Tuesday 28 May 2019

Whose Turn Is it? An OpenHAB / Google Home / now.sh Hack (part 4 - The Rethink)

The "whose turn is it?" system was working great, and the kids loved it, but the SAF (Spousal Acceptance Factor) was lower than optimal, because she didn't trust that it was being kept up-to-date. We had a number of "unusual" weekends where we didn't have a Movie Night, and she was concerned that the "roll back" (which of course, has to be manually performed) was not being done. The net result of which being, a human still had to cast their mind back to when the last movie night was, whose turn it was, and what they chose! FAIL.

Version 2 of this system takes these human factors into account, and leverages the truly "conversational" aspect of using DialogFlow, to actually extract NOUNS from a conversation and store them in OpenHAB. Instead of an automated weekly rotation scheme which you ASK for information, the system has morphed to a TELL interaction. When it IS a Movie Night, a human TELLS the Google Home Mini somewhat like this:

Hey Google, for Movie Night tonight we watched Movie Name. It was Person's choice.


Hey Google, last Friday it was Person's turn for Movie Night. we watched Movie Name.

To do this, we use the "parameters" feature of DialogFlow to punch the nouns out of a templated phrase. It's not quite as rigid as it sounds due to the machine-learning magic that Google runs on your phrases when you save them in DialogFlow. Here's how it's set up; with the training phrases:

Kudos to Google for the UI and UX of this tricky stuff - it's extremely intuitive to set up, and easy to spot errors thanks to the use of coloured regions. Here's where the parameters get massaged into a suitable state for my webhook Lambda. Note the conversion into a single pipe-separated variable (requestBody) which is then PUT into the OpenHAB state for the item that has the same name as this Intent, e.g. LastMovieNight.

Within OpenHAB, almost all of the complexity in working out "who has the next turn" is now gone. There's just a tiny rule that, when the item called LastMovieNight is updated (i.e. by the REST interface), appends it to a "log" file for persistence purposes:

rule "Append Last Movie Night"
    Item LastMovieNight received update
      "/home/pi/writelog.sh /var/lib/openhab2/movienight-logs.txt " + 

(writelog.sh is just a script that effectively just does echo ${2} >> $1 - it seems like OpenHAB's executeCommandLine really should be called executeScript because you can't do anything directly).

The flip side is being able to query the last entry. In this case the querying side is very straightforward, but the trick is splitting out the |-separated data into something that the Google Home can speak intelligibly. I've seen this called "having a good VUI" (Voice User Interface) so let's call it that.

Given that the result of querying the MyOpenHAB's interface for /rest/items/LastMovieNight/state will return:

Sophie|2019-05-26T19:00:00+10:00|Toy Story 2

I needed to be able to "slice" up the pipe-separated string into parts, in order to form a nice sentence. Here's what I came up with in the webhook lambda:

const { restItem, responseForm, responseSlices } = 
// omitted - make the REST call to /rest/items/${restItem}/state,
// and put the resulting string into "body"
if (responseSlices) {
   const expectedSlices = responseSlices.split('|');
   const bodySlices = body.split('|');
   if (expectedSlices.length !== bodySlices.length) {
     fulfillmentText = `Didn't get ${expectedSlices.length} slices`;       
   } else {
     const responseMap = expectedSlices.map((es, i) => {
       return { name: es, value: bodySlices[i] } 

     fulfillmentText = responseMap.reduce((accum, pair) => {
       const regex = new RegExp(`\\\$${pair.name}`);
       let replacementValue = pair.value;
       if (pair.name === 'RELATIVE_DATE') {
         replacementValue = moment(pair.value).fromNow();        
       return accum.replace(regex, replacementValue);  
     }, responseForm);   

Before I try and explain that, take a look at how it's used:

The whole thing hinges on the pipe-separators. By supplying a responseSlices string, the caller sets up a mapping of variable names to array slices, the corresponding values of which are then substituted into the responseForm. It's completely neutral about what the variable names are, with the one exception: if it finds a variable named RELATIVE_DATE it will treat the corresponding value as a date, and apply the fromNow() function from moment.js to give a nicely VUI-able string like "3 days ago". The result of applying these transformations to the above pipe-separated string is thus:

"The last movie night was 3 days ago, when Sophie chose Toy Story 2"

Job done!