/********************************************************************************
 *   Prometheus exporter for monitoring network connectivity using icmp pings   *
 *                                                                              *
 *   Copyright (C) 2019-2022 Jan Christian Grünhage                             *
 *   Copyright (C) 2020-2021 Famedly GmbH                                            *
 *                                                                              *
 *   This program is free software: you can redistribute it and/or modify       *
 *   it under the terms of the GNU Affero General Public License as             *
 *   published by the Free Software Foundation, either version 3 of the         *
 *   License, or (at your option) any later version.                            *
 *                                                                              *
 *   This program is distributed in the hope that it will be useful,            *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of             *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the               *
 *   GNU Affero General Public License for more details.                        *
 *                                                                              *
 *   You should have received a copy of the GNU Affero General Public License   *
 *   along with this program.  If not, see <https://www.gnu.org/licenses/>.     *
 ********************************************************************************/
use crate::config::Config;
use anyhow::{Context, Result};
use async_anyhow_logger::catch;
use log::{info, trace};
use metrics::histogram;
use std::net::IpAddr;
use std::time::Duration;
use tokio_icmp_echo::{PingFuture, Pinger};

pub(crate) async fn start_pinging_hosts(config: &Config) -> Result<()> {
    let pinger = Pinger::new().await.context("Couldn't create pinger")?;
    let mut handles = vec![];
    for (host, interval) in config.ping.hosts.clone() {
        info!("Spawn ping task for {}", host);
        handles.push(tokio::spawn(ping_host(
            pinger.clone(),
            host,
            interval,
            config.ping.timeout,
        )));
    }
    let (result, _, _) = futures::future::select_all(handles).await;
    result??;
    Ok(())
}

async fn ping_host(pinger: Pinger, host: IpAddr, interval: u64, timeout: Duration) -> Result<()> {
    let mut pingchain = pinger.chain(host).timeout(timeout);
    let mut interval = tokio::time::interval(Duration::from_millis(interval));
    let host_string = host.to_string();
    loop {
        interval.tick().await;
        tokio::spawn(catch(handle_ping_result(
            pingchain.send(),
            host_string.clone(),
            timeout,
        )));
    }
}

async fn handle_ping_result(result: PingFuture, host: String, timeout: Duration) -> Result<()> {
    let pong = result.await.context(format!("Couldn't ping {}", &host))?;
    match pong {
        Some(time) => {
            let ms = time.as_millis();
            trace!("Received pong from {} after {} ms", &host, &ms);
            histogram!("ping_rtt_milliseconds", ms as f64, "target" => host);
        }
        None => {
            trace!("Received no response from {} within timeout", &host);
            histogram!("ping_rtt_milliseconds", timeout.as_millis() as f64, "target" => host);
        }
    };

    Ok(())
}