Build an AI Meme Generator with OpenAI's function calls, Part 2: Cron Jobs ⏰☎️

vincanger - Sep 12 '23 - - Dev Community

TL;DR

In this two-part tutorial, we’re going to build a full-stack instant Meme Generator app using:

You can check out a deployed version of the app we’re going to build here: The Memerator

If you just want to see the code for the finished app, check out the Memerator’s GitHub Repo

In Part 1 of this tutorial we built the instant meme generation functionality of the app.

In order to create a meme image using ImgFlip.com’s API, we had to send a request with:

  • the meme template id we want to use
  • and the two text blocks that will accompany the meme, e.g. text0 and text1

Rather than doing this manually, we used OpenAI’s API to ask GPT to generate the meme text boxes for us.

To do this, we used their function calling feature to describe the function that includes our ImgFlip API request. This made sure that OpenAI’s response would always contain two text arguments in JSON format so that we could pass them correctly to the ImgFlip.com API.

The result is that we could get our app to instantly generate meme Images for us by just submitting some topics! 🤯

Image description

Now, in Part 2 of this tutorial, we will:

  • add a daily recurring cron job to fetch more meme templates
  • implement edit and delete meme functionality

Oh, and if you get stuck / have any questions, feel free to hop into the Wasp Discord Server and ask us!

Now let’s go 🚀

Before We Begin

We’re working hard at Wasp to help you build web apps as easily as possible — including making these tutorials, which are released weekly!

We would be super grateful if you could help us out by starring our repo on GitHub: https://www.github.com/wasp-lang/wasp 🙏

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⭐️ Thanks For Your Support 🙏

Part 2.

So we’ve got ourselves a really good basis for an app at this point.

We’re using OpenAI’s function calling feature to explain a function to GPT, and get it to return results for us in a format we can use to call that function.

This allows us to be certain GPT’s result will be usable in further parts of our application and opens up the door to creating AI agents.

If you think about it, we’ve basically got ourselves a really simple Meme generating “agent”. How cool is that?!

Fetching & Updating Templates with Cron Jobs

To be able to generate our meme images via ImgFlip’s API, we have to choose and send a meme template id to the API, along with the text arguments we want to fill it in with.

For example, the Grandma Finds Internet meme template has the following id:

Image description

But the only way for us to get available meme templates from ImgFlip is to send a GET request to
https://api.imgflip.com/get_memes. And according to ImgFlip, the /get-memes endpoint works like this:

Gets an array of popular memes that may be captioned with this API. The size of this array and the order of memes may change at any time. When this description was written, it returned 100 memes ordered by how many times they were captioned in the last 30 days

So it returns a list of the top 100 memes from the last 30 days. And as this is always changing, we can run a daily cron job to fetch the list and update our database with any new templates that don’t already exist in it.

We know this will work because the ImgFlip docs for the /caption-image endpoint — which we use to create a meme image — says this:

key: template_id
value: A template ID as returned by the get_memes response. Any ID that was ever returned from the get_memes response should work for this parameter…

Awesome!

Defining our Daily Cron Job

Now, to create an automatically recurring cron job in Wasp is really easy.

First, go to your main.wasp file and add:

job storeMemeTemplates {
  executor: PgBoss,
  perform: {
    fn: import { fetchAndStoreMemeTemplates } from "@server/workers.js",
  },
  schedule: {
    // daily at 7 a.m.
    cron: "0 7 * * *" 
  },
  entities: [Template],
}
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This is telling Wasp to run the fetchAndStoreMemeTemplates function every day at 7 a.m.

Next, create a new file in src/server called workers.ts and add the function:

import axios from 'axios';

export const fetchAndStoreMemeTemplates = async (_args: any, context: any) => {
  console.log('.... ><><>< get meme templates cron starting ><><>< ....');

  try {
    const response = await axios.get('https://api.imgflip.com/get_memes');

    const promises = response.data.data.memes.map((meme: any) => {
      return context.entities.Template.upsert({
        where: { id: meme.id },
        create: {
          id: meme.id,
          name: meme.name,
          url: meme.url,
          width: meme.width,
          height: meme.height,
          boxCount: meme.box_count,
        },
        update: {},
      });
    });

    await Promise.all(promises);
  } catch (error) {
    console.error('error fetching meme templates: ', error);
  }
};
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You can see that we send a GET request to the proper endpoint, then we loop through the array of memes it returns to us add any new templates to the database.

Notice that we use Prisma’s upsert method here. This allows us to create a new entity in the database if it doesn’t already exist. If it does, we don’t do anything, which is why update is left blank.

We use [Promise.all() to call that array of promises](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/all) correctly.

Testing

Now, assuming you’ve got your app running with wasp start, you will see the cron job run in the console every day at 7 a.m.

If you want to test that the cron job is working correctly, you could run it on a faster schedule. Let’s try that now by changing it in our main.wasp file to run every minute:

//...
  schedule: {
    // runs every minute.
    cron: "* * * * *" 
  },
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First, your terminal where you ran wasp start to start your app should output the following:

[Server]  🔍 Validating environment variables...
[Server]  🚀 "Username and password" auth initialized
[Server]  Starting pg-boss...
[Server]  pg-boss started!
[Server]  Server listening on port 3001
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…followed shortly after by:

[Server]  .... ><><>< get meme templates cron starting ><><>< ....
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Great. We’ve got an automatically recurring cron job going.

You can check your database for saved templates by opening another terminal window and running:

wasp db studio
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Image description

Editing Memes

Unfortunately, sometimes GPT’s results have some mistakes. Or sometimes the idea is really good, but we want to further modify it to make it even better.

Well, that’s pretty simple for us to do since we can just make another call to ImgFlip’s API.

So let’s set do that by setting up a dedicated page where we:

  • fetch that specific meme based on its id
  • display a form to allow the user to edit the meme text
  • send that info to a server-side Action which calls the ImgFlip API, generates a new image URL, and updates our Meme entity in the DB.

Server-Side Code

To make sure we can fetch the individual meme we want to edit, we first need to set up a Query that does this.

Go to your main.wasp file and add this Query declaration:

query getMeme {
  fn: import { getMeme } from "@server/queries.js",
  entities: [Meme]
}
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Now go to src/server/queries.ts and add the following function:

import type { Meme, Template } from '@wasp/entities';
import type { GetAllMemes, GetMeme } from '@wasp/queries/types';

type GetMemeArgs = { id: string };
type GetMemeResult = Meme & { template: Template };

//...

export const getMeme: GetMeme<GetMemeArgs, GetMemeResult> = async ({ id }, context) => {
  if (!context.user) {
    throw new HttpError(401);
  }

  const meme = await context.entities.Meme.findUniqueOrThrow({
    where: { id: id },
    include: { template: true },
  });

  return meme;
};
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We’re just fetching the single meme based on its id from the database.

We’re also including the related meme Template so that we have access to its id as well, because we need to send this to the ImgFlip API too.

Pretty simple!

Now let’s create our editMeme action by going to our main.wasp file and adding the following Action:

//...

action editMeme {
  fn: import { editMeme } from "@server/actions.js",
  entities: [Meme, Template, User]
}
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Next, move over to the server/actions.ts file and let’s add the following server-side function:

//... other imports
import type { EditMeme } from '@wasp/actions/types';

//... other types
type EditMemeArgs = Pick<Meme, 'id' | 'text0' | 'text1'>;

export const editMeme: EditMeme<EditMemeArgs, Meme> = async ({ id, text0, text1 }, context) => {
  if (!context.user) {
    throw new HttpError(401, 'You must be logged in');
  }

  const meme = await context.entities.Meme.findUniqueOrThrow({
    where: { id: id },
    include: { template: true },
  });

  if (!context.user.isAdmin && meme.userId !== context.user.id) {
    throw new HttpError(403, 'You are not the creator of this meme');
  }

  const memeUrl = await generateMemeImage({
    templateId: meme.template.id,
    text0: text0,
    text1: text1,
  });

  const newMeme = await context.entities.Meme.update({
    where: { id: id },
    data: {
      text0: text0,
      text1: text1,
      url: memeUrl,
    },
  });

  return newMeme;
};
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As you can see, this function expects the id of the already existing meme, along with the new text boxes. That’s because we’re letting the user manually input/edit the text that GPT generated, rather than making another request the the OpenAI API.

Next, we look for that specific meme in our database, and if we don’t find it we throw an error (findUniqueOrThrow).

We check to make sure that that meme belongs to the user that is currently making the request, because we don’t want a different user to edit a meme that doesn’t belong to them.

Then we send the template id of that meme along with the new text to our previously created generateMemeImage function. This function calls the ImgFlip API and returns the url of the newly created meme image.

We then update the database to save the new URL to our Meme.

Awesome!

Client-Side Code

Let’s start by adding a new route and page to our main.wasp file:

//...

route EditMemeRoute { path: "/meme/:id", to: EditMemePage }
page EditMemePage {
  component: import { EditMemePage } from "@client/pages/EditMemePage",
  authRequired: true
}
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There are two important things to notice:

  1. the path includes the :id parameter, which means we can access page for any meme in our database by going to, e.g. memerator.com/meme/5
  2. by using the authRequired option, we tell Wasp to automatically block this page from unauthorized users. Nice!

Now, create this page by adding a new file called EditMemePage.tsx to src/client/pages. Add the following code:

import { useState, useEffect, FormEventHandler } from 'react';
import { useQuery } from '@wasp/queries';
import editMeme from '@wasp/actions/editMeme';
import getMeme from '@wasp/queries/getMeme';
import { useParams } from 'react-router-dom';
import { AiOutlineEdit } from 'react-icons/ai';

export function EditMemePage() {
  // http://localhost:3000/meme/573f283c-24e2-4c45-b6b9-543d0b7cc0c7
  const { id } = useParams<{ id: string }>();

  const [text0, setText0] = useState('');
  const [text1, setText1] = useState('');
  const [isLoading, setIsLoading] = useState(false);

  const { data: meme, isLoading: isMemeLoading, error: memeError } = useQuery(getMeme, { id: id });

  useEffect(() => {
    if (meme) {
      setText0(meme.text0);
      setText1(meme.text1);
    }
  }, [meme]);

  const handleSubmit: FormEventHandler<HTMLFormElement> = async (e) => {
    e.preventDefault();
    try {
      setIsLoading(true);
      await editMeme({ id, text0, text1 });
    } catch (error: any) {
      alert('Error generating meme: ' + error.message);
    } finally {
      setIsLoading(false);
    }
  };

  if (isMemeLoading) return 'Loading...';
  if (memeError) return 'Error: ' + memeError.message;

  return (
    <div className='p-4'>
      <h1 className='text-3xl font-bold mb-4'>Edit Meme</h1>
      <form onSubmit={handleSubmit}>
        <div className='flex gap-2 items-end'>
          <div className='mb-2'>
            <label htmlFor='text0' className='block font-bold mb-2'>
              Text 0:
            </label>
            <textarea
              id='text0'
              value={text0}
              onChange={(e) => setText0(e.target.value)}
              className='border rounded px-2 py-1'
            />
          </div>
          <div className='mb-2'>
            <label htmlFor='text1' className='block font-bold mb-2'>
              Text 1:
            </label>

            <div className='flex items-center mb-2'>
              <textarea
                id='text1'
                value={text1}
                onChange={(e) => setText1(e.target.value)}
                className='border rounded px-2 py-1'
              />
            </div>
          </div>
        </div>

        <button
          type='submit'
          className={`flex items-center gap-1 bg-primary-200 hover:bg-primary-300 border-2 text-black text-sm py-1 px-2 rounded ${
            isLoading ? 'opacity-50 cursor-not-allowed' : 'cursor-pointer'
          } $}`}
        >
          <AiOutlineEdit />
          {!isLoading ? 'Save Meme' : 'Saving...'}
        </button>
      </form>
      {!!meme && (
        <div className='mt-4  mb-2 bg-gray-100 rounded-lg p-4'>
          <img src={meme.url} width='500px' />
          <div className='flex flex-col items-start mt-2'>
            <div>
              <span className='text-sm text-gray-700'>Topics: </span>
              <span className='text-sm italic text-gray-500'>{meme.topics}</span>
            </div>
            <div>
              <span className='text-sm text-gray-700'>Audience: </span>
              <span className='text-sm italic text-gray-500'>{meme.audience}</span>
            </div>
            <div>
              <span className='text-sm text-gray-700'>ImgFlip Template: </span>
              <span className='text-sm italic text-gray-500'>{meme.template.name}</span>
            </div>
          </div>
        </div>
      )}
    </div>
  );
}
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Some things to notice here are:

  1. because we’re using dynamic routes (/meme/:id), we pull the URL paramater id from the url with useParams hook.
  2. we then pass that id within the getMemes Query to fetch that specific meme to edit: useQuery(getMeme, { id: id })
    1. remember, our server-side action depends on this id in order to fetch the meme from our database

The rest of the page is just our form for calling the editMeme Action, as well as displaying the meme we want to edit.

That’s great!

Now that we have that EditMemePage, we need a way to navigate to it from the home page.

To do that, go back to the Home.tsx file, add the following imports at the top, and find the comment that says {/* TODO: implement edit and delete meme features */} and replace it with the following code:

import { Link } from '@wasp/router';
import { AiOutlineEdit } from 'react-icons/ai';

//...

{user && (user.isAdmin || user.id === memeIdea.userId) && (
  <div className='flex items-center mt-2'>
    <Link key={memeIdea.id} params={{ id: memeIdea.id }} to={`/meme/:id`}>
      <button className='flex items-center gap-1 bg-primary-200 hover:bg-primary-300 border-2 text-black text-xs py-1 px-2 rounded'>
        <AiOutlineEdit />
        Edit Meme
      </button>
    </Link>
    {/* TODO: add delete meme functionality */}
  </div>
)}
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What’s really cool about this, is that Wasp’s Link component will give you type-safe routes, by making sure you’re following the pattern you defined in your main.wasp file.

And with that, so long as the authenticated user was the creator of the meme (or is an admin), the Edit Meme button will show up and direct the user to the EditMemePage

Give it a try now. It should look like this:

Deleting Memes

Ok. When I initially started writing this tutorial, I thought I’d also explain how to add delete meme functionality to the app as well.

But seeing as we’ve gotten this far, and as the entire two-part tutorial is pretty long, I figured you should be able to implement yourself by this point.

So I’ll leave you guide as to how to implement it yourself. Think of it as a bit of homework:

  1. define the deleteMeme Action in your main.wasp file
  2. export the async function from the actions.ts file
  3. import the Action in your client-side code
  4. create a button which takes the meme’s id as an argument in your deleteMeme Action.

If you get stuck, you can use the editMeme section as a guide. Or you can check out the finished app’s GitHub repo for the completed code!

Conclusion

There you have it! Your own instant meme generator 🤖😆

BTW, If you found this useful, please show us your support by giving us a star on GitHub! It will help us continue to make more stuff just like it.

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⭐️ Thanks For Your Support 🙏

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