bootstrap

#!/usr/bin/env ngs

# https://docs.aws.amazon.com/lambda/latest/dg/runtimes-custom.html
# https://docs.aws.amazon.com/lambda/latest/dg/runtimes-walkthrough.html
# https://aws.amazon.com/blogs/apn/aws-lambda-custom-runtime-for-php-a-practical-example/

ns {


	F _to_lowercase(s:Str) s.mapo(F(ch) if ord(ch) in ord('A')...ord('Z') chr(ord('a') + ord(ch) - ord('A')) else ch)

	ENV_CONTEXT = ENV.filterk(Pfx('AWS_LAMBDA_')).mapk(F(k) _to_lowercase(k - Pfx('AWS_LAMBDA_')))

	log("Starting")

	# AWS layer is exracted there
	NGS_PATH.unshift('/opt/lib/ngs')

	# Handler format idea is from https://docs.aws.amazon.com/lambda/latest/dg/java-handler.html and conveys that a namespace is in play
	# TODO: try/catch to handle missing ::
	t = ENV._HANDLER.split('::')
	file = t[0]
	func = t[1]

	F _debug(s:Str) debug('aws_lambda_bootstrap', s)

	F _make_error(e:Exception) {
		{
			'errorMessage': exception_specific_message(e).join("\n")
			'errorType': e.typeof().name
			'stackTrace': collector print_exception(e, echo=F(message) message.ensure(Lines).each(collect))
		}
	}

	try {
		log("Loading ${ENV.LAMBDA_TASK_ROOT / file}")
		handler = require(ENV.LAMBDA_TASK_ROOT / file)[func]
		_debug("Loaded ${ENV.LAMBDA_TASK_ROOT / file}")
	} catch(e) {
		error("Failed to load ${ENV.LAMBDA_TASK_ROOT / file}")
		# https://docs.aws.amazon.com/lambda/latest/dg/runtimes-api.html#runtimes-api-initerror
		$(curl -sS -X POST "http://${ENV.AWS_LAMBDA_RUNTIME_API}/2018-06-01/runtime/init/error" -H 'Lambda-Runtime-Function-Error-Type: Runtime.NoSuchHandler' -d ${_make_error(e).encode_json()})
		error("Reported initialization error - failed to load ${ENV.LAMBDA_TASK_ROOT / file}")
		exit(1)
	}

	while true {
		# https://docs.aws.amazon.com/lambda/latest/dg/runtimes-api.html#runtimes-api-next
		_debug("Waiting for invocation")
		event = ``curl -sS -L -i "http://${ENV.AWS_LAMBDA_RUNTIME_API}/2018-06-01/runtime/invocation/next"``
		request_id = event.headers['Lambda-Runtime-Aws-Request-Id']
		_debug("Handling request ${request_id}")
		try {
			if event.headers.has('Lambda-Runtime-Trace-Id') {
				ENV._X_AMZN_TRACE_ID = event.headers['Lambda-Runtime-Trace-Id']
			}
			# "inspired" by https://github.com/aws/aws-lambda-ruby-runtime-interface-client -- lib/aws_lambda_ric/lambda_context.rb
			# XXX: identity and client_context were not tested
			context = ENV_CONTEXT + {
				'deadline_ms': event.headers['Lambda-Runtime-Deadline-Ms'].Int()
				'aws_request_id': request_id
				'invoked_function_arn': event.headers['Lambda-Runtime-Invoked-Function-Arn']
				'identity': event.headers.get('Lambda-Runtime-Cognito-Identity', '{}').decode_json()
				'client_context': event.headers.get('Lambda-Runtime-Client-Context', '{}').decode_json()
			}
			response = handler(event.body.decode_json(), context)
			_debug("Sending response ${request_id}")
			# https://docs.aws.amazon.com/lambda/latest/dg/runtimes-api.html#runtimes-api-response
			$(curl -sS -X POST "http://${ENV.AWS_LAMBDA_RUNTIME_API}/2018-06-01/runtime/invocation/$request_id/response" -d ${response.encode_json()})
		} catch(e) {
			# https://docs.aws.amazon.com/lambda/latest/dg/runtimes-api.html#runtimes-api-invokeerror
			$(curl -sS -X POST "http://${ENV.AWS_LAMBDA_RUNTIME_API}/2018-06-01/runtime/invocation/$request_id/error" -d ${_make_error(e).encode_json()})
		}
		_debug("Sent response")
	}
}