Todo

FIX: on delete, bot is not deleted. fix the python provider handler for lex bot.
separate policies. 1 for webhandler, 1 for lambda providers.
update this doc to reflect the now automated lex bot creation
add method response template
create alias, delete alias
consider https://github.com/aws-cloudformation/custom-resource-helper
enable cors for both GET and POST /webhook
test integration works

Problem statement

For chatbot integrations, sometimes, you need to do some preprocessing with a message before it hits Lex. For example, you might be dealing with informal language and need to normalise the message using an external API before sending it over to Lex.

Solution overview

Setup a custom webhook to be supplied to the chat platform. The webhook will be handled by an API Gateway endpoint that is integrated with a Lambda function. In that Lambda function, Lex is called, amongst other things.

Pre-requisites

cdk installed on local machine

Setup:

1. Prepare the Facebook components

Create Facebook page
Create Facebook app
in Facebook app, add Product 'Messenger'
link product to created page
click on generate token for that page. note this for Step 3

2. Create the Lexbot

use the quick launch template or create your own, note the bot name for the next step.
create an alias, such as 'latest', note this for the next step.

3. Deploy the stack

run cdk deploy
Go to the created Lamdba, fill the env vars:
- BOT_NAME from Step 2
- BOT_ALIAS from Step 2
- PAGE_TOKEN from Step 1
- VERIFY_TOKEN can be any string you set. note this for Step 4.

4. Connect the webhook

go back to the product setup page. click on 'add webook'
paste in the API_URL/webhook
paste in the same verify token from Step 3
it should be added if you've done everything above correctly. a common cause of error is not having the correct mapping template.

5. Test it

send a message to the page using the developer's facebook account. it should work.

nazreen/aws-cdk-for-lex-messenger