adk_agent/workflow/
conditional_agent.rs

1//! Rule-based conditional routing agent.
2//!
3//! `ConditionalAgent` provides **synchronous, rule-based** conditional routing.
4//! The condition function is evaluated synchronously and must return a boolean.
5//!
6//! # When to Use
7//!
8//! Use `ConditionalAgent` for **deterministic** routing decisions:
9//! - A/B testing based on session state or flags
10//! - Environment-based routing (e.g., production vs staging)
11//! - Feature flag checks
12//!
13//! # For Intelligent Routing
14//!
15//! If you need **LLM-based intelligent routing** where the model classifies
16//! user intent and routes accordingly, use [`LlmConditionalAgent`] instead:
17//!
18//! ```rust,ignore
19//! // LLM decides which agent to route to
20//! let router = LlmConditionalAgent::new("router", model)
21//!     .instruction("Classify as 'technical' or 'general'")
22//!     .route("technical", tech_agent)
23//!     .route("general", general_agent)
24//!     .build()?;
25//! ```
26//!
27//! See [`crate::workflow::LlmConditionalAgent`] for details.
28
29use adk_core::{
30    AfterAgentCallback, Agent, BeforeAgentCallback, EventStream, InvocationContext, Result,
31};
32use async_trait::async_trait;
33use std::sync::Arc;
34
35type ConditionFn = Box<dyn Fn(&dyn InvocationContext) -> bool + Send + Sync>;
36
37/// Rule-based conditional routing agent.
38///
39/// Executes one of two sub-agents based on a synchronous condition function.
40/// For LLM-based intelligent routing, use [`LlmConditionalAgent`] instead.
41///
42/// # Example
43///
44/// ```rust,ignore
45/// // Route based on session state flag
46/// let router = ConditionalAgent::new(
47///     "premium_router",
48///     |ctx| ctx.session().state().get("is_premium").map(|v| v.as_bool()).flatten().unwrap_or(false),
49///     Arc::new(premium_agent),
50/// ).with_else(Arc::new(basic_agent));
51/// ```
52pub struct ConditionalAgent {
53    name: String,
54    description: String,
55    condition: ConditionFn,
56    if_agent: Arc<dyn Agent>,
57    else_agent: Option<Arc<dyn Agent>>,
58    before_callbacks: Vec<BeforeAgentCallback>,
59    after_callbacks: Vec<AfterAgentCallback>,
60}
61
62impl ConditionalAgent {
63    pub fn new<F>(name: impl Into<String>, condition: F, if_agent: Arc<dyn Agent>) -> Self
64    where
65        F: Fn(&dyn InvocationContext) -> bool + Send + Sync + 'static,
66    {
67        Self {
68            name: name.into(),
69            description: String::new(),
70            condition: Box::new(condition),
71            if_agent,
72            else_agent: None,
73            before_callbacks: Vec::new(),
74            after_callbacks: Vec::new(),
75        }
76    }
77
78    pub fn with_description(mut self, desc: impl Into<String>) -> Self {
79        self.description = desc.into();
80        self
81    }
82
83    pub fn with_else(mut self, else_agent: Arc<dyn Agent>) -> Self {
84        self.else_agent = Some(else_agent);
85        self
86    }
87
88    pub fn before_callback(mut self, callback: BeforeAgentCallback) -> Self {
89        self.before_callbacks.push(callback);
90        self
91    }
92
93    pub fn after_callback(mut self, callback: AfterAgentCallback) -> Self {
94        self.after_callbacks.push(callback);
95        self
96    }
97}
98
99#[async_trait]
100impl Agent for ConditionalAgent {
101    fn name(&self) -> &str {
102        &self.name
103    }
104
105    fn description(&self) -> &str {
106        &self.description
107    }
108
109    fn sub_agents(&self) -> &[Arc<dyn Agent>] {
110        &[]
111    }
112
113    async fn run(&self, ctx: Arc<dyn InvocationContext>) -> Result<EventStream> {
114        let agent = if (self.condition)(ctx.as_ref()) {
115            self.if_agent.clone()
116        } else if let Some(else_agent) = &self.else_agent {
117            else_agent.clone()
118        } else {
119            return Ok(Box::pin(futures::stream::empty()));
120        };
121
122        agent.run(ctx).await
123    }
124}
adk_agent/workflow/conditional_agent.rs

adk_agent/workflow/
conditional_agent.rs
