Starting point.

makefile

@@ -0,0 +1,23 @@
+all: build
+
+build:
+	npm run build
+
+bundle:
+	spago bundle-app
+
+serve:
+	npm run serve
+
+spagobuild:
+	spago build
+
+#HTTPD_ACCESS_LOGS ?= /tmp/access.log
+#HTTPD_ADDR        ?= 127.0.0.1
+#HTTPD_PORT        ?= 35000
+#DIR               ?= output
+#serve:
+#	darkhttpd $(DIR) --addr $(HTTPD_ADDR) --port $(HTTPD_PORT) --log $(HTTPD_ACCESS_LOGS)
+
+# You can add your specific instructions there.
+-include makefile.user

spago.dhall

@@ -1,5 +1,29 @@
 { name = "halogen-project"
-, dependencies = [ "console", "effect", "halogen", "prelude" ]
+, dependencies =
+  [ "aff"
+  , "argonaut-core"
+  , "arraybuffer"
+  , "arraybuffer-builder"
+  , "arraybuffer-types"
+  , "arrays"
+  , "codec-argonaut"
+  , "console"
+  , "const"
+  , "effect"
+  , "either"
+  , "foreign"
+  , "halogen"
+  , "halogen-subscriptions"
+  , "lists"
+  , "maybe"
+  , "prelude"
+  , "strings"
+  , "transformers"
+  , "uint"
+  , "web-encoding"
+  , "web-events"
+  , "web-socket"
+  ]
 , packages = ./packages.dhall
 , sources = [ "src/**/*.purs", "test/**/*.purs" ]
 }

src/App/IPC.purs

@@ -0,0 +1,56 @@
+module App.IPC (toIPC, fromIPC) where
+
+import Prelude
+
+import Effect (Effect)
+import Effect.Class (class MonadEffect, liftEffect)
+import Effect.Class.Console as Console
+
+import Data.Maybe
+import Data.UInt (UInt, fromInt, toInt)
+import Data.Array (drop, cons)
+import Data.ArrayBuffer.Types (DataView, ArrayBuffer(..))
+import Data.ArrayBuffer.Typed (buffer)
+import Data.ArrayBuffer.ArrayBuffer as AB
+import Data.ArrayBuffer.Builder (PutM, putArrayBuffer, execPut, putUint32be)
+
+import Data.String.CodeUnits as CU
+
+import Web.Encoding.TextEncoder (new, TextEncoder, encode)
+import Web.Encoding.TextDecoder as TD
+
+import Data.Char (fromCharCode)
+
+import Data.ArrayBuffer.DataView as DV
+import Effect.Unsafe
+
+putStringUtf8 :: forall m. MonadEffect m => String -> PutM m Unit
+putStringUtf8 s = do
+  textEncoder <- liftEffect new
+  let stringbuf = buffer $ encode s textEncoder
+  -- Put a 32-bit big-endian length for the utf8 string, in bytes.
+  putUint32be $ fromInt $ AB.byteLength stringbuf
+  putArrayBuffer stringbuf
+
+toIPC :: String -> Effect ArrayBuffer
+toIPC s = execPut $ putStringUtf8 s
+
+-- TODO: fix this implementation. Use an actual text decoder.
+arraybufferToString :: ArrayBuffer -> Effect String
+arraybufferToString arraybuffer
+  = case (AB.byteLength arraybuffer) of
+      0 -> pure ""
+      _ -> do
+        maybeFirstByte <- DV.getUint8 (DV.whole arraybuffer) 0
+        rest <- arraybufferToString $ AB.slice 1 (AB.byteLength arraybuffer) arraybuffer
+        pure $ (CU.singleton $ firstChar maybeFirstByte) <> rest
+        where
+          firstChar :: Maybe UInt -> Char
+          firstChar byte = fromMaybe '\n' (fromCharCode (toInt (fromMaybe (fromInt 10) byte)))
+
+dataviewToString :: DataView -> Effect String
+dataviewToString dataview = arraybufferToString $ DV.buffer dataview
+
+-- TODO: make sure the String length is correct.
+fromIPC :: ArrayBuffer -> Effect String
+fromIPC ab = arraybufferToString (AB.slice 4 (AB.byteLength ab) ab)

src/Main.purs

@@ -2,12 +2,409 @@ module Main where
 
 import Prelude
 
-import App.Button as Button
+import Control.Monad.Except (runExcept)
+import Control.Monad.State (class MonadState)
+import Data.Argonaut.Core as AC
+import Data.Argonaut.Parser as AP
+import Data.Array as A
+import Data.Codec.Argonaut (JsonCodec, JsonDecodeError)
+import Data.Codec.Argonaut as CA
+import Data.Const (Const)
+import Data.Either (Either(..))
+import Data.List.NonEmpty (NonEmptyList)
+import Data.List.NonEmpty as NEL
+import Data.Maybe (Maybe(..), isJust, isNothing, maybe)
+import Data.String as String
 import Effect (Effect)
-import Halogen.Aff as HA
+import Effect.Aff.Class (class MonadAff)
+import Foreign (Foreign)
+import Foreign as F
+import Halogen as H
+import Halogen.Aff (awaitBody, runHalogenAff) as HA
+import Halogen.HTML as HH
+import Halogen.HTML.Events as HE
+import Halogen.HTML.Properties as HP
+import Halogen.Query.Event as HQE
+import Halogen.Subscription as HS
 import Halogen.VDom.Driver (runUI)
+import Web.Event.Event (Event)
+import Web.Event.Event as Event
+import Web.Socket.Event.CloseEvent as WSCE
+import Web.Socket.Event.EventTypes as WSET
+import Web.Socket.Event.MessageEvent as WSME
+import Web.Socket.ReadyState (ReadyState(Connecting, Open, Closing, Closed))
+import Web.Socket.WebSocket as WS
 
+
+--------------------------------------------------------------------------------
+-- WebSocketEvent type
+--------------------------------------------------------------------------------
+
+data WebSocketEvent :: Type -> Type
+data WebSocketEvent msg
+  = WebSocketMessage { message :: msg, origin :: String, lastEventId :: String }
+  | WebSocketOpen
+  | WebSocketClose { code :: Int, reason :: String, wasClean :: Boolean }
+  | WebSocketError ErrorType
+
+webSocketEmitter :: forall msg. WS.WebSocket -> JsonCodec msg -> HS.Emitter (WebSocketEvent msg)
+webSocketEmitter socket codec = do
+
+  HS.makeEmitter \push -> do
+
+    openId <- HS.subscribe openEmitter push
+    errorId <- HS.subscribe errorEmitter push
+    closeId <- HS.subscribe closeEmitter push
+    messageId <- HS.subscribe messageEmitter push
+
+    pure do
+      HS.unsubscribe openId
+      HS.unsubscribe errorId
+      HS.unsubscribe closeId
+      HS.unsubscribe messageId
+
+  where
+  target = WS.toEventTarget socket
+
+  openEmitter :: HS.Emitter (WebSocketEvent msg)
+  openEmitter =
+    HQE.eventListener WSET.onOpen target \_ ->
+      Just WebSocketOpen
+
+  errorEmitter :: HS.Emitter (WebSocketEvent msg)
+  errorEmitter =
+    HQE.eventListener WSET.onError target \_ ->
+      Just (WebSocketError UnknownWebSocketError)
+
+  closeEmitter :: HS.Emitter (WebSocketEvent msg)
+  closeEmitter =
+    HQE.eventListener WSET.onClose target \event ->
+      WSCE.fromEvent event >>= \closeEvent ->
+        Just $ WebSocketClose  { code: WSCE.code closeEvent
+                               , reason: WSCE.reason closeEvent
+                               , wasClean: WSCE.wasClean closeEvent
+                               }
+
+  messageEmitter :: HS.Emitter (WebSocketEvent msg)
+  messageEmitter = HQE.eventListener WSET.onMessage target (WSME.fromEvent >=> decodeMessageEvent codec)
+
+decodeMessageEvent :: forall msg. JsonCodec msg -> WSME.MessageEvent -> Maybe (WebSocketEvent msg)
+decodeMessageEvent codec = \msgEvent -> do
+  let
+    foreign' :: Foreign
+    foreign' = WSME.data_ msgEvent
+  case runExcept (F.readString foreign') of
+    Left errList -> pure $ WebSocketError $ MessageJsonError (JsonForeignError errList)
+    Right string
+      | String.contains (String.Pattern "sponsored by") string ->
+          pure $ WebSocketError $ MessageIsServerAdvertisement string
+      | otherwise ->
+          case AP.jsonParser string of
+            Left parseError -> pure $ WebSocketError $ MessageJsonError $ JsonParseError parseError
+            Right json -> case CA.decode codec json of
+              Left decodeError -> pure $ WebSocketError $ MessageJsonError $ JsonDecodeError decodeError
+              Right message ->
+                pure $ WebSocketMessage { message, origin: WSME.origin msgEvent, lastEventId: WSME.lastEventId msgEvent }
+
+---------------------------
+-- Errors
+---------------------------
+data ErrorType
+  = MessageJsonError JsonError
+  | MessageIsServerAdvertisement String
+  | UnknownWebSocketError
+
+data JsonError
+  = JsonForeignError (NonEmptyList F.ForeignError)
+  | JsonParseError String
+  | JsonDecodeError JsonDecodeError
+
+renderError :: ErrorType -> String
+renderError = case _ of
+  MessageJsonError jsonErr ->
+    renderJsonError jsonErr
+  MessageIsServerAdvertisement str ->
+    "Received following advertisment from server: " <> str
+  UnknownWebSocketError ->
+    "Unknown 'error' event has been fired by WebSocket event listener"
+
+renderJsonError :: JsonError -> String
+renderJsonError = case _ of
+  JsonForeignError frgn ->
+    "JsonForeignError: " <> String.joinWith "; " (NEL.toUnfoldable $ map F.renderForeignError frgn)
+  JsonParseError str ->
+    "JsonParseError: " <> str
+  JsonDecodeError jde ->
+    "JsonDecodeError: " <> CA.printJsonDecodeError jde
+
+
+--------------------------------------------------------------------------------
+-- Example `Main` module
+--------------------------------------------------------------------------------
 main :: Effect Unit
-main = HA.runHalogenAff do
-  body <- HA.awaitBody
-  runUI Button.component unit body
+main = do
+  HA.runHalogenAff do
+    body <- HA.awaitBody
+    let url = "ws://localhost:8080"
+    runUI rootComponent url body
+
+--------------------------------------------------------------------------------
+-- WebSocket message type
+--------------------------------------------------------------------------------
+
+-- Not going to have anything elaborate in terms of actual websocket messages
+-- for an echo server example.
+type ExampleMessage = String
+
+exampleMessageCodec :: JsonCodec ExampleMessage
+exampleMessageCodec = CA.string
+
+--------------------------------------------------------------------------------
+-- Example root component module
+--------------------------------------------------------------------------------
+type Query = Const Void
+type Input = String
+type Output = Void
+
+data Action
+  = Initialize
+  | ConnectWebSocket
+  | HandleInputUpdate String
+  | SendMessage Event
+  | HandleWebSocket (WebSocketEvent ExampleMessage)
+
+type State =
+  { messages             :: Array String
+  , messageHistoryLength :: Int
+  , inputText            :: String
+  , wsUrl                :: String
+  , wsConnection         :: Maybe WS.WebSocket
+  , canReconnect         :: Boolean
+  }
+
+rootComponent :: forall m. MonadAff m => H.Component Query Input Output m
+rootComponent =
+  H.mkComponent
+    { initialState
+    , render
+    , eval: H.mkEval $ H.defaultEval
+        { initialize = Just Initialize
+        , handleAction = handleAction
+        }
+    }
+
+initialState :: Input -> State
+initialState input =
+  { messages: []
+  , messageHistoryLength: 10
+  , inputText: ""
+  , wsUrl: input
+  , wsConnection: Nothing
+  , canReconnect: false
+  }
+
+wrapperStyle :: String
+wrapperStyle =
+  """
+  display: block;
+  flex-direction: column;
+  justify-content: space-between;
+  height: calc(100vh - 30px);
+  background: #282c34;
+  color: #e06c75;
+  font-family: 'Consolas';
+  padding: 5px 20px 5px 20px;
+  """
+
+render :: forall m. State -> H.ComponentHTML Action () m
+render { messages, inputText, wsConnection, canReconnect, messageHistoryLength  } =
+  HH.div
+  [ HP.style wrapperStyle ]
+  [ HH.h2_ [ HH.text "WebSocket example for PureScript Halogen" ]
+  , HH.form
+      [ HE.onSubmit SendMessage ]
+      [ HH.ul_ $ map (\msg -> HH.li_ [ HH.text msg ]) messages
+      , HH.p_
+          [ HH.div_
+              [ HH.input
+                [ HP.style "padding: 0.5rem 0.75rem; margin-bottom: 0.25rem;"
+                , HP.type_ HP.InputText
+                , HP.value inputText
+                , HE.onValueInput HandleInputUpdate
+                , maybe (HP.disabled true) (\_ -> HP.enabled true) wsConnection
+                ]
+              ]
+          , HH.div_
+              [ HH.button
+                  [ HP.style "padding: 0.5rem 1.25rem;"
+                  , HP.type_ HP.ButtonSubmit
+                  , maybe (HP.disabled true) (\_ -> HP.enabled true) wsConnection
+                  ]
+                  [ HH.text "Send Message to Server" ]
+              ]
+          ]
+      , renderMaxHistoryLength messageHistoryLength
+      , renderReconnectButton (isNothing wsConnection && canReconnect)
+      ]
+  ]
+  where
+  renderFootnote :: String -> H.ComponentHTML Action () m
+  renderFootnote txt =
+    HH.div [ HP.style "margin-bottom: 0.125rem; color: grey;" ] [ HH.small_ [ HH.text txt ] ]
+
+  renderMaxHistoryLength :: Int -> H.ComponentHTML Action () m
+  renderMaxHistoryLength len =
+    renderFootnote ("NOTE: Maximum chat history length is " <> show len <> " messages")
+
+  renderReconnectButton :: Boolean -> H.ComponentHTML Action () m
+  renderReconnectButton cond =
+    if cond
+    then
+      HH.p_
+        [ HH.button
+          [ HP.type_ HP.ButtonButton
+          , HE.onClick \_ -> ConnectWebSocket
+          ]
+          [ HH.text "Reconnect?" ]
+        ]
+    else
+      HH.p_
+        [ renderFootnote "NOTE: A 'Reconnect?' button will appear if the connection drops"
+        , renderFootnote "NOTE: You can type /disconnect to manually disconnect"
+        ]
+
+handleAction :: forall m. MonadAff m => Action -> H.HalogenM State Action () Output m Unit
+handleAction = case _ of
+  Initialize ->
+    handleAction ConnectWebSocket
+
+  ConnectWebSocket -> do
+    { wsUrl } <- H.get
+    systemMessage ("Connecting to \"" <> wsUrl <>  "\"...")
+    webSocket <- H.liftEffect $ WS.create wsUrl []
+    H.modify_ _ { wsConnection = Just webSocket }
+    void $ H.subscribe (HandleWebSocket <$> webSocketEmitter webSocket exampleMessageCodec)
+
+  HandleInputUpdate text -> do
+    H.modify_ _ { inputText = text }
+
+  SendMessage ev -> do
+    H.liftEffect $ Event.preventDefault ev
+
+    { wsConnection, inputText } <- H.get
+
+    case wsConnection, inputText of
+      Nothing, _ ->
+        unableToSend "Not connected to server."
+
+      Just _ , "" ->
+        unableToSend "Cannot send an empty message"
+
+      Just webSocket, outgoingMessage -> do
+        H.liftEffect (WS.readyState webSocket) >>= case _ of
+          Connecting ->
+            unableToSend "Still connecting to server."
+
+          Closing ->
+            unableToSend "Connection to server is closing."
+
+          Closed -> do
+            unableToSend "Connection to server has been closed."
+            maybeCurrentConnection <- H.gets _.wsConnection
+            when (isJust maybeCurrentConnection) do
+              H.modify_ _ { wsConnection = Nothing, canReconnect = true }
+
+          Open -> do
+            case outgoingMessage of
+              "/disconnect" -> do
+                H.liftEffect $ WS.close webSocket
+                systemMessageReset $ "You have requested to disconnect from the server"
+              otherMessage -> do
+                H.liftEffect $ WS.sendString webSocket (AC.stringify $ CA.encode exampleMessageCodec otherMessage)
+                appendMessageReset $ "[😇] You: " <> otherMessage
+
+  HandleWebSocket wsEvent ->
+    case wsEvent of
+      WebSocketMessage messageEvent -> do
+        appendMessage $ "[😈] Server: " <> messageEvent.message
+
+
+      WebSocketOpen -> do
+        { wsUrl } <- H.get
+        systemMessage ("Successfully connected to WebSocket at \"" <> wsUrl <>  "\"!🎉")
+
+
+      WebSocketClose { code, reason, wasClean } -> do
+        systemMessage $ renderCloseMessage code wasClean reason
+        maybeCurrentConnection <- H.gets _.wsConnection
+        when (isJust maybeCurrentConnection) do
+          H.modify_ _ { wsConnection = Nothing, canReconnect = true }
+
+      WebSocketError errorType ->
+        systemMessage $ renderError errorType
+
+  where
+  renderCloseMessage
+    :: Int
+    -> Boolean
+    -> String
+    -> String
+  renderCloseMessage code wasClean = case _ of
+      ""     -> baseCloseMessage
+      reason -> baseCloseMessage <> "Reason: " <> reason
+    where
+    baseCloseMessage :: String
+    baseCloseMessage =
+      String.joinWith " "
+        [ "Connection to WebSocket closed"
+        , "[ CODE:"
+        , show code
+        , "|"
+        , if wasClean then "CLEAN" else "DIRTY"
+        , "]"
+        ]
+
+--------------------------------------------------------------------------------
+-- Helpers for updating the array of messages sent/received
+--------------------------------------------------------------------------------
+-- Append a new message to the chat history, with a boolean that allows you to
+-- clear the text input field or not. The number of displayed `messages` in the
+-- chat history (including system) is controlled by the `messageHistoryLength`
+-- field in the component `State`.
+appendMessageGeneric :: forall m. MonadState State m => Boolean -> String -> m Unit
+appendMessageGeneric clearField msg = do
+  histSize <- H.gets _.messageHistoryLength
+  if clearField
+    then H.modify_ \st ->
+           st { messages = appendSingle histSize msg st.messages, inputText = "" }
+    else H.modify_ \st ->
+           st { messages = appendSingle histSize msg st.messages }
+  where
+  -- Limits the nnumber of recent messages to `maxHist`
+  appendSingle :: Int -> String -> Array String -> Array String
+  appendSingle maxHist x xs
+    | A.length xs < maxHist = xs `A.snoc` x
+    | otherwise             = (A.takeEnd (maxHist-1) xs) `A.snoc` x
+
+-- Append a new message to the chat history, while not clearing
+-- the user input field
+appendMessage :: forall m. MonadState State m => String -> m Unit
+appendMessage = appendMessageGeneric false
+
+-- Append a new message to the chat history and also clear
+-- the user input field
+appendMessageReset :: forall m. MonadState State m => String -> m Unit
+appendMessageReset = appendMessageGeneric true
+
+-- Append a system message to the chat log.
+systemMessage :: forall m. MonadState State m => String -> m Unit
+systemMessage msg = appendMessage ("[🤖] System: " <> msg)
+
+-- As above, but also clears the user input field. e.g. in
+-- the case of a "/disconnect" command
+systemMessageReset :: forall m. MonadState State m => String -> m Unit
+systemMessageReset msg = appendMessageReset ("[🤖] System: " <> msg)
+
+-- A system message to use when a message cannot be sent.
+unableToSend :: forall m. MonadState State m => String -> m Unit
+unableToSend reason = systemMessage ("Unable to send. " <> reason)