-- LUALOCALS < ---------------------------------------------------------
local math, minetest, nodecore
    = math, minetest, nodecore
local math_pi, math_sin
    = math.pi, math.sin
-- LUALOCALS > ---------------------------------------------------------

local autorun_walkspeed = 1.25 * nodecore.rate_adjustment("autorun", "walkspeed")
local autorun_walktime = 2 * nodecore.rate_adjustment("autorun", "walktime")
local autorun_acceltime = 4 * nodecore.rate_adjustment("autorun", "acceltime")
local autorun_ratio = 2 * nodecore.rate_adjustment("autorun", "ratio")

local function solid(pos)
	local node = minetest.get_node(pos)
	local def = minetest.registered_items[node.name]
	if not def then return true end
	return def.liquidtype == "none" and def.walkable
end

nodecore.register_playerstep({
		label = "autorun",
		action = function(player, data)
			local ctl = data.control
			local walking = ctl.up and not ctl.down
			if (not walking) and ctl.jump and (not ctl.sneak) then
				local def = minetest.registered_nodes[minetest.get_node(player:get_pos()).name]
				walking = def and (def.climbable or def.liquidtype ~= "none")
			end
			if walking and ctl.sneak then
				local pos = player:get_pos()
				if not solid(pos) then
					pos.y = pos.y - 1
					walking = not solid(pos)
				end
			end
			local speed = autorun_walkspeed
			local max = autorun_walkspeed * autorun_ratio
			if walking and data.autoruntime then
				local t = nodecore.gametime - data.autoruntime - autorun_walktime
				if t > math_pi * autorun_acceltime then
					nodecore.player_discover(player, "autorun")
					speed = max
				elseif t > 0 then
					local hr = (autorun_ratio - 1) / 2
					speed = autorun_walkspeed * (1 + hr + hr * math_sin(t
							/ autorun_acceltime - math_pi / 2))
				end
			else
				data.autoruntime = nodecore.gametime
			end
			local oldspeed = data.physics.speed or 0
			if oldspeed > speed or oldspeed < (speed - 0.05)
			or (speed == max and oldspeed ~= max) then
				data.physics.speed = speed
			end
		end
	})
