# servant-swagger

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This project converts [servant](https://github.com/haskell-servant/servant) APIs into Swagger 2.0 conforming json.

![servant-swagger robot](http://s16.postimg.org/rndz1wbyt/servant.png)

<hr>

Given the following `servant` API, `servant-swagger` generates the following json.

### [Input](example/File.hs)

```haskell
{-# LANGUAGE DataKinds                  #-}
{-# LANGUAGE DeriveGeneric              #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE OverloadedStrings          #-}
{-# LANGUAGE TypeOperators              #-}
module Main where

import Control.Lens
import Data.Aeson
import qualified Data.ByteString.Lazy.Char8 as BL8
import Data.Proxy
import Data.Swagger
import GHC.Generics
import Servant
import Servant.Swagger

-- Types
data Todo = Todo
  { created     :: Int
  , description :: String
  } deriving (Show, Eq, Generic)

instance ToJSON Todo

newtype TodoId = TodoId String deriving (FromText, Generic)

-- API
type API = "todo" :> Capture "id" TodoId :> Get '[JSON] Todo

-- Swagger Doc
swagDoc :: Swagger
swagDoc = toSwagger (Proxy :: Proxy API)
  & info.infoTitle   .~ "Todo API"
  & info.infoVersion .~ "1.0"
  & info.infoDescription ?~ "This is an API that tests servant-swagger support for a Todo"
  & info.infoLicense ?~ License "MIT" (Just (URL "http://mit.com"))

-- Documentation and annotations
instance ToParamSchema TodoId

instance ToSchema Todo where
  declareNamedSchema proxy = do
    (name, schema) <- genericDeclareNamedSchema defaultSchemaOptions proxy
    return (name, schema
      & schemaDescription ?~ "This is some real Todo right here"
      & schemaExample ?~ toJSON (Todo 100 "get milk"))

-- Main, create swaggger.json
main :: IO ()
main = BL8.writeFile "swagger.json" (encode swagDoc)
```

### Output

```json
{
   "swagger":"2.0",
   "info":{
      "version":"1.0",
      "title":"Todo API",
      "license":{
         "url":"http://mit.com",
         "name":"MIT"
      },
      "description":"This is an API that tests servant-swagger support for a Todo"
   },
   "definitions":{
      "Todo":{
         "example":{
            "created":100,
            "description":"get milk"
         },
         "required":[
            "created",
            "description"
         ],
         "type":"object",
         "description":"This is some real Todo right here",
         "properties":{
            "created":{
               "maximum":9223372036854775807,
               "minimum":-9223372036854775808,
               "type":"integer"
            },
            "description":{
               "type":"string"
            }
         }
      }
   },
   "paths":{
      "/todo/{id}":{
         "get":{
            "responses":{
               "404":{
                  "description":"`id` not found"
               },
               "200":{
                  "schema":{
                     "$ref":"#/definitions/Todo"
                  },
                  "description":""
               }
            },
            "produces":[
               "application/json"
            ],
            "parameters":[
               {
                  "required":true,
                  "in":"path",
                  "name":"id",
                  "type":"string"
               }
            ]
         }
      }
   }
}
```

## Try it out

All generated swagger specifications can be interactively viewed on [Swagger Editor](http://editor.swagger.io/).

Ready-to-use specification can be served as JSON and interactive API documentation
can be displayed using [Swagger UI](https://github.com/swagger-api/swagger-ui).

Many Swagger tools, including server and client code generation for many languages, can be found on
[Swagger's Tools and Integrations page](http://swagger.io/open-source-integrations/).

## Contributing

We are happy to receive bug reports, fixes, documentation enhancements, and other improvements.

Please report bugs via the [github issue tracker](https://github.com/dmjio/servant-swagger/issues).