logtimes/src/main.rs

use chrono::prelude::*;
use std::{
    env::args,
    fs::File,
    io::{stdin, stdout, Error as IoError, Read, StdoutLock, Write},
};

type LogtimesResult = Result<(), IoError>;

#[inline(always)]
fn print_time<T>(output: &mut T) -> LogtimesResult
where
    T: Write,
{
    let date_now = Local::now().format("%H:%M:%S%.9f");

    write!(output, "[{}] ", &date_now)
}

#[inline(always)]
fn print_time_color(output: &mut StdoutLock) -> Result<(), std::io::Error> {
    let date_now = Local::now().format("%H:%M:%S%.9f");

    let color_green = "\x1b\x5b\x30\x3b\x33\x32\x6d";
    let color_off = "\x1b\x5b\x30\x6d";

    write!(output, "{}[{}]{} ", color_green, &date_now, color_off)
}

#[inline(always)]
fn print_delete_line(output: &mut StdoutLock) -> LogtimesResult {
    // tput dl1 und tput hpa 0
    let bytes = "\x1b\x5b\x4d\x1b\x5b\x31\x47";
    write!(output, "{}", bytes)
}

fn run() -> LogtimesResult {
    let mut log_file = args().nth(1).map(|f| {
        File::options()
            .create(true)
            .append(true)
            .open(f)
            .expect("Could not open log file")
    });

    let out = stdout();
    let mut output = out.lock();

    let inp = stdin();
    let mut input = inp.lock();

    let mut buf = [0; 1];

    let mut linebuf = Vec::with_capacity(64 * 1024);

    loop {
        // read 1 char
        input.read_exact(&mut buf)?;

        // push that char to the "current line" buffer
        linebuf.push(buf[0]);

        // we encounter a newline -> delete the line and write it new as:
        //     [timestamp] actual content\n
        //  also write the line to the log file if there is one
        if buf[0] == 0xa {
            print_delete_line(&mut output)?;
            print_time_color(&mut output)?;
            output.write_all(&linebuf)?;
            output.flush()?;

            if let Some(ref mut f) = log_file {
                print_time(f)?;
                f.write_all(&linebuf)?;
                f.flush()?;
            };

            // clear line buffer so it is fresh for the next line
            linebuf.clear();
            continue;
        }

        output.write_all(&buf)?;
        output.flush()?;
    }
}

fn main() {
    if let Err(e) = run() {
        println!("{:?}", e);
        std::process::exit(1);
    }
}