bitrouter 1.0.0-alpha.34

//! The wire half of the session's effects — the one interpreter every loop
//! shares.
//!
//! The reducer in `bitrouter_tui::machine` names what a session does as an
//! [`Effect`]; some of those are the view's and some are the wire's. The
//! piped loop and the headless `acp prompt` loop used to each hand-roll the
//! wire half — copies of "remove the request, resolve it" and "cancel, then
//! deny what is outstanding". `Wire` is that half, written once, so a policy
//! answer reaches the agent consistently on both surfaces.
//!
//! What it reaches is the ACP client and nothing else. The daemon bridges the
//! launch half builds, the config, the metering store — none of it is named
//! here, and the guard in [`crate::chat`] scans this file to keep it so.

use std::collections::HashMap;

use bitrouter_sdk::acp::client::{AcpClient, PendingPermission};
use bitrouter_tui::machine::Effect;
use bitrouter_tui::permission::{Decision, Policy, Prompt};

/// The session's wire, and the requests it is holding open.
pub(crate) struct Wire<'a> {
    client: &'a AcpClient,
    session_id: &'a str,
    /// Requests admitted and not yet answered, keyed the way the machine
    /// routes answers. Entries are **removed** when answered: a retained entry
    /// holds a strong handle on the resolver, and the client's ledger holds a
    /// weak one on purpose so that a dropped request still denies itself.
    outstanding: HashMap<String, PendingPermission>,
}

impl<'a> Wire<'a> {
    /// A wire over one client and one harness-native session.
    pub(crate) fn new(client: &'a AcpClient, session_id: &'a str) -> Self {
        Self {
            client,
            session_id,
            outstanding: HashMap::new(),
        }
    }

    /// Hold a request open and hand back the prompt it is drawn and answered
    /// as. The tool kind rides along: it is the only classification the wire
    /// carries, and a headless policy reads it.
    pub(crate) fn admit(&mut self, request: PendingPermission) -> Prompt {
        let prompt = Prompt::new(
            request.request_id.clone(),
            request.tool_call.fields.title.clone(),
            request.tool_call.tool_call_id.0.to_string(),
            request.tool_call.fields.kind,
            request.options.clone(),
        );
        self.outstanding.insert(request.request_id.clone(), request);
        prompt
    }

    /// Answer a request the way a headless policy says to, on the spot.
    ///
    /// Returns the decision the agent heard and the prompt, so the caller can
    /// say what was decided and count it. The answer goes through
    /// [`Wire::apply`] like a keystroke's would.
    pub(crate) async fn answer(
        &mut self,
        request: PendingPermission,
        policy: &Policy,
    ) -> (Decision, Prompt) {
        let prompt = self.admit(request);
        let (decision, effect) = bitrouter_tui::machine::decide(policy, &prompt);
        // `decide` only ever produces a `Resolve`, which `apply` consumes.
        let _ = self.apply(effect).await;
        (decision, prompt)
    }

    /// Run the effect if it is the wire's. Returns it untouched if it is not,
    /// for whoever owns the view.
    pub(crate) async fn apply(&mut self, effect: Effect) -> Option<Effect> {
        match effect {
            Effect::Resolve { id, outcome } => {
                if let Some(request) = self.outstanding.remove(&id) {
                    request.resolve(outcome);
                }
            }
            Effect::Cancel => {
                // Tell the agent, not merely ourselves: dropping the turn
                // future stops this side waiting and leaves the agent working.
                let told = self.client.cancel(self.session_id).await;
                // And leave no question hanging. The machine has already
                // answered whatever it was holding; this answers anything the
                // client emitted that never reached it — while the connection
                // is still live, rather than at teardown.
                self.outstanding.clear();
                self.client.deny_session_permissions(self.session_id);
                if let Err(error) = told {
                    tracing::warn!(%error, "cancelling the turn");
                }
            }
            other => return Some(other),
        }
        None
    }
}