"""
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())