AWS Lambda Function to create a Slash-Command for Giphy-Integration in Mattermost

This is pretty simple AWS Lamba function to use with Mattermost for Giphy-Integration. It allows to create a slash-command such as "/giphy " to post a random gif for that keyword from giphy into a channel or chat.

1. Create a new lambda function with the "Node.js 6.10" runtime.
2. Copy-paste the content of index.js into it.
3. Save

Add a new API Gateway POST endpoint. It should have "integration type" Lambda and point to your Lambda function from the previous step.

Mattermost submits its request using POST and as x-www-form-urlencoded, but Lambda expects JSON.

Therefore, you need to edit the "Integration Request" and add the following Body Mapping Template for application/x-www-form-urlencoded:

#set($allParams = $input.params())
{
  "body" : $input.json('$')
}

This should convert the x-www-form-urlencoded'ed data to JSON.

https://docs.mattermost.com/developer/slash-commands.html

Add a slash command according to the documentation and point it at your API Gateway URL.

Mattermost creates a random verification token for each slash command. You can go back to your Lambda function and add it to the TOKEN constant to enable verification of incoming requests.

The API-Key in the current implementation is simply the public "beta" API key from giphy. You should probably request your own API key and add it to the API_KEY constant in the Lambda function.