/********************************************************************************
 *   Prometheus exporter for monitoring network connectivity using icmp pings   *
 *                                                                              *
 *   Copyright (C) 2019-2020 Jan Christian Grünhage                             *
 *   Copyright (C) 2020 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 futures_util::stream::StreamExt;
use lazy_static::lazy_static;
use log::{error, info, trace};
use prometheus::*;
use std::time::Duration;
use tokio::time::delay_for;

lazy_static! {
    static ref PING_HISTOGRAM: HistogramVec = register_histogram_vec!(
        "ping_rtt_milliseconds",
        "The ping round trip time in milliseconds",
        &["target"],
        vec![
            0.5, 1.0, 5.0, 10.0, 15.0, 20.0, 25.0, 50.0, 75.0, 100.0, 150.0, 200.0, 250.0, 300.0,
            350.0, 400.0, 450.0, 500.0, 550.0, 600.0, 650.0, 700.0, 750.0, 800.0, 900.0, 1000.0,
            1250.0, 1500.0, 1750.0, 2000.0
        ]
    )
    .unwrap();
}

pub(crate) async fn start_pinging_hosts(
    config: Config,
) -> std::result::Result<(), tokio_ping::Error> {
    let pinger = match tokio_ping::Pinger::new().await {
        Ok(pinger) => pinger,
        Err(error) => {
            error!("Couldn't create pinger: {}", error);
            std::process::exit(1);
        }
    };
    for (host, interval) in config.hosts.clone() {
        info!("Spawn ping task for {}", host);
        let pingchain = pinger.chain(host).timeout(Duration::from_secs(3));
        let host = host.to_string();
        tokio::spawn(pingchain.stream().for_each(move |ping_result| {
            match ping_result {
                Ok(time) => match time {
                    Some(time) => {
                        let ms = time.as_millis();
                        trace!("Received pong from {} after {} ms", &host, &ms);
                        PING_HISTOGRAM
                            .with_label_values(&[&host])
                            .observe(ms as f64);
                    }
                    None => {
                        trace!("Received no response from {} within timeout", &host);
                        PING_HISTOGRAM.with_label_values(&[&host]).observe(3000.0);
                    }
                },
                Err(error) => error!("Couldn't ping {}: {}", &host, error),
            }
            delay_for(Duration::from_millis(interval))
        }));
    }
    Ok(())
}