haskell-servant/servant-js

Name: servant-js

Owner: servant

Description: Automatically derive javascript functions to query servant webservices.

Created: 2016-10-08 13:33:15.0

Updated: 2018-05-18 09:20:01.0

Pushed: 2018-05-23 07:58:16.0

Homepage: null

Size: 217

Language: Haskell

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README

servant-js

This library lets you derive automatically Javascript functions that let you query each endpoint of a servant webservice.

It contains a powerful system allowing you to generate functions for several frameworks (Angular, AXios, JQuery) as well as vanilla (framework-free) javascript code.

Example

Read more about the following example here.

LANGUAGE DataKinds #-}
LANGUAGE TypeOperators #-}
LANGUAGE DeriveGeneric #-}
LANGUAGE GeneralizedNewtypeDeriving #-}

rt Control.Concurrent.STM
rt Control.Monad.IO.Class
rt Data.Aeson
rt Data.Proxy
rt GHC.Generics
rt Network.Wai.Handler.Warp (run)
rt Servant
rt Servant.JS
rt System.FilePath

 A simple Counter data type
ype Counter = Counter { value :: Int }
riving (Generic, Show, Num)

ance ToJSON Counter

 Shared counter operations

reating a counter that starts from 0
ounter :: IO (TVar Counter)
ounter = newTVarIO 0

ncreasing the counter by 1
terPlusOne :: MonadIO m => TVar Counter -> m Counter
terPlusOne counter = liftIO . atomically $ do
dValue <- readTVar counter
t newValue = oldValue + 1
iteTVar counter newValue
turn newValue

entValue :: MonadIO m => TVar Counter -> m Counter
entValue counter = liftIO $ readTVarIO counter

 Our API type
 TestApi = "counter" :> Post '[JSON] Counter -- endpoint for increasing the counter
      :<|> "counter" :> Get  '[JSON] Counter -- endpoint to get the current value

 TestApi' = TestApi -- The API we want a JS handler for
       :<|> Raw     -- used for serving static files

his proxy only targets the proper endpoints of our API,
ot the static file serving bit
Api :: Proxy TestApi
Api = Proxy

his proxy targets everything
Api' :: Proxy TestApi'
Api' = Proxy

 Server-side handler

here our static files reside
:: FilePath
= "examples/www"

efining handlers
er :: TVar Counter -> Server TestApi
er counter = counterPlusOne counter     -- (+1) on the TVar
        :<|> currentValue counter       -- read the TVar

er' :: TVar Counter -> Server TestApi'
er' counter = server counter
         :<|> serveDirectory www         -- serve static files

erver :: TVar Counter -- ^ shared variable for the counter
      -> Int          -- ^ port the server should listen on
      -> IO ()
erver var port = run port (serve testApi' $ server' var)

 :: IO ()
 = do
 write the JS code to www/api.js at startup
iteJSForAPI testApi jquery (www </> "api.js")

 setup a shared counter
t <- newCounter

 listen to requests on port 8080
nServer cnt 8080