function ctf_classes.register(cname, def)
	assert(not ctf_classes.__classes[cname])
	def.name = cname
	ctf_classes.__classes[cname] = def
	table.insert(ctf_classes.__classes_ordered, def)

	def.max_hp = def.max_hp or 20
	def.speed  = def.speed or 1
	def.pros   = def.pros or {}
	def.cons   = def.cons or {}
end

function ctf_classes.set_skin(player, color, class)
	player:set_properties({
		textures = {"ctf_classes_skin_" .. class.name .. "_" .. (color or "blue") .. ".png"}
	})
end

function ctf_classes.get(player)
	if type(player) == "string" then
		player = minetest.get_player_by_name(player)
	end

	local cname = player:get_meta():get("ctf_classes:class") or "knight"
	return ctf_classes.__classes[cname]
end

function ctf_classes.set(player, cname)
	assert(type(cname) == "string")
	local class = ctf_classes.__classes[cname]
	assert(class)

	local meta = player:get_meta()
	local old = meta:get("ctf_classes:class")
	meta:set_string("ctf_classes:class", cname)
	ctf_classes.update(player)

	if old ~= nil and old ~= cname then
		local pname = player:get_player_name()
		ctf.chat_send_team(ctf.player(pname).team,
				minetest.colorize("#ABCDEF", pname .. " is now a " .. class.description))
	end
end

local function set_max_hp(player, max_hp)
	local cur_hp = player:get_hp()
	local new_hp = cur_hp + max_hp - player:get_properties().hp_max
	player:set_properties({
		hp_max = max_hp
	})

	assert(new_hp <= max_hp)
	if cur_hp > max_hp then
		player:set_hp(max_hp)
	elseif new_hp > cur_hp then
		player:set_hp(new_hp)
	end
end

function ctf_classes.update(player)
	local class = ctf_classes.get(player)
	local color, _ = ctf_colors.get_color(ctf.player(player:get_player_name()))

	set_max_hp(player, class.max_hp)
	ctf_classes.set_skin(player, color, class)
	physics.set(player:get_player_name(), "ctf_classes:speed", {
		speed = class.speed,
	})
end

local function sqdist(a, b)
	local x = a.x - b.x
	local y = a.y - b.y
	local z = a.z - b.z
	return x*x + y*y + z*z
end

local function get_flag_pos(player)
	local tplayer = ctf.player(player:get_player_name())
	if not tplayer or not tplayer.team then
		return nil
	end

	local team = ctf.team(tplayer.team)
	if team and team.flags[1] then
		return vector.new(team.flags[1])
	end
	return nil
end

function ctf_classes.can_change(player)
	local flag_pos = get_flag_pos(player)
	if not flag_pos then
		return false
	end

	return sqdist(player:get_pos(), flag_pos) < 25
end