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

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())