This is the new go to place for API help for WoW
https://wow.gamepedia.com/World_of_Warcraft_API
I would suggest looking at some small recent addons to see how things are coded now to give you a start and then slowly relearn some of the addon stuff thats still hidden somewhere in your programming memory
What I find useful is to create a template addon so to speak that has the pure basics and then build any specifics into it for any addon I want to write.
For example:
This is a simple addon template that nearly all of my addons have used as their starting point. Feel free to utilise yourself if you want.
Good Luck
Lua Code:
--[[ Localise the Addon Wide Data Table ]]--
local addonName, addonData = ...
--[[ Localise any Addon Wide Sub Tables that are frequently accessed ]]--
local Translate = addonData.Translate
--[[ Addon Specific Functionality ]]--
...
--[[ Monitor registered events ]]--
local function EventWatcher(self,event,...)
-- Store the arguments into an array to access when needed
local args = { ... }
if event == "PLAYER_ENTERING_WORLD" then
-- Deal with player entering world
elseif event == "ADDON_LOADED" then
-- Deal with any addons being loaded that you want to watch for ( args[1] is addon being loaded )
end
end
local f = CreateFrame("Frame")
f:RegisterEvent("ADDON_LOADED")
f:RegisterEvent("PLAYER_ENTERING_WORLD")
f:SetScript("OnEvent", EventWatcher)