const Discord = require("discord.js");
const Jimp = require("jimp");

const client = new Discord.Client();

client.on("ready", async () => {
    console.log(`Logged in as ${client.user.tag}!`);
});

client.on("message", async (message) => {

    if (message.author.bot) return;

    const imageTemp = "https://upload.wikimedia.org/wikipedia/commons/8/8a/Banana-Single.jpg";
    const messageAttachment = message.attachments.size > 0 ? message.attachments.array()[0].url : null;

    // Exit if there is no message attachment present in the message
    if (!messageAttachment) return;

    // Resolve the temporary image url to Jimp object
    const firstImage = await Jimp.read(imageTemp);
    // Resolve the message attachment image url to Jimp object
    const secondImage = await Jimp.read(messageAttachment);

    // Composite the two images together (modifies the firstImage object)
    firstImage.composite(secondImage, 10, 10);

    // Save the resulting image to buffer
    const buffer = await firstImage.getBufferAsync(Jimp.MIME_JPEG);

    // Send the buffer as a message attachment
    message.channel.send("Combined image:", {files: [{ attachment: buffer }]});

});

client.login("...");