Add rp_checkitem mod

mods/rp_checkitem/API.md

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+This tiny mod lets you know when a player got a new item.
+This mod is currently not recommended to be used outside of Repixture yet.
+
+Its only function is:
+
+## `rp_checkitem.register_on_got_item(item, callback)`
+
+Registers the function `callback(player)` as an callback for when a player got
+or has an item. `callback` might be called repeatedly.
+
+* `item`: Raw item name of item to check for (no `ItemStack` or item count)
+* `callback(player)`: Function that is called if `player` has the item
+
+NOTE: `callback` is currently very limited. It might not be called instantly,
+depending on how the item got into the player inventory, and it might not
+always recognize a gotten item if it was too briefly in the inventory.
+Only when the player held on to the item for at least 10 seconds, `callback` is
+guaranteed to be called. This behavior might be improved in later versions.
+

mods/rp_checkitem/init.lua

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+rp_checkitem = {}
+
+-- Time in seconds to check inventory for items
+local ITEM_CHECK_TIME = 10
+
+local items_to_watch = {}
+
+function rp_checkitem.register_on_got_item(item, callback)
+	table.insert(items_to_watch, {item=item, callback=callback})
+end
+
+minetest.register_on_joinplayer(function(player)
+	local inv = player:get_inventory()
+	for i=1, #items_to_watch do
+		local entry = items_to_watch[i]
+		if inv:contains_item("main", entry.item) then
+			entry.callback(player)
+		end
+	end
+end)
+
+minetest.register_on_player_inventory_action(function(player, action, inventory, inventory_info)
+	if action == "put" then
+		local itemname = inventory_info.stack:get_name()
+		for i=1, #items_to_watch do
+			local entry = items_to_watch[i]
+			if inventory_info.stack:get_name() == entry.item then
+				entry.callback(player)
+			end
+		end
+	end
+end)
+
+local timer = 0
+minetest.register_globalstep(function(dtime)
+	timer = timer + dtime
+	if timer < ITEM_CHECK_TIME then
+		return
+	end
+	timer = 0
+
+	local players = minetest.get_connected_players()
+	for p=1, #players do
+		local player = players[p]
+		local inv = player:get_inventory()
+		for i=1, #items_to_watch do
+			local entry = items_to_watch[i]
+			if inv:contains_item("main", entry.item) then
+				entry.callback(player)
+			end
+		end
+	end
+end)
+

mods/rp_checkitem/mod.conf

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+name = rp_checkitem
+description = Helper mod, provides callback to be called when player got an item