LangGraph로 사고하기

import { StateGraph, START, END, Command } from "@langchain/langgraph";
import { HumanMessage } from "@langchain/core/messages";
import { ChatAnthropic } from "@langchain/anthropic";

const llm = new ChatAnthropic({ model: "claude-sonnet-4-5" });

async function readEmail(state: EmailAgentStateType) {
// Extract and parse email content
// In production, this would connect to your email service
console.log(`Processing email: ${state.emailContent}`);
return {};
}

async function classifyIntent(state: EmailAgentStateType) {
// Use LLM to classify email intent and urgency, then route accordingly

// Create structured LLM that returns EmailClassification object
const structuredLlm = llm.withStructuredOutput(EmailClassificationSchema);

// Format the prompt on-demand, not stored in state
const classificationPrompt = `
Analyze this customer email and classify it:

Email: ${state.emailContent}
From: ${state.senderEmail}

Provide classification including intent, urgency, topic, and summary.
`;

// Get structured response directly as object
const classification = await structuredLlm.invoke(classificationPrompt);

// Determine next node based on classification
let nextNode: "searchDocumentation" | "humanReview" | "draftResponse" | "bugTracking";

if (classification.intent === "billing" || classification.urgency === "critical") {
    nextNode = "humanReview";
} else if (classification.intent === "question" || classification.intent === "feature") {
    nextNode = "searchDocumentation";
} else if (classification.intent === "bug") {
    nextNode = "bugTracking";
} else {
    nextNode = "draftResponse";
}

// Store classification as a single object in state
return new Command({
    update: { classification },
    goto: nextNode,
});
}

async function searchDocumentation(state: EmailAgentStateType) {
// Search knowledge base for relevant information

// Build search query from classification
const classification = state.classification!;
const query = `${classification.intent} ${classification.topic}`;

let searchResults: string[];

try {
    // Implement your search logic here
    // Store raw search results, not formatted text
    searchResults = [
    "Reset password via Settings > Security > Change Password",
    "Password must be at least 12 characters",
    "Include uppercase, lowercase, numbers, and symbols",
    ];
} catch (error) {
    // For recoverable search errors, store error and continue
    searchResults = [`Search temporarily unavailable: ${error}`];
}

return new Command({
    update: { searchResults },  // Store raw results or error
    goto: "draftResponse",
});
}

async function bugTracking(state: EmailAgentStateType) {
// Create or update bug tracking ticket

// Create ticket in your bug tracking system
const ticketId = "BUG-12345";  // Would be created via API

return new Command({
    update: { searchResults: [`Bug ticket ${ticketId} created`] },
    goto: "draftResponse",
});
}

import { Command, interrupt } from "@langchain/langgraph";

async function draftResponse(state: EmailAgentStateType) {
// Generate response using context and route based on quality

const classification = state.classification!;

// Format context from raw state data on-demand
const contextSections: string[] = [];

if (state.searchResults) {
    // Format search results for the prompt
    const formattedDocs = state.searchResults.map(doc => `- ${doc}`).join("\n");
    contextSections.push(`Relevant documentation:\n${formattedDocs}`);
}

if (state.customerHistory) {
    // Format customer data for the prompt
    contextSections.push(`Customer tier: ${state.customerHistory.tier ?? "standard"}`);
}

// Build the prompt with formatted context
const draftPrompt = `
Draft a response to this customer email:
${state.emailContent}

Email intent: ${classification.intent}
Urgency level: ${classification.urgency}

${contextSections.join("\n\n")}

Guidelines:
- Be professional and helpful
- Address their specific concern
- Use the provided documentation when relevant
`;

const response = await llm.invoke([new HumanMessage(draftPrompt)]);

// Determine if human review needed based on urgency and intent
const needsReview = (
    classification.urgency === "high" ||
    classification.urgency === "critical" ||
    classification.intent === "complex"
);

// Route to appropriate next node
const nextNode = needsReview ? "humanReview" : "sendReply";

return new Command({
    update: { responseText: response.content.toString() },  // Store only the raw response
    goto: nextNode,
});
}

async function humanReview(state: EmailAgentStateType) {
// Pause for human review using interrupt and route based on decision
const classification = state.classification!;

// interrupt() must come first - any code before it will re-run on resume
const humanDecision = interrupt({
    emailId: state.emailId,
    originalEmail: state.emailContent,
    draftResponse: state.responseText,
    urgency: classification.urgency,
    intent: classification.intent,
    action: "Please review and approve/edit this response",
});

// Now process the human's decision
if (humanDecision.approved) {
    return new Command({
    update: { responseText: humanDecision.editedResponse || state.responseText },
    goto: "sendReply",
    });
} else {
    // Rejection means human will handle directly
    return new Command({ update: {}, goto: END });
}
}

async function sendReply(state: EmailAgentStateType): Promise<{}> {
// Send the email response
// Integrate with email service
console.log(`Sending reply: ${state.responseText!.substring(0, 100)}...`);
return {};
}