Automatic Calendar Management — Notmuch + Calypso

One of the big “features” of outlook/exchange in my world is automatically merging of incoming calendar updates from email. This makes my calendar actually useful in knowing what meetings people have asked me to attend. As I'm not willing to otherwise tolerate outlook, I decided to try and provide that in my preferred environment; notmuch and calypso.

Identifying calendar updates

The first trick is how to identify incoming messages with calendar updates. I'd love to be able to search for specific mime content types, but I haven't been able to construct such a search. Failing that, I'm just looking for messages containing the string 'text/calendar':

notmuch search --output=messages tag:inbox AND text/calendar

Next, I want to skip over previously scanned calendar updates, so I'll plan on tagging messages that have been scanned with the 'calendar' tag and skip those:

notmuch search --output=messages tag:inbox AND text/calendar AND not tag:calendar

jq — sed for json

With the messages containing likely calendar entries identified, the remaining task is to extract the MIME section containing the actual calendar data. Notmuch can generate json for the message, leaving us only needing to parse the json and extract the relevant section. I found the 'jq' tool in the archive, which looks like a rather complicated parsing and reformatting tool for json data. It took a while to understand, but I managed to generate a command string that takes a notmuch message and pulls out the content for all text/calendar elements:

jq -r '..| select(."content-type"? == "text/calendar") | .content'

This is a recursive walk over the data structure. It looks for structures with "content-type": "text/calendar" and dumps their "content" elements in raw text form.

Putting it all together

Here's the complete script:


SEARCH="tag:inbox AND not tag:calendar AND text/calendar"


trap "rm -r $TMP" 0 1 15

notmuch search --output=messages $SEARCH | while read message; do
    notmuch show --format=json $message | 
        jq -r '.. | select(."content-type"? == "text/calendar") | .content' > $TMP
    if [ -s $TMP ]; then
        calypso --import private/calendar $TMP && notmuch tag +calendar $message
        notmuch tag +calendar $message

I'd love to fix calypso's --import operation to talk to the local calypso daemon with the database loaded; the current mechanism actually loads the entire database into a new process and then applies the new data to that. With my calendar often containing hundreds of entries, that takes a while.