hex}.tmp"
+                    )
+                    await self._decrypt_file(
+                        result, temp_path, key, iv, sha256
+                    )
+                    temp_path.replace(result)
+                    temp_path = None
+                # in memory
+                else:
+                    result = await self._decrypt_bytes(
+                        result, key, iv, sha256
+                    )
+        finally:
+            if isinstance(temp_path, Path) and isinstance(result, Path):
+                result.unlink(missing_ok=True)
+                temp_path.unlink(missing_ok=True)
+        # return the result
+        return result

src/mab/bot/_client_sender.py

@@ -361,4 +361,123 @@ class ClientSender:
             }
         }
         # send
+        return (await self.send_content(room, content)).event_id
+
+    async def send_file(self,
+                        room: MatrixRoom | str,
+                        path: Path | str,
+                        *,
+                        filename: str | None = None,
+                        mime_type: str | None = None,
+                        text: str | None = None,
+                        is_html: bool | None = None,
+                        timeout: float | None = 60 * 60):
+        """
+        Send the file to `room`. Please note that formatted text is displayed
+        incorrectly in some clients as of September 8th, 2026.
+
+        Args:
+            - room - the room to send the file to
+            - path - path to the file
+            - filename - filename to use for upload (`None` to use basename from
+              `path`)
+            - mime_type - mime type to use (`None` for autodetect using content
+              of `path`)
+            - text - caption to use (`None` to disable)
+            - is_html - whether the text is HTML-formatted (`None` for auto)
+            - timeout - upload timeout in seconds (`None` to disable)
+        
+        Returns:
+            - `event_id` of sent message on success
+            - Raises an exception on error
+        """
+        if self._client is None or self._config is None:
+            raise RuntimeError("ClientSender is not set up")
+        # get filename if not set
+        if not filename:
+            filename = os.path.basename(path)
+        # caption must not actually be empty
+        if text is None or not text.strip():
+            text = filename
+            is_html = False
+        # get the mime type if not specified
+        if mime_type is None:
+            mime_type = magic.from_file(path, mime=True)
+        # upload
+        async with asyncio.timeout(timeout):
+            upload_result = await self._uploader.upload_file(
+                path, mime_type=mime_type, filename=filename)
+        # send
+        content = {
+            "msgtype": "m.file",
+            "filename": filename,
+            **self._process_html_text(text, is_html),
+            "file": {
+                "url": upload_result.response.content_uri,
+                "mimetype": mime_type,
+                **upload_result.keys
+            },
+            "info": {
+                "mimetype": mime_type,
+                "size": upload_result.filesize
+            }
+        }
+        return (await self.send_content(room, content)).event_id
+    
+    async def send_file_bytes(self,
+                              room: MatrixRoom | str,
+                              data: bytes,
+                              filename: str,
+                              *,
+                              mime_type: str | None = None,
+                              text: str | None = None,
+                              is_html: bool | None = None,
+                              timeout: float | None = 60 * 60) -> str:
+        """
+        Send the file to `room`.
+
+        Args:
+            - room - the room to send the file to
+            - data - the content of the file to send
+            - filename - filename to use for the file
+            - mime_type - mime type to use (`None` for autodetect using `data`
+              content)
+            - text - caption to use (`None` to disable)
+            - is_html - whether the text is HTML-formatted (`None` for auto)
+            - timeout - upload timeout in seconds (`None` to disable)
+        
+        Returns:
+            - `event_id` of sent message on success
+            - Raises an exception on error
+        """
+        # caption must not actually be empty
+        if text is None or not text.strip():
+            text = filename
+            is_html = False
+        # check if the file is image
+        if not mime_type:
+            mime_type = magic.from_buffer(data, mime=True)
+        # upload
+        buffer = BytesIO(data)
+        async with asyncio.timeout(timeout):
+            upload_result = await self._uploader.upload_using_provider(
+                provider=buffer,
+                mime_type=mime_type,
+                filename=filename,
+                filesize=len(data))
+        # prepare the content and send
+        content = {
+            "msgtype": "m.file",
+            "filename": filename,
+            **self._process_html_text(text, is_html),
+            "file": {
+                "url": upload_result.response.content_uri,
+                "mimetype": mime_type,
+                **upload_result.keys
+            },
+            "info": {
+                "mimetype": mime_type,
+                "size": upload_result.filesize
+            }
+        }
         return (await self.send_content(room, content)).event_id

src/mab/bot/bot.py

@@ -1,9 +1,9 @@
 import asyncio
 import logging
 
-from typing import Callable, Coroutine, Any
+from typing import Callable, Coroutine, Any, overload
 
-from nio import AsyncClient, MatrixRoom
+from nio import AsyncClient, MatrixRoom, Event
 
 from ..filters.base import BaseEventFilter
 from ..types import *
@@ -12,6 +12,7 @@ from ..context import EventContext
 from ._validation import Validator
 from ._storage import Storage
 from ._client_auth import ClientAuth
+from ._client_downloader import ClientDownloader
 from ._client_manager import ClientManager
 from ._client_uploader import ClientUploader
 from ._client_sender import ClientSender
@@ -33,6 +34,7 @@ class MatrixBot:
         self._client_auth = ClientAuth(self._storage)
         self._client_manager = ClientManager(self._client_auth, self._storage)
         self._client_uploader = ClientUploader(self._storage)
+        self._client_downloader = ClientDownloader()
         self._client_sender = ClientSender()
         self._callbacks = Callbacks(self._storage, self)
         # validate the config and save it
@@ -80,6 +82,10 @@ class MatrixBot:
             self._config,
             self._client_manager.get_client()
         )
+        await self._client_downloader.setup(
+            self._config,
+            self._client_manager.get_client()
+        )
         await self._client_sender.setup(
             self._config,
             self._client_manager.get_client(),
@@ -244,4 +250,110 @@ class MatrixBot:
             text=text,
             is_html=is_html,
             timeout=timeout
+        )
+
+    async def send_file(self,
+                        room: MatrixRoom | str,
+                        path: Path | str,
+                        *,
+                        filename: str | None = None,
+                        mime_type: str | None = None,
+                        text: str | None = None,
+                        is_html: bool | None = None,
+                        timeout: float | None = 60 * 60):
+        """
+        Send the file to `room`. Please note that formatted text is displayed
+        incorrectly in some clients as of September 8th, 2026.
+
+        Args:
+            - room - the room to send the file to
+            - path - path to the file
+            - filename - filename to use for upload (`None` to use basename from
+              `path`)
+            - mime_type - mime type to use (`None` for auto)
+            - text - caption to use (`None` to disable)
+            - is_html - whether the text is HTML-formatted (`None` for auto)
+            - timeout - upload timeout in seconds (`None` to disable)
+        
+        Returns:
+            - `event_id` of sent message on success
+            - Raises an exception on error
+        """
+        return await self._client_sender.send_file(
+            room=room,
+            path=path,
+            filename=filename,
+            mime_type=mime_type,
+            text=text,
+            is_html=is_html,
+            timeout=timeout
+        )
+
+    async def send_file_bytes(self,
+                              room: MatrixRoom | str,
+                              data: bytes,
+                              filename: str,
+                              *,
+                              mime_type: str | None = None,
+                              text: str | None = None,
+                              is_html: bool | None = None,
+                              timeout: float | None = 60 * 60) -> str:
+        """
+        Send the file to `room`.
+
+        Args:
+            - room - the room to send the file to
+            - data - the content of the file to send
+            - filename - filename to use for the file
+            - text - caption to use (`None` to disable)
+            - is_html - whether the text is HTML-formatted (`None` for auto)
+            - timeout - upload timeout in seconds (`None` to disable)
+        
+        Returns:
+            - `event_id` of sent message on success
+            - Raises an exception on error
+        """
+        return await self._client_sender.send_file_bytes(
+            room=room,
+            data=data,
+            filename=filename,
+            mime_type=mime_type,
+            text=text,
+            is_html=is_html,
+            timeout=timeout
+        )
+
+    @overload
+    async def download_file(self,
+                            source: EventContext | Event,
+                            *,
+                            path: str | Path) -> Path: ...
+    
+    @overload
+    async def download_file(self,
+                            source: EventContext | Event,
+                            *,
+                            path: None = None) -> bytes: ...
+    
+    async def download_file(self,
+                            source: EventContext | Event,
+                            *,
+                            path: str | Path | None = None) -> Path | bytes:
+        """
+        Download the file from the event. Automatically dechiphers encrypted
+        media.
+
+        Args:
+            - source - event that has a file in its `content`
+            - path - where to save the file to. Use `None` to store the file in
+                     memory. Use path to specify file download path.
+        
+        Returns:
+            - Returns `Path` to the file on success (if `path` isn't `None`)
+            - Returns `bytes` of the file on success (if `path` is `None`)
+            - Raises an exception on error
+        """
+        return await self._client_downloader.download_file(
+            source=source,
+            path=path
         )

src/mab/context.py

@@ -34,6 +34,15 @@ CTX_CMD_ARGS = ContextDataKey[list[str]]("CTX_CMD_ARGS")
 CTX_ROOM_ENCRYPTED = ContextDataKey[bool]("CTX_ROOM_ENCRYPTED")
 """True if the room is encrypted"""
 
+CTX_FILE_SIZE = ContextDataKey[int]("CTX_FILE_SIZE")
+"""Size of the file attached to the message (bytes)"""
+
+CTX_FILE_MIME = ContextDataKey[str]("CTX_FILE_MIME")
+"""Mime type of the file attached to the message"""
+
+CTX_FILE_NAME = ContextDataKey[str]("CTX_FILE_NAME")
+"""Name of the file attached to the message"""
+
 
 #
 # EventContext implementation

src/mab/filters/message.py

@@ -1,7 +1,12 @@
 import traceback
 from .base import BaseEventFilter, EventTypeFilter
 from ..types import MessageType
-from ..context import EventContext, CTX_MESSAGE_TYPE, CTX_SENDER
+from ..context import (EventContext,
+                       CTX_MESSAGE_TYPE,
+                       CTX_SENDER,
+                       CTX_FILE_SIZE,
+                       CTX_FILE_MIME,
+                       CTX_FILE_NAME)
 
 from nio import AsyncClient
 from nio import MatrixRoom, Event
@@ -118,4 +123,29 @@ class SenderIsBotFilter(BaseEventFilter):
     async def __call__(self, context: EventContext) -> bool:
         if not await super().__call__(context):
             return False
-        return context.bot.get_client().user_id == context.event.sender
+        return context.bot.get_client().user_id == context.event.sender
+
+class MessageHasFile(BaseEventFilter):
+    """
+    This filter returns True if the message contains file that can be
+    downloaded.
+
+    This filter sets `CTX_FILE_NAME`, `CTX_FILE_SIZE` and `CTX_FILE_MIME`
+    variables in the context (if they are present in the).
+    """
+    def __init__(self, **kwargs):
+        super().__init__(**kwargs)
+
+    async def __call__(self, context: EventContext) -> bool:
+        if not await super().__call__(context):
+            return False
+        content: dict | None = context.event.source.get("content")
+        if content is None:
+            return False
+        # `file` if encrypted, `url` if not encrypted
+        if "file" not in content and "url" not in content:
+            return False
+        context[CTX_FILE_NAME] = content.get("filename") or content.get("body")
+        context[CTX_FILE_SIZE] = content["info"].get("size")
+        context[CTX_FILE_MIME] = content["info"].get("mimetype")
+        return True