MoreMesecons/moremesecons_entity_detector/init.lua

-- Entity detector
-- Detects entitys in a certain radius
-- The radius can be changes by right-click (by default 6)

local function make_formspec(meta)
	meta:set_string("formspec", "size[9,5]" ..
		"field[0.3,  0;9,2;scanname;Name (itemstring) of entity to scan for (empty for any):;${scanname}]"..
		"field[0.3,1.5;4,2;digiline_channel;Digiline Channel (optional):;${digiline_channel}]"..
		"field[0.3,3;2,2;radius;Detection radius:;${radius}]"..
		"button_exit[3.5,3.5;2,3;;Save]")
end

local function object_detector_make_formspec(pos)
	make_formspec(minetest.get_meta(pos))
end

local function object_detector_on_receive_fields(pos, formname, fields)
	if not fields.scanname
	or not fields.digiline_channel then
		return
	end

	local meta = minetest.get_meta(pos)
	meta:set_string("scanname", fields.scanname)
	meta:set_string("digiline_channel", fields.digiline_channel)
	local r = tonumber(fields.radius)
	if r then
		meta:set_int("radius", r)
	end
end

-- returns true if entity was found, false if not
local object_detector_scan = function (pos)
	local meta = minetest.get_meta(pos)
	local scanname = meta:get_string("scanname")
	local scan_all = scanname == ""
	local radius = meta:get_int("radius")
	if radius == 0 then
		radius = 6
	end
	for _,obj in pairs(minetest.get_objects_inside_radius(pos, radius)) do
		if not obj:is_player() then
			local luaentity = obj:get_luaentity()
			local isname = luaentity.name
			if isname
			and (scan_all or isname == scanname or (isname == "__builtin:item" and luaentity.itemstring == scanname)) then -- entity with scanname found or not scanname specified
				return true
			end
		end
	end
	return false
end

-- set entity name when receiving a digiline signal on a specific channel
local object_detector_digiline = {
	effector = {
		action = function (pos, node, channel, msg)
			local meta = minetest.get_meta(pos)
			local active_channel = meta:get_string("digiline_channel")
			if channel ~= active_channel then
				return
			end
			meta:set_string("scanname", msg)
			if meta:get_string("formspec") ~= "" then
				make_formspec(meta)
			end
		end,
	}
}

minetest.register_node("moremesecons_entity_detector:entity_detector_off", {
	tiles = {"default_steel_block.png", "default_steel_block.png", "moremesecons_entity_detector_off.png"},
	paramtype = "light",
	walkable = true,
	groups = {cracky=3},
	description="Entity Detector",
	mesecons = {receptor = {
		state = mesecon.state.off,
		rules = mesecon.rules.pplate
	}},
	on_construct = object_detector_make_formspec,
	on_receive_fields = object_detector_on_receive_fields,
	sounds = default.node_sound_stone_defaults(),
	digiline = object_detector_digiline
})

minetest.register_node("moremesecons_entity_detector:entity_detector_on", {
	tiles = {"default_steel_block.png", "default_steel_block.png", "moremesecons_entity_detector_on.png"},
	paramtype = "light",
	walkable = true,
	groups = {cracky=3,not_in_creative_inventory=1},
	drop = 'mesecons_detector:object_detector_off',
	mesecons = {receptor = {
		state = mesecon.state.on,
		rules = mesecon.rules.pplate
	}},
	on_construct = object_detector_make_formspec,
	on_receive_fields = object_detector_on_receive_fields,
	sounds = default.node_sound_stone_defaults(),
	digiline = object_detector_digiline
})

minetest.register_craft({
	output = 'moremesecons_entity_detector:entity_detector_off',
	recipe = {
		{"mesecons_detector:object_detector_off"},
		{"default:mese_crystal_fragment"}
	}
})

minetest.register_abm({
	nodenames = {"moremesecons_entity_detector:entity_detector_off"},
	interval = 1.0,
	chance = 1,
	action = function(pos)
		if object_detector_scan(pos) then
			minetest.swap_node(pos, {name = "moremesecons_entity_detector:entity_detector_on"})
			mesecon.receptor_on(pos, mesecon.rules.pplate)
		end
	end,
})

minetest.register_abm({
	nodenames = {"moremesecons_entity_detector:entity_detector_on"},
	interval = 1.0,
	chance = 1,
	action = function(pos)
		if not object_detector_scan(pos) then
			minetest.swap_node(pos, {name = "moremesecons_entity_detector:entity_detector_off"})
			mesecon.receptor_off(pos, mesecon.rules.pplate)
		end
	end,
})