Crafter/mods/drowning/init.lua

local minetest,vector,hud_manager = minetest,vector,hud_manager

local mod_storage = minetest.get_mod_storage()
local pool = {}

-- updates bubble bar
local update_breath_bar = function(player,breath)
	if breath > 20 then
		if hud_manager.hud_exists(player,"breath_bg") then
			hud_manager.remove_hud(player,"breath_bg")
		end
		if hud_manager.hud_exists(player,"breath") then
			hud_manager.remove_hud(player,"breath")
		end
	else
		if not hud_manager.hud_exists(player,"breath_bg") then
			hud_manager.add_hud(player,"breath_bg",{
				hud_elem_type = "statbar",
				position = {x = 0.5, y = 1},
				text = "bubble_bg.png",
				number = 20,
				direction = 1,
				size = {x = 24, y = 24},
				offset = {x = 24*10, y= -(48 + 52 + 39)},
			})
		end
		if not hud_manager.hud_exists(player,"breath") then
			hud_manager.add_hud(player,"breath",{
				hud_elem_type = "statbar",
				position = {x = 0.5, y = 1},
				text = "bubble.png",
				number = breath,
				direction = 1,
				size = {x = 24, y = 24},
				offset = {x = 24*10, y= -(48 + 52 + 39)},
			})
		end

		hud_manager.change_hud({
			player    =  player ,
			hud_name  = "breath",
			element   = "number",
			data      =  breath
		})
	end
end

-- loads data from mod storage
local name
local temp_pool
local load_data = function(player)
	name = player:get_player_name()
	pool[name] = {}
	temp_pool = pool[name]
	if mod_storage:get_int(name.."d_save") > 0 then
		temp_pool.breath   = mod_storage:get_float(name.."breath"       )
		temp_pool.ticker   = mod_storage:get_float(name.."breath_ticker")
		temp_pool.drowning = mod_storage:get_float(name.."drowning"     )
	else
		temp_pool.breath        = 21
		temp_pool.ticker = 0 
		temp_pool.drowning      = 0 
	end
end

-- saves data to be utilized on next login
local temp_pool
local save_data = function(name)
	if type(name) ~= "string" and name:is_player() then
		name = name:get_player_name()
	end
	temp_pool = pool[name]

	mod_storage:set_float(name.."breath",        temp_pool.breath)
	mod_storage:set_float(name.."breath_ticker", temp_pool.ticker)
	mod_storage:set_float(name.."drowning",      temp_pool.drowning)
	mod_storage:set_int(name.."d_save", 1)

	pool[name] = nil
end

-- is used for shutdowns to save all data
local save_all = function()
	for name,_ in pairs(pool) do
		save_data(name)
	end
end


-- remove stock health bar
minetest.hud_replace_builtin("breath",{
	hud_elem_type = "statbar",
	position = {x = 0, y = 0},
	text = "nothing.png",
	number = 0,
	direction = 0,
	size = {x = 0, y = 0},
	offset = {x = 0, y= 0},
})

minetest.register_on_joinplayer(function(player)
	load_data(player)
	player:hud_set_flags({breathbar=false})
end)

-- saves specific users data for when they relog
minetest.register_on_leaveplayer(function(player)
	save_data(player)
end)

-- save all data to mod storage on shutdown
minetest.register_on_shutdown(function()
	save_all()
end)

local name
is_player_drowning = function(player)
	name = player:get_player_name()
	return(pool[name].drowning)
end

-- reset the player's data
local name
local temp_pool
minetest.register_on_respawnplayer(function(player)
	name = player:get_player_name()
	temp_pool = pool[name]
	temp_pool.breath   = 21
	temp_pool.ticker   = 0
	temp_pool.drowning = 0
	update_breath_bar(player,temp_pool.breath)
end)

--handle the breath bar
local name
local temp_pool
local head
local hp
local handle_breath = function(player,dtime)
	name = player:get_player_name()
	head = get_player_head_env(player)
	temp_pool = pool[name]
	hp = player:get_hp()
	if hp <= 0 then
		return
	end
	if minetest.get_item_group(head, "drowning") > 0 then

		temp_pool.ticker = temp_pool.ticker + dtime
		
		if temp_pool.breath > 0 and temp_pool.ticker >= 1.3 then

			if temp_pool.breath == 21 then
				temp_pool.breath = 20
			end	
			temp_pool.breath = temp_pool.breath - 2

			temp_pool.drowning = 0

			update_breath_bar(player,temp_pool.breath)
		elseif temp_pool.breath <= 0 and temp_pool.ticker >= 1.3 then

			temp_pool.drowning = 1

			if hp > 0 then
				player:set_hp( hp - 2 )
			end
		end

		if temp_pool.ticker >= 1.3 then
			temp_pool.ticker = 0
		end

	else

		temp_pool.ticker = temp_pool.ticker + dtime		

		if temp_pool.breath < 21 and temp_pool.ticker >= 0.25 then
			
			temp_pool.breath = temp_pool.breath + 2
			
			temp_pool.drowning      = 0
			
			temp_pool.ticker = 0

			update_breath_bar(player,temp_pool.breath)
		end
	end
end

-- inject into main loop
minetest.register_globalstep(function(dtime)
	for _,player in ipairs(minetest.get_connected_players()) do
		handle_breath(player,dtime)
	end
end)