Build a Chat App with NextJS + Supabase

In this tutorial we will create a simple chat app using NextJS (Typescript) and Supabase.

Yong Zhen

8 min read

In this project, users will sign in using magic email link and exchange messages in a single chatroom.

💡

Update 27th Aug 2022
The issue with React Strictmode and Supabase Realtime has been fixed with the release of supabase-js v2, and this article as well as the Github repo has been updated.

Overview

The complete code for this tutorial can be found here.

Supabase setup

Before we start building our app, we're going to setup our database and API in Supabase.

Create a project

Go to app.supabase.com (and create a free account if you haven't already)
Click on "New Project"
Enter your project details
Wait for project to complete initializing

Database schema setup: Auth

For this, we can use the "User Management Starter" quickstart in the SQL Editor.

Go to the "SQL Editor" section.
Click "User Management Starter"
Click "Run".

That's all. Next, we will setup the schema to store our messages.

Database schema setup: Messages

Go to "Table Editor"
Add a table named messages with the following settings and columns:

`user_id` references the`id` column in auth.users table

Setup table policies

We will need to setup our policies to allow read and write access to our messages tables.

Go to "Authentication" and click on "Policies"
Under messages, add the following 2 policies

Policy name: "Users can insert their own messages."

Under "Target roles", add the "authenticated" role

Policy name: "Users can read messages."

Same as before, add the "authenticated" role

API credentials

Go to "Settings" > "API"
Under "Project API keys", there's your API URL and anon key. We will be using them later for the connection to Supabase

Building the app

The app will consist of 2 parts - user authentication and the chat functionality. We will be using NextJS/React/Typescript and TailwindCSS to style our components.

To speed things up, clone the following starter template to your preferred directory.

git clone https://github.com/yongzhenlow/nextjs-starter chat-app

This is a NextJS starter template that comes with the base dependencies you'll need.

Then, install the Supabase JS client library (using v2, note the @rc at the end)

yarn add @supabase/supabase-js@rc

Environment variables

Create a file .env.local with the API credentials from before

NEXT_PUBLIC_SUPABASE_URL=https://example.supabase.co
NEXT_PUBLIC_SUPABASE_ANON_KEY=youranonkey

.env.local

Now let's create a helper to initialize the Supabase client

import { createClient } from '@supabase/supabase-js'

export const supabase = createClient(
  process.env.NEXT_PUBLIC_SUPABASE_URL!,
  process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!
)

utils/supabase-client.ts

Since we are using TailwindCSS, we can just create and style the form right in our component.

💡

The starter template has absolute imports configured, so you can use imports from "utils/example.ts" instead of "../utils/example.ts"

import { useState } from 'react'
import { supabase } from 'utils/supabase-client'
import type { ChangeEvent, FormEvent } from 'react'

const Auth = () => {
  const [isLoading, setIsLoading] = useState<boolean>(false)
  const [email, setEmail] = useState<string>('')

  const handleLogin = async (e: FormEvent<HTMLFormElement>) => {
    e.preventDefault()

    // @todo handle validation here
    if (isLoading || !email?.length) {
      return false
    }

    try {
      setIsLoading(true)
      const { error } = await supabase.auth.signInWithOtp({ email })
      if (error) throw error
      alert('Check your email for the login link!')
    } catch (error: any) {
      alert(error.error_description || error.message)
    } finally {
      setIsLoading(false)
    }
  }

  return (
    <div className="container max-w-md mx-auto mt-10 px-6 text-slate-900 text-center">
      <div className="rounded border border-slate-200 p-10">
        <h1 className="font-medium text-2xl mb-6">Login to Chat</h1>

        <form onSubmit={handleLogin} className="space-y-6">
          <label className="block">
            <span>
              Get a magic link sent to your email that&rsquo;ll sign you in
              instantly
            </span>
            <input
              className="block mt-3 w-full rounded border text-slate-900 border-slate-400 py-3 px-3"
              type="email"
              placeholder="Your email"
              value={email}
              onChange={(e: ChangeEvent<HTMLInputElement>) =>
                setEmail(e.target.value)
              }
            />
          </label>

          <button
            className="block w-full rounded py-3 px-5 text-white bg-blue-800 hover:bg-blue-700 disabled:bg-slate-400"
            disabled={isLoading}
          >
            {isLoading ? 'Loading...' : 'Send Magic Link'}
          </button>
        </form>
      </div>
    </div>
  )
}

export default Auth

components/Auth.tsx

Let's add the Auth component to pages/index.tsx, and leave the authenticated state empty for now while we start building the Chat components:

import type { NextPage } from 'next'
import { useState, useEffect } from 'react'
import type { Session } from '@supabase/supabase-js'
import { supabase } from 'utils/supabase-client'
import Auth from 'components/Auth'

const Home: NextPage = () => {
  const [session, setSession] = useState<Session | null>(null)

  useEffect(() => {
    const fetchSession = async () => {
      const {
        data: { session },
      } = await supabase.auth.getSession()
      setSession(session)
    }

    fetchSession()

    const {
      data: { subscription },
    } = supabase.auth.onAuthStateChange((_event, session) => {
      setSession(session)
    })

    return subscription.unsubscribe
  }, [])

  return session === null ? (
    <Auth />
  ) : (
    <>{/** @todo replace with Chat component */}</>
  )
}

export default Home

pages/index.tsx

Creating the chat components

Let's create 3 components, the 1. main chat window, 2. the chat message, and 3. a "dirty little trick", AlwaysScrollIntoView component, to scroll our latest message into view whenever the DOM updates, such as receiving or typing new messages.

In a chat app, the direction of the messages are usually reversed, so many of our implementations are also reversed. For example, we prepend new messages received instead of appending. The messages are also reversed using the flex-col-reverse CSS property, which is why we need to add the AlwaysScrollIntoView component before the messages so that it renders at the bottom.

import { useEffect, useState } from 'react'
import { supabase } from 'utils/supabase-client'
import ChatMessage from 'components/ChatMessage'
import AlwaysScrollIntoView from 'components/AlwaysScrollIntoView'
import type { FormEvent, ChangeEvent, TouchEvent } from 'react'
import type { Session } from '@supabase/supabase-js'
import type { Message } from 'types'

interface ChatProps {
  session: Session
}

const Chat = ({ session }: ChatProps) => {
  const [messages, setMessages] = useState<Message[]>([])
  const [message, setMessage] = useState<string>('')
  const [isLoading, setIsLoading] = useState<boolean>(false)

  const handleSendMessage = async (
    e: FormEvent<HTMLFormElement> | TouchEvent<HTMLButtonElement>
  ) => {
    e.preventDefault()

    // Handle validation here
    if (isLoading || !session?.user) return false

    try {
      setIsLoading(true)

      await supabase
        .from('messages')
        .insert([{ content: message, user_id: session.user.id }])

      // Reset message input field
      setMessage('')
    } catch (error: any) {
      console.error(error)
    } finally {
      setIsLoading(false)
    }
  }

  // Fetch initial messages
  useEffect(() => {
    const fetchMessages = async () => {
      const { data: messages, error } = await supabase
        .from('messages')
        .select()
        .order('created_at', { ascending: false })

      if (!error) {
        setMessages(messages)
      } else {
        console.error(error)
      }
    }

    fetchMessages()
  }, [])

  // Listen to messages updates
  useEffect(() => {
    const messagesChannel = supabase
      .channel('public:messages')
      .on(
        'postgres_changes',
        { event: 'INSERT', schema: 'public', table: 'messages' },
        (payload: any) => {
          // Prepend new messages received
          setMessages((m) => [payload.new as Message, ...m])
        }
      )
      .subscribe()

    return () => {
      supabase.removeChannel(messagesChannel)
    }
  }, [])

  return (
    <div className="w-screen h-screen flex flex-col bg-slate-50">
      <div className="flex flex-row flex-none p-3 justify-between bg-slate-600">
        <h1 className="font-bold text-white">Chat App</h1>
        <button
          className="bg-rose-700 hover:bg-rose-600 text-white p-2 rounded"
          type="button"
          onClick={() => supabase.auth.signOut()}
        >
          <svg
            className="w-3 h-3 fill-white"
            xmlns="http://www.w3.org/2000/svg"
            viewBox="0 0 512 512"
          >
            <path d="M96 480h64C177.7 480 192 465.7 192 448S177.7 416 160 416H96c-17.67 0-32-14.33-32-32V128c0-17.67 14.33-32 32-32h64C177.7 96 192 81.67 192 64S177.7 32 160 32H96C42.98 32 0 74.98 0 128v256C0 437 42.98 480 96 480zM504.8 238.5l-144.1-136c-6.975-6.578-17.2-8.375-26-4.594c-8.803 3.797-14.51 12.47-14.51 22.05l-.0918 72l-128-.001c-17.69 0-32.02 14.33-32.02 32v64c0 17.67 14.34 32 32.02 32l128 .001l.0918 71.1c0 9.578 5.707 18.25 14.51 22.05c8.803 3.781 19.03 1.984 26-4.594l144.1-136C514.4 264.4 514.4 247.6 504.8 238.5z" />
          </svg>
        </button>
      </div>

      <div className="flex flex-col-reverse flex-auto p-6 overflow-y-auto space-y-6 space-y-reverse min-h-[0px] text-slate-900">
        <AlwaysScrollIntoView />

        {messages.length > 0 &&
          messages.map((msg) => (
            <ChatMessage
              key={msg.id}
              fromCurrentUser={msg.user_id === session!.user!.id}
              content={msg.content ?? ''}
            />
          ))}
      </div>

      <form
        className="flex flex-row flex-none p-2 bg-slate-300 gap-x-3"
        onSubmit={handleSendMessage}
      >
        <input
          className={`flex-grow bg-white rounded p-2 focus:outline-none ${
            isLoading ? 'text-slate-600' : 'text-slate-900'
          }`}
          autoFocus
          type="text"
          value={message}
          required
          onChange={(e: ChangeEvent<HTMLInputElement>) =>
            setMessage(e.target.value)
          }
        />

        <button
          className="rounded text-white px-6 bg-blue-800 hover:bg-blue-700 disabled:bg-slate-400"
          type="submit"
          disabled={isLoading || !message || !message.length}
          onTouchEnd={handleSendMessage}
        >
          {isLoading ? 'Sending...' : 'Send'}
        </button>
      </form>
    </div>
  )
}

export default Chat

components/Chat.tsx

interface ChatMessageProps {
  fromCurrentUser: boolean
  content: string
}

const ChatMessage = ({ fromCurrentUser, content }: ChatMessageProps) => {
  return (
    <div className={`flex flex-row w-full ${fromCurrentUser && 'justify-end'}`}>
      <div
        className={`max-w-xl break-words break-all rounded rounded-tr-none p-3 ${
          fromCurrentUser ? 'bg-blue-200' : 'bg-slate-200'
        }`}
      >
        {content}
      </div>
    </div>
  )
}

export default ChatMessage

components/ChatMessage.tsx

import { useEffect, useRef } from 'react'

/**
 * Scroll to this component when DOM updates, similar to
 * React Native's Flatlist inverted prop.
 *
 * @returns HTMLDivElement
 */
const AlwaysScrollIntoView = () => {
  const elementRef = useRef<HTMLDivElement | null>(null)

  useEffect(() => elementRef?.current?.scrollIntoView())

  return <div ref={elementRef} className="-mt-6" />
}

export default AlwaysScrollIntoView

components/AlwaysScrollIntoView.tsx

Putting everything together

Now that we have everything in place, it is time to add our Chat component to pages/index.tsx :

import type { NextPage } from 'next'
import { useState, useEffect } from 'react'
import type { Session } from '@supabase/supabase-js'
import { supabase } from 'utils/supabase-client'
import Auth from 'components/Auth'
import Chat from 'components/Chat'

const Home: NextPage = () => {
  const [session, setSession] = useState<Session | null>(null)

  useEffect(() => {
    const fetchSession = async () => {
      const {
        data: { session },
      } = await supabase.auth.getSession()
      setSession(session)
    }

    fetchSession()

    const {
      data: { subscription },
    } = supabase.auth.onAuthStateChange((_event, session) => {
      setSession(session)
    })

    return subscription.unsubscribe
  }, [])

  return session === null ? (
    <Auth />
  ) : (
    <Chat key={session.user?.id} session={session} />
  )
}

export default Home