nng 1.0.1

//! Survey (everybody votes) example.
//!
//! The surveyor pattern is used to send a timed survey out, with responses being individually
//! returned until the survey has expired. This pattern is useful for service discovery and voting
//! algorithms.
//!
//! This example was derived from [this NNG example][1].
//!
//! [1]: https://nanomsg.org/gettingstarted/nng/survey.html
use nng::{Error, Protocol, Socket};
use std::{convert::TryInto, env, process, str, time::SystemTime};

const DATE: &str = "DATE";

/// Entry point of the application.
pub fn main() -> Result<(), Error> {
    let args: Vec<_> = env::args().take(4).collect();

    match &args[..] {
        [_, t, url] if t == "surveyor" => surveyor(url),
        [_, t, url, name] if t == "respondent" => respondent(url, name),
        _ => {
            println!("Usage: pipeline surveyor|respondent <URL> <NAME> ...");
            process::exit(1);
        }
    }
}

/// Surveyor socket.
fn surveyor(url: &str) -> Result<(), Error> {
    let s = Socket::new(Protocol::Surveyor0)?;
    s.listen(url)?;

    loop {
        println!("SURVEYOR: SENDING DATE SURVEY REQUEST");
        s.send(DATE.as_bytes())?;

        loop {
            let msg = match s.recv() {
                Ok(m) => m,
                Err(Error::TimedOut) => break,
                Err(e) => return Err(e),
            };

            let date = u64::from_le_bytes(msg[..].try_into().unwrap());
            println!("SURVEYOR: RECEIVED \"{}\" SURVEY RESPONSE", date);
        }

        println!("SURVEYOR SURVEY COMPLETE");
    }
}

/// Respondent socket.
fn respondent(url: &str, name: &str) -> Result<(), Error> {
    let s = Socket::new(Protocol::Respondent0)?;
    s.dial(url)?;

    loop {
        let mut msg = s.recv()?;

        let survey = str::from_utf8(&msg).expect("invalid UTF-8");
        println!(
            "RESPONDENT ({}): RECEIVED \"{}\" SURVEY REQUEST",
            name, survey
        );

        // Reuse the message to avoid allocation.
        msg.clear();
        let date = SystemTime::now()
            .duration_since(SystemTime::UNIX_EPOCH)
            .expect("system time is before Unix epoch")
            .as_secs();

        msg.push_back(&date.to_le_bytes());

        println!("RESPONDENT ({}): SENDING \"{}\"", name, date);
        s.send(msg)?;
    }
}