ui: Add an Effect system to handle global state and Elm Cmds (#176)

All pages now leverage Effects for most of their Session and Cmd requests. More work required for routing and other lingering Cmd use.

ui/src/Api.elm

@@ -1,5 +1,7 @@
 module Api exposing
-    ( deleteMessage
+    ( DataResult
+    , HttpResult
+    , deleteMessage
     , getGreeting
     , getHeaderList
     , getMessage

ui/src/Effect.elm

@@ -0,0 +1,304 @@
+module Effect exposing
+    ( Effect
+    , addRecent
+    , batch
+    , deleteMessage
+    , disableRouting
+    , enableRouting
+    , getGreeting
+    , getHeaderList
+    , getMessage
+    , getServerConfig
+    , getServerMetrics
+    , map
+    , markMessageSeen
+    , none
+    , perform
+    , posixTime
+    , purgeMailbox
+    , schedule
+    , showFlash
+    , wrap
+    )
+
+import Api exposing (DataResult, HttpResult)
+import Data.Message exposing (Message)
+import Data.MessageHeader exposing (MessageHeader)
+import Data.Metrics exposing (Metrics)
+import Data.ServerConfig exposing (ServerConfig)
+import Data.Session as Session exposing (Session)
+import Task
+import Time
+import Timer exposing (Timer)
+
+
+type Effect msg
+    = None
+    | Batch (List (Effect msg))
+    | Command (Cmd msg)
+    | PosixTime (Time.Posix -> msg)
+    | ScheduleTimer (Timer -> msg) Timer Float
+    | ApiEffect (ApiEffect msg)
+    | SessionEffect SessionEffect
+
+
+type ApiEffect msg
+    = DeleteMessage (HttpResult msg) String String
+    | GetGreeting (DataResult msg String)
+    | GetServerConfig (DataResult msg ServerConfig)
+    | GetServerMetrics (DataResult msg Metrics)
+    | GetHeaderList (DataResult msg (List MessageHeader)) String
+    | GetMessage (DataResult msg Message) String String
+    | MarkMessageSeen (HttpResult msg) String String
+    | PurgeMailbox (HttpResult msg) String
+
+
+type SessionEffect
+    = FlashClear
+    | FlashShow Session.Flash
+    | RecentAdd String
+    | RoutingDisable
+    | RoutingEnable
+
+
+{-| Packs a List of Effects into a single Effect
+-}
+batch : List (Effect msg) -> Effect msg
+batch effects =
+    Batch effects
+
+
+{-| Transform message types produced by an effect.
+-}
+map : (a -> b) -> Effect a -> Effect b
+map f effect =
+    case effect of
+        None ->
+            None
+
+        Batch effects ->
+            Batch <| List.map (map f) effects
+
+        Command cmd ->
+            Command <| Cmd.map f cmd
+
+        PosixTime toMsg ->
+            PosixTime <| toMsg >> f
+
+        ScheduleTimer toMsg timer millis ->
+            ScheduleTimer (toMsg >> f) timer millis
+
+        ApiEffect apiEffect ->
+            ApiEffect <| mapApi f apiEffect
+
+        SessionEffect sessionEffect ->
+            SessionEffect sessionEffect
+
+
+mapApi : (a -> b) -> ApiEffect a -> ApiEffect b
+mapApi f effect =
+    case effect of
+        DeleteMessage result mailbox id ->
+            DeleteMessage (result >> f) mailbox id
+
+        GetGreeting result ->
+            GetGreeting (result >> f)
+
+        GetServerConfig result ->
+            GetServerConfig (result >> f)
+
+        GetServerMetrics result ->
+            GetServerMetrics (result >> f)
+
+        GetHeaderList result mailbox ->
+            GetHeaderList (result >> f) mailbox
+
+        GetMessage result mailbox id ->
+            GetMessage (result >> f) mailbox id
+
+        MarkMessageSeen result mailbox id ->
+            MarkMessageSeen (result >> f) mailbox id
+
+        PurgeMailbox result mailbox ->
+            PurgeMailbox (result >> f) mailbox
+
+
+{-| Applies an effect by updating the session and/or producing a Cmd.
+-}
+perform : ( Session, Effect msg ) -> ( Session, Cmd msg )
+perform ( session, effect ) =
+    case effect of
+        None ->
+            ( session, Cmd.none )
+
+        Batch effects ->
+            List.foldl batchPerform ( session, [] ) effects
+                |> Tuple.mapSecond Cmd.batch
+
+        Command cmd ->
+            ( session, cmd )
+
+        PosixTime toMsg ->
+            ( session, Task.perform toMsg Time.now )
+
+        ScheduleTimer toMsg timer millis ->
+            ( session, Timer.schedule toMsg timer millis )
+
+        ApiEffect apiEffect ->
+            performApi ( session, apiEffect )
+
+        SessionEffect sessionEffect ->
+            performSession ( session, sessionEffect )
+
+
+performApi : ( Session, ApiEffect msg ) -> ( Session, Cmd msg )
+performApi ( session, effect ) =
+    case effect of
+        DeleteMessage toMsg mailbox id ->
+            ( session, Api.deleteMessage session toMsg mailbox id )
+
+        GetGreeting toMsg ->
+            ( session, Api.getGreeting session toMsg )
+
+        GetServerConfig toMsg ->
+            ( session, Api.getServerConfig session toMsg )
+
+        GetServerMetrics toMsg ->
+            ( session, Api.getServerMetrics session toMsg )
+
+        GetHeaderList toMsg mailbox ->
+            ( session, Api.getHeaderList session toMsg mailbox )
+
+        GetMessage toMsg mailbox id ->
+            ( session, Api.getMessage session toMsg mailbox id )
+
+        MarkMessageSeen toMsg mailbox id ->
+            ( session, Api.markMessageSeen session toMsg mailbox id )
+
+        PurgeMailbox toMsg mailbox ->
+            ( session, Api.purgeMailbox session toMsg mailbox )
+
+
+performSession : ( Session, SessionEffect ) -> ( Session, Cmd msg )
+performSession ( session, effect ) =
+    case effect of
+        RecentAdd mailbox ->
+            ( Session.addRecent mailbox session, Cmd.none )
+
+        FlashClear ->
+            ( Session.clearFlash session, Cmd.none )
+
+        FlashShow flash ->
+            ( Session.showFlash flash session, Cmd.none )
+
+        RoutingDisable ->
+            ( Session.disableRouting session, Cmd.none )
+
+        RoutingEnable ->
+            ( Session.enableRouting session, Cmd.none )
+
+
+
+-- EFFECT CONSTRUCTORS
+
+
+none : Effect msg
+none =
+    None
+
+
+{-| Adds specified mailbox to the recently viewed list
+-}
+addRecent : String -> Effect msg
+addRecent mailbox =
+    SessionEffect (RecentAdd mailbox)
+
+
+disableRouting : Effect msg
+disableRouting =
+    SessionEffect RoutingDisable
+
+
+enableRouting : Effect msg
+enableRouting =
+    SessionEffect RoutingEnable
+
+
+clearFlash : Effect msg
+clearFlash =
+    SessionEffect FlashClear
+
+
+showFlash : Session.Flash -> Effect msg
+showFlash flash =
+    SessionEffect (FlashShow flash)
+
+
+deleteMessage : HttpResult msg -> String -> String -> Effect msg
+deleteMessage toMsg mailboxName id =
+    ApiEffect (DeleteMessage toMsg mailboxName id)
+
+
+getGreeting : DataResult msg String -> Effect msg
+getGreeting toMsg =
+    ApiEffect (GetGreeting toMsg)
+
+
+getHeaderList : DataResult msg (List MessageHeader) -> String -> Effect msg
+getHeaderList toMsg mailboxName =
+    ApiEffect (GetHeaderList toMsg mailboxName)
+
+
+getServerConfig : DataResult msg ServerConfig -> Effect msg
+getServerConfig toMsg =
+    ApiEffect (GetServerConfig toMsg)
+
+
+getServerMetrics : DataResult msg Metrics -> Effect msg
+getServerMetrics toMsg =
+    ApiEffect (GetServerMetrics toMsg)
+
+
+getMessage : DataResult msg Message -> String -> String -> Effect msg
+getMessage toMsg mailboxName id =
+    ApiEffect (GetMessage toMsg mailboxName id)
+
+
+markMessageSeen : HttpResult msg -> String -> String -> Effect msg
+markMessageSeen toMsg mailboxName id =
+    ApiEffect (MarkMessageSeen toMsg mailboxName id)
+
+
+posixTime : (Time.Posix -> msg) -> Effect msg
+posixTime toMsg =
+    PosixTime toMsg
+
+
+purgeMailbox : HttpResult msg -> String -> Effect msg
+purgeMailbox toMsg mailboxName =
+    ApiEffect (PurgeMailbox toMsg mailboxName)
+
+
+{-| Schedules a Timer to fire after the specified delay.
+-}
+schedule : (Timer -> msg) -> Timer -> Float -> Effect msg
+schedule toMsg timer millis =
+    ScheduleTimer toMsg timer millis
+
+
+{-| Wrap a Cmd into an Effect. This is a temporary function to aid in the transition to the effect
+pattern.
+-}
+wrap : Cmd msg -> Effect msg
+wrap cmd =
+    Command cmd
+
+
+
+-- UTILITY
+
+
+batchPerform : Effect msg -> ( Session, List (Cmd msg) ) -> ( Session, List (Cmd msg) )
+batchPerform effect ( session, cmds ) =
+    perform ( session, effect )
+        |> Tuple.mapSecond (\cmd -> cmd :: cmds)

ui/src/Main.elm

@@ -4,6 +4,7 @@ import Browser exposing (Document, UrlRequest)
 import Browser.Navigation as Nav
 import Data.AppConfig as AppConfig exposing (AppConfig)
 import Data.Session as Session exposing (Session)
+import Effect exposing (Effect)
 import Html exposing (Html)
 import Json.Decode as D exposing (Value)
 import Layout
@@ -58,6 +59,8 @@ init configValue location key =
                     Session.initError key location (D.errorToString error)
 
         ( subModel, _ ) =
+            -- Home.init effect is discarded because this subModel will be immediately replaced
+            -- when we change routes to the specified location.
             Home.init session
 
         initModel =
@@ -67,11 +70,9 @@ init configValue location key =
 
         route =
             session.router.fromUrl location
-
-        ( model, cmd ) =
-            changeRouteTo route initModel
     in
-    ( model, Cmd.batch [ cmd, Task.perform TimeZoneLoaded Time.here ] )
+    changeRouteTo route initModel
+        |> Tuple.mapSecond (\cmd -> Cmd.batch [ cmd, Task.perform TimeZoneLoaded Time.here ])
 
 
 type Msg
@@ -206,12 +207,12 @@ updateMain msg model session =
             )
 
         _ ->
-            updatePage msg model
+            updatePage msg model |> performEffects
 
 
 {-| Delegate incoming messages to their respective sub-pages.
 -}
-updatePage : Msg -> Model -> ( Model, Cmd Msg )
+updatePage : Msg -> Model -> ( Model, Effect Msg )
 updatePage msg model =
     case ( msg, model.page ) of
         ( HomeMsg subMsg, Home subModel ) ->
@@ -232,61 +233,70 @@ updatePage msg model =
 
         ( _, _ ) ->
             -- Disregard messages destined for the wrong page.
-            ( model, Cmd.none )
+            ( model, Effect.none )
 
 
 changeRouteTo : Route -> Model -> ( Model, Cmd Msg )
 changeRouteTo route model =
     let
         session =
-            getSession model |> Session.clearFlash
+            Session.clearFlash (getSession model)
 
         newModel =
             { model | layout = Layout.reset model.layout }
     in
-    case route of
+    performEffects <|
-        Route.Home ->
+        case route of
-            Home.init session
+            Route.Home ->
-                |> updateWith Home HomeMsg newModel
+                Home.init session
+                    |> updateWith Home HomeMsg newModel
 
-        Route.Mailbox name ->
+            Route.Mailbox name ->
-            Mailbox.init session name Nothing
+                Mailbox.init session name Nothing
-                |> updateWith Mailbox MailboxMsg newModel
+                    |> updateWith Mailbox MailboxMsg newModel
 
-        Route.Message mailbox id ->
+            Route.Message mailbox id ->
-            Mailbox.init session mailbox (Just id)
+                Mailbox.init session mailbox (Just id)
-                |> updateWith Mailbox MailboxMsg newModel
+                    |> updateWith Mailbox MailboxMsg newModel
 
-        Route.Monitor ->
+            Route.Monitor ->
-            if session.config.monitorVisible then
+                if session.config.monitorVisible then
-                Monitor.init session
+                    Monitor.init session
-                    |> updateWith Monitor MonitorMsg newModel
+                        |> updateWith Monitor MonitorMsg newModel
 
-            else
+                else
+                    let
+                        flash =
+                            { title = "Disabled route requested"
+                            , table = [ ( "Error", "Monitor disabled by configuration." ) ]
+                            }
+                    in
+                    ( applyToModelSession (Session.showFlash flash) newModel
+                    , Effect.none
+                    )
+
+            Route.Status ->
+                Status.init session
+                    |> updateWith Status StatusMsg newModel
+
+            Route.Unknown path ->
+                -- Unknown routes display Home with an error flash.
                 let
                     flash =
-                        { title = "Disabled route requested"
+                        { title = "Unknown route requested"
-                        , table = [ ( "Error", "Monitor disabled by configuration." ) ]
+                        , table = [ ( "Path", path ) ]
                         }
                 in
-                ( applyToModelSession (Session.showFlash flash) newModel
+                Home.init (Session.showFlash flash session)
-                , Cmd.none
+                    |> updateWith Home HomeMsg newModel
-                )
 
-        Route.Status ->
-            Status.init session
-                |> updateWith Status StatusMsg newModel
 
-        Route.Unknown path ->
+{-| Perform effects by updating model and/or producing Cmds to be executed.
-            -- Unknown routes display Home with an error flash.
+-}
-            let
+performEffects : ( Model, Effect Msg ) -> ( Model, Cmd Msg )
-                flash =
+performEffects ( model, effect ) =
-                    { title = "Unknown route requested"
+    Effect.perform ( getSession model, effect )
-                    , table = [ ( "Path", path ) ]
+        |> Tuple.mapFirst (\newSession -> updateSession model newSession)
-                    }
-            in
-            Home.init (Session.showFlash flash session)
-                |> updateWith Home HomeMsg newModel
 
 
 getSession : Model -> Session
@@ -332,11 +342,11 @@ updateWith :
     (subModel -> PageModel)
     -> (subMsg -> Msg)
     -> Model
-    -> ( subModel, Cmd subMsg )
+    -> ( subModel, Effect subMsg )
-    -> ( Model, Cmd Msg )
+    -> ( Model, Effect Msg )
-updateWith toPage toMsg model ( subModel, subCmd ) =
+updateWith toPage toMsg model ( subModel, subEffect ) =
     ( { model | page = toPage subModel }
-    , Cmd.map toMsg subCmd
+    , Effect.map toMsg subEffect
     )
 
 

ui/src/Page/Home.elm

@@ -1,7 +1,7 @@
 module Page.Home exposing (Model, Msg, init, update, view)
 
-import Api
+import Data.Session exposing (Session)
-import Data.Session as Session exposing (Session)
+import Effect exposing (Effect)
 import Html exposing (Html)
 import Html.Attributes exposing (class, property)
 import HttpUtil
@@ -18,9 +18,9 @@ type alias Model =
     }
 
 
-init : Session -> ( Model, Cmd Msg )
+init : Session -> ( Model, Effect Msg )
 init session =
-    ( Model session "", Api.getGreeting session GreetingLoaded )
+    ( Model session "", Effect.getGreeting GreetingLoaded )
 
 
 
@@ -31,16 +31,14 @@ type Msg
     = GreetingLoaded (Result HttpUtil.Error String)
 
 
-update : Msg -> Model -> ( Model, Cmd Msg )
+update : Msg -> Model -> ( Model, Effect Msg )
 update msg model =
     case msg of
         GreetingLoaded (Ok greeting) ->
-            ( { model | greeting = greeting }, Cmd.none )
+            ( { model | greeting = greeting }, Effect.none )
 
         GreetingLoaded (Err err) ->
-            ( { model | session = Session.showFlash (HttpUtil.errorFlash err) model.session }
+            ( model, Effect.showFlash (HttpUtil.errorFlash err) )
-            , Cmd.none
-            )
 
 
 

ui/src/Page/Mailbox.elm

@@ -1,12 +1,13 @@
-module Page.Mailbox exposing (Model, Msg, init, load, subscriptions, update, view)
+module Page.Mailbox exposing (Model, Msg, init, subscriptions, update, view)
 
 import Api
 import Browser.Navigation as Nav
 import Data.Message as Message exposing (Message)
 import Data.MessageHeader exposing (MessageHeader)
-import Data.Session as Session exposing (Session)
+import Data.Session exposing (Session)
 import DateFormat as DF
 import DateFormat.Relative as Relative
+import Effect exposing (Effect)
 import Html
     exposing
         ( Attribute
@@ -54,7 +55,6 @@ import Json.Decode as D
 import Json.Encode as E
 import Modal
 import Route
-import Task
 import Time exposing (Posix)
 import Timer exposing (Timer)
 
@@ -103,7 +103,7 @@ type alias Model =
     }
 
 
-init : Session -> String -> Maybe MessageID -> ( Model, Cmd Msg )
+init : Session -> String -> Maybe MessageID -> ( Model, Effect Msg )
 init session mailboxName selection =
     ( { session = session
       , mailboxName = mailboxName
@@ -114,16 +114,11 @@ init session mailboxName selection =
       , markSeenTimer = Timer.empty
       , now = Time.millisToPosix 0
       }
-    , load session mailboxName
+    , Effect.batch
-    )
+        [ Effect.posixTime Tick
-
+        , Effect.getHeaderList ListLoaded mailboxName
-
-load : Session -> String -> Cmd Msg
-load session mailboxName =
-    Cmd.batch
-        [ Task.perform Tick Time.now
-        , Api.getHeaderList session ListLoaded mailboxName
         ]
+    )
 
 
 
@@ -159,38 +154,38 @@ type Msg
     | ModalFocused Modal.Msg
 
 
-update : Msg -> Model -> ( Model, Cmd Msg )
+update : Msg -> Model -> ( Model, Effect Msg )
 update msg model =
     case msg of
         ClickMessage id ->
-            ( updateSelected { model | session = Session.disableRouting model.session } id
+            ( updateSelected model id
-            , Cmd.batch
+            , Effect.batch
                 [ -- Update browser location.
-                  Route.Message model.mailboxName id
+                  Effect.disableRouting
+                , Route.Message model.mailboxName id
                     |> model.session.router.toPath
                     |> Nav.replaceUrl model.session.key
-                , Api.getMessage model.session MessageLoaded model.mailboxName id
+                    |> Effect.wrap
+                , Effect.getMessage MessageLoaded model.mailboxName id
                 ]
             )
 
         CloseMessage ->
             case model.state of
                 ShowingList list _ ->
-                    ( { model | state = ShowingList list NoMessage }, Cmd.none )
+                    ( { model | state = ShowingList list NoMessage }, Effect.none )
 
                 _ ->
-                    ( model, Cmd.none )
+                    ( model, Effect.none )
 
         DeleteMessage message ->
             updateDeleteMessage model message
 
         DeletedMessage (Ok _) ->
-            ( model, Cmd.none )
+            ( model, Effect.none )
 
         DeletedMessage (Err err) ->
-            ( { model | session = Session.showFlash (HttpUtil.errorFlash err) model.session }
+            ( model, Effect.showFlash (HttpUtil.errorFlash err) )
-            , Cmd.none
-            )
 
         ListKeyPress id keyCode ->
             case keyCode of
@@ -198,7 +193,7 @@ update msg model =
                     updateOpenMessage model id
 
                 _ ->
-                    ( model, Cmd.none )
+                    ( model, Effect.none )
 
         ListLoaded (Ok headers) ->
             case model.state of
@@ -214,63 +209,51 @@ update msg model =
                             updateOpenMessage newModel id
 
                         Nothing ->
-                            ( { newModel
+                            ( newModel, Effect.addRecent newModel.mailboxName )
-                                | session = Session.addRecent model.mailboxName model.session
-                              }
-                            , Cmd.none
-                            )
 
                 _ ->
-                    ( model, Cmd.none )
+                    ( model, Effect.none )
 
         ListLoaded (Err err) ->
-            ( { model | session = Session.showFlash (HttpUtil.errorFlash err) model.session }
+            ( model, Effect.showFlash (HttpUtil.errorFlash err) )
-            , Cmd.none
-            )
 
         MarkSeenLoaded (Ok _) ->
-            ( model, Cmd.none )
+            ( model, Effect.none )
 
         MarkSeenLoaded (Err err) ->
-            ( { model | session = Session.showFlash (HttpUtil.errorFlash err) model.session }
+            ( model, Effect.showFlash (HttpUtil.errorFlash err) )
-            , Cmd.none
-            )
 
         MessageLoaded (Ok message) ->
             updateMessageResult model message
 
         MessageLoaded (Err err) ->
-            ( { model | session = Session.showFlash (HttpUtil.errorFlash err) model.session }
+            ( model, Effect.showFlash (HttpUtil.errorFlash err) )
-            , Cmd.none
-            )
 
         MessageBody bodyMode ->
-            ( { model | bodyMode = bodyMode }, Cmd.none )
+            ( { model | bodyMode = bodyMode }, Effect.none )
 
         ModalFocused message ->
             ( { model | session = Modal.updateSession message model.session }
-            , Cmd.none
+            , Effect.none
             )
 
         OnSearchInput searchInput ->
             updateSearchInput model searchInput
 
         PurgeMailboxPrompt ->
-            ( { model | promptPurge = True }, Modal.resetFocusCmd ModalFocused )
+            ( { model | promptPurge = True }, Modal.resetFocusCmd ModalFocused |> Effect.wrap )
 
         PurgeMailboxCanceled ->
-            ( { model | promptPurge = False }, Cmd.none )
+            ( { model | promptPurge = False }, Effect.none )
 
         PurgeMailboxConfirmed ->
             updateTriggerPurge model
 
         PurgedMailbox (Ok _) ->
-            ( model, Cmd.none )
+            ( model, Effect.none )
 
         PurgedMailbox (Err err) ->
-            ( { model | session = Session.showFlash (HttpUtil.errorFlash err) model.session }
+            ( model, Effect.showFlash (HttpUtil.errorFlash err) )
-            , Cmd.none
-            )
 
         MarkSeenTriggered timer ->
             if timer == model.markSeenTimer then
@@ -278,15 +261,15 @@ update msg model =
                 updateMarkMessageSeen model
 
             else
-                ( model, Cmd.none )
+                ( model, Effect.none )
 
         Tick now ->
-            ( { model | now = now }, Cmd.none )
+            ( { model | now = now }, Effect.none )
 
 
 {-| Replace the currently displayed message.
 -}
-updateMessageResult : Model -> Message -> ( Model, Cmd Msg )
+updateMessageResult : Model -> Message -> ( Model, Effect Msg )
 updateMessageResult model message =
     let
         bodyMode =
@@ -298,7 +281,7 @@ updateMessageResult model message =
     in
     case model.state of
         LoadingList _ ->
-            ( model, Cmd.none )
+            ( model, Effect.none )
 
         ShowingList list _ ->
             let
@@ -314,38 +297,38 @@ updateMessageResult model message =
                 , markSeenTimer = newTimer
               }
               -- Set 1500ms delay before reporting message as seen to backend.
-            , Timer.schedule MarkSeenTriggered newTimer 1500
+            , Effect.schedule MarkSeenTriggered newTimer 1500
             )
 
 
 {-| Updates model and triggers commands to purge this mailbox.
 -}
-updateTriggerPurge : Model -> ( Model, Cmd Msg )
+updateTriggerPurge : Model -> ( Model, Effect Msg )
 updateTriggerPurge model =
     let
-        cmd =
+        effects =
-            Cmd.batch
+            Effect.batch
                 [ Route.Mailbox model.mailboxName
                     |> model.session.router.toPath
                     |> Nav.replaceUrl model.session.key
-                , Api.purgeMailbox model.session PurgedMailbox model.mailboxName
+                    |> Effect.wrap
+                , Effect.purgeMailbox PurgedMailbox model.mailboxName
                 ]
     in
     case model.state of
         ShowingList _ _ ->
             ( { model
                 | promptPurge = False
-                , session = Session.disableRouting model.session
                 , state = ShowingList (MessageList [] Nothing "") NoMessage
               }
-            , cmd
+            , Effect.batch [ Effect.disableRouting, effects ]
             )
 
         _ ->
-            ( model, cmd )
+            ( model, effects )
 
 
-updateSearchInput : Model -> String -> ( Model, Cmd Msg )
+updateSearchInput : Model -> String -> ( Model, Effect Msg )
 updateSearchInput model searchInput =
     let
         searchFilter =
@@ -357,14 +340,14 @@ updateSearchInput model searchInput =
     in
     case model.state of
         LoadingList _ ->
-            ( model, Cmd.none )
+            ( model, Effect.none )
 
         ShowingList list messageState ->
             ( { model
                 | searchInput = searchInput
                 , state = ShowingList { list | searchFilter = searchFilter } messageState
               }
-            , Cmd.none
+            , Effect.none
             )
 
 
@@ -396,7 +379,7 @@ updateSelected model id =
                     { model | state = ShowingList newList (Transitioning visible) }
 
 
-updateDeleteMessage : Model -> Message -> ( Model, Cmd Msg )
+updateDeleteMessage : Model -> Message -> ( Model, Effect Msg )
 updateDeleteMessage model message =
     let
         filter f messageList =
@@ -404,26 +387,24 @@ updateDeleteMessage model message =
     in
     case model.state of
         ShowingList list _ ->
-            ( { model
+            ( { model | state = ShowingList (filter (\x -> x.id /= message.id) list) NoMessage }
-                | session = Session.disableRouting model.session
+            , Effect.batch
-                , state =
+                [ Effect.deleteMessage DeletedMessage message.mailbox message.id
-                    ShowingList (filter (\x -> x.id /= message.id) list) NoMessage
+                , Effect.disableRouting
-              }
-            , Cmd.batch
-                [ Api.deleteMessage model.session DeletedMessage message.mailbox message.id
                 , Route.Mailbox model.mailboxName
                     |> model.session.router.toPath
                     |> Nav.replaceUrl model.session.key
+                    |> Effect.wrap
                 ]
             )
 
         _ ->
-            ( model, Cmd.none )
+            ( model, Effect.none )
 
 
 {-| Updates both the active message, and the message list to mark the currently viewed message as seen.
 -}
-updateMarkMessageSeen : Model -> ( Model, Cmd Msg )
+updateMarkMessageSeen : Model -> ( Model, Effect Msg )
 updateMarkMessageSeen model =
     case model.state of
         ShowingList messages (ShowingMessage visibleMessage) ->
@@ -442,21 +423,20 @@ updateMarkMessageSeen model =
                 | state =
                     ShowingList newMessages (ShowingMessage { visibleMessage | seen = True })
               }
-            , Api.markMessageSeen model.session MarkSeenLoaded visibleMessage.mailbox visibleMessage.id
+            , Effect.markMessageSeen MarkSeenLoaded visibleMessage.mailbox visibleMessage.id
             )
 
         _ ->
-            ( model, Cmd.none )
+            ( model, Effect.none )
 
 
-updateOpenMessage : Model -> String -> ( Model, Cmd Msg )
+updateOpenMessage : Model -> String -> ( Model, Effect Msg )
 updateOpenMessage model id =
-    let
+    ( updateSelected model id
-        newModel =
+    , Effect.batch
-            { model | session = Session.addRecent model.mailboxName model.session }
+        [ Effect.addRecent model.mailboxName
-    in
+        , Effect.getMessage MessageLoaded model.mailboxName id
-    ( updateSelected newModel id
+        ]
-    , Api.getMessage model.session MessageLoaded model.mailboxName id
     )
 
 

ui/src/Page/Monitor.elm

@@ -5,6 +5,7 @@ import Browser.Navigation as Nav
 import Data.MessageHeader as MessageHeader exposing (MessageHeader)
 import Data.Session as Session exposing (Session)
 import DateFormat as DF
+import Effect exposing (Effect)
 import Html
     exposing
         ( Attribute
@@ -41,9 +42,9 @@ type alias Model =
     }
 
 
-init : Session -> ( Model, Cmd Msg )
+init : Session -> ( Model, Effect Msg )
 init session =
-    ( Model session False [], Cmd.none )
+    ( Model session False [], Effect.none )
 
 
 
@@ -58,20 +59,20 @@ type Msg
     | MessageKeyPress MessageHeader Int
 
 
-update : Msg -> Model -> ( Model, Cmd Msg )
+update : Msg -> Model -> ( Model, Effect Msg )
 update msg model =
     case msg of
         Connected True ->
-            ( { model | connected = True, messages = [] }, Cmd.none )
+            ( { model | connected = True, messages = [] }, Effect.none )
 
         Connected False ->
-            ( { model | connected = False }, Cmd.none )
+            ( { model | connected = False }, Effect.none )
 
         MessageReceived value ->
             case D.decodeValue (MessageHeader.decoder |> D.at [ "detail" ]) value of
                 Ok header ->
                     ( { model | messages = header :: List.take 500 model.messages }
-                    , Cmd.none
+                    , Effect.none
                     )
 
                 Err err ->
@@ -81,12 +82,10 @@ update msg model =
                             , table = [ ( "Error", D.errorToString err ) ]
                             }
                     in
-                    ( { model | session = Session.showFlash flash model.session }
+                    ( model, Effect.showFlash flash )
-                    , Cmd.none
-                    )
 
         Clear ->
-            ( { model | messages = [] }, Cmd.none )
+            ( { model | messages = [] }, Effect.none )
 
         OpenMessage header ->
             openMessage header model
@@ -97,15 +96,16 @@ update msg model =
                     openMessage header model
 
                 _ ->
-                    ( model, Cmd.none )
+                    ( model, Effect.none )
 
 
-openMessage : MessageHeader -> Model -> ( Model, Cmd Msg )
+openMessage : MessageHeader -> Model -> ( Model, Effect Msg )
 openMessage header model =
     ( model
     , Route.Message header.mailbox header.id
         |> model.session.router.toPath
         |> Nav.replaceUrl model.session.key
+        |> Effect.wrap
     )
 
 

ui/src/Page/Status.elm

@@ -1,10 +1,10 @@
 module Page.Status exposing (Model, Msg, init, subscriptions, update, view)
 
-import Api
 import Data.Metrics exposing (Metrics)
 import Data.ServerConfig exposing (ServerConfig)
-import Data.Session as Session exposing (Session)
+import Data.Session exposing (Session)
 import DateFormat.Relative as Relative
+import Effect exposing (Effect)
 import Filesize
 import Html
     exposing
@@ -19,7 +19,6 @@ import Html.Attributes exposing (class)
 import HttpUtil
 import Sparkline as Spark
 import Svg.Attributes as SvgAttrib
-import Task
 import Time exposing (Posix)
 
 
@@ -60,7 +59,7 @@ type alias Metric =
     }
 
 
-init : Session -> ( Model, Cmd Msg )
+init : Session -> ( Model, Effect Msg )
 init session =
     ( { session = session
       , now = Time.millisToPosix 0
@@ -82,9 +81,9 @@ init session =
       , retainedCount = Metric "Stored Messages" 0 fmtInt graphZero initDataSet 60
       , retainedSize = Metric "Store Size" 0 Filesize.format graphZero initDataSet 60
       }
-    , Cmd.batch
+    , Effect.batch
-        [ Task.perform Tick Time.now
+        [ Effect.posixTime Tick
-        , Api.getServerConfig session ServerConfigLoaded
+        , Effect.getServerConfig ServerConfigLoaded
         ]
     )
 
@@ -114,27 +113,25 @@ type Msg
     | Tick Posix
 
 
-update : Msg -> Model -> ( Model, Cmd Msg )
+update : Msg -> Model -> ( Model, Effect Msg )
 update msg model =
     case msg of
         MetricsReceived (Ok metrics) ->
-            ( updateMetrics metrics model, Cmd.none )
+            ( updateMetrics metrics model, Effect.none )
 
         MetricsReceived (Err err) ->
-            ( { model | session = Session.showFlash (HttpUtil.errorFlash err) model.session }
+            ( model, Effect.showFlash (HttpUtil.errorFlash err) )
-            , Cmd.none
-            )
 
         ServerConfigLoaded (Ok config) ->
-            ( { model | config = Just config }, Cmd.none )
+            ( { model | config = Just config }, Effect.none )
 
         ServerConfigLoaded (Err err) ->
-            ( { model | session = Session.showFlash (HttpUtil.errorFlash err) model.session }
+            ( model, Effect.showFlash (HttpUtil.errorFlash err) )
-            , Cmd.none
-            )
 
         Tick time ->
-            ( { model | now = time }, Api.getServerMetrics model.session MetricsReceived )
+            ( { model | now = time }
+            , Effect.getServerMetrics MetricsReceived
+            )
 
 
 {-| Update all metrics in Model; increment xCounter.

ui/src/Timer.elm

@@ -49,6 +49,8 @@ cancel previous =
             previous
 
 
+{-| Increments the timer identity, preventing integer overflow.
+-}
 next : Int -> Int
 next index =
     if index > 2 ^ 30 then