Building A Better Digital Bat Signal - Part 2 - The Server

I want my phone's background to automatically update to a dramatic looking image when there's an urgent email in my inbox. To implement this, I need to scan my Gmail inbox for such a message and report this to my phone. I've implemented this behavior using a bit of shell scripting on a nano-sized AWS Linux server.

I can access my inbox via the Gmail API. Years ago, I wrote gmail_tool to manage an overrun Gmail inbox from the command line. I recently implemented a cleaned up version of this script, as gmailassist.

gmailassist lets me run a search for matching Gmail threads. Consider this search of my SPAM folder:

  $ gmailassist -p i2x -a threads -q 'label:spam' | head -3
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With this command line tool in place, it's straightforward to generate a single 'inbox-status'. Here's the current logic for doing so:

  checks="work_urgent|work|label:inbox_label:unread_subject:urgent"
  checks="$checks personal_urgent|personal|label:inbox_label:unread_subject:urgent_category:primary"
  checks="$checks wife|personal|label:inbox_label:unread_from:wife@gmail.com"
  checks="$checks ok|work|ben" # [A]
  now=$(date +%Y-%m-%d)

  for check in $checks ; do
    status=$(echo $check | cut -d'|' -f1)
    profile=$(echo $check | cut -d'|' -f2)
    query=$(echo $check | cut -d'|' -f3 | tr '_' ' ')

    gmailassist -a threads -q "$query" -p $profile > $TMP/inbox-status.hits
    hits=$(cat $TMP/inbox-status.hits | wc -l)
    if [ "$hits" -gt 0 ] ; then
      echo "$now $status" >> $TMP/inbox-status.log
      if [ -n "$V" ] ; then
        cat $TMP/inbox-status.hits
      else
        echo $status
      fi
      exit
    fi
  done

  echo "$now unknown" >> $TMP/inbox-status.log
  echo "unknown" # [B]
  ;;

This bit of code loops through each $checks. Each 'check' has the format:

• Status - the value that will be printed to the screen if the Gmail search returns any rows.
• Profile - the Gmail profile to search. I've set up work and personal so I can get alerts from both my personal and work email.
• Query - The search to use against Gmail. This looks odd because spaces are replaced with _. Other than this, however, this is a normal Gmail search.

In the first version of inbox-status I neglected to include the last check, [A]. I assumed that if none of the queries returned any rows, then all must be ok. The problem is, occasionally the API glitches. In this case, the searches return no rows not because they are empty queries, but because the API has failed. By setting up [A], the inbox status will only be OK if a search actively returns rows.

[B] is also essential, it says that if none of the rows match then the status is unknown. This will be skipped by the phone, so that when the API is down, the results are ignored.

Finally, I added support for a -v option when querying the inbox status. This reports the matching threads that correspond to the status. This is useful for quickly seeing which message has triggered the inbox status logic.

With a script to derive my inbox status, all that was left was to deliver this information to my phone. I make use of AutoRemote to accomplish this.

AutoRemote is a magic service that allows information to be delivered to an Android phone via a web request.

In my Linux server's crontab I have:

  */10 * * * * i2xassist -a inbox-status | andsend SetInboxStatus

andsend is little more than a simple wrapper around curl. It invokes the URL:

  $ status=$(i2xassist -a inbox-status)
  $ curl -s https://autoremotejoaomgcd.appspot.com/sendmessage \
    -d key=YOUR_AUTO_REMOTE_KEY \
    -d "message=SetInboxStatus=:=$status"

Every 10 minutes, my phone receives a SetInboxStatus message with the current inbox status. Up next is to have the phone react to this. We're almost there!