invoke-lambdas-locally.js

const aws = require('aws-sdk')
const express = require('express')
const bodyParser = require('body-parser')

const config = require('./lib/config')

// API Gateway
const apiLambdas = [
	{name: 'GetListOfUsers', endpoint: '/users', handler: require('./users-lambda').handler},
]

// Functions invoked manually
const invokedLambdas = [
	{name: 'ImageBucketTrigger', handler: require('./resize-image-lambda').handler},
]

const app = express()
const port = process.env.PORT || 3001

app.use(bodyParser.json())
app.use(bodyParser.raw({type: 'binary/octet-stream', limit : '100kb'}))

function apiInvocation(req, res, handler) {
	const context = {}
	const body = req.body

	const event = {
		"resource": req.path,
		"path": req.path,
		"httpMethod": req.method,
		"headers": null,
		"queryStringParameters": req.query,
		"pathParameters": null,
		"stageVariables": null,
		"requestContext": {
			"path": req.path,
			"accountId": "000000000000",
			"resourceId": "aztkla",
			"stage": "test-invoke-stage",
			"requestId": "test-invoke-request",
			"identity": {
				"cognitoIdentityPoolId": null,
				"cognitoIdentityId": null,
				"apiKey": "test-invoke-api-key",
				"cognitoAuthenticationType": null,
				"userArn": "arn:aws:iam::000000000000:root",
				"apiKeyId": "test-invoke-api-key-id",
				"userAgent": "userAgent",
				"accountId": "000000000000",
				"caller": "000000000000",
				"sourceIp": "sourceIp",
				"accessKey": "AADGAFCSFCSBCSBFCS",
				"cognitoAuthenticationProvider": null,
				"user": "000000000000"
			},
			"resourcePath": req.path,
			"httpMethod": req.method,
			"extendedRequestId": "test-invoke-extendedRequestId",
			"apiId": "inahj2igtc"
		},
		"body": JSON.stringify(body),
		"isBase64Encoded": false
	}

	handler(event, context, (error, response) => {
		res.status(response.statusCode).set(response.headers).send(response.body)
	})
}

function manualInvocation(req, res, handler) {
	const event = req.body
	const context = {}

	handler(event, context, (error, response) => {
		res.status(response.statusCode).set(response.headers).send(response.body)
	})
}

app.use((req, res, next) => {
	if (Buffer.isBuffer(req.body)) {
		req.body = JSON.parse(req.body)
	}
	next()
})

// Register Gateway API lambdas
apiLambdas.map((lambda) => {
	app.get(lambda.endpoint, (req, res) => {
		apiInvocation(req, res, lambda.handler)
	})
})

// Register manually invoked lambdas
invokedLambdas.map((lambda) => {
	app.post(`/:version/functions/${lambda.name}/invocations`, (req, res) => {
		manualInvocation(req, res, lambda.handler)
	})
})

app.post('/invoke/:func', async (req, res) => {
	try {
		const lambda = new aws.Lambda({
			endpoint: config.AWS_LAMBDA_ENDPOINT,
			region: config.AWS_REGION,
		})

		const data = await lambda.invoke({
			FunctionName: req.params.func,
			Payload: JSON.stringify(req.body),
			InvocationType: 'RequestResponse',
		}).promise()

		console.log('INVOCATION RETURN:', data)
		res.status(data.StatusCode).send(JSON.parse(data.Payload))
	}
	catch (e) {
		console.error('INVOCATION ERROR:', e)
		res.status(e.StatusCode).send(data.stack)
	}
})

module.exports = app

app.listen(port, () => console.log(`app listening on port ${port}!`))