From 350370a084aa92f97a4a566f10c009a9456d9643 Mon Sep 17 00:00:00 2001
From: Mikayla Fischler <mikayla@ky8.io>
Date: Thu, 8 Sep 2022 12:19:19 -0400
Subject: [PATCH] notify subscriber right away if there is already a value
 present

---
 scada-common/psil.lua | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/scada-common/psil.lua b/scada-common/psil.lua
index 9901e97..ddadf36 100644
--- a/scada-common/psil.lua
+++ b/scada-common/psil.lua
@@ -13,17 +13,26 @@ function psil.create()
     -- allocate a new interconnect field
     ---@key string data key
     local function alloc(key)
-        self.ic[key] = { subscribers = {}, value = 0 }
+        self.ic[key] = { subscribers = {}, value = nil }
     end
 
     ---@class psil
     local public = {}
 
     -- subscribe to a data object in the interconnect
+    --
+    -- will call func() right away if a value is already avaliable
     ---@param key string data key
     ---@param func function function to call on change
     function public.subscribe(key, func)
-        if self.ic[key] == nil then alloc(key) end
+        -- allocate new key if not found or notify if value is found
+        if self.ic[key] == nil then
+            alloc(key)
+        elseif self.ic[key].value ~= nil then
+            func(self.ic[key].value)
+        end
+
+        -- subscribe to key
         table.insert(self.ic[key].subscribers, { notify = func })
     end