docs.md

CORS

OPTIONS requests are automatically responded to.

Specify a corsOrigin in the request environment you wish to allow and it will automatically add the required headers.

Usage

You choose a wrapper function and pass it a single argument: your function.

The library exposes three functions, you choose one depending on the kind of request you're accepting:

• jsonRequestHandler - Handle JSON requests
• formRequestHandler - Handle url-encoded form requests
• requestHandler - Raw request handler, for anything else

The functions accept two type arguments: EnvType and BodyType. EnvType defined what will be accessible in request.env, and BodyType optionally on request.body.

You can also explicitly specify a response type for your function so that it can be included in the swagger docs. Response types available are:

• JSONResponse<T> where T is the being returned.
• RedirectionResponse for 302s.

Your function will be called with a single argument: the request. The request object includes:

Property	Type	Description
path	string	e.g. '/api/resource'
method	HTTPMethod (string)	e.g. 'GET'
body	undefined or string or BodyType (type argument)
headers	`Record<string, string	string[]>`
host	string	The requested host e.g. 'google.com'
cookies	string[]	Unparsed cookies e.g. ['a=b', 'c=d']
query	undefined or `Record<string, string	string[]>`
env	EnvType (type argument)	The environment, or config, passed into the request by the cdk stack. Useful for passing resource arns etc.
region	AWSRegion (string)	The region the lambda is currently executing in. e.g. 'us-east-1'

Example of a simple function that accepts a JSON request and returns a JSON response:

import { jsonRequestHandler, JSONResponse } from '@reapit-cdk/edge-api-sdk'

type EnvType = {
  awsResourceArn: string
}
type BodyType = {
  something: string
}
type ResponseBodyType = {
  success: boolean
}

export const handler = jsonRequestHandler<EnvType, BodyType>(
  async (request): Promise<JSONResponse<ResponseBodyType>> => {
    const {
      env: { awsResourceArn },
      body,
    } = request

    if (body) {
      const { something } = body
      console.log('heres something', something, awsResourceArn)

      return {
        body: {
          success: true,
        },
      }
    }

    return {
      body: {
        success: false,
      },
    }
  },
)

Testing your function

If we were to import { handler } from the above file, handler would be a function that accepted CloudFront/API Gateway events and returned appropriate responses. We could test this function but it would involve a lot of marshalling code to create inputs and parse the outputs.

In order to fix this, the nested function (the one you wrote) is exposed via handler.handler, so you can write test code which looks like this:

import { handler } from './lambda'

describe('example', () => {
  beforeAll(() => {
    process.env.AWS_REGION = 'eu-west-2'
  })

  it('returns success true if a body is supplied', async () => {
    const result = await handler.handler({
      headers: {},
      cookies: [],
      host: 'google.com',
      region: 'eu-west-2',
      path: '/',
      method: 'POST',
      body: { something: 'example' },
      env: {
        awsResourceArn: 'aws-resource-arn',
      },
    })
    expect(result.body.success).toBe(true)
  })

  it('returns success false if a body is not supplied', async () => {
    const result = await handler.handler({
      headers: {},
      cookies: [],
      host: 'google.com',
      region: 'eu-west-2',
      path: '/',
      method: 'GET',
      env: {
        awsResourceArn: 'aws-resource-arn',
      },
    })
    expect(result.body.success).toBe(false)
  })
})