AWS Serverless Chatbot Sample

Example code for running a Slack chatbot using AWS Lambda and Amazon API Gateway.

Getting Started

1. Create your Lambda function that will process all Slack Requests
2. Create an API Gateway API
3. Create a method of type: POST
4. Select Integration Type: Lambda
5. Select the region in which you created your Lambda function
6. Select the Lambda Function you created
7. Click "Integration Request"
8. At the bottom of this Page select "Add mapping Template"
9. For content type please specify: "application/x-www-form-urlencoded"
10. Insert the template code below into the text field for the template. This code converts a URL Encoded form post into JSON for your Lambda function to parse
11. Deploy your API
12. In Slack, Go to Apps and Integrations
13. Click Build in the top right
14. Select Make a Custom Integration
15. Select Outgoing Webhooks
16. Pick a trigger word for your Bot!
17. In URL, put the URL created by your API Gateway Deployment

Template code for Integration Request:

## convert HTML POST data or HTTP GET query string to JSON
 
## get the raw post data from the AWS built-in variable and give it a nicer name
#if ($context.httpMethod == "POST")
 #set($rawAPIData = $input.path('$'))
#elseif ($context.httpMethod == "GET")
 #set($rawAPIData = $input.params().querystring)
 #set($rawAPIData = $rawAPIData.toString())
 #set($rawAPIDataLength = $rawAPIData.length() - 1)
 #set($rawAPIData = $rawAPIData.substring(1, $rawAPIDataLength))
 #set($rawAPIData = $rawAPIData.replace(", ", "&"))
#else
 #set($rawAPIData = "")
#end
 
## first we get the number of "&" in the string, this tells us if there is more than one key value pair
#set($countAmpersands = $rawAPIData.length() - $rawAPIData.replace("&", "").length())
 
## if there are no "&" at all then we have only one key value pair.
## we append an ampersand to the string so that we can tokenise it the same way as multiple kv pairs.
## the "empty" kv pair to the right of the ampersand will be ignored anyway.
#if ($countAmpersands == 0)
 #set($rawPostData = $rawAPIData + "&")
#end
 
## now we tokenise using the ampersand(s)
#set($tokenisedAmpersand = $rawAPIData.split("&"))
 
## we set up a variable to hold the valid key value pairs
#set($tokenisedEquals = [])
 
## now we set up a loop to find the valid key value pairs, which must contain only one "="
#foreach( $kvPair in $tokenisedAmpersand )
 #set($countEquals = $kvPair.length() - $kvPair.replace("=", "").length())
 #if ($countEquals == 1)
  #set($kvTokenised = $kvPair.split("="))
  #if ($kvTokenised[0].length() > 0)
   ## we found a valid key value pair. add it to the list.
   #set($devNull = $tokenisedEquals.add($kvPair))
  #end
 #end
#end
 
## next we set up our loop inside the output structure "{" and "}"
{
#foreach( $kvPair in $tokenisedEquals )
  ## finally we output the JSON for this pair and append a comma if this isn't the last pair
  #set($kvTokenised = $kvPair.split("="))
 "$util.urlDecode($kvTokenised[0])" : #if($kvTokenised[1].length() > 0)"$util.urlDecode($kvTokenised[1])"#{else}""#end#if( $foreach.hasNext ),#end
#end
}