2023-06-18 13:03:37 +03:00
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# Airlock
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## Usage
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2023-06-29 11:02:57 +03:00
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### Demo
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2023-07-29 12:52:32 +03:00
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[](https://www.youtube.com/watch?v=tynCzifvIzE)
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2023-06-29 11:02:57 +03:00
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2023-06-18 13:03:37 +03:00
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### FFI
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Urbit subscriptions require [server-side event (SSE)](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events).
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Unfortunately, Elm does not provide a native implementation.
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This means that we will need to use [JS FFI (aka ports)](https://guide.elm-lang.org/interop/ports.html).
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#### Setting up the Elm side
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You would need to declare two ports for Airlock to use:
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1. `port createEventSource : String -> Cmd msg`
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This sets up the SSE channel.
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2. `port onEventSourceMessage : (JD.Value -> msg) -> Sub msg`
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This recieves the actual messages from the SSE channel.
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These two functions need to be passed to one of the functions from `Ur.Run` module.
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The functions in `Ur.Run` are the same as functions from `Browser`, but have a couple of extra urbit-specific fields.
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#### Setting up the JS side
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The SSE JS code is neatly packed into [example/fetch-event-source.js](example/fetch-event-source.js).
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All you need to do is pass them to Elm ports like in [example/script.js](example/script.js).
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You can see a full working example in [example](example).
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