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step-5.md

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Step 5 - Configure API Gateway endpoint

Before writing the handler, you need to configure API Gateway to pass the url querystring parameter to the lambda function.

Modify the Request template

First, modify the s-function.json file in the urlToMd directory so that it will pass on the url parameter from the endpoint querystring.

In the endpoints array, edit requestTemplates to look like this:

"requestTemplates": {
  "application/json": {
    "url" : "$input.params().querystring.url"
  }
}

See the edited file on GitHub.

Retrieve the url parameter

Next, edit handler.ts to return the url parameter that API Gateway passed to it. Delete the scaffolded code that Serverless created and replace it with

export interface MarkdownEvent {
  url: string
}

export const handler = (event: MarkdownEvent, context: Object, cb: Function) => {
  return cb(null, {
    url: event.url
  });
};

Now that you're using TypeScript, you need to define the object structure you expect to receive from Lambda - in the case a single url parameter that is a string. Additionally, the function now uses ES2015 arrow function syntax.

See the edited file on Github.

Test the function

To test the function locally, edit the event.json (GitHub link) file to create a mock Lambda event.

{
  "url": "http://www.bbc.com/culture/story/20160704-mount-rushmore-at-75-how-did-it-come-to-be"
}

Next, run tsc to compile your Typescript then, from within the urlToMd directory, run serverless function run.

You should receive the following output:

Serverless: Success! - This Response Was Returned:
Serverless: {
    "url": "http://www.bbc.com/culture/story/20160704-mount-rushmore-at-75-how-did-it-come-to-be"
}

Deploy the revised endpoint and function

serverless dash Deploy

As in Step 2, select both the endpoint and function, then select deploy. Once deployed, navigate to the API endpoint but this time, append a url parameter, i.e.

https://abcdefg12.execute-api.us-east-1.amazonaws.com/dev/urlToMd?url=http://www.bbc.com/culture/story/20160704-mount-rushmore-at-75-how-did-it-come-to-be

You should receive a JSON response with the URL echoed back to you!