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timer event sourcing elm
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| module Main exposing (main) | |
| import Browser | |
| import Browser.Events exposing (onAnimationFrame) | |
| import Html exposing (Html, button, div, p, table, tbody, td, text, th, thead, tr) | |
| import Html.Events exposing (onClick) | |
| import List | |
| import Task | |
| import Time | |
| import Tuple | |
| main = | |
| Browser.element { init = init, update = update, view = view, subscriptions = subscriptions } | |
| type alias ElapsedTimeMillis = | |
| Int | |
| type EventType | |
| = Started | |
| | Stopped | |
| eventTypeToString : EventType -> String | |
| eventTypeToString eventType = | |
| case eventType of | |
| Started -> | |
| "started" | |
| Stopped -> | |
| "stopped" | |
| type alias Event = | |
| { eventType : EventType | |
| , occurredAt : Time.Posix | |
| } | |
| type alias Model = | |
| { events : List Event | |
| , now : Time.Posix | |
| } | |
| init : () -> ( Model, Cmd Msg ) | |
| init _ = | |
| ( { events = [], now = Time.millisToPosix 0 }, Task.perform Tick Time.now ) | |
| isStopped : Model -> Bool | |
| isStopped model = | |
| let | |
| isEven : Int -> Bool | |
| isEven int = | |
| modBy 2 int == 0 | |
| in | |
| isEven (List.length model.events) | |
| getElapsedTime : Model -> ElapsedTimeMillis | |
| getElapsedTime model = | |
| let | |
| chunk : Int -> List a -> List (List a) | |
| chunk i list = | |
| case List.take i list of | |
| [] -> | |
| [] | |
| listHead -> | |
| listHead :: chunk i (List.drop i list) | |
| calcTimeForSpan : Time.Posix -> List Event -> ElapsedTimeMillis | |
| calcTimeForSpan now span = | |
| case span of | |
| [ startedEvent, stoppedEvent ] -> | |
| Time.posixToMillis stoppedEvent.occurredAt - Time.posixToMillis startedEvent.occurredAt | |
| [ startedEvent ] -> | |
| Time.posixToMillis now - Time.posixToMillis startedEvent.occurredAt | |
| _ -> | |
| 0 | |
| in | |
| chunk 2 model.events | |
| |> List.map (calcTimeForSpan model.now) | |
| |> List.sum | |
| type Msg | |
| = Tick Time.Posix | |
| | StartStop Time.Posix | |
| | Click | |
| update : Msg -> Model -> ( Model, Cmd Msg ) | |
| update msg model = | |
| case msg of | |
| Tick currentTime -> | |
| ( { model | now = currentTime }, Cmd.none ) | |
| StartStop occurredAt -> | |
| let | |
| getEventType = | |
| if isStopped model then | |
| Started | |
| else | |
| Stopped | |
| in | |
| ( { model | |
| | events = List.append model.events [ { eventType = getEventType, occurredAt = occurredAt } ] | |
| , now = occurredAt | |
| } | |
| , Cmd.none | |
| ) | |
| Click -> | |
| ( model, Task.perform StartStop Time.now ) | |
| eventTableRow : ( Int, Event ) -> Html Msg | |
| eventTableRow ( index, event ) = | |
| tr [] | |
| [ td [] [ text <| String.fromInt (index + 1) ] | |
| , td [] [ text <| eventTypeToString event.eventType ] | |
| , td [] [ text <| String.fromInt <| Time.posixToMillis event.occurredAt ] | |
| ] | |
| view : Model -> Html Msg | |
| view model = | |
| div [] | |
| [ p [] [ text <| "timer (sec): " ++ (String.fromInt <| getElapsedTime model // 1000) ] | |
| , p [] [ text <| "timer (ms): " ++ String.fromInt (getElapsedTime model) ] | |
| , button [ onClick Click ] | |
| [ text <| | |
| if isStopped model then | |
| "start" | |
| else | |
| "stop" | |
| ] | |
| , table [] | |
| [ thead [] | |
| [ tr [] | |
| [ th [] [ text <| "id" ] | |
| , th [] [ text <| "event" ] | |
| , th [] [ text <| "occurred at" ] | |
| ] | |
| ] | |
| , tbody [] (List.map eventTableRow (List.indexedMap Tuple.pair model.events)) | |
| ] | |
| ] | |
| subscriptions : Model -> Sub Msg | |
| subscriptions _ = | |
| onAnimationFrame Tick |
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