# Delay

Elm utilities to trigger updates after a delay

example: https://andrewmacmurray.github.io/elm-delay/

### Why?

Sometimes you need to trigger updates after a period of time (i.e. to wait for a css transition or animation to complete) or maybe you need to chain a sequence of these updates (for more complex states).

This library provides utilities to express this more tidily.

### How?

#### Send a single delayed `Msg`

To trigger a single update after a period of time pass `Delay.after` as a command to the elm runtime:

```elm
FirstMessage ->
    model ! [ Delay.after 500 millisecond SecondMessage ]
```

After triggering `FirstMessage`, `500ms` later update will be called with `SecondMessage`

#### Send a sequence of delayed `Msg`s

```elm
Trigger ->
    model
        ! [ Delay.sequence
                [ ( 1000, millisecond, FirstMessage )
                , ( 2000, millisecond, SecondMessage )
                , ( 1000, millisecond, ThirdMessage )
                ]
          ]
```

by sending a `Trigger` `Msg`:

+ after `1000ms` update will be called with `FirstMessage`
+ then after `2000ms` update will be called with `SecondMessage`
+ then after `1000ms` update will be called with `ThirdMessage`


As a convenience if you'd only like to start a sequence if the model is in a particular shape you can use `Delay.sequenceIf`

```elm
Trigger ->
    model
        ! [ Delay.sequenceIf (not model.updating)
                [ ( 1000, millisecond, FirstMessage )
                , ( 2000, millisecond, SecondMessage )
                , ( 1000, millisecond, ThirdMessage )
                ]
          ]
```

If you'd like all the steps to have the same unit of time, use the `Delay.withUnit` helper

```elm
Trigger ->
    model
        ! [ Delay.withUnit millisecond
                [ ( 1000, FirstMessage )
                , ( 2000, SecondMessage )
                , ( 1000, ThirdMessage )
                ]
                |> Delay.sequence
          ]
```