# Morpheus GraphQL [](https://hackage.haskell.org/package/morpheus-graphql) [](https://circleci.com/gh/morpheusgraphql/morpheus-graphql)
Build GraphQL APIs with your favourite functional language!
Morpheus GraphQL (Server & Client) helps you to build GraphQL APIs in Haskell with native haskell types.
Morpheus will convert your haskell types to a GraphQL schema and all your resolvers are just native Haskell functions. Mopheus GraphQL can also convert your GraphQL Schema or Query to Haskell types and validate them in compile time.
Morpheus is still in an early stage of development, so any feedback is more than welcome, and we appreciate any contribution!
Just open an issue here on GitHub, or join [our Slack channel](https://morpheus-graphql-slack-invite.herokuapp.com/) to get in touch.
## Getting Started
### Setup
To get started with Morpheus, you first need to add it to your project's dependencies, as follows (assuming you're using hpack):
_package.yml_
```yaml
dependencies:
- morpheus-graphql
```
Additionally, you should tell stack which version to pick:
_stack.yml_
```yaml
resolver: lts-14.8
extra-deps:
- morpheus-graphql-0.6.0
```
As Morpheus is quite new, make sure stack can find morpheus-graphql by running `stack upgrade` and `stack update`
### Building your first GraphQL API
### with GraphQL syntax
_schema.gql_
```gql
type Query {
deity(name: String!): Deity!
}
type Deity {
name: String!
power: String
}
```
_API.hs_
```haskell
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeFamilies #-}
module API (api) where
import qualified Data.ByteString.Lazy.Char8 as B
import Data.Morpheus (interpreter)
import Data.Morpheus.Document (importGQLDocumentWithNamespace)
import Data.Morpheus.Types (GQLRootResolver (..), IORes)
import Data.Text (Text)
importGQLDocumentWithNamespace "schema.gql"
rootResolver :: GQLRootResolver IO () Query Undefined Undefined
rootResolver =
GQLRootResolver
{
queryResolver = Query {queryDeity},
mutationResolver = Undefined,
subscriptionResolver = Undefined
}
where
queryDeity QueryDeityArgs {queryDeityArgsName} = pure Deity {deityName, deityPower}
where
deityName _ = pure "Morpheus"
deityPower _ = pure (Just "Shapeshifting")
api :: ByteString -> IO ByteString
api = interpreter rootResolver
```
Template Haskell Generates types: `Query` , `Deity`, `DeityArgs`, that can be used by `rootResolver`
`importGQLDocumentWithNamespace` will generate Types with namespaced fields. if you don't need napespacing use `importGQLDocument`
### with Native Haskell Types
To define a GraphQL API with Morpheus we start by defining the API Schema as a native Haskell data type,
which derives the `Generic` typeclass. Lazily resolvable fields on this `Query` type are defined via `a -> IORes b`, representing resolving a set of arguments `a` to a concrete value `b`.
```haskell
data Query m = Query
{ deity :: DeityArgs -> m Deity
} deriving (Generic, GQLType)
data Deity = Deity
{ fullName :: Text -- Non-Nullable Field
, power :: Maybe Text -- Nullable Field
} deriving (Generic)
instance GQLType Deity where
type KIND Deity = OBJECT
data DeityArgs = DeityArgs
{ name :: Text -- Required Argument
, mythology :: Maybe Text -- Optional Argument
} deriving (Generic)
```
For each field in the `Query` type defined via `a -> m b` (like `deity`) we will define a resolver implementation that provides the values during runtime by referring to
some data source, e.g. a database or another API. Fields that are defined without `a -> m b` you can just provide a value.
In above example, the field of `DeityArgs` could also be named using reserved identities (such as: `type`, `where`, etc), in order to avoid conflict, a prime symbol (`'`) must be attached. For example, you can have:
```haskell
data DeityArgs = DeityArgs
{ name :: Text -- Required Argument
, mythology :: Maybe Text -- Optional Argument
, type' :: Text
} deriving (Generic)
```
The field name in the final request will be `type` instead of `type'`. The Morpheus request parser converts each of the reserved identities in Haskell 2010 to their corresponding names internally. This also applies to selections.
```haskell
resolveDeity :: DeityArgs -> IORes e Deity
resolveDeity DeityArgs { name, mythology } = liftEitherM $ dbDeity name mythology
askDB :: Text -> Maybe Text -> IO (Either String Deity)
askDB = ...
```
Note that the type `a -> IORes b` is just Synonym for `a -> ExceptT String IO b`
To make this `Query` type available as an API, we define a `GQLRootResolver` and feed it to the Morpheus `interpreter`. A `GQLRootResolver` consists of `query`, `mutation` and `subscription` definitions, while we omit the latter for this example:
```haskell
rootResolver :: GQLRootResolver IO () Query Undefined Undefined
rootResolver =
GQLRootResolver
{ queryResolver = Query {deity = resolveDeity}
, mutationResolver = Undefined
, subscriptionResolver = Undefined
}
gqlApi :: ByteString -> IO ByteString
gqlApi = interpreter rootResolver
```
As you can see, the API is defined as `ByteString -> IO ByteString` which we can either invoke directly or use inside an arbitrary web framework
such as `scotty` or `serverless-haskell`. We'll go for `scotty` in this example:
```haskell
main :: IO ()
main = scotty 3000 $ post "/api" $ raw =<< (liftIO . gqlApi =<< body)
```
If we now send a POST request to `http://localhost:3000/api` with a GraphQL Query as body for example in a tool like `Insomnia`:
```GraphQL
query GetDeity {
deity (name: "Morpheus") {
fullName
power
}
}
```
our query will be resolved!
```JSON
{
"data": {
"deity": {
"fullName": "Morpheus",
"power": "Shapeshifting"
}
}
}
```
## Serverless Example
If you are interested in creating a `Morpheus GraphQL` API with `Serverless`, you should take a look at our example in this repository:
[_Mythology API_](https://github.com/morpheusgraphql/mythology-api) it is our example project build with `Morpheus GraphQL` and `Serverless-Haskell`,
where you can query different mythology characters with `GraphiQL`.
Mythology API is deployed on : [_api.morpheusgraphql.com_](https://api.morpheusgraphql.com) where you can test it with `GraphiQL`
## Advanced topics
### Enums
You can use Union Types as Enums, but they're not allowed to have any parameters.
```haskell
data City
= Athens
| Sparta
| Corinth
| Delphi
| Argos
deriving (Generic)
instance GQLType City where
type KIND City = ENUM
```
### Union types
To use union type, all you have to do is derive the `GQLType` class. Using GraphQL [_fragments_](https://graphql.org/learn/queries/#fragments), the arguments of each data constructor can be accessed from the GraphQL client.
```haskell
data Character
= DEITY Deity
| HUMAN Human
deriving (Generic)
instance GQLType Character where
type KIND City = UNION
```
### Scalar types
To use custom scalar types, you need to provide implementations for `parseValue` and `serialize` respectively.
```haskell
data Odd = Odd Int deriving (Generic)
instance GQLScalar Odd where
parseValue (Int x) = pure $ Odd (... )
parseValue (String x) = pure $ Odd (... )
serialize (Odd value) = Int value
instance GQLType Odd where
type KIND Odd = SCALAR
```
### Applicative and Monad instance
The `Resolver` type has `Applicative` and `Monad` instances that can be used to compose resolvers.
### Introspection
Morpheus converts your schema to a GraphQL introspection automatically. You can use tools like `Insomnia` to take a
look at the introspection and validate your schema.
If you need a description for your GQLType inside of the introspection you can define the GQLType instance manually
and provide an implementation for the `description` function:
```haskell
data Deity = Deity
{ ...
} deriving (Generic)
instance GQLType Deity where
description = const "A supernatural being considered divine and sacred"
```
screenshots from `Insomnia`
### Mutations
In addition to queries, Morpheus also supports mutations. The behave just like regular queries and are defined similarly:
Just exchange deriving `GQLQuery` for `GQLMutation` and declare them separately at the `GQLRootResolver` definition
```haskell
newtype Mutation m = Mutation
{ createDeity :: Form -> m Deity
} deriving (Generic, GQLType)
createDeityMutation :: Form -> m (Deity m)
createDeityMutation = ...
rootResolver :: GQLRootResolver IO Query Mutation Undefined
rootResolver =
GQLRootResolver
{ queryResolver = Query {...}
, mutationResolver = Mutation {
createDeity = createDeityMutation
}
, subscriptionResolver = Undefined
}
gqlApi :: ByteString -> IO ByteString
gqlApi = interpreter rootResolver
```
### Subscriptions
im morpheus subscription and mutation communicating with Events,
`Event` consists with user defined `Channel` and `Content`.
every subscription has own Channel by which will be triggered
```haskell
data Channel
= ChannelA
| ChannelB
data Content
= ContentA Int
| ContentB Text
newtype Query m = Query
{ deity :: () -> m Deity
} deriving (Generic)
newtype Mutation m = Mutation
{ createDeity :: () -> m Deity
} deriving (Generic)
newtype Subscription m = Subscription
{ newDeity :: () -> m Deity
} deriving (Generic)
type APIEvent = Event Channel Content
rootResolver :: GQLRootResolver IO APIEvent Query Mutation Subscription
rootResolver =
GQLRootResolver
{ queryResolver = Query {deity = const fetchDeity}
, mutationResolver = Mutation {createDeity}
, subscriptionResolver = Subscription {newDeity}
}
where
createDeity _args = MutResolver events updateDeity
where
events = [Event {channels = [ChannelA], content = ContentA 1}]
updateDeity = updateDBDeity
newDeity _args = SubResolver [ChannelA] subResolver
where
subResolver (Event [ChannelA] (ContentA _value)) = fetchDeity -- resolve New State
subResolver (Event [ChannelA] (ContentB _value)) = fetchDeity -- resolve New State
subResolver _ = fetchDeity -- Resolve Old State
```
## Morpheus `GraphQL Client` with Template haskell QuasiQuotes
```hs
defineByDocumentFile
"./schema.gql"
[gql|
query GetHero ($character: Character)
{
deity (fatherOf:$character) {
name
power
worships {
deity2Name: name
}
}
}
|]
```
with schema:
```gql
input Character {
name: String!
}
type Deity {
name: String!
worships: Deity
}
```
will validate query and Generate:
- namespaced response and variable types
- instance for `Fetch` typeClass
```hs
data GetHero = GetHero {
deity: DeityDeity
}
-- from: {user
data DeityDeity = DeityDeity {
name: Text,
worships: Maybe DeityWorshipsDeity
}
-- from: {deity{worships
data DeityWorshipsDeity = DeityWorshipsDeity {
name: Text,
}
data GetHeroArgs = GetHeroArgs {
getHeroArgsCharacter: Character
}
data Character = Character {
characterName: Person
}
```
as you see, response type field name collision can be handled with GraphQL `alias`.
with `fetch` you can fetch well typed response `GetHero`.
```haskell
fetchHero :: Args GetHero -> m (Either String GetHero)
fetchHero = fetch jsonRes args
where
args = GetHeroArgs {getHeroArgsCharacter = Person {characterName = "Zeus"}}
jsonRes :: ByteString -> m ByteString
jsonRes = <GraphQL APi>
```
types can be generatet from `introspection` too:
```haskell
defineByIntrospectionFile "./introspection.json"
```
## Morpheus CLI for Code Generating
you should use [morpheus-graphql-cli](https://github.com/morpheusgraphql/morpheus-graphql-cli)
# About
## The name
_Morpheus_ is the greek god of sleep and dreams whose name comes from the greek word _μορφή_ meaning form or shape.
He is said to be able to mimic different forms and GraphQL is good at doing exactly that: Transforming data in the shape
of many different APIs.
## Team
Morpheus is written and maintained by [_nalchevanidze_](https://github.com/nalchevanidze)
## Roadmap
- Medium future:
- Stabilize API
- Specification-isomorphic error handling
- Long term:
- Support all possible GQL features
- Performance optimization