wavekat-sip 0.1.0

//! Shared SIP endpoint: a bound UDP transport + the clean-room engine, with
//! inbound requests routed to new calls or auto-answered in-dialog.
//!
//! `SipEndpoint` owns the `Ua` (engine + router) and a
//! background task that drains inbound requests:
//!
//! - a brand-new `INVITE` (no `To` tag) becomes a [`crate::IncomingCall`] on
//!   the `next_incoming_call` stream;
//! - in-dialog requests (`BYE`, `OPTIONS`, `INFO`, re-`INVITE`) are
//!   auto-answered `200 OK`;
//! - the `ACK` for a 2xx is absorbed.

use std::collections::HashMap;
use std::net::{IpAddr, SocketAddr};
use std::sync::{Arc, Mutex as StdMutex};

use rsip::headers::ToTypedHeader;
use rsip::message::HeadersExt;
use rsip::{Method, Request, StatusCode};
use tokio::sync::{mpsc, Mutex};
use tokio_util::sync::CancellationToken;
use tracing::{debug, info, warn};

use crate::account::{SipAccount, Transport};
use crate::callee::IncomingCall;
use crate::inbound::InboundRequest;
use crate::resolve::resolve_sip_server;
use crate::sdp::parse_sdp;
use crate::stack::dialog::DialogId;
use crate::stack::response::build_response;
use crate::stack::transaction::{gen_tag, TransactionKey};
use crate::stack::ua::{Incoming, Ua};

type BoxError = Box<dyn std::error::Error + Send + Sync>;

/// Dialogs whose owning [`crate::Call`] has opted in to handle inbound
/// in-dialog requests itself, mapped to the channel that delivers them.
type DialogRegistry = Arc<StdMutex<HashMap<DialogId, mpsc::Sender<InboundRequest>>>>;

/// Confirmed dialogs whose owning [`crate::Call`] wants to be told when the
/// peer ends the call (an in-dialog `BYE`). The endpoint still auto-answers the
/// BYE `200 OK`; firing the token is how [`crate::Call::terminated`] resolves.
type TerminationRegistry = Arc<StdMutex<HashMap<DialogId, CancellationToken>>>;

/// A not-yet-accepted inbound INVITE, kept so a later `CANCEL` (which shares the
/// INVITE's branch, RFC 3261 §9.1) can `487` the INVITE transaction and notify
/// the waiting [`crate::IncomingCall`]. Keyed by the INVITE's transaction key.
struct PendingInvite {
    /// The original INVITE, needed to build the `487 Request Terminated`.
    invite: Request,
    /// Fired when a `CANCEL` for this INVITE arrives; surfaced as
    /// [`crate::IncomingCall::cancelled`].
    cancel: CancellationToken,
}

/// Inbound INVITEs awaiting an accept/reject decision, so a racing `CANCEL` can
/// terminate them. Keyed by the INVITE's transaction key.
type IncomingRegistry = Arc<StdMutex<HashMap<TransactionKey, PendingInvite>>>;

/// A bound SIP endpoint: the engine, plus inbound-call routing.
pub struct SipEndpoint {
    ua: Arc<Ua>,
    account: SipAccount,
    server: SocketAddr,
    local_ip: IpAddr,
    transport: Transport,
    cancel: CancellationToken,
    incoming_calls: Mutex<mpsc::Receiver<Incoming>>,
    /// Calls that have opted in to receive their dialog's re-INVITE / INFO.
    dialogs: DialogRegistry,
    /// Confirmed calls waiting to be told the peer hung up (in-dialog `BYE`).
    terminations: TerminationRegistry,
    /// Inbound INVITEs not yet accepted/rejected, for `CANCEL` handling.
    incoming_invites: IncomingRegistry,
}

impl SipEndpoint {
    /// Bind transport, start the engine, and begin routing inbound requests.
    ///
    /// The account's `server`/`port` are resolved (RFC 3263 subset) to the
    /// next-hop address all requests are sent to.
    pub async fn new(
        account: &SipAccount,
        cancel: CancellationToken,
    ) -> Result<Arc<Self>, BoxError> {
        Self::new_with_app(account, None, cancel).await
    }

    /// Like [`SipEndpoint::new`], but advertise `product` as the `User-Agent` on
    /// every outbound request (e.g. `"my-app/1.2.3"`). `None` emits no header.
    pub async fn new_with_app(
        account: &SipAccount,
        product: Option<&str>,
        cancel: CancellationToken,
    ) -> Result<Arc<Self>, BoxError> {
        let local_ip = detect_local_ip(account)?;
        let bind_addr = SocketAddr::new(local_ip, 0);
        info!("Binding SIP transport to {bind_addr}");

        let ua = Arc::new(
            Ua::bind_with_app(bind_addr, product.map(String::from), cancel.clone()).await?,
        );
        let server = resolve_sip_server(account)
            .await?
            .ok_or("could not resolve SIP server address")?;
        info!(%server, "resolved SIP server");

        let (calls_tx, calls_rx) = mpsc::channel(16);
        let dialogs: DialogRegistry = Arc::new(StdMutex::new(HashMap::new()));
        let terminations: TerminationRegistry = Arc::new(StdMutex::new(HashMap::new()));
        let incoming_invites: IncomingRegistry = Arc::new(StdMutex::new(HashMap::new()));
        let endpoint = Arc::new(Self {
            ua: ua.clone(),
            account: account.clone(),
            server,
            local_ip,
            transport: account.transport,
            cancel,
            incoming_calls: Mutex::new(calls_rx),
            dialogs: dialogs.clone(),
            terminations: terminations.clone(),
            incoming_invites: incoming_invites.clone(),
        });

        // Inbound router: new INVITE → calls stream; in-dialog re-INVITE / INFO
        // → the owning Call if it opted in, else auto-answer; BYE → fire the
        // owning Call's termination signal; CANCEL → 487 the pending INVITE.
        tokio::spawn(async move {
            let routing = Routing {
                dialogs,
                terminations,
                incoming_invites,
            };
            while let Some(inc) = ua.next_incoming().await {
                route_inbound(&ua, &routing, inc, &calls_tx).await;
            }
        });

        Ok(endpoint)
    }

    /// Register `id` to receive its dialog's inbound re-INVITE / INFO requests.
    /// Returns the channel they arrive on; until this is called (and while it
    /// stays registered) those requests are auto-answered `200 OK` instead.
    pub(crate) fn register_dialog(&self, id: DialogId) -> mpsc::Receiver<InboundRequest> {
        let (tx, rx) = mpsc::channel(16);
        if let Ok(mut map) = self.dialogs.lock() {
            map.insert(id, tx);
        }
        rx
    }

    /// Stop routing `id`'s inbound requests to a Call; they revert to being
    /// auto-answered.
    pub(crate) fn unregister_dialog(&self, id: &DialogId) {
        if let Ok(mut map) = self.dialogs.lock() {
            map.remove(id);
        }
    }

    /// Register `id` to be told when the peer ends the call (an in-dialog
    /// `BYE`). Returns a token the endpoint cancels on BYE; the BYE itself is
    /// still auto-answered. Called once per [`crate::Call`] at setup.
    pub(crate) fn register_termination(&self, id: DialogId) -> CancellationToken {
        let token = CancellationToken::new();
        if let Ok(mut map) = self.terminations.lock() {
            map.insert(id, token.clone());
        }
        token
    }

    /// Drop a dialog's termination registration (on [`crate::Call`] drop).
    pub(crate) fn unregister_termination(&self, id: &DialogId) {
        if let Ok(mut map) = self.terminations.lock() {
            map.remove(id);
        }
    }

    /// Register a not-yet-accepted inbound INVITE so a racing `CANCEL` can
    /// `487` it. Returns a token cancelled if that CANCEL arrives. Cleared by
    /// [`Self::unregister_incoming`] once the call is accepted or rejected.
    pub(crate) fn register_incoming(
        &self,
        key: TransactionKey,
        invite: Request,
    ) -> CancellationToken {
        let token = CancellationToken::new();
        if let Ok(mut map) = self.incoming_invites.lock() {
            map.insert(
                key,
                PendingInvite {
                    invite,
                    cancel: token.clone(),
                },
            );
        }
        token
    }

    /// Drop a pending-INVITE registration once it is accepted or rejected, so a
    /// late `CANCEL` no longer tries to `487` an answered call.
    pub(crate) fn unregister_incoming(&self, key: &TransactionKey) {
        if let Ok(mut map) = self.incoming_invites.lock() {
            map.remove(key);
        }
    }

    /// Local IP this endpoint is bound to.
    pub fn local_ip(&self) -> IpAddr {
        self.local_ip
    }

    /// Local socket address (IP + port) this endpoint is bound to.
    pub fn local_addr(&self) -> SocketAddr {
        self.ua.local_addr()
    }

    /// Transport this endpoint was bound for.
    pub fn transport(&self) -> Transport {
        self.transport
    }

    /// Stop the engine and free the socket.
    pub fn shutdown(&self) {
        self.cancel.cancel();
    }

    /// Await the next inbound call (a new `INVITE`). Returns `None` when the
    /// endpoint shuts down. Unparseable offers are skipped.
    pub async fn next_incoming_call(self: &Arc<Self>) -> Option<IncomingCall> {
        loop {
            let incoming = self.incoming_calls.lock().await.recv().await?;
            match parse_sdp(&incoming.request.body) {
                Ok(remote_media) => {
                    // Register the INVITE so a CANCEL before the call is
                    // accepted/rejected `487`s it and cancels this token.
                    let cancelled =
                        self.register_incoming(incoming.key.clone(), incoming.request.clone());
                    return Some(IncomingCall::new(
                        self.clone(),
                        incoming.key,
                        incoming.peer,
                        incoming.request,
                        remote_media,
                        cancelled,
                    ));
                }
                Err(e) => warn!(error = %e, "inbound INVITE has no usable SDP offer; skipping"),
            }
        }
    }

    pub(crate) fn ua(&self) -> &Ua {
        &self.ua
    }

    pub(crate) fn server(&self) -> SocketAddr {
        self.server
    }

    pub(crate) fn account(&self) -> &SipAccount {
        &self.account
    }
}

/// The registries the inbound router consults, bundled so the router signature
/// stays readable.
struct Routing {
    dialogs: DialogRegistry,
    terminations: TerminationRegistry,
    incoming_invites: IncomingRegistry,
}

/// Route one inbound request: new call, surface to a Call, auto-answer, fire a
/// termination, terminate a cancelled INVITE, or drop.
async fn route_inbound(
    ua: &Arc<Ua>,
    routing: &Routing,
    inc: Incoming,
    calls_tx: &mpsc::Sender<Incoming>,
) {
    let has_to_tag = inc
        .request
        .to_header()
        .ok()
        .and_then(|to| to.typed().ok())
        .map(|to| to.tag().is_some())
        .unwrap_or(false);

    match inc.request.method() {
        // A fresh INVITE (no dialog tag yet) is a new inbound call.
        Method::Invite if !has_to_tag => {
            let _ = calls_tx.send(inc).await;
        }
        // The ACK for a 2xx we sent: it confirms our dialog; nothing to reply.
        Method::Ack => debug!("absorbing 2xx ACK"),
        // In-dialog re-INVITE or INFO: hand to the owning Call if it opted in
        // to handle these (e.g. answer a session refresh, read INFO DTMF),
        // otherwise auto-answer so the peer's transaction still completes.
        Method::Invite | Method::Info => {
            let sender = DialogId::from_request(&inc.request).and_then(|id| {
                routing
                    .dialogs
                    .lock()
                    .ok()
                    .and_then(|map| map.get(&id).cloned())
            });
            match sender {
                Some(sender) => {
                    let req = InboundRequest::new(ua.clone(), inc.key, inc.request);
                    if sender.send(req).await.is_err() {
                        warn!("in-dialog request dropped: Call no longer listening");
                    }
                }
                None => auto_answer_200(ua, inc.key, &inc.request).await,
            }
        }
        // The peer ended the call: auto-answer the BYE, then fire the owning
        // Call's termination signal so `Call::terminated` resolves.
        Method::Bye => {
            let dialog_id = DialogId::from_request(&inc.request);
            auto_answer_200(ua, inc.key, &inc.request).await;
            let token = dialog_id.as_ref().and_then(|id| {
                routing
                    .terminations
                    .lock()
                    .ok()
                    .and_then(|map| map.get(id).cloned())
            });
            match token {
                Some(token) => {
                    info!(?dialog_id, "peer BYE — firing call termination");
                    token.cancel();
                }
                // A BYE we 200'd but couldn't tie to a live Call: the dialog
                // identity on the wire didn't match any registered termination,
                // so the owning Call never learns the peer hung up and its
                // consumer is left believing the call is still up. Log loudly —
                // this is the silent "stuck on the call screen after the far end
                // hangs up" failure, and the keys are what we need to see why the
                // match missed (e.g. a gateway tagging the BYE differently).
                None => {
                    let known: Vec<DialogId> = routing
                        .terminations
                        .lock()
                        .ok()
                        .map(|map| map.keys().cloned().collect())
                        .unwrap_or_default();
                    warn!(
                        ?dialog_id,
                        registered = ?known,
                        "peer BYE matched no live dialog — call will not tear down from this BYE"
                    );
                }
            }
        }
        // The peer cancelled a still-ringing inbound INVITE (RFC 3261 §9.2):
        // 200 the CANCEL, 487 the matching INVITE transaction, and notify the
        // waiting IncomingCall.
        Method::Cancel => {
            let invite_key = inc.key.invite_target();
            auto_answer_200(ua, inc.key, &inc.request).await;
            let pending = routing
                .incoming_invites
                .lock()
                .ok()
                .and_then(|mut map| map.remove(&invite_key));
            if let Some(pending) = pending {
                if let Some(resp) = build_response(
                    &pending.invite,
                    StatusCode::RequestTerminated,
                    Some(&gen_tag()),
                    None,
                    None,
                ) {
                    ua.answer(invite_key, resp).await;
                }
                debug!("peer CANCEL — 487ed the INVITE, notifying IncomingCall");
                pending.cancel.cancel();
            }
        }
        // Any other in-dialog request (OPTIONS / …): auto-answer so the peer's
        // transaction completes.
        _ => auto_answer_200(ua, inc.key, &inc.request).await,
    }
}

/// Auto-answer an inbound request `200 OK` (no body) on its transaction.
async fn auto_answer_200(ua: &Ua, key: TransactionKey, request: &Request) {
    if let Some(response) = build_response(request, StatusCode::OK, Some(&gen_tag()), None, None) {
        let _ = ua.answer(key, response).await;
    }
}

/// Detect the local IP that routes to the SIP server.
///
/// Opens a temporary UDP socket, connects to the server (no data sent), and
/// reads back the OS-chosen source address. Uses the OS resolver, not the
/// SRV-aware [`crate::resolve`] path: it only needs *a* route to pick a source
/// IP.
fn detect_local_ip(account: &SipAccount) -> Result<IpAddr, BoxError> {
    let dest = format!("{}:{}", account.server(), account.port());
    let sock = std::net::UdpSocket::bind("0.0.0.0:0")?;
    sock.connect(&dest)?;
    Ok(sock.local_addr()?.ip())
}

#[cfg(test)]
mod tests {
    use super::*;

    fn make_account(server: Option<&str>, port: Option<u16>) -> SipAccount {
        SipAccount {
            display_name: "Test".to_string(),
            username: "1001".to_string(),
            password: "secret".to_string(),
            domain: "localhost".to_string(),
            auth_username: None,
            server: server.map(|s| s.to_string()),
            port,
            transport: Transport::default(),
        }
    }

    #[test]
    fn detect_local_ip_returns_non_unspecified() {
        let account = make_account(Some("1.1.1.1"), Some(5060));
        let ip = detect_local_ip(&account).expect("detects a local ip");
        assert!(!ip.is_unspecified());
    }

    #[test]
    fn detect_local_ip_uses_server_field() {
        let account = make_account(Some("8.8.8.8"), Some(5060));
        assert!(detect_local_ip(&account).is_ok());
    }

    #[test]
    fn detect_local_ip_falls_back_to_domain() {
        // No explicit server → uses the domain (localhost resolves locally).
        let account = make_account(None, None);
        assert!(detect_local_ip(&account).is_ok());
    }
}