Add initial discovery logic

Cargo.toml

@@ -8,5 +8,15 @@ repository = "https://github.com/sifis-home/wot-discovery"
 keywords = ["wot", "WebofThings"]
 
 [dependencies]
-webthing = "0.15"
 serde_json = "1.0"
+mdns-sd = "0.5.1"
+thiserror = "1.0"
+reqwest = { version = "0.11", features = ["json"] }
+wot-td = { git = "https://github.com/sifis-home/wot-td", version = "0.1.0" }
+futures-core = "0.3"
+futures-util = "0.3.21"
+tracing = "0.1.35"
+
+[dev-dependencies]
+tokio = { version = "1.19.2", features = ["macros", "rt-multi-thread"] }
+tracing-subscriber = "0.3.11"

examples/list.rs

@@ -0,0 +1,21 @@
+use std::future::ready;
+
+use futures_util::StreamExt;
+use tracing::info;
+use wot_discovery::discovery::Discovery;
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    tracing_subscriber::fmt().init();
+
+    let d = Discovery::new()?;
+
+    d.stream()?
+        .for_each(|thing| {
+            info!("* {:?}", thing);
+            ready(())
+        })
+        .await;
+
+    Ok(())
+}

src/discovery.rs

@@ -0,0 +1,70 @@
+use futures_core::Stream;
+use futures_util::StreamExt;
+use mdns_sd::{ServiceDaemon, ServiceEvent, ServiceInfo};
+use tracing::debug;
+
+use wot_td::thing::Thing;
+
+// TODO: move in crate::error later
+#[derive(thiserror::Error, Debug)]
+pub enum Error {
+    #[error("mdns cannot be accessed {0}")]
+    Mdns(#[from] mdns_sd::Error),
+    #[error("reqwest error {0}")]
+    Reqwest(#[from] reqwest::Error),
+    #[error("Missing address")]
+    NoAddress,
+}
+
+pub type Result<T> = std::result::Result<T, Error>;
+
+const WELL_KNOWN: &str = "/.well-known/wot";
+
+pub struct Discovery {
+    mdns: ServiceDaemon,
+    service_type: String,
+}
+
+async fn get_thing(info: ServiceInfo) -> Result<Thing> {
+    let host = info.get_addresses().iter().next().ok_or(Error::NoAddress)?;
+    let port = info.get_port();
+    let props = info.get_properties();
+    let path = props.get("td").map(|s| s.as_str()).unwrap_or(WELL_KNOWN);
+    let proto = match props.get("tls") {
+        Some(x) if x == "1" => "https",
+        _ => "http",
+    };
+
+    debug!("Got {proto} {host} {port} {path}");
+
+    let r = reqwest::get(format!("{proto}://{host}:{port}{path}")).await?;
+
+    let t = r.json().await?;
+
+    Ok(t)
+}
+
+impl Discovery {
+    /// Creates a new Context composed by a series of Thing.
+    pub fn new() -> Result<Self> {
+        let mdns = ServiceDaemon::new()?;
+        let service_type = "_wot._tcp.local.".to_owned();
+        Ok(Self { mdns, service_type })
+    }
+
+    /// Returns an Stream of discovered things
+    pub fn stream(&self) -> Result<impl Stream<Item = Result<Thing>>> {
+        let receiver = self.mdns.browse(&self.service_type)?;
+
+        let s = receiver.into_stream().filter_map(|v| async move {
+            if let ServiceEvent::ServiceResolved(info) = v {
+                let t = get_thing(info).await;
+                Some(t)
+            } else {
+                None
+            }
+        });
+
+        Ok(s)
+    }
+}