a3s-code-core 2.0.1

//! SubAgent wrapper — executes a real AgentSession and forwards events to the
//! Orchestrator event bus, with pause/resume/cancel control signal support.

use crate::agent::AgentEvent;
use crate::error::Result;
use crate::orchestrator::{
    ControlSignal, OrchestratorEvent, SubAgentActivity, SubAgentConfig, SubAgentState,
};
use std::sync::Arc;
use tokio::sync::{broadcast, mpsc, RwLock};

struct PendingToolCall {
    id: String,
    name: String,
    args_buffer: String,
    started_at: std::time::Instant,
    emitted: bool,
}

fn parse_tool_args(raw: &str) -> serde_json::Value {
    let trimmed = raw.trim();
    if trimmed.is_empty() {
        serde_json::Value::Null
    } else {
        serde_json::from_str(trimmed)
            .unwrap_or_else(|_| serde_json::Value::String(trimmed.to_string()))
    }
}

fn tool_duration_ms(started_at: std::time::Instant) -> u64 {
    std::cmp::max(1, started_at.elapsed().as_millis() as u64)
}

pub(crate) struct SubAgentWrapper {
    id: String,
    config: SubAgentConfig,
    agent: Arc<crate::Agent>,
    event_tx: broadcast::Sender<OrchestratorEvent>,
    subagent_event_tx: broadcast::Sender<OrchestratorEvent>,
    event_history: Arc<RwLock<std::collections::VecDeque<OrchestratorEvent>>>,
    control_rx: mpsc::Receiver<ControlSignal>,
    state: Arc<RwLock<SubAgentState>>,
    activity: Arc<RwLock<SubAgentActivity>>,
}

impl SubAgentWrapper {
    #[allow(clippy::too_many_arguments)]
    pub(crate) fn new(
        id: String,
        config: SubAgentConfig,
        agent: Arc<crate::Agent>,
        event_tx: broadcast::Sender<OrchestratorEvent>,
        subagent_event_tx: broadcast::Sender<OrchestratorEvent>,
        event_history: Arc<RwLock<std::collections::VecDeque<OrchestratorEvent>>>,
        control_rx: mpsc::Receiver<ControlSignal>,
        state: Arc<RwLock<SubAgentState>>,
        activity: Arc<RwLock<SubAgentActivity>>,
    ) -> Self {
        Self {
            id,
            config,
            agent,
            event_tx,
            subagent_event_tx,
            event_history,
            control_rx,
            state,
            activity,
        }
    }

    async fn emit(&self, event: OrchestratorEvent) {
        let _ = self.event_tx.send(event.clone());
        let _ = self.subagent_event_tx.send(event.clone());

        let mut history = self.event_history.write().await;
        history.push_back(event);
        while history.len() > 1024 {
            history.pop_front();
        }
    }

    async fn flush_tool_start(
        &self,
        pending_tool: &mut Option<PendingToolCall>,
    ) -> std::time::Instant {
        let pending = pending_tool
            .as_mut()
            .expect("flush_tool_start called without a pending tool");
        if pending.emitted {
            return pending.started_at;
        }

        let args = parse_tool_args(&pending.args_buffer);
        self.emit(OrchestratorEvent::ToolExecutionStarted {
            id: self.id.clone(),
            tool_id: pending.id.clone(),
            tool_name: pending.name.clone(),
            args: args.clone(),
        })
        .await;

        *self.activity.write().await = SubAgentActivity::CallingTool {
            tool_name: pending.name.clone(),
            args,
        };
        pending.emitted = true;
        pending.started_at
    }

    /// Run the SubAgent against the configured real Agent.
    pub(crate) async fn execute(mut self) -> Result<String> {
        self.update_state(SubAgentState::Running).await;
        let start = std::time::Instant::now();

        let agent = Arc::clone(&self.agent);
        let result = self.execute_with_agent(agent).await;

        let duration_ms = start.elapsed().as_millis() as u64;

        match &result {
            Ok(output) => {
                self.update_state(SubAgentState::Completed {
                    success: true,
                    output: output.clone(),
                })
                .await;
                self.emit(OrchestratorEvent::SubAgentCompleted {
                    id: self.id.clone(),
                    success: true,
                    output: output.clone(),
                    duration_ms,
                    token_usage: None,
                })
                .await;
            }
            Err(e) => {
                let current = self.state.read().await.clone();
                if !matches!(current, SubAgentState::Cancelled) {
                    self.update_state(SubAgentState::Error {
                        message: e.to_string(),
                    })
                    .await;
                }
                self.emit(OrchestratorEvent::SubAgentCompleted {
                    id: self.id.clone(),
                    success: false,
                    output: e.to_string(),
                    duration_ms,
                    token_usage: None,
                })
                .await;
            }
        }

        result
    }

    // -------------------------------------------------------------------------
    // Real execution via AgentSession
    // -------------------------------------------------------------------------

    async fn execute_with_agent(&mut self, agent: Arc<crate::Agent>) -> Result<String> {
        // Build an AgentRegistry from built-ins + extra agent_dirs.
        let registry = crate::subagent::AgentRegistry::new();
        for dir in &self.config.agent_dirs {
            let agents = crate::subagent::load_agents_from_dir(std::path::Path::new(dir));
            for def in agents {
                registry.register(def);
            }
        }

        // Build session options from SubAgentConfig fields.
        let mut opts = crate::SessionOptions::new();

        // Pass agent_dirs and skill_dirs to session options
        for dir in &self.config.agent_dirs {
            opts = opts.with_agent_dir(dir.as_str());
        }
        if !self.config.skill_dirs.is_empty() {
            opts = opts.with_skill_dirs(self.config.skill_dirs.iter().map(|s| s.as_str()));
        }

        if let Some(steps) = self.config.max_steps {
            opts = opts.with_max_tool_rounds(steps);
        }
        // Create session: use the named agent definition if found, otherwise
        // fall back to a plain session so unknown agent_types still work.
        let session = Arc::new(if let Some(def) = registry.get(&self.config.agent_type) {
            agent.session_for_agent(&self.config.workspace, &def, Some(opts))?
        } else {
            agent.session(&self.config.workspace, Some(opts))?
        });

        // Stream execution.
        let (mut rx, _task) = session.stream(&self.config.prompt, None).await?;

        let mut output = String::new();
        let mut step: usize = 0;
        let mut pending_tool: Option<PendingToolCall> = None;

        loop {
            // Drain pending control signals before each event.
            while let Ok(signal) = self.control_rx.try_recv() {
                self.handle_control_signal(signal).await?;
            }

            // Abort if cancelled.
            if matches!(*self.state.read().await, SubAgentState::Cancelled) {
                // Drop rx to signal the background streaming task to stop.
                drop(rx);
                return Err(anyhow::anyhow!("Cancelled by orchestrator").into());
            }

            // Wait while paused (backpressure on rx naturally slows the agent).
            while matches!(*self.state.read().await, SubAgentState::Paused) {
                *self.activity.write().await = SubAgentActivity::WaitingForControl {
                    reason: "Paused by orchestrator".to_string(),
                };
                tokio::time::sleep(tokio::time::Duration::from_millis(50)).await;
                while let Ok(signal) = self.control_rx.try_recv() {
                    self.handle_control_signal(signal).await?;
                }
                if matches!(*self.state.read().await, SubAgentState::Cancelled) {
                    drop(rx);
                    return Err(anyhow::anyhow!("Cancelled by orchestrator").into());
                }
            }

            // Consume the next agent event.
            match rx.recv().await {
                Some(AgentEvent::TurnStart { turn }) => {
                    *self.activity.write().await =
                        SubAgentActivity::RequestingLlm { message_count: 0 };
                    self.emit(OrchestratorEvent::SubAgentInternalEvent {
                        id: self.id.clone(),
                        event: AgentEvent::TurnStart { turn },
                    })
                    .await;
                }
                Some(AgentEvent::ToolStart { id, name }) => {
                    pending_tool = Some(PendingToolCall {
                        id,
                        name,
                        args_buffer: String::new(),
                        started_at: std::time::Instant::now(),
                        emitted: false,
                    });
                }
                Some(AgentEvent::ToolInputDelta { delta }) => {
                    if let Some(pending) = pending_tool.as_mut() {
                        pending.args_buffer.push_str(&delta);
                    }
                    self.emit(OrchestratorEvent::SubAgentInternalEvent {
                        id: self.id.clone(),
                        event: AgentEvent::ToolInputDelta { delta },
                    })
                    .await;
                }
                Some(AgentEvent::ToolEnd {
                    id,
                    name,
                    output: tool_out,
                    exit_code,
                    ..
                }) => {
                    step += 1;
                    let started_at =
                        if pending_tool.as_ref().map(|p| p.id.as_str()) == Some(id.as_str()) {
                            self.flush_tool_start(&mut pending_tool).await
                        } else {
                            std::time::Instant::now()
                        };
                    *self.activity.write().await = SubAgentActivity::Idle;
                    self.emit(OrchestratorEvent::ToolExecutionCompleted {
                        id: self.id.clone(),
                        tool_id: id,
                        tool_name: name,
                        result: tool_out,
                        exit_code,
                        duration_ms: tool_duration_ms(started_at),
                    })
                    .await;
                    pending_tool = None;
                    self.emit(OrchestratorEvent::SubAgentProgress {
                        id: self.id.clone(),
                        step,
                        total_steps: self.config.max_steps.unwrap_or(0),
                        message: format!("Completed tool call {step}"),
                    })
                    .await;
                }
                Some(AgentEvent::TextDelta { text }) => {
                    if pending_tool.is_some() {
                        self.flush_tool_start(&mut pending_tool).await;
                    }
                    output.push_str(&text);
                    self.emit(OrchestratorEvent::SubAgentInternalEvent {
                        id: self.id.clone(),
                        event: AgentEvent::TextDelta { text },
                    })
                    .await;
                }
                Some(AgentEvent::End { text, .. }) => {
                    if pending_tool.is_some() {
                        self.flush_tool_start(&mut pending_tool).await;
                    }
                    output = text;
                    break;
                }
                Some(AgentEvent::Error { message }) => {
                    return Err(anyhow::anyhow!("Agent error: {message}").into());
                }
                // Forward all other events as internal events for observability.
                Some(event) => {
                    if pending_tool.is_some() {
                        self.flush_tool_start(&mut pending_tool).await;
                    }
                    self.emit(OrchestratorEvent::SubAgentInternalEvent {
                        id: self.id.clone(),
                        event,
                    })
                    .await;
                }
                None => break, // stream closed
            }
        }

        Ok(output)
    }

    async fn handle_control_signal(&mut self, signal: ControlSignal) -> Result<()> {
        self.emit(OrchestratorEvent::ControlSignalReceived {
            id: self.id.clone(),
            signal: signal.clone(),
        })
        .await;

        let result = match signal {
            ControlSignal::Pause => {
                self.update_state(SubAgentState::Paused).await;
                Ok(())
            }
            ControlSignal::Resume => {
                self.update_state(SubAgentState::Running).await;
                Ok(())
            }
            ControlSignal::Cancel => {
                self.update_state(SubAgentState::Cancelled).await;
                Err(anyhow::anyhow!("Cancelled by orchestrator").into())
            }
            ControlSignal::AdjustParams { max_steps, .. } => {
                if let Some(steps) = max_steps {
                    self.config.max_steps = Some(steps);
                }
                Ok(())
            }
            ControlSignal::InjectPrompt { ref prompt } => {
                // Append the injected prompt so the next LLM turn sees it.
                self.config.prompt.push('\n');
                self.config.prompt.push_str(prompt);
                Ok(())
            }
        };

        self.emit(OrchestratorEvent::ControlSignalApplied {
            id: self.id.clone(),
            signal,
            success: result.is_ok(),
            error: result.as_ref().err().map(|e| format!("{e}")),
        })
        .await;

        result
    }

    async fn update_state(&self, new_state: SubAgentState) {
        let old_state = {
            let mut state = self.state.write().await;
            let old = state.clone();
            *state = new_state.clone();
            old
        };

        self.emit(OrchestratorEvent::SubAgentStateChanged {
            id: self.id.clone(),
            old_state,
            new_state,
        })
        .await;
    }
}

#[cfg(test)]
mod tests {
    use super::{parse_tool_args, tool_duration_ms};
    use serde_json::json;
    use std::time::{Duration, Instant};

    #[test]
    fn parse_tool_args_parses_json_object() {
        assert_eq!(
            parse_tool_args(r#"{"path":"README.md"}"#),
            json!({"path": "README.md"})
        );
    }

    #[test]
    fn parse_tool_args_returns_null_for_empty_input() {
        assert_eq!(parse_tool_args("   "), serde_json::Value::Null);
    }

    #[test]
    fn parse_tool_args_preserves_non_json_input_as_string() {
        assert_eq!(
            parse_tool_args(r#"{"path":"README.md""#),
            serde_json::Value::String(r#"{"path":"README.md""#.to_string())
        );
    }

    #[test]
    fn tool_duration_ms_has_one_millisecond_floor() {
        let started_at = Instant::now();
        assert_eq!(tool_duration_ms(started_at), 1);
    }

    #[test]
    fn tool_duration_ms_preserves_elapsed_milliseconds() {
        let started_at = Instant::now() - Duration::from_millis(12);
        assert!(tool_duration_ms(started_at) >= 12);
    }
}