robertdp/purescript-wai

Purescript Web Application Interface. Port of the Haskell WAI library.

WAI
Web Application Interface

     

A library that provides common protocol (types) for communication between web applications and web servers.

Installation

This library is not yet published to pursuit.
You can install this package by adding the details below to your packages.dhall:

let additions =
  { wai =
      { dependencies = [ "aff", "effect", "http-types", "node-net", "vault" ]
      , repo =
          "https://github.com/Woody88/purescript-wai.git"
      , version =
          "master"
      }
  , http-types =
      { dependencies = [ "tuples", "unicode", "generics-rep" ]
      , repo =
          "https://github.com/Woody88/purescript-http-types.git"
      , version =
          "master"
      }
    , vault =
        { dependencies =   [ "console", "effect" , "functions" , "maybe" , "prelude" , "psci-support" , "refs" ]
        , repo = "https://github.com/Woody88/purescript-vault.git"
        , version = "master"
        }
  }

user@user:~$ spago install wai

WAI Application

WAI represents request/response flow, referred to as Application, as a simple CPS function. An Application will accept a request and a continuation function that asynchronously performs the response. If the continuation function successfully sends the response, a ResponseReceived value is returned.

type Application = Request -> (Response -> Aff ResponseReceived) -> Aff ResponseReceived

WAI Middleware

By composing two Applications we can model a Middleware. This gives the ability to transform/inspect the request/response before it is delagated to the main Application.

type Middleware = Application -> Application

-- Creating 'Response' from a string
-- This function is provided by this library. 
responseStr :: Status -> ResponseHeaders -> String -> Response

myCustomMiddleware :: Middleware 
myCustomMiddleware app req send 
    | validatTokenHeader req = app req send 
    | otherwise              = send $ responseStr badRequest400 [] "Invalid Token!"
    where 
        validatTokenHeader :: Request -> Boolean
        validatTokenHeader req = ...

Because we are modelling the middleware as a function we can just compose more middleware onto one another — this means that we can control the order of the middlewares based on how we compose the functions.

type Middleware = Application -> Application

middlewares :: Middleware 
middlewares = myCustomMiddleware1 >>> myCustomMiddleware2

myCustomMiddleware1 :: Middleware 
myCustomMiddleware1 app1 app2 = ...

myCustomMiddleware2 :: Middleware 
myCustomMiddleware app1 app2 = ...

WAI Request Vault (Under Construction)