graph.ts

/**
 * Starter LangGraph.js Template
 * Make this code your own!
 */
import { StateGraph } from "@langchain/langgraph";
import { RunnableConfig } from "@langchain/core/runnables";
import { StateAnnotation } from "./state.js";

/**
 * Define a node, these do the work of the graph and should have most of the logic.
 * Must return a subset of the properties set in StateAnnotation.
 * @param state The current state of the graph.
 * @param config Extra parameters passed into the state graph.
 * @returns Some subset of parameters of the graph state, used to update the state
 * for the edges and nodes executed next.
 */
const callModel = async (
  state: typeof StateAnnotation.State,
  _config: RunnableConfig,
): Promise<typeof StateAnnotation.Update> => {
  /**
   * Do some work... (e.g. call an LLM)
   * For example, with LangChain you could do something like:
   *
   * ```bash
   * $ npm i @langchain/anthropic
   * ```
   *
   * ```ts
   * import { ChatAnthropic } from "@langchain/anthropic";
   * const model = new ChatAnthropic({
   *   model: "claude-3-5-sonnet-20240620",
   *   apiKey: process.env.ANTHROPIC_API_KEY,
   * });
   * const res = await model.invoke(state.messages);
   * ```
   *
   * Or, with an SDK directly:
   *
   * ```bash
   * $ npm i openai
   * ```
   *
   * ```ts
   * import OpenAI from "openai";
   * const openai = new OpenAI({
   *   apiKey: process.env.OPENAI_API_KEY,
   * });
   *
   * const chatCompletion = await openai.chat.completions.create({
   *   messages: [{
   *     role: state.messages[0]._getType(),
   *     content: state.messages[0].content,
   *   }],
   *   model: "gpt-4o-mini",
   * });
   * ```
   */
  console.log("Current state:", state);
  return {
    messages: [
      {
        role: "assistant",
        content: `Hi there! How are you?`,
      },
    ],
  };
};

/**
 * Routing function: Determines whether to continue research or end the builder.
 * This function decides if the gathered information is satisfactory or if more research is needed.
 *
 * @param state - The current state of the research builder
 * @returns Either "callModel" to continue research or END to finish the builder
 */
export const route = (
  state: typeof StateAnnotation.State,
): "__end__" | "callModel" => {
  if (state.messages.length > 0) {
    return "__end__";
  }
  // Loop back
  return "callModel";
};

// Finally, create the graph itself.
const builder = new StateGraph(StateAnnotation)
  // Add the nodes to do the work.
  // Chaining the nodes together in this way
  // updates the types of the StateGraph instance
  // so you have static type checking when it comes time
  // to add the edges.
  .addNode("callModel", callModel)
  // Regular edges mean "always transition to node B after node A is done"
  // The "__start__" and "__end__" nodes are "virtual" nodes that are always present
  // and represent the beginning and end of the builder.
  .addEdge("__start__", "callModel")
  // Conditional edges optionally route to different nodes (or end)
  .addConditionalEdges("callModel", route);

export const graph = builder.compile();

graph.name = "New Agent";