protector_template.lua

-- maximum distance a protector can have
local MAX_DISTANCE = 10

local function get(tab, pname,z,y,x)
	local data = tab[pname]
	if data then
		local data = tab[z]
		if data then
			data = data[y]
			if data then
				return data[x]
			end
		end
	end
end

function set(tab, pname,z,y,x, data)
	if tab[pname] then
		if tab[pname][z] then
			if tab[pname][z][y] then
				tab[pname][z][y][x] = data
				return
			end
			tab[pname][z][y] = {[x] = data}
			return
		end
		tab[pname][z] = {[y] = {[x] = data}}
		return
	end
	tab[pname] = {[z] = {[y] = {[x] = data}}}
end

local function remove(tab, pname,z,y,x)
	if vector.get_data_from_pos(tab, pname,z,y,x) == nil then
		return
	end
	tab[pname][z][y][x] = nil
	if not next(tab[pname][z][y]) then
		tab[pname][z][y] = nil
	end
	if not next(tab[pname][z]) then
		tab[pname][z] = nil
	end
	if not next(tab[pname]) then
		tab[pname] = nil
	end
end

local cached_protectors = {}
local function set_protector(pos, pname, range, members)
	set(cached_protectors, pname,pos.z,pos.y,pos.x, {range, members})
end

local function remove_protector(pos, pname)
	remove(cached_protectors, pname,pos.z,pos.y,pos.x)
end

local function table_find(t, v)
	for i = 1,#t do
		if t[i] == v then
			return true
		end
	end
	return false
end

local function is_protected(pos, pname)
	local pz,py,px = vector.unpack(pos)
	for name,zyxs in pairs(cached_protectors) do
		-- test if it doesn't belong to you
		if name ~= pname then
			-- test if the protector is near enough
			for z,yxs in pairs(zyxs) do
				local dist = math.abs(pz-z)
				if dist <= MAX_DISTANCE then
					for y,xs in pairs(yxs) do
						local yrel = math.abs(py-y)
						if yrel <= MAX_DISTANCE then
							dist = math.min(dist, yrel)
							for x,prot in pairs(xs) do
								-- test the range of the protector
								if math.min(dist, math.abs(px-x)) <= prot[1]
								-- test if you aren't a member
								and not table_find(prot[2], pname) then
									return true
								end
							end
						end
					end
				end
			end
		end
	end
	return false
end

-- add the small protector with range 3
minetest.register_node("protector:small", {
	description = "small protector",
	after_place_node = function(pos, player)
		if not pos
		or not player then
			minetest.log("error", "[protector] something went wrong after placing a protector")
			return
		end

		local pname = player:get_player_name()
		minetest.get_meta(pos):set_string("owner", pname)

		set_protector(pos, pname, 3, {})
	end,
	on_destruct = function(pos)
		remove_protector(pos, minetest.get_meta(pos):get_string("owner"))
	end,
})

-- cache it when it gets loaded
minetest.register_lbm({
	name = "protector:load_small",
	nodenames = { "protector:small"},
	action = function(pos)
		local meta = minetest.get_meta(pos)
		local owner = meta:get_string("owner")
		if owner == "" then
			minetest.log("error", "[protector] protector at "..minetest.pos_to_string(pos).." seems to be owned by nobody")
			return
		end
		set_protector(pos, owner, 3, string.split(meta:get_string("members"), " "))
	end
})