oatmeal-fastify/src/index.ts

import { fastifyPlugin } from 'fastify-plugin';
import * as oatmeal from '@modal-sh/oatmeal-core';
import { FastifyReply, FastifyRequest} from 'fastify';

const JSON_TYPES = [
  'application/json',
] as const

interface SendX {
  (contentType?: string, data?: unknown): void;
}

const sendX: SendX = function sendX(this: FastifyReply, contentType?: string, data?: unknown) {
  if (typeof contentType !== 'undefined' && typeof data !== 'undefined') {
    const content = oatmeal.serialize(data, { type: contentType })
    // TODO add error handling when payload can't be serialized
    this.type(contentType).send(content);
    return;
  }
  this.send();
}

export const fastifyOatmeal = fastifyPlugin(async (fastify) => {
  oatmeal.AVAILABLE_TYPES
    .filter((type) => !JSON_TYPES.includes(type as typeof JSON_TYPES[number]))
    .forEach((type) => {
      fastify.addContentTypeParser(type, { parseAs: 'buffer' }, async (_: FastifyRequest, body: Buffer) => {
        return oatmeal.deserialize(body.toString('utf-8'), { type });
        // TODO add error handling when body can't be deserialized
      });
    });

  fastify.decorateReply('sendX', sendX);
});

declare module 'fastify' {
  interface FastifyReply {
    sendX: SendX;
  }
}