https://github.com/marcodaniels/elm-aws-cloudfront

Create AWS CloudFront Lambda@Edge functions in Elm
https://github.com/marcodaniels/elm-aws-cloudfront

aws-cloudfront elm lambda-edge

Last synced: 3 days ago
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Create AWS CloudFront Lambda@Edge functions in Elm

• Host: GitHub
• URL: https://github.com/marcodaniels/elm-aws-cloudfront
• Owner: MarcoDaniels
• License: bsd-3-clause
• Created: 2024-01-06T10:00:54.000Z (12 months ago)
• Default Branch: main
• Last Pushed: 2024-01-14T13:11:43.000Z (12 months ago)
• Last Synced: 2024-11-05T15:34:16.048Z (about 2 months ago)
• Topics: aws-cloudfront, elm, lambda-edge
• Language: Elm
• Homepage: https://package.elm-lang.org/packages/marcodaniels/elm-aws-cloudfront/latest/
• Size: 22.5 KB
• Stars: 1
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# elm-aws-cloudfront

Create [AWS CloudFront Lambda@Edge](https://docs.aws.amazon.com/lambda/latest/dg/lambda-edge.html) functions in Elm.

---

This package uses an [Elm headless worker](https://package.elm-lang.org/packages/elm/core/latest/Platform#worker) under

the hood requiring [ports](https://guide.elm-lang.org/interop/ports) and a small JavaScript snippet to be bundled and

deployed into AWS CloudFront Lambda@Edge. Check the [examples folder](/examples).

Elm part:

```elm

port module MyModule exposing (main)

import CloudFront exposing (Model, Msg, cloudFront)

import CloudFront.Header exposing (withHeader)

import CloudFront.Lambda exposing (originResponse, toResponse)

import Json.Decode as Decode

import Json.Encode as Encode

port inputEvent : (Decode.Value -> msg) -> Sub msg

port outputEvent : Encode.Value -> Cmd msg

-- Optional flags can be used on init

-- main : Program {token : String} (Model {token : String}) Msg

main : Program () (Model ()) Msg

main =

    ( inputEvent, outputEvent )

        |> (originResponse

                (\{ response, request } _ ->

                    response

                        |> withHeader { key = "cache-control", value = "public, max-age=1000" }

                        |> toResponse

                )

                |> cloudFront

           )

```

JavaScript part:

```javascript

const {Elm} = require('./elm');

// optinal flags can be passed on init

// const app = Elm.MyModule.init({flags: {token: 'my-token'}});

const app = Elm.MyModule.init();

exports.handler = (event, context, callback) => {

    const caller = (output) => {

        callback(null, output);

        app.ports.outputEvent.unsubscribe(caller);

    }

    app.ports.outputEvent.subscribe(caller);

    app.ports.inputEvent.send(event);

}

```

This repository also provides a nix builder to build and bundle the application to be ready to deploy into AWS. This

requires to have the Elm ports named with:

```elm

port inputEvent : (Decode.Value -> msg) -> Sub msg

port outputEvent : Encode.Value -> Cmd msg

```

As the bundled JavasScript will automatically add the input and output ports with the specific name.

The nix builder requires the `elm-srcs.nix` and `registry.dat` files, and for that

the [elm2nix package](https://github.com/cachix/elm2nix) is needed to generate them.

```nix

makeLambda.buildElmAWSCloudFront {

  src = ./src;

  elmSrc = ./elm-srcs.nix;

  elmRegistryDat = ./registry.dat;

  lambdas = [

    { module = ./src/MyModuleTwo.elm; }

    {

      module = ./src/MyModuleOne.elm;

      flags = [ ''token:"token-goes-here"'' ''url:"url-goes-here"'' ];

    }

  ];

}

```