basic_graph.rs

//! A minimal durable graph: a whole-state agent/tool loop.
//!
//! Builds a [`GraphBuilder`] over `Update == State` with the overwrite reducer
//! (each node returns the full next state). The `agent` node appends an
//! assistant message and is wired with conditional edges: while `needs_tool` is
//! set the run routes to `tool`, otherwise it ends. The `tool` node appends a
//! tool result, clears the flag, and loops back to `agent`.
//!
//! Run with:
//!
//! ```text
//! cargo run --example basic_graph
//! ```

use tinyagents::graph::END;
use tinyagents::harness::message::Message;
use tinyagents::{GraphBuilder, NodeContext, NodeResult, Result};

#[derive(Clone, Debug)]
struct AgentState {
 messages: Vec<Message>,
 needs_tool: bool,
}

#[tokio::main]
async fn main() -> Result<()> {
 let graph = GraphBuilder::<AgentState, AgentState>::overwrite()
 .add_node(
 "agent",
 |mut state: AgentState, _ctx: NodeContext| async move {
 state
 .messages
 .push(Message::assistant("I should check the local tool."));
 Ok(NodeResult::Update(state))
 },
 )
 .add_node(
 "tool",
 |mut state: AgentState, _ctx: NodeContext| async move {
 state
 .messages
 .push(Message::tool("echo", "tool result: hello from tinyagents"));
 state.needs_tool = false;
 // A whole-state continue: the static edge `tool -> agent` routes us.
 Ok(NodeResult::Update(state))
 },
 )
 .set_entry("agent")
 .add_conditional_edges(
 "agent",
 |state: &AgentState| {
 if state.needs_tool {
 "tool".to_string()
 } else {
 "done".to_string()
 }
 },
 [("tool", "tool"), ("done", END)],
 )
 .add_edge("tool", "agent")
 .compile()?;

 let run = graph
 .run(AgentState {
 messages: vec![Message::user("Can you use a tool?")],
 needs_tool: true,
 })
 .await?;

 for message in &run.state.messages {
 let role = match message {
 Message::System(_) => "system",
 Message::User(_) => "user",
 Message::Assistant(_) => "assistant",
 Message::Tool(_) => "tool",
 };
 println!("{role}: {}", message.text());
 }
 println!("visited: {:?}", run.visited);

 Ok(())
}