Elm Web Server

An API with Node.js-bindings for Elm WebSocket/HTTP-servers.

Warnings

This package contains no native/kernel-code - All interop with Node.js is implemented using Elm's ports-API. Modules with ports are not intended for distribution on package-managers, as they can be unreliably implemented compared to regular Elm-modules, so open an issue if you encounter problems!

Elm, along with the Elm architecture, is designed for browser-applications; This project in an experimental attempt to embed the architecture inside Node.js.

Taking the unreasonable performance implications aside, it is fun to experience Elm as a shared language between client and server, with all of it's nice properties for refactoring and extension.

Features

• A small API to hook Elm's Platform.program into Node/http and/or Websockets/ws in Node.js.
• Modules for working with Http-Request/Response & WebSocket messages on the server.
• Emulation for XmlHttpRequest & WebSocket to run elm-lang/http & elm-lang/websocket on the server.

Installation

The package is implemented using JavaScript language-features supported >= v6.13.1 of Node.js.

The package is distributed through NPM:

npm install -S elm-web-server

if you're going to use the Server.WebSocket-module, you will need to install the following package from NPM:

npm install -S ws

Open elm-package.json and expose the internal Elm-modules from the package like this:

{   
    ...
    "source-directories": [
        ...
        "node_modules/elm-web-server/source"
    ]
}

Take a look at the examples-directory for inspiration.

JavaScript Interface

in Node.js, assuming an Elm module named Main compiled to main.elm.js in the same directory, the API can be used as such:

const Ews = require("elm-web-server")
const Http = require("http")
const Ws = require("ws")
const App = require("./main.elm.js")
 
const PORT = process.env.PORT || 3000
 
const worker = App.Main.worker()
 
const server = Http.createServer(Ews.createRequestListener(worker))
 
Ews.attachMessageListener(worker, new Ws.Server({ server }))
 
Ews.attachConsoleListener(worker)
 
server.listen(PORT, () => {
    console.log(`listening at http://localhost:${PORT}`)
})

Importing elm-web-server automatically exposes XmlHttpRequest & WebSocket globally to enable server-side usage of elm-lang/http & elm-lang/websocket.

Elm Interface

There is a couple of small modules for Elm, written to facilitate some basic server-logic.

Server.Http

The HTTP-module exposes utility for working with HTTP-requests/responses.

type alias Request =
    { connection : Connection
    , method : Method
    , headers : List Header
    , url : Url
    , body : Maybe String
    }

type Error
    = ConnectionClosed Connection
    | Error String

listen : (Result Error Request -> msg) -> Sub msg

respondWith : (a -> String) -> Status -> List Header -> Maybe a -> Connection -> Response

respondWithJson : Status -> List Header -> Json.Encode.Value -> Connection -> Response

respondWithText : Status -> List Header -> String -> Connection -> Response

respondWithNothing : Status -> List Header -> Connection -> Response

send : Response -> Cmd msg

compareConnection : Connection -> Connection -> Bool

Server.Http.Url

The Http.Url module exposes types, decoding for Http-request urls.

toLocation is helpful if you want to parse urls using evancz/url-parser, as shown in examples/routing.

type alias Url =
    { pathname : String
    , search : String
    }

decoder : Decoder Url

toLocation :
    Url
    ->
        { href : String
        , host : String
        , hostname : String
        , protocol : String
        , origin : String
        , port_ : String
        , pathname : String
        , search : String
        , hash : String
        , username : String
        , password : String
        }

Server.Http.Method

The Http.Method module exposes types, encoding, and decoding for Http-request methods.

type Method
    = Get
    | Head
    | Post
    | Put
    | Delete
    | Trace
    | Options
    | Connect
    | Patch
    | Method String

encode : Method -> Json.Encode.Value

decoder : Decoder Method

Server.Http.Status

The Http.Status module exposes types, encoding, and decoding for Http-request statuses.

type Status
    = Ok
    | Created
    | Accepted
    | NonAuthoritativeInformation
    | NoContent
    | ResetContent
    | PartialContent
    | MultiStatus
    | AlreadyReported
    | ImUsed
    | MultipleChoices
    | MovedPermanently
    | Found
    | SeeOther
    | NotModified
    | UseProxy
    | SwitchProxy
    | TemporaryRedirect
    | PermanentRedirect
    | BadRequest
    | Unauthorized
    | PaymentRequired
    | Forbidden
    | NotFound
    | MethodNotAllowed
    | NotAcceptable
    | ProxyAuthenticationRequired
    | RequestTimeout
    | Conflict
    | Gone
    | LengthRequired
    | PreconditionFailed
    | PayloadTooLarge
    | URITooLong
    | UnsupporedMediaType
    | RangeNotSatisfiable
    | ExpectationFailed
    | ImATeapot
    | MisdirectedRequest
    | UnprocessableEntity
    | Locked
    | FailedDependency
    | UpgradeRequired
    | PreconditionRequired
    | TooManyRequests
    | RequestHeaderFieldsTooLarge
    | UnavailableForLegalReasons
    | InternalServerError
    | NotImplemented
    | BadGateway
    | ServiceUnavailable
    | GatewayTimeout
    | HTTPVersionNotSupported
    | VariantAlsoNegotiates
    | InsufficientStorage
    | LoopDetected
    | NotExtended
    | NetworkAuthenticationRequired
    | Status Int String

encode : Status -> Json.Encode.Value

decoder : Decoder Status

Server.Http.Header

The Http.Header module exposes types, encoding, and decoding for Http-request headers.

byteLength is helpful if you want to set the ContentLength-header, as shown in examples/routing.

type Header
    = ContentType MimeType
    | Accept (List MimeType)
    | ContentLength Int
    | Header String String

type MimeType
    = TextPlain
    | TextHtml
    | TextCss
    | ApplicationJson
    | ApplicationJavascript
    | MimeType String

encode : List Header -> Json.Encode.Value

decoder : Decoder (List Header)

byteLength : String -> Int

Server.WebSocket

The WebSocket-module exposes utility for working with WebSocket connections & messages.

type Message
    = Connected Connection
    | Disconnected Connection
    | Received Connection String

type Error
    = ConnectionClosed Connection
    | FailedToSend Connection String
    | Error String

listen : (Result Error Message -> msg) -> Sub msg

send : String -> Connection -> Cmd msg

disconnect : Connection -> Cmd msg

compareConnection : Connection -> Connection -> Bool

Server.Console

The Console-module allows you to print information to the console in different formats.

log : String -> Cmd msg

logError : String -> Cmd msg

logWarning : String -> Cmd msg