pass_manager/src/handlers/commands/gen_password.rs

use crate::handlers::markups::deletion_markup;
use arrayvec::{ArrayString, ArrayVec};
use rand::{rngs::OsRng, seq::SliceRandom};
use std::{iter, str::from_utf8_unchecked};
use teloxide::{adaptors::Throttle, prelude::*, types::ParseMode};
use tokio::task::JoinSet;

const CHARS: &[u8] = br##"!"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[]^_abcdefghijklmnopqrstuvwxyz{|}~"##;

/// Returns true if the generated master password is valid.
/// It checks that it has at least one lowercase, one lowercase and one punctuation char
#[inline]
fn check_generated_password(password: &[u8]) -> bool {
    let mut flags: u8 = 0;
    for &byte in password {
        match byte {
            b'a'..=b'z' => flags |= 0b1,
            b'A'..=b'Z' => flags |= 0b10,
            b'0'..=b'9' => flags |= 0b100,
            b'!'..=b'/' | b':'..=b'@' | b'['..=b'`' | b'{'..=b'~' => flags |= 0b1000,
            _ => (),
        }
        if flags == 0b1111 {
            return true;
        }
    }
    false
}

/// Continuously generates the password until it passes the checks
fn generete_password() -> ArrayString<34> {
    loop {
        let password: ArrayVec<u8, 32> = iter::repeat_with(|| *CHARS.choose(&mut OsRng).unwrap())
            .take(32)
            .collect();
        if check_generated_password(&password) {
            let mut string = ArrayString::<34>::new_const();
            string.push('`');
            unsafe { string.push_str(from_utf8_unchecked(&password)) };
            string.push('`');
            return string;
        }
    }
}

/// Handles /gen_password command by generating 10 copyable passwords and sending them to the user
pub async fn gen_password(bot: Throttle<Bot>, msg: Message) -> crate::Result<()> {
    let mut message = ArrayString::<{ 11 + 35 * 10 }>::new();
    message.push_str("Passwords:\n");
    let mut join_set = JoinSet::new();
    for _ in 0..10 {
        join_set.spawn_blocking(generete_password);
    }
    while let Some(password) = join_set.join_next().await {
        message.push_str(password?.as_str());
        message.push('\n')
    }
    bot.send_message(msg.chat.id, message.as_str())
        .parse_mode(ParseMode::MarkdownV2)
        .reply_markup(deletion_markup())
        .await?;
    Ok(())
}