controls/init.lua

controls = {
    registered_on_press = {},
    registered_on_hold = {},
    registered_on_release = {},
    players = {},
}

function controls.register_on_press(callback)
    table.insert(controls.registered_on_press, callback)
end

function controls.register_on_hold(callback)
    table.insert(controls.registered_on_hold, callback)
end

function controls.register_on_release(callback)
    table.insert(controls.registered_on_release, callback)
end

minetest.register_on_joinplayer(function(player)
    local name = player:get_player_name()
    controls.players[name] = {}
    for key in pairs(player:get_player_control()) do
        controls.players[name][key] = {false}
    end
end)

minetest.register_on_leaveplayer(function(player)
    local name = player:get_player_name()
    controls.players[name] = nil
end)

local function update_player_controls(player, player_controls)
	local time_now = minetest.get_us_time()
	for key, pressed in pairs(player:get_player_control()) do
		if pressed and not player_controls[key][1] then
			for _, callback in pairs(controls.registered_on_press) do
				callback(player, key)
			end
			player_controls[key] = {true, time_now}
		elseif pressed and player_controls[key][1] then
			for _, callback in pairs(controls.registered_on_hold) do
				callback(player, key, (time_now - player_controls[key][2]) / 1e6)
			end
		elseif not pressed and player_controls[key][1] then
			for _, callback in pairs(controls.registered_on_release) do
				callback(player, key, (time_now - player_controls[key][2]) / 1e6)
			end
			player_controls[key] = {false}
		end
	end
end

minetest.register_globalstep(function()
    for _, player in pairs(minetest.get_connected_players()) do
        local name = player:get_player_name()
        if controls.players[name] then
			update_player_controls(player, controls.players[name])
		end
    end
end)

if minetest.settings:get_bool("controls_enable_debug", false) then
    dofile(minetest.get_modpath("controls") .. "/debug.lua")
end