areas/api.lua

local protection_detectors = {}

-- Other protection mods should be able to display their protection in the hud
areas.register_hud_handler = function(handler)
	protection_detectors[#protection_detectors + 1] = handler
end

-- Generalized call to registered handlers to add their proeciton labels to the areas list
local detect_extra_protection = function(pos,area_list)
	if #protection_detectors <= 0 then
		return area_list
	end

	for idx=1,#protection_detectors do
		local func = protection_detectors[idx]
		area_list = func(pos,area_list)
	end
	return area_list
end

--- Returns a list of areas that include the provided position.
function areas:getAreasAtPos(pos)
	local res = {}
	res = detect_extra_protection(pos,res)

	if self.store then
		local a = self.store:get_areas_for_pos(pos, false, true)
		for store_id, store_area in pairs(a) do
			local id = tonumber(store_area.data)
			res[id] = self.areas[id]
		end
	else
		local px, py, pz = pos.x, pos.y, pos.z
		for id, area in pairs(self.areas) do
			local ap1, ap2 = area.pos1, area.pos2
			if
			  (px >= ap1.x and px <= ap2.x) and
			  (py >= ap1.y and py <= ap2.y) and
			  (pz >= ap1.z and pz <= ap2.z)
			  then
				res[id] = area
			end
		end
	end
	return res
end

--- Returns areas that intersect with the passed area.
function areas:getAreasIntersectingArea(pos1, pos2)
	local res = {}
	if self.store then
		local a = self.store:get_areas_in_area(pos1, pos2,
				true, false, true)
		for store_id, store_area in pairs(a) do
			local id = tonumber(store_area.data)
			res[id] = self.areas[id]
		end
	else
		self:sortPos(pos1, pos2)
		local p1x, p1y, p1z = pos1.x, pos1.y, pos1.z
		local p2x, p2y, p2z = pos2.x, pos2.y, pos2.z
		for id, area in pairs(self.areas) do
			local ap1, ap2 = area.pos1, area.pos2
			if
					(ap1.x <= p2x and ap2.x >= p1x) and
					(ap1.y <= p2y and ap2.y >= p1y) and
					(ap1.z <= p2z and ap2.z >= p1z) then
				-- Found an intersecting area.
				res[id] = area
			end
		end
	end
	return res
end

-- Checks if the area is unprotected or owned by you
function areas:canInteract(pos, name)
	if minetest.check_player_privs(name, self.adminPrivs) then
		return true
	end
	local owned = false
	for _, area in pairs(self:getAreasAtPos(pos)) do
		if area.owner == name or area.open then
			return true
		else
			owned = true
		end
	end
	return not owned
end

-- Returns a table (list) of all players that own an area
function areas:getNodeOwners(pos)
	local owners = {}
	for _, area in pairs(self:getAreasAtPos(pos)) do
		table.insert(owners, area.owner)
	end
	return owners
end

--- Checks if the area intersects with an area that the player can't interact in.
-- Note that this fails and returns false when the specified area is fully
-- owned by the player, but with multiple protection zones, none of which
-- cover the entire checked area.
-- @param name (optional) Player name.  If not specified checks for any intersecting areas.
-- @param allow_open Whether open areas should be counted as if they didn't exist.
-- @return Boolean indicating whether the player can interact in that area.
-- @return Un-owned intersecting area ID, if found.
function areas:canInteractInArea(pos1, pos2, name, allow_open)
	if name and minetest.check_player_privs(name, self.adminPrivs) then
		return true
	end
	self:sortPos(pos1, pos2)

	-- Intersecting non-owned area ID, if found.
	local blocking_area = nil

	local areas = self:getAreasIntersectingArea(pos1, pos2)
	for id, area in pairs(areas) do
		-- First check for a fully enclosing owned area.
		-- A little optimization: isAreaOwner isn't necessary
		-- here since we're iterating over all relevant areas.
		if area.owner == name and
				self:isSubarea(pos1, pos2, id) then
			return true
		end

		-- Then check for intersecting non-owned (blocking) areas.
		-- We don't bother with this check if we've already found a
		-- blocking area, as the check is somewhat expensive.
		-- The area blocks if the area is closed or open areas aren't
		-- acceptable to the caller, and the area isn't owned.
		-- Note: We can't return directly here, because there might be
		-- an exclosing owned area that we haven't gotten to yet.
		if not blocking_area and
				(not allow_open or not area.open) and
				(not name or not self:isAreaOwner(id, name)) then
			blocking_area = id
		end
	end

	if blocking_area then
		return false, blocking_area
	end

	-- There are no intersecting areas or they are only partially
	-- intersecting areas and they are all owned by the player.
	return true
end