punktfunk/crates/pf-client-core/src/discovery.rs

//! LAN host discovery: browse the host's mDNS advert (`_punktfunk._udp`, TXT keys
//! `fp`/`pair`/`id` — see the host crate's `discovery.rs`) on a worker thread and stream
//! results to the UI. Removal events are forwarded too, so the hosts page can drop stale
//! cards and flip a saved host's online pip when its advert disappears.

use mdns_sd::{ServiceDaemon, ServiceEvent};

#[derive(Clone, Debug)]
pub struct DiscoveredHost {
    /// Stable row key: the advertised host id, falling back to the mDNS fullname.
    pub key: String,
    /// The mDNS service fullname — what a later `Removed` event identifies the advert by.
    pub fullname: String,
    pub name: String,
    pub addr: String,
    pub port: u16,
    /// Host certificate fingerprint to pin (lowercase hex), empty if not advertised.
    pub fp_hex: String,
    /// Pairing requirement: `"required"` or `"optional"`.
    pub pair: String,
    /// The management API's port (mDNS `mgmt` TXT) — where the game library is served.
    /// `None` when not advertised (older host / standalone `punktfunk1-host`); the
    /// library client then falls back to the well-known default.
    pub mgmt_port: Option<u16>,
    /// Wake-on-LAN MAC(s) from the mDNS `mac` TXT (comma-separated `aa:bb:cc:dd:ee:ff`), which the
    /// hosts page persists onto the matching saved host so it can wake it later. Empty if absent.
    pub mac: Vec<String>,
}

/// One discovery update for the UI's advert map.
pub enum DiscoveryEvent {
    /// A host advert appeared or refreshed (new address, pairing flipped, …).
    Resolved(DiscoveredHost),
    /// The advert went away (host stopped / left the network).
    Removed { fullname: String },
}

/// Browse continuously for the app's lifetime. The thread exits when the receiver is
/// dropped (the send fails) or the daemon dies.
pub fn browse() -> async_channel::Receiver<DiscoveryEvent> {
    let (tx, rx) = async_channel::unbounded();
    std::thread::Builder::new()
        .name("punktfunk-mdns".into())
        .spawn(move || {
            let daemon = match ServiceDaemon::new() {
                Ok(d) => d,
                Err(e) => {
                    tracing::warn!(error = %e, "mDNS daemon failed — discovery disabled");
                    return;
                }
            };
            let receiver = match daemon.browse("_punktfunk._udp.local.") {
                Ok(r) => r,
                Err(e) => {
                    tracing::warn!(error = %e, "mDNS browse failed — discovery disabled");
                    return;
                }
            };
            while let Ok(event) = receiver.recv() {
                let update = match event {
                    ServiceEvent::ServiceResolved(info) => {
                        let props = info.get_properties();
                        let val = |k: &str| props.get_property_val_str(k).unwrap_or("").to_string();
                        // IPv4 only, on purpose (same policy as the Android client): the core
                        // dials `format!("{host}:{port}").parse::<SocketAddr>()` over IPv4-bound
                        // sockets, so a v6 pick from this unordered address set (the host's OS
                        // responder often answers AAAA for its hostname) would render a host card
                        // that fails on every click. A v6-only advert is dropped — the honest
                        // "not found" — until the stack actually speaks IPv6.
                        let Some(addr) =
                            info.get_addresses_v4().iter().next().map(|a| a.to_string())
                        else {
                            continue;
                        };
                        let id = val("id");
                        DiscoveryEvent::Resolved(DiscoveredHost {
                            key: if id.is_empty() {
                                info.get_fullname().to_string()
                            } else {
                                id
                            },
                            fullname: info.get_fullname().to_string(),
                            name: info
                                .get_fullname()
                                .split('.')
                                .next()
                                .unwrap_or("?")
                                .to_string(),
                            addr,
                            port: info.get_port(),
                            fp_hex: val("fp"),
                            pair: val("pair"),
                            mgmt_port: val("mgmt").parse().ok(),
                            mac: val("mac")
                                .split(',')
                                .map(|s| s.trim().to_string())
                                .filter(|s| !s.is_empty())
                                .collect(),
                        })
                    }
                    ServiceEvent::ServiceRemoved(_ty, fullname) => {
                        DiscoveryEvent::Removed { fullname }
                    }
                    _ => continue,
                };
                if tx.send_blocking(update).is_err() {
                    break; // UI gone — stop browsing
                }
            }
            let _ = daemon.shutdown();
        })
        .expect("spawn mdns thread");
    rx
}