How to transform HTTP requests to Lambda events exactly as AWS API Gateway does as an HTTP proxy?

Question

I'm developing a Lambda service behind an API Gateway as an HTTP proxy[1].

As the docs say, API Gateway basically transforms the HTTP request into a JSON Lambda Event.

In order to support the development process, I wonder if there is a library I could use to do that: transform an HTTP request into a JSON Lambda Event.

That way I could develop locally, wrapping my lambda implementation in a dummy web server whose work would be to transform and pass the event to my code.

[1] https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-develop-integrations-lambda.html

Answer

I recommends that you use [SAM CLI](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/install-sam-cli.html) for local testing. Using SAM CLI you can invoke your functions locally using the [`sam local start-api`](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-using-start-api.html) command, that will start also a local API gateway and will invoke your code when you CURL the local end-point. You could also use [`sam local generate-event`](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-using-generate-event.html) to create the event object that is used by API Gateway and use it when invoking the function directly using [`sam local invoke`](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-using-invoke.html).

How to transform HTTP requests to Lambda events exactly as AWS API Gateway does as an HTTP proxy?

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