Perl 6 GraphQL
==============

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A [Perl 6](https://perl6.org/) implementation of the
[GraphQL](http://graphql.org/) standard.  GraphQL is a query language
for APIs originally created by Facebook.

## Intro

Before we get into all the details, here's the Perl 6 GraphQL "Hello World"
[hello.pl](https://github.com/CurtTilmes/Perl6-GraphQL/blob/master/eg/hello.pl)


```
use GraphQL;
use GraphQL::Server;

class Query
{
    method hello(--> Str) { 'Hello World' }
}

my $schema = GraphQL::Schema.new(Query);

GraphQL-Server($schema);

```

You can run this with a GraphQL query on the command line:
```
$ perl6 hello.pl --help
Usage:
  hello.pl <query>
  hello.pl [--filename=<Str>]
  hello.pl [--port=<Int>]

$ perl6 hello.pl '{hello}'
{
  "data": {
    "hello": "Hello World"
  }
}
```

You can even ask for information about the schema and types:
```
$ perl6 hello.pl '{ __schema { queryType { name } } }'
{
  "data": {
    "__schema": {
      "queryType": {
        "name": "Query"
      }
    }
  }
}

$ perl6 hello.pl '{ __type(name: "Query") { fields { name type { name }}}}'
{
  "data": {
    "__type": {
      "fields": [
        {
          "name": "hello",
          "type": {
            "name": "String"
          }
        }
      ]
    }
  }
}
```

## Running as a server

That's fine for the command line, but you can also easily wrap GraphQL
into a web server to expose that API to external clients.  GraphQL::Server
uses the Perl 6 web framework
[Bailador](https://github.com/ufobat/Bailador) to do that:

```
$ ./hello.pl
Entering the development dance floor: http://0.0.0.0:3000
[2016-12-21T13:02:38Z] Started HTTP server.

```

The server takes any GraphQL query sent with HTTP POST to /graphql,
executes it against the GraphQL Schema, and returns the result in
JSON.

There is one additional feature.  If it receives a GET request to
"/graphql", it sends back the
[GraphiQL](https://github.com/graphql/graphiql) graphical interactive
in-browser GraphQL IDE.

![](eg/hello-graphiql.png)

You can use that to explore the schema (though the Hello World schema
is very simple, that won't take long), and interactively construct and
execute GraphQL queries.

## Embedding in a Cro server

As an alternative to Bailador, you can use `Cro::HTTP::Router::GraphQL`
to embed GraphQL into [Cro](http://mi.cro.services/) HTTP routes:

```
use GraphQL;
use Cro::HTTP::Router::GraphQL;
use Cro::HTTP::Router;
use Cro::HTTP::Server;

class Query
{
    method hello(--> Str) { 'Hello World' }
}

my $schema = GraphQL::Schema.new(Query);

my Cro::Service $hello = Cro::HTTP::Server.new:
    :host<localhost>, :port<10000>,
    application => route
    {
        get -> { redirect '/graphql' }

        get -> 'graphql' { graphiql }

        post -> 'graphql' { graphql($schema) }
    }

$hello.start;

react whenever signal(SIGINT) { $hello.stop; exit; }
```

You can mix/match with other routes you want your server to handle.

There is also a `Cro::HTTP::Transform::GraphQL` you can easily delegate
to from Cro routes:

```
route {
    delegate graphql => Cro::HTTP::Transform::GraphQL.new(:$schema, :graphiql);
}
```

Pass in your GraphQL schema, and optionall `:graphiql` to enable
GraphiQL support on an http GET.

`Cro::HTTP::Transform::GraphQL` is a `Cro::HTTP::Transform` that
consumes `Cro::HTTP::Request`s and produces `Cro::HTTP::Response`s.
It is still pretty basic.  A planned enhancement is caching parsed
GraphQL query documents.  (Patches or advice welcome!)

## More documentation

See [eg/usersexample.md](/eg/usersexample.md) for a more complicated example.

See [slides](https://curttilmes.github.com/2017-GraphQL-PHLPM) from a
presentation about Perl 6 GraphQL at the Philadelphia Perl Mongers.

[GraphQL Documentation](/doc/GraphQL.md)

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