datafire/web-docs/markdown/Hello World.md

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# DataFire "Hello World" Project
This is a small sample project to demonstrate DataFire's features. It will create
a single Action, which takes in a name, and outputs a greeting. We'll also link
that action to an HTTP endpoint and a scheduled task.

## The Basics

### Action
We'll create our action in `hello.js`.

#### hello.js
```js
var datafire = require('datafire');
module.exports = new datafire.Action({
  handler: input => "Hello, world",
})
```

### Trigger
Now let's create a `GET /hello` API endpoint in `DataFire.yml` that will trigger the Action:

#### DataFire.yml
```yaml
paths:
  /hello:
    get:
      action: ./hello.js
```

### Running

We can try it out with `datafire serve`
```bash
datafire serve --port 3000 &
# DataFire listening on port 3000

curl http://localhost:3000/hello
# "Hello, world"

kill $! # stop the server
```

## Adding Inputs
You can add inputs with [JSON Schema](http://json-schema.org/).

```js
var datafire = require('datafire');
module.exports = new datafire.Action({
  handler: input => 'Hello, ' + input.name,
  inputs: [{
    title: 'name',
    type: 'string',
    maxLength: 20,
    pattern: '\\w+',
  }],
})
```

Then we can run:
```bash
datafire serve --port 3000 &
# DataFire listening on port 3000

curl http://localhost:3000/hello?name=world
# "Hello, world"

curl http://localhost:3000/hello
# {"error": "Missing required query parameter 'name'"}
```

## HTTP Responses
By default, DataFire will return your handler's output as JSON with a 200 status
code (as well as 404/400/500 errors when appropriate). However, you can specify
custom response codes, content types, and bodies in your Action.

```js
module.exports = new datafire.Action({
  inputs: [{title: 'name'}],
  handler: input => {
    if (input.name === 'Voldemort') {
      return new datafire.Response({
        statusCode: 401,
        headers: {'Content-Type': 'text/html'},
        body: "<h1>Nope.</h1>",
      });
    } else {
      return "Hello, " + input.name;
    }
  }
})
```