# Talk Plugins

Plugins for Talk can take various forms, currently we are only supporting server
side plugins.

## Plugin Registration

The parsing order for the plugin registration is as follows:

- `TALK_PLUGINS_JSON` environment variable
- `plugins.json` file
- `plugins.default.json` file

If you need to "disable all plugins", you can simply provide `{}` as the
contents of `process.env.TALK_PLUGINS_JSON` or the `plugins.json`.

The format for this is thus:

```json
{
  "server": [
    "people"
  ]
}
```

Where we have a `server` key with an array of plugins that match the folder
name in the `plugins/` folder. For example, the above config would
require a plugin from `plugins/people`, which must provide a `index.js` file
that returns an object that matches the Plugin Specification.

If the package is external (available on NPM) you can specify the string for
the version by using an object instead, for example:

```json
{
  "server": [
    {"people": "^1.2.0"}
  ]
}
```

External plugins can be resolved by running:

```bash
./bin/cli plugins reconcile
```

This achieves two things:

1. It will traverse into local plugin folders and install their dependencies.
  _Note that if the plugin is already installed and available in the node_modules folder, it will not be
  fetched again unless there is a version mismatch._ This will result in the
  project `package.json` and `yarn.lock` files to be modified, this is normal as
  this ensures that repeated deployments (with the same config) will have the
  same config, these changes should not be committed to source control.
2. It will seek out dependencies that are listed in the object notation and try
  to install them from npm.

## Plugin Dependencies

You may also include additional external dependencies in your local packages by
specifying a `package.json` at your plugin root which will result in a
`node_modules` folder being generated at the plugin root with your specific
dependencies.

## Deployment Solutions

Plugins can be deployed with a production instance of Talk.

### Source

Source deployments can just modify the `plugins.json` file and include any
local plugins into the `plugins/` directory. After including the config, you
need to reconcile the plugins and build the static assets:

```bash
# get plugin dependancies and remote plugins
./bin/cli plugins reconcile

# build staic assets (including enabled client side plugins)
yarn build
```

Then the application can be started as is.

### Docker

If you deploy using Docker, you can extend from the `*-onbuild` image, an
example `Dockerfile` for your project could be:

```Dockerfile
FROM coralproject/talk:latest-onbuild
```

Where the directory for your instance would contain a `plugins.json` file
describing the plugin requirements and a `plugins` directory containing any
other local plugins that should be included.

Onbuild triggers will execute when the image is building with your custom
configuration and will ensure that the image is ready to use by building all
assets inside the image as well.

## Server Plugins

### API

You can access any API available inside the talk directory in a plugin by simply
importing the file relative to the talk project root. An example would be if you
wanted to import the `MetadataService`, you would simply write:

```javascript
const MetadataService = require('services/metadata');
```

### Specification

Each plugin should export a single object with all hooks available on it.

_**Note: You will have access to the whole core and other plugin's typeDefs,
context, loaders, mutators, resolvers, hooks. This is intentional, as it
encourages composing plugins to merge functionality, like a Slack plugin which
provides a Slack notify context function as well as having the loader for
comments.**_

The following are the hooks available:

#### Field: `typeDefs`

```graphql
enum COLOUR {
  RED
  BLUE
}

type Person {
  name: String!
  colour: COLOUR!
}

type RootMutation {
  createPerson(name: String!): Person
}

type RootQuery {
  people: [Person!]
}

type Subscription {
  leader: Person
}
```

Thanks to [gql-merge](https://www.npmjs.com/package/gql-merge) the contents of
`typeDefs` should be a string that will be _merged_ with the existing type
definitions. `enum`'s will be appended to, types will be appended, and new types
will be added.

#### Field: `context`

```js
{
  Slack: (context) => ({
    notify: (message) => {
      // return a promise after we're done sending notifications.
    }
  })
}
```

Any property provided here will be added to the context parameter available
inside all resolvers, loaders, mutators, and of course, other context based
plugins.

The top level item must accept a context for the request which it should use to
configure the context plugin before it would be mounted at `context.plugins`.
This plugin above would mount at: `context.plugins.Slack`, or, if you're using
[object destructuring](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment), `{plugins: {Slack}}`.

#### Field: `loaders`

```js
(context) => ({
  People: {
    load: () => db.people.find({user: context.user})
  }
})
```

Loaders should be provided as a function which returns a map which is used in
the resolvers function. These must return a promise or a value.

#### Field: `mutators`

```js
(context) => ({
  People: {
    create: (name) => {
      return db.people.insert({user: context.user, name});
    }
  }
})
```

Mutators should be provided as a function which returns a map which is used in
the resolvers function. These must return a promise or a value.

#### Field: `resolvers`

```js
{
  Person: {
    name(obj, args, context) {
      return obj.name;
    },
    colour(obj, args, context) {
      // Bill likes the colour red, everyone else likes blue.
      return obj.name === 'bill' ? 'RED' : 'BLUE';
    }
  },
  RootQuery: {
    people(obj, args, {loaders: {People}}) {
      return People.load();
    }
  },
  RootMutation: {
    createPerson(obj, {name}, {mutators: {People}}) {
      return People.create(name);
    }
  }
}
```

Should return a resolver map as described in the
[Apollo Docs](http://dev.apollodata.com/tools/graphql-tools/resolvers.html#Resolver-map).

This will merge with the existing resolvers in core and from previous plugins.

#### Field: `hooks`

```js
{
  RootMutation: {
    createPerson: {
      post: async (obj, args, {plugins: {Slack}}, info, person) {
        if (!person) {
          return person;
        }

        await Slack.notify(`A new person just was created with name ${person.name}`);

        return person;
      }
    }
  }
}
```

Hooks here are pretty special, for each resolver field, you can specify a
pre/post hook that will execute pre and post field resolution.

If your post function accepts four parameters, then it can modify the field
result. It is *required* that the function resolves a promise (or returns) with
the modified value or simply the original if you didn't modify it.

#### Field: `setupFunctions`

```js
setupFunctions: {
  leader: (options, args) => ({
    leader: {
      filter: (person) => person.place === 1
    },
  }),
}
```

Setup functions allow you to create filters that control which pubsub.publish() events
send data to the client. If the type in question contains args, clients may subscribe using those arguments to further filter their subscription.

For more information, see the [Apollo Docs](https://github.com/apollographql/graphql-subscriptions).

#### Field: `router`

```js
(router) => {
  router.get('/api/v1/people', (req, res) => {
    res.json({people: [{name: 'Bob'}]});
  });
}
```

The Router hook allows you to create a function that accepts the base express
router where you can mount any amount of middleware/routes to do any form of
action needed by external applications. We also provide the authorization
middleware via:

```js
const authorization = require('middleware/authorization');

module.exports = {
  router(router) {
    router.get('/api/v1/people', authorization.needed('ADMIN'), (req, res) => {
      res.json({people: [{name: 'SECRET PEOPLE'}]});
    });
  }
}
```

#### Field: `passport`

```js
const FacebookStrategy = require('passport-facebook').Strategy;
const UsersService = require('services/users');
const {ValidateUserLogin, HandleAuthPopupCallback} = require('services/passport');

module.exports = {
  passport(passport) {
    passport.use(new FacebookStrategy({
      clientID: process.env.TALK_FACEBOOK_APP_ID,
      clientSecret: process.env.TALK_FACEBOOK_APP_SECRET,
      callbackURL: `${process.env.TALK_ROOT_URL}/api/v1/auth/facebook/callback`,
      passReqToCallback: true,
      profileFields: ['id', 'displayName', 'picture.type(large)']
    }, async (req, accessToken, refreshToken, profile, done) => {

      let user;
      try {
        user = await UsersService.findOrCreateExternalUser(profile);
      } catch (err) {
        return done(err);
      }

      return ValidateUserLogin(profile, user, done);
    }));
  },
  router(router) {

    // Note that we have to import the passport instance here, it is
    // instantiated after all the strategies have been mounted.
    const {passport} = require('services/passport');

    /**
     * Facebook auth endpoint, this will redirect the user immediatly to facebook
     * for authorization.
     */
    router.get('/facebook', passport.authenticate('facebook', {display: 'popup', authType: 'rerequest', scope: ['public_profile']}));

    /**
     * Facebook callback endpoint, this will send the user a html page designed to
     * send back the user credentials upon sucesfull login.
     */
    router.get('/facebook/callback', (req, res, next) => {

      // Perform the facebook login flow and pass the data back through the opener.
      passport.authenticate('facebook', HandleAuthPopupCallback(req, res, next))(req, res, next);
    });
  }
};
```

This is a full example including the routes hook to add the required components
to the application router to support a different auth strategy.

### Full Example

Contents of `plugins.json`:

```json
{
  "server": [
    "people"
  ]
}
```

Located in `plugins/people/index.js`:

```js
module.exports = {
  typeDefs: `
  enum COLOUR {
    RED
    BLUE
  }

  type Person {
    name: String!
    colour: COLOUR!
  }

  type RootMutation {
    createPerson(name: String!): Person
  }

  type RootQuery {
    people: [Person!]
  }

  type Subscription {
    leader: Person
  }
  `,
  context: {
    Slack: () => ({
      notify: (message) => {
        // return a promise after we're done sending notifications.
      }
    })
  },
  loaders: ({user}) => ({
    People: {
      load: () => db.people.find({user})
    }
  }),
  mutators: ({user}) => ({
    People: {
      create: (name) => {
        return db.people.insert({user, name});
      }
    }
  }),
  resolvers: {
    Person: {
      name(obj, args, context) {
        return obj.name;
      },
      colour(obj, args, context) {
        // Bill likes the colour red, everyone else likes blue.
        return obj.name === 'bill' ? 'RED' : 'BLUE';
      }
    },
    RootQuery: {
      people(obj, args, {loaders: {People}}) {
        return People.load();
      }
    },
    RootMutation: {
      createPerson(obj, {name}, {mutators: {People}}) {
        return People.create(name);
      }
    }
  },
  hooks: {
    RootMutation: {
      createPerson: {
        post: async (obj, args, {plugins: {Slack}}, info, person) => {
          if (!person) {
            return person;
          }

          await Slack.notify(`A new person just was created with name ${person.name}`);

          return person;
        }
      }
    }
  },
  setupFunctions: {
    leader: (options, args) => ({
      leader: {
        filter: (person) => person.place === 1
      }
    }
  }
};

```