Adapter for express js middleware

[srghma]

For example hyper has mkMiddlewareFromForeign method

purescript-hyper/hyper#47 (comment)

Is the same possible with warp?

[Woody88]

Hi @srghma,

Yes, it's actually a great idea! warp is built as a handler for wai, so as long as you can get the express middleware to match the Application type. It should be possible. So, we could make a wai-express-js middleware. Have a look at this https://github.com/Woody88/purescript-wai-websockets.

I will try to look more into it later on.

[Woody88]

@srghma Sorry it took me a bit of time to get on this issue. I was focusing more on my other library (purescript-swerve). So, I implemented a solution that can allow you to add express middleware using purescript-vault.

Here is a working example using express static.

Main.js

const serveStatic = require('serve-static')

exports._serveStatic = serveStatic('public')

Main.purs

import Prelude

import Data.Maybe (Maybe(..))
import Data.Tuple.Nested ((/\))
import Data.Vault as V
import Effect (Effect)
import Effect.Class.Console as Console
import Network.HTTP.Types (ok200)
import Network.HTTP.Types.Header (hContentType)
import Network.Wai (Application, Middleware, responseStr)
import Network.Warp.FFI.Server (ForeignApplication, HttpHandles, httpHandlesKey, mkMiddlewareFromForeign)
import Network.Warp.Run (runSettings)
import Network.Warp.Settings (defaultSettings)
 
main :: Effect Unit
main = do 
  let beforeMainLoop = Console.log $ "Listening on port " <> show defaultSettings.port
  httpKey' <- httpHandlesKey  -- creates key that will allow the middleware to access node HTTP request and response object
  void $ runSettings defaultSettings { beforeMainLoop = beforeMainLoop, httpKey = Just httpKey' } 
       $ serverStatic httpKey' 
       $ app 

app :: Application 
app req f = do
    f $ responseStr ok200 [(hContentType /\ "text/plain")] "Hello World!"

serverStatic :: V.Key HttpHandles -> Middleware 
serverStatic k = mkMiddlewareFromForeign k _serveStatic

foreign import _serveStatic :: ForeignApplication

Let me know if you need more details. I will be working on polishing warp's codebase and docs soon.

[robertdp]

My PR simplifies this even further, and httpKey creation and setting is no longer required.

mkMiddlewareFromForeign :: ForeignMiddleware -> Middleware

The serveStatic example becomes:

main :: Effect Unit
main =
  void
    $ runSettings defaultSettings
    $ serveStatic "public"
    $ app

app :: Application 
app _ send = send $ responseStr ok200 [(hContentType /\ "text/plain")] "Hello World!"

foreign import _serveStatic :: String -> ForeignMiddleware

serveStatic :: String -> Middleware 
serveStatic = mkMiddlewareFromForeign <<< _serveStatic