Objective

The objective of this lab is learn how to 

• use modules in KRL
• wrap an external API call and make it available from a module
• use ruleset configuration to securely use API keys

Reading and Reference

Read the following:

• Modules and External APIs Links to an external site.

The following video may be helpful:

APIs and Picos Video Links to an external site.

Note:

1. the video talks about having to explicitly declare the _testing value for the testing tab to work. The latest release of the pico engine (1.x.x) automatically configures this value, so you do not have to manually create it. 
2. the video uses an old method of using API keys (the keys pragma) which has been deprecated in favor of ruleset configuration. 

You may find the following resources useful:

• KRL Manual 
• Developer Tips for the Pico Engine 
• Twilio API Explorer Links to an external site. (you need to already have an account with Twilio first)
• Handling Secrets in Rulesets Links to an external site.

Prerequisites

You should have completed:

• Lab 0: Events and Queries

Implementation Notes

• Read carefully about how to configure a ruleset to handle secrets Links to an external site.. 
• Modules can provide a KRL interface for an API. They encapsulate the complexity and hide the details of the API so that other rulesets can more easily use them. 
• You'll have to create a number on Twlio. If you have problems with this, be sure to ask one of the TAs.
• An example of how to clean up HTTP get requests with decode in KRL can be found here Links to an external site..
• Note that the Twilio API wants you to use a POST for sending messages. This is consistent with good API design (don't use GET for requests that affect resource state). The HTTP library in KRL (Links to an external site.)Links to an external site. supports http:post() as an action. 
• You may find a tool like Postman (Links to an external site.) useful for exploring the Twilio API and ensuring you are making the calls correctly before encoding them in KRL functions and actions. 

Do This

1. Sign up for a developer account at Twilio Links to an external site.. 
2. Find your Twilio keys in the Twilio account. You'll need the SID and the auth token. 
3. Create a Twilio module that includes the action from the Modules and External APIs lesson.  Be sure the ruleset implementing your module is set up to be configured for the Twilio keys. Do not put your keys directly in the ruleset!
4. Install your ruleset, inserting the proper JSON into the configuration field to ensure the module has the Twilio keys. 
5. Write a ruleset to use and test your Twilio module by using the action you defined in the module to send an SMS to yourself or a friend. Read the Twilio docs to understand the prerequisites for sending SMS messages. 
6. Extend your module to have a messages() function that uses the Twilio SMS API to retrieve one or more messages (see message logs in the Twilio documentation):
   1. The function should return all messages if no argument is given. Be sure to include optional arguments for controlling pagination of long lists of data. 
   2. Include a means of filtering the result set by sending and receiving number. You can ignore filtering by date. 
7. Modify your ruleset to test your messages() function. 

Deliverables

Turn in the following:

1. URLs for the Twilio module and test ruleset. 
2. Short screencast (with sound) showing:
   1. Ruleset installation with configuration for keys. 
   2. Twilio module with messages() function. 
   3. Test rule
   4. Several interactions with the test rule with results
3. Answer the following questions:
   1. Why does this assignment ask you to create a function for messages but an action for sending the SMS message? What's the difference? 
   2. Why did we introduce the secrets for the Twilio module by configuring the rule that uses the module, rather than configuring the module directly?