//! Live network status, scraped from the ircd's Prometheus/OpenMetrics endpoint
//! (`metrics_bind` on the daemon). A background task GETs it every minute over
//! plain HTTP on localhost — no IRC client, so it never shows up as a connecting
//! user. If the endpoint is unreachable the state simply reads "offline".

use std::sync::{Arc, RwLock};
use std::time::Duration;
use tokio::io::{AsyncReadExt, AsyncWriteExt};
use tokio::net::TcpStream;
use tokio::time::{sleep, timeout};

#[derive(Clone, Default)]
pub struct NetStats {
    pub online: bool,
    pub users: Option<u64>,
    pub channels: Option<u64>,
}

pub type Shared = Arc<RwLock<NetStats>>;

/// Spawn the background poller. Refreshes every 60s.
pub fn spawn_updater(shared: Shared) {
    tokio::spawn(async move {
        loop {
            let next = match timeout(Duration::from_secs(6), probe()).await {
                Ok(Some(s)) => s,
                _ => NetStats::default(),
            };
            if let Ok(mut g) = shared.write() {
                *g = next;
            }
            sleep(Duration::from_secs(60)).await;
        }
    });
}

async fn probe() -> Option<NetStats> {
    let addr = std::env::var("ECHO_METRICS_ADDR").unwrap_or_else(|_| "127.0.0.1:9109".into());
    let mut stream = TcpStream::connect(&addr).await.ok()?;
    stream
        .write_all(b"GET / HTTP/1.0\r\nHost: localhost\r\nConnection: close\r\n\r\n")
        .await
        .ok()?;

    let mut buf = Vec::with_capacity(4096);
    let mut chunk = [0u8; 4096];
    loop {
        let n = stream.read(&mut chunk).await.ok()?;
        if n == 0 || buf.len() > 65536 {
            break;
        }
        buf.extend_from_slice(&chunk[..n]);
    }
    let text = String::from_utf8_lossy(&buf);
    let body = text.split("\r\n\r\n").nth(1).unwrap_or(&text);

    let (mut users, mut channels) = (None, None);
    for line in body.lines() {
        if line.starts_with('#') {
            continue;
        }
        let mut it = line.split_whitespace();
        match (it.next(), it.next()) {
            (Some("echoircd_users"), Some(v)) => users = v.parse().ok(),
            (Some("echoircd_channels"), Some(v)) => channels = v.parse().ok(),
            _ => {}
        }
    }
    Some(NetStats { online: true, users, channels })
}