//! Outgoing core calls and notification callbacks.
use super::*;
/// Removes a dropped call's local routing state, without cancelling host work.
struct PendingCall(u64);
impl Drop for PendingCall {
    fn drop(&mut self) {
        let pending = STATE.with(|s| s.borrow_mut().pending.remove(&self.0));
        if let Some(mut pending) = pending {
            // A lock may still be granted: release it when its late response arrives.
            if let Some(lease) = pending.unlock.take() {
                STATE.with(|s| s.borrow_mut().abandoned_locks.insert(self.0, lease));
            }
            // Drop user-owned callback captures outside the STATE borrow.
        }
    }
}
/// An outgoing request builder.
#[must_use = "await the call to send it"]
pub struct Call {
    method: String,
    params: Value,
    detach: bool,
    notify: Option<Notify>,
    pub(super) unlock: Option<std::rc::Rc<Lease>>,
}
/// Build an outgoing call with object parameters.
pub fn call(method: impl Into<String>, params: impl serde::Serialize) -> Call {
    Call {
        method: method.into(),
        params: serde_json::to_value(params).expect("serializable params"),
        detach: false,
        notify: None,
        unlock: None,
    }
}
impl Call {
    /// Detach the child process from its caller.
    pub fn detach(mut self) -> Self {
        self.detach = true;
        self
    }
    /// Receive progress notifications before the result arrives.
    /// Dropping the call future removes its local pending entry and callback;
    /// later notifications and responses are ignored. It does not cancel host work.
    ///
    /// For `core.watch`, poll the call future alongside work in the handler, then
    /// drop it when the handler returns. Do not put it in `background()` just to
    /// keep the watch alive: background tasks keep the process alive, while the
    /// watch only ends when the process ends. Dropping the future does not cancel
    /// the host watch, but it lets an otherwise idle process exit normally. A
    /// long-lived service should keep one watch per purpose for its lifetime,
    /// rather than repeatedly opening and dropping watches on the host.
    ///
    /// Scan only after `armed`, and rescan on `changed`. Events may coalesce, but
    /// are not rate-limited: watch the narrowest useful path to avoid rescanning
    /// for unrelated writes (for example, watch a mailbox, not all session data).
    /// Do not use endpoint connect retries to wait for file publication.
    pub fn on_notify(mut self, f: impl FnMut(&str, Value) + 'static) -> Self {
        self.notify = Some(Box::new(f));
        self
    }
}
impl IntoFuture for Call {
    type Output = Result<Value>;
    type IntoFuture = LocalBoxFuture<'static, Self::Output>;
    fn into_future(self) -> Self::IntoFuture {
        Box::pin(async move {
            if !self.params.is_object() {
                return Err(Error::params_not_object(&self.params));
            }
            let (tx, rx) = oneshot::channel();
            let id = STATE.with(|s| {
                let mut s = s.borrow_mut();
                if !s.active || s.stopping {
                    return Err(Error::new(
                        -32000,
                        "no core transport (or stdin reached EOF)",
                    ));
                }
                s.next += 1;
                let id = s.next;
                s.pending.insert(
                    id,
                    Pending {
                        tx,
                        notify: self.notify,
                        unlock: self.unlock,
                    },
                );
                Ok(id)
            })?;
            let _pending = PendingCall(id);
            let (method, params) = if self.detach {
                (
                    "core.call".to_string(),
                    json!({"method":self.method,"params":self.params,"detach":true}),
                )
            } else {
                (self.method, self.params)
            };
            if let Err(e) = send(json!({"jsonrpc":"2.0","id":id,"method":method,"params":params})) {
                let pending = STATE.with(|s| s.borrow_mut().pending.remove(&id));
                drop(pending);
                return Err(e);
            }
            rx.await
                .unwrap_or_else(|_| Err(Error::new(-32000, "core transport closed")))
        })
    }
}

#[cfg(test)]
mod tests {
    use super::{STATE, State, block_on, call, clear_pending, lock, receive};
    use crate::Result;
    use futures::{FutureExt, future::LocalBoxFuture};
    use serde_json::{Value, json};
    use std::{cell::RefCell, future::IntoFuture, rc::Rc, task::Context};

    fn activate() {
        STATE.with(|s| {
            *s.borrow_mut() = State {
                active: true,
                ..State::default()
            };
        });
    }
    fn start(
        mut call: LocalBoxFuture<'static, Result<Value>>,
    ) -> (u64, LocalBoxFuture<'static, Result<Value>>) {
        assert!(
            call.as_mut()
                .poll(&mut Context::from_waker(std::task::Waker::noop()))
                .is_pending()
        );
        (STATE.with(|s| s.borrow().next), call)
    }
    fn notification(id: u64, name: &str) {
        receive(json!({"method":"core.notify","params":{"call":id,"name":name,"params":{}}}));
    }
    fn response(id: u64, result: Value) {
        receive(json!({"id":id,"result":result}));
    }

    #[test]
    fn dropped_call_removes_pending_and_callback() {
        activate();
        let events = Rc::new(RefCell::new(Vec::new()));
        let captured = events.clone();
        let (id, future) = start(
            call("core.watch", json!({"path":"/mailbox"}))
                .on_notify(move |name, _| captured.borrow_mut().push(name.to_owned()))
                .into_future(),
        );
        notification(id, "armed");
        assert_eq!(&*events.borrow(), &["armed"]);
        assert_eq!(Rc::strong_count(&events), 2);
        drop(future);
        STATE.with(|s| {
            assert!(s.borrow().pending.is_empty());
            assert!(s.borrow().abandoned_locks.is_empty());
        });
        assert_eq!(Rc::strong_count(&events), 1);
        notification(id, "changed");
        response(id, Value::Null);
        receive(json!({"id":id,"error":{"code":-32000,"message":"late error"}}));
        assert_eq!(&*events.borrow(), &["armed"]);
    }

    #[test]
    fn kept_watch_delivers_until_result() {
        activate();
        let events = Rc::new(RefCell::new(Vec::new()));
        let captured = events.clone();
        let (id, future) = start(
            call("core.watch", json!({"path":"/mailbox"}))
                .on_notify(move |name, _| captured.borrow_mut().push(name.to_owned()))
                .into_future(),
        );
        notification(id, "armed");
        notification(id, "changed");
        notification(id, "changed");
        response(id, json!({"done":true}));
        assert_eq!(block_on(future).unwrap(), json!({"done":true}));
        notification(id, "late");
        assert_eq!(&*events.borrow(), &["armed", "changed", "changed"]);
        STATE.with(|s| assert!(s.borrow().pending.is_empty()));
        assert_eq!(Rc::strong_count(&events), 1);
    }

    #[test]
    fn callback_can_drop_its_own_call_without_being_restored() {
        activate();
        let holder = Rc::new(RefCell::new(None));
        let captured = holder.clone();
        let (id, future) = start(
            call("core.watch", json!({"path":"/mailbox"}))
                .on_notify(move |_, _| {
                    // Panics on a second invocation; the first must remove the entry.
                    drop(captured.borrow_mut().take().expect("live call"));
                })
                .into_future(),
        );
        *holder.borrow_mut() = Some(future);
        notification(id, "armed");
        STATE.with(|s| assert!(s.borrow().pending.is_empty()));
        notification(id, "changed");
        response(id, Value::Null);
        assert_eq!(Rc::strong_count(&holder), 1);
    }

    #[test]
    fn eof_cleanup_can_drop_callback_owned_futures() {
        activate();
        let holder = Rc::new(RefCell::new(None));
        let weak = Rc::downgrade(&holder);
        let captured = holder.clone();
        let (_, future) = start(
            call("core.watch", json!({"path":"/mailbox"}))
                .on_notify(move |_, _| {
                    let _ = &captured;
                })
                .into_future(),
        );
        *holder.borrow_mut() = Some(future);
        drop(holder);
        STATE.with(|s| s.borrow_mut().stopping = true);
        clear_pending();
        assert!(weak.upgrade().is_none());
        STATE.with(|s| assert!(s.borrow().pending.is_empty()));
    }

    #[test]
    fn unpolled_call_never_registers() {
        activate();
        drop(call("core.watch", json!({"path":"/mailbox"})).into_future());
        STATE.with(|s| {
            assert!(s.borrow().pending.is_empty());
            assert_eq!(s.borrow().next, 0);
        });
    }

    #[test]
    fn dropped_lock_keeps_only_late_grant_cleanup() {
        activate();
        let (id, future) = start(
            lock("/late")
                .into_future()
                .map(|r| r.map(|_| Value::Null))
                .boxed_local(),
        );
        drop(future);
        STATE.with(|s| {
            assert!(s.borrow().pending.is_empty());
            assert_eq!(s.borrow().abandoned_locks.len(), 1);
        });
        notification(id, "ignored");
        response(id, json!({"held":true}));
        STATE.with(|s| assert!(s.borrow().abandoned_locks.is_empty()));
    }
}