-- set up our initial values
local running = false
local run_discharge_timer = 0
local old_up = false
local channel
local channel_name

-- receive the server states
minetest.register_on_modchannel_message(function(cname, sender, message)
	if sender == "" and cname == channel_name then
		running = false
		run_discharge_timer = 0
	end
end)

-- check player's input on the "up" key
minetest.register_globalstep(function(dtime)
	local player = minetest.localplayer

	if not player then
		return
	elseif not channel then
		channel_name = "mcl_sprint:" .. player:get_name()
		channel = minetest.mod_channel_join(channel_name)
	end

	local old_running = running
	
	local control = player:get_control()
	local velocity = player:get_velocity()
	local last_velocity = player:get_last_velocity()

	-- cancel running if the player bumps into something
	if running and (velocity.x == 0 and last_velocity.x ~= 0 or velocity.z == 0 and last_velocity.z ~= 0) then
		running = false
		run_discharge_timer = 0
	end

	-- reset the run flag
	if running and (not control.up or control.sneak or control.down) then
		running = false
	end

	-- half second window to double tap running
	if run_discharge_timer > 0 then
		run_discharge_timer = run_discharge_timer - dtime
		
		-- initialize double tap run
		if not old_up and control.up == true and velocity.x ~= 0 and velocity.z ~= 0 then
			run_discharge_timer = 0
			running = true
		end
	end

	-- check if new input of walking forwards
	if control.up and not control.down and not control.sneak and not old_up and not running and run_discharge_timer <= 0 then
		run_discharge_timer = 0.2
	end
	
	-- add this here so the player can sneak
	if control.sneak then
		running = false
		run_discharge_timer = 0
	end
	
	-- only send if state has changed
	if running ~= old_running then
		channel:send_all(running and "true" or "false")
	end

	old_up = control.up
end)