Building a One-to-One/Group Chat in Astro

The One‑to‑One/Group chat layout focuses on a single conversation, ideal for support chats and private messaging. This guide uses Astro with React islands and the CometChat React UI Kit.

User Interface Preview

Dedicated one-to-one or group chat screen

Key Components

Chat Header – recipient details and status
Message View – history and live messages
Message Composer – text, media, attachments

Prerequisites

Astro project with React integration
CometChat credentials in .env

Create or open an Astro project

npm create astro@latest
cd <my-astro-app>
npm install

If you already have the sample astro-one-to-one-chat project, open it instead.

Add React and install CometChat UI Kit

npx astro add react
npm i @cometchat/chat-uikit-react react react-dom

Add required environment variables to .env:

PUBLIC_COMETCHAT_APP_ID=your_app_id
PUBLIC_COMETCHAT_REGION=your_region
PUBLIC_COMETCHAT_AUTH_KEY=your_auth_key
# Login user and the peer for one-to-one
PUBLIC_COMETCHAT_LOGIN_UID=cometchat-uid-3
PUBLIC_COMETCHAT_TARGET_UID=cometchat-uid-1

Use Auth Tokens in production instead of Auth Keys.

Initialize CometChat (src/lib/cometchat-init.js)

Create src/lib/cometchat-init.js used by the island to initialize the UI Kit and handle login.

src/lib/cometchat-init.js

import { CometChatUIKit, UIKitSettingsBuilder } from "@cometchat/chat-uikit-react";

const APP_ID   = import.meta.env.PUBLIC_COMETCHAT_APP_ID;
const REGION   = import.meta.env.PUBLIC_COMETCHAT_REGION;
const AUTH_KEY = import.meta.env.PUBLIC_COMETCHAT_AUTH_KEY;

export async function initCometChat() {
  if (!APP_ID || !REGION || !AUTH_KEY) {
    throw new Error("Missing PUBLIC_COMETCHAT_* env vars.");
  }

  const settings = new UIKitSettingsBuilder()
    .setAppId(APP_ID)
    .setRegion(REGION)
    .setAuthKey(AUTH_KEY) // use Auth Tokens in prod
    .subscribePresenceForAllUsers()
    .build();

  await CometChatUIKit.init(settings);
}

export async function ensureLogin(uid) {
  const existing = await CometChatUIKit.getLoggedinUser();
  if (!existing) await CometChatUIKit.login(uid);
}

Build the React island (src/components/OneToOneChat.jsx)

This component initializes CometChat, logs in the desired user, and loads a single peer (user or group) to chat with.

src/components/OneToOneChat.jsx

import { useEffect, useState } from "react";
import {
  CometChatUIKit,
  CometChatMessageHeader,
  CometChatMessageList,
  CometChatMessageComposer,
} from "@cometchat/chat-uikit-react";
import "@cometchat/chat-uikit-react/css-variables.css";
import { initCometChat, ensureLogin } from "../lib/cometchat-init.js";

// current user + peer
const LOGIN_UID  = import.meta.env.PUBLIC_COMETCHAT_LOGIN_UID;   // e.g., cometchat-uid-3
const TARGET_UID = import.meta.env.PUBLIC_COMETCHAT_TARGET_UID;  // e.g., cometchat-uid-1

export default function OneToOneChat() {
  const [phase, setPhase] = useState("boot"); // boot | ready | error
  const [errorMsg, setErrorMsg] = useState("");
  const [peer, setPeer] = useState(null);     // CometChat.User

  useEffect(() => {
    let cancelled = false;

    (async () => {
      try {
        if (!LOGIN_UID || !TARGET_UID) {
          throw new Error("Missing PUBLIC_COMETCHAT_LOGIN_UID or PUBLIC_COMETCHAT_TARGET_UID.");
        }

        // 1) Initialize CometChat
        await initCometChat();

        // 2) Handle user switching - logout if different user
        try {
          const currentUser = await CometChatUIKit.getLoggedinUser();
          if (currentUser && currentUser.uid !== LOGIN_UID) {
            await CometChatUIKit.logout();
          }
        } catch (error) {
          // No existing user session
        }

        // 3) Ensure logged in as correct user
        await ensureLogin(LOGIN_UID);

        // 4) Fetch the peer user
        const { CometChat } = await import("@cometchat/chat-sdk-javascript");
        const u = await CometChat.getUser(TARGET_UID);

        if (!cancelled) {
          setPeer(u);
          setPhase("ready");
        }
      } catch (e) {
        if (!cancelled) {
          setErrorMsg(String(e?.message || e));
          setPhase("error");
        }
      }
    })();

    return () => { cancelled = true; };
  }, [LOGIN_UID, TARGET_UID]); // Re-run when these change

  if (phase === "boot")  return (
    <div style={{ padding: 16 }}>
      <div>Loading…</div>
    </div>
  );
  
  if (phase === "error") return (
    <div style={{ padding: 16, color: "crimson" }}>
      <div><b>Error:</b> {errorMsg}</div>
    </div>
  );

  if (!peer) return <div className="cc-one-to-one__empty">Invalid target user.</div>;

  return (
    <div className="cc-one-to-one">
      <CometChatMessageHeader user={peer} />
      <div className="cc-one-to-one__list-slot">
        <CometChatMessageList user={peer} />
      </div>
      <CometChatMessageComposer user={peer} />
    </div>
  );
}

Render the page (src/pages/index.astro)

Import the island and styles, then hydrate on the client.

src/pages/index.astro

---
import OneToOneChat from "../components/OneToOneChat.jsx";
import "../styles/globals.css";        // your existing base CSS (optional, recommended)
import "../styles/one-to-one.css";     // the file from this setup
---

<html lang="en">
  <head>
    <meta charset="utf-8" />
    <title>One-to-One Chat</title>
    <meta name="viewport" content="width=device-width, initial-scale=1" />
  </head>
  <body>
    <!-- client-only island; CometChat needs browser APIs -->
    <OneToOneChat client:only="react" />
  </body>
</html>

Run and verify

npm run dev

Set PUBLIC_COMETCHAT_LOGIN_UID and PUBLIC_COMETCHAT_TARGET_UID then verify messages appear for the selected peer.

Switch to Group Chat

To load a group instead of a user, fetch it with the SDK and pass it to the UI Kit components.

const { CometChat } = await import("@cometchat/chat-sdk-javascript");
const group = await CometChat.getGroup("YOUR_GROUP_ID");
// Then render header, list, composer with group prop instead of user

When switching between user and group, keep only one of user or group props set at a time.

Troubleshooting

Blank screen or hydration error

Ensure the component is rendered as a React island (client:only=\"react\").

Missing credentials

Verify .env contains PUBLIC_COMETCHAT_APP_ID, PUBLIC_COMETCHAT_REGION, PUBLIC_COMETCHAT_AUTH_KEY, and both PUBLIC_COMETCHAT_LOGIN_UID and PUBLIC_COMETCHAT_TARGET_UID.

Wrong user appears

The island logs out if a different user session is active, then logs in with PUBLIC_COMETCHAT_LOGIN_UID.

Next Steps

Add typing indicators and read receipts
Apply theming and component overrides
Extend to conversations list + messages or tabbed layout

You can reuse src/lib/cometchat-init.js across different chat experiences and swap the island component.

​User Interface Preview

​Prerequisites

​Switch to Group Chat

​Troubleshooting

​Next Steps

User Interface Preview

Prerequisites

Switch to Group Chat

Troubleshooting

Next Steps