gfa

gfa

gfa (generate-fake-api) is a LLM-powered command-line tool that generates structured data based on Zod schemas and serves it as a REST API. You can think of it as an AI-driven json-server. Just define a seed file with the resources you want to generate, and gfa will take care of the rest.

Usage

gfa currently supports the following AI providers for generating data:

• OpenAI API
• Anthropic API

You need an API key from one of these providers to use gfa. Once you have your API key, set it as an environment variable called OPENAI_API_KEY or ANTHROPIC_API_KEY. You can set the environment variable by using the export command. For example:

export OPENAI_API_KEY=your-api-key

After setting the API key, install the dependencies in your project:

npm install gfa zod --save-dev

Next, create a seed file. The seed file should export an object that satisfies the Seed type exported from gfa. The seed object should have keys that represent the resources you want to generate. Each resource should have a schema key that describes the shape of the resource using a ZodObject instance. Resources can also have an optional prompt key that describes the prompt to generate the resource. Resources are considered to be plural by default, i.e., they are arrays of objects. If you want to generate a single object instead of an array, you can set the single key to true.

Here is an example seed file:

import type { Seed } from "gfa";
import { z } from "zod";

export default {
  posts: {
    prompt: "Generate 3 posts",
    schema: z.object({
      id: z.number(),
      title: z.string(),
      views: z.number(),
    }),
  },
  comments: {
    prompt: "Generate 5 comments. postIds should be between 1 and 3",
    schema: z.object({
      id: z.number(),
      text: z.string(),
      postId: z.number(),
    }),
  },
  profile: {
    single: true,
    prompt: "Generate a profile",
    schema: z.object({
      name: z.string(),
    }),
  },
} satisfies Seed;

Now you can run the gfa command to generate resources and serve the API:

$ npx gfa seed.ts
✔ Resources generated (total tokens: 383)

Serving API on http://localhost:3000 (Press Ctrl-C to quit)

Available routes:
GET     /api/posts
GET     /api/posts/:id
POST    /api/posts
PUT     /api/posts/:id
PATCH   /api/posts/:id
DELETE  /api/posts/:id
GET     /api/comments
GET     /api/comments/:id
POST    /api/comments
PUT     /api/comments/:id
PATCH   /api/comments/:id
DELETE  /api/comments/:id
GET     /api/profile
PUT     /api/profile
PATCH   /api/profile

The API is now running on http://localhost:3000. You can make requests to the API using curl or a tool like Postman. Here is an example request using curl:

$ curl -s http://localhost:3000/api/posts | jq .
[
  {
    "id": 1,
    "title": "Exploring the Wonders of Nature",
    "views": 150
  },
  {
    "id": 2,
    "title": "The Future of Technology: Trends to Watch",
    "views": 200
  },
  {
    "id": 3,
    "title": "Healthy Eating: Tips for a Balanced Diet",
    "views": 120
  }
]
$ curl -s 'http://localhost:3000/api/posts?page=2&per_page=2' | jq .
[
  {
    "id": 3,
    "title": "Healthy Eating: Tips for a Balanced Diet",
    "views": 120
  }
]

Changelog

0.2.0

Minor Changes

• #23 4abe30b Thanks @morinokami! - Support pagination

Patch Changes

• #25 25bc1a1 Thanks @morinokami! - Add examples directory