import difflib
from io import BytesIO

import discord


def diff_file(before: str, after: str, filename: str = "changes.diff") -> discord.File:
    """
    Generates a diff from two strings and returns it as a discord.File.

    Args:
        before (str): The original string content.
        after (str): The modified string content.
        filename (str, optional): The name for the output file. Defaults to "changes.diff".

    Returns:
        discord.File: A file object ready to be sent in a Discord message.
    """
    diff_generator = difflib.ndiff(
        before.splitlines(),
        after.splitlines(),
    )
    diff_text = "\n".join(diff_generator) or "No changes."
    diff_bytes = diff_text.encode('utf-8')

    with BytesIO(diff_bytes) as buffer:
        buffer.seek(0)
        return discord.File(buffer, filename=filename)