Applescript to delete message conversation that matches regex - regex

Question

I'm trying to create an AppleScript to delete messages conversations that match a particular regex pattern. I tried to follow an example I found, but it seems to be using code that no longer works (perhaps High Sierra limitations).
The following is the code doesn't seem to work.
set chatsToKill to {}
tell application "Messages"
set allChats to every chat
repeat with eachChat in allChats
--
-- The example fails because ScriptEditor would error saying it could get participants of the value returned for the first (or any of eachChat).
--
set thePeeps to participants of eachChat
repeat with oneParticipant in thePeeps
set theHandle to handle of oneParticipant
try
do shell script "echo " & quoted form of theHandle & " | egrep '^SMS;-;141'"
if chatsToKill does not contain eachChat's id then set end of chatsToKill to eachChat's id
end try
end repeat
end repeat
repeat with deathChat in chatsToKill
-- This should be a delete of the deathChat
end repeat
end tell

Answer 1

Perhaps things have changed since that script was written, but it is flawed and will not work, and I'm not sure it can be made to work as of macOS 10.11.6+.
Apple has greatly limited scripting access to the Messages app.
When I step through your script, I get an error on this line:
set thePeeps to participants of eachChat
The error is:
Messages got an error: Can’t get participants of text chat id
"iMessage;-;[phone]".
Even when I put the code in a try/catch block, it failed for all messages.
Even if that worked, I don't see how the remainder of your script would work. You execute a do shell script without assigning the results to anything.
You need something like this:
set scriptResults to do shell script "echo " & quoted form of theHandle & " | egrep '^SMS;-;141'"
-- do something with scriptResults
if chatsToKill does not contain eachChat's id then set end of chatsToKill to eachChat's id
Sorry I can't offer something better.