Usefull Lua code snippets for configurations

This page, is meant for users of imapfilter to add Lua code snippets which may come useful for everyone when writing their config.lua.

Getting all messages in a thread

Say you are running imapfilter with something along the lines of:

my_message = account["my-folder"]:contain_from("my@email.com")
for _, message in ipairs(my_messages) do
    local mailbox, uid = table.unpack(message)
    if mailbox[uid]:fetch_field("X-my-header") == "something" then
        -- do something
    end
end

You might find yourself in a need to fetch all messages which are linked to the thread of this message. To do that, you'll need to recursively search for all messages with a In-Reply-To header identical to this message Message-ID header and for every message hit with any of those headers' values, you'll need to do the same to make sure you've hit the whole thread - That's why it's recursive.

A request for such a function to be included in the standard library was made in #177 but since it's rather complicated and since it'd probably be hard to maintain, the request was rejected.

However, @doronbehar who is the initial writer of this WiKi page :), has implemented this function and commented with an example usage of it in #177. Here's the most updated version of this function:

local function get_message_id(msg)
	local id = msg:fetch_field("Message-ID"):gsub("[Mm]essage%-[Ii][Dd]: ", "")
	return id
end
local function get_reply_id(msg)
	local id = msg:fetch_field("In-Reply-To"):gsub("[Ii]n%-[Rr]eply%-[Tt]o: ", "")
	return id
end
function thread_messages(msg, mbox, related_messages, examined_ids)
	-- initilize examined_ids in case it's the first call of this function
	if not examined_ids then examined_ids = {} end
	-- This message
	local this_msgid = get_message_id(msg)
	table.insert(examined_ids, this_msgid)
	local this_message = mbox:match_field("Message-ID", this_msgid)
	-- The messages directly replyed to our `msg`
	local currently_related_messages = mbox:match_field("In-Reply-To", this_msgid)
	if related_messages then
		related_messages = related_messages + currently_related_messages
	else
		related_messages = currently_related_messages
	end
	-- The messages our `msg` was replyed to
	local prev_msgid = get_reply_id(msg)
	if string.len(prev_msgid) > 1 then
		related_messages = related_messages + mbox:match_field("Message-ID", prev_msgid)
	end
	-- Recursively add up messages related in the same way to the related_messages
	for _, related_msg in ipairs(related_messages) do
		local mailbox_related, uid_related = table.unpack(related_msg)
		local related_msgid = get_message_id(mailbox_related[uid_related])
		-- will check for every known related message if the messages replyed to `related_msgid` have been examined
		local skip = false
		for i=1,#examined_ids do
			if related_msgid == examined_ids[i] then
				skip = true
			end
		end
		if not skip then
			related_messages = related_messages + thread_messages(mailbox_related[uid_related], mbox, related_messages, examined_ids)
		end
	end
	return related_messages + this_message
end

You can use it as so:

local mbox = account[mailbox_name]
local my_messages = mbox:contain_from("my@email.com")
for _, message in ipairs(my_messages) do
    local mailbox, uid = table.unpack(message)
    local my_related_messages = thread_messages(mailbox[uid], mbox)
    my_related_messages:copy_messages(account[another_mailbox_name])
end