creative_regions/player.lua

function creative_regions:initial_stuff()
	local stuff_string = minetest.settings:get("initial_stuff") or
		"default:pick_steel,default:axe_steel,default:shovel_steel," ..
		"default:torch 99,default:cobble 99"
	local itemtable = {}
	local items = stuff_string:split(",")
	for _, stack in ipairs(items) do
		table.insert(itemtable, ItemStack(stack))
	end
	return itemtable
end

--[[
function creative_regions:save_player_privs(player)
	local name = player:get_player_name()
	local pmeta = player:get_meta()
	local privs = minetest.get_player_privs(name)
	pmeta:set_string("creative_regions.saved_privs", minetest.serialize(privs))
end

function creative_regions:restore_player_privs(player)
	local name = player:get_player_name()
	local pmeta = player:get_meta()
	local privs = minetest.deserialize(pmeta:get_string("creative_regions.saved_privs"))
	if privs then
		minetest.set_player_privs(name, privs)
		pmeta:set_string("creative_regions.saved_privs", nil)
	end
end
--]]

function creative_regions:save_player_inventory(player, listname)
	local name = player:get_player_name()
	local pmeta = player:get_meta()
	local inv = player:get_inventory()
	local player_items = inv:get_list("main")
	inv:set_list(listname, player_items)
end

function creative_regions:restore_player_inventory(player, listname)
	local name = player:get_player_name()
	local pmeta = player:get_meta()
	local inv = player:get_inventory()
	local player_items = inv:get_list(listname)
	local give_initial = false
	if not player_items then
		player_items = {}
		give_initial = true
	end
	inv:set_list("main", player_items)
	if give_initial then
		local initial_items = creative_regions:initial_stuff()
		for _, stack in ipairs(initial_items) do
			inv:add_item("main", stack)
		end
	end
end

function creative_regions:player_enter_region(player, new_privs_table)
	local name = player:get_player_name()
	local has_creative = minetest.check_player_privs(name, {creative=true})
	local has_arena = minetest.check_player_privs(name, {arena=true})
	
	local old_mode = nil
	if has_arena then
		old_mode = "arena"
	elseif has_creative then
		old_mode = "creative"
	else
		old_mode = "survival"
	end

	local privs_grant, privs_revoke = creative_regions:decode_privs_table(new_privs_table)

	local new_mode = nil
	if privs_grant.arena and not privs_revoke.arena then
		new_mode = "arena"
	elseif privs_grant.creative and not privs_revoke.creative then
		new_mode = "creative"
	else
		new_mode = "survival"
	end

	if new_mode ~= old_mode then

		if old_mode == "arena" then
			-- leaving arena (alive)
			creative_regions.drop_everything(player, false)
		end

		minetest.chat_send_player(name, "You entered "..new_mode.." mode")
		creative_regions:save_player_inventory(player, "saved_"..old_mode)
		creative_regions:restore_player_inventory(player, "saved_"..new_mode)

		if new_mode == "creative" then
			if minetest.get_modpath("unified_inventory") then
				unified_inventory.set_inventory_formspec(player, unified_inventory.default)
			end
		elseif new_mode == "arena" then
			local inv = player:get_inventory()
			inv:set_list("main", {})
		end

	end
	
	local has_privs = minetest.get_player_privs(name)
	local privs = has_privs
	for _, p in pairs(non_sticky_privs) do
		privs[p] = nil
	end
	for newpriv, _ in pairs(privs_grant) do
		privs[newpriv] = true
	end
	for newpriv, _ in pairs(privs_revoke) do
		privs[newpriv] = nil
	end
	minetest.set_player_privs(name, privs)
end