local rules_flat = {
	{ x = 0, y = 0, z = -1, spread = true },
}
local get_rules_flat = function(node)
	local rules = rules_flat
	for i=1, node.param2 do
		rules = mesecon.rotate_rules_left(rules)
	end
	return rules
end

local rules_down = {{ x = 0, y = 1, z = 0, spread = true }}
local rules_up = {{ x = 0, y = -1, z = 0, spread = true }}

-- Scan the node in front of the observer
-- and update the observer state if needed.
-- TODO: Also scan metadata changes.
-- TODO: Ignore some node changes.
local observer_scan = function(pos, initialize)
	local node = minetest.get_node(pos)
	local front
	if node.name == "mcl_observers:observer_up_off" or node.name == "mcl_observers:observer_up_on" then
		front = vector.add(pos, {x=0, y=1, z=0})
	elseif node.name == "mcl_observers:observer_down_off" or node.name == "mcl_observers:observer_down_on" then
		front = vector.add(pos, {x=0, y=-1, z=0})
	else
		front = vector.add(pos, minetest.facedir_to_dir(node.param2))
	end
	local frontnode = minetest.get_node(front)
	local meta = minetest.get_meta(pos)
	local oldnode = meta:get_string("node_name")
	local oldparam2 = meta:get_string("node_param2")
	local meta_needs_updating = false
	if oldnode ~= "" and not initialize then
		if not (frontnode.name == oldnode and frontnode.param2) then
			-- Node state changed! Activate observer
			if node.name == "mcl_observers:observer_off" then
				minetest.set_node(pos, {name = "mcl_observers:observer_on", param2 = node.param2})
				mesecon.receptor_on(pos, get_rules_flat(node))
			elseif node.name == "mcl_observers:observer_down_off" then
				minetest.set_node(pos, {name = "mcl_observers:observer_down_on"})
				mesecon.receptor_on(pos, rules_down)
			elseif node.name == "mcl_observers:observer_up_off" then
				minetest.set_node(pos, {name = "mcl_observers:observer_up_on"})
				mesecon.receptor_on(pos, rules_up)
			end
			meta_needs_updating = true
		end
	else
		meta_needs_updating = true
	end
	if meta_needs_updating then
		meta:set_string("node_name", frontnode.name)
		meta:set_string("node_param2", frontnode.param2)
	end
	return frontnode
end

-- Vertical orientation (CURRENTLY DISABLED)
local observer_orientate = function(pos, placer)
	-- Not placed by player
	if not placer then return end

	-- Placer pitch in degrees
	local pitch = placer:get_look_vertical() * (180 / math.pi)

	local node = minetest.get_node(pos)
	if pitch > 55 then -- player looking upwards
		-- Observer looking downwards
		minetest.set_node(pos, {name="mcl_observers:observer_down_off"})
	elseif pitch < -55 then -- player looking downwards
		-- Observer looking upwards
		minetest.set_node(pos, {name="mcl_observers:observer_up_off"})
	end
end

mesecon.register_node("mcl_observers:observer",
{
	is_ground_content = false,
	sounds = mcl_sounds.node_sound_stone_defaults(),
	paramtype2 = "facedir",
	on_rotate = false,
	_mcl_blast_resistance = 17.5,
	_mcl_hardness = 3.5,
},
{
	description = "Observer",
	_doc_items_longdesc = "An observer is a redstone component which observes the block in front of it and sends a very short redstone pulse whenever this block changes.",
	_doc_items_usagehelp = "Place the observer directly in front of the block you want to observe with the “face” looking at the block. The arrow shows you the side of the output, which is at the opposite side of the “face”. The arrow points to it. You need to place your redstone wire or any other component you want to power here.",
	groups = {pickaxey=1, material_stone=1, not_opaque=1, },
	tiles = {
		"mcl_observers_observer_top.png^[transformR180", "default_furnace_bottom.png",
		"mcl_observers_observer_side.png", "mcl_observers_observer_side.png",
		"mcl_observers_observer_front.png", "mcl_observers_observer_back.png",
	},
	mesecons = { receptor = {
		state = mesecon.state.off,
		rules = get_rules_flat,
	}},
	on_construct = function(pos)
		observer_scan(pos, true)
	end,
	after_place_node = observer_orientate,
},
{
	_doc_items_create_entry = false,
	groups = {pickaxey=1, material_stone=1, not_opaque=1, not_in_creative_inventory=1 },
	tiles = {
		"mcl_observers_observer_top.png^[transformR180", "default_furnace_bottom.png",
		"mcl_observers_observer_side.png", "mcl_observers_observer_side.png",
		"mcl_observers_observer_front.png", "mcl_observers_observer_back_lit.png",
	},
	mesecons = { receptor = {
		state = mesecon.state.on,
		rules = get_rules_flat,
	}},

	-- VERY quickly disable observer after construction
	on_construct = function(pos)
		local timer = minetest.get_node_timer(pos)
		-- 1 redstone tick = 0.1 seconds
		timer:start(0.1)
	end,
	on_timer = function(pos, elapsed)
		local node = minetest.get_node(pos)
		minetest.set_node(pos, {name = "mcl_observers:observer_off", param2 = node.param2})
		mesecon.receptor_off(pos, get_rules_flat(node))
	end,
}
)

mesecon.register_node("mcl_observers:observer_down",
{
	is_ground_content = false,
	sounds = mcl_sounds.node_sound_stone_defaults(),
	groups = {pickaxey=1, material_stone=1, not_opaque=1, not_in_creative_inventory=1 },
	on_rotate = false,
	_mcl_blast_resistance = 17.5,
	_mcl_hardness = 3.5,
	drop = "mcl_observers:observer_off",
},
{
	tiles = {
		"mcl_observers_observer_back.png", "mcl_observers_observer_front.png",
		"mcl_observers_observer_side.png^[transformR90", "mcl_observers_observer_side.png^[transformR90",
		"mcl_observers_observer_top.png", "mcl_observers_observer_top.png",
	},
	mesecons = { receptor = {
		state = mesecon.state.off,
		rules = rules_down,
	}},
	on_construct = function(pos)
		observer_scan(pos, true)
	end,
},
{
	_doc_items_create_entry = false,
	tiles = {
		"mcl_observers_observer_back_lit.png", "mcl_observers_observer_front.png",
		"mcl_observers_observer_side.png^[transformR90", "mcl_observers_observer_side.png^[transformR90",
		"mcl_observers_observer_top.png", "mcl_observers_observer_top.png",
	},
	mesecons = { receptor = {
		state = mesecon.state.on,
		rules = rules_down,
	}},

	-- VERY quickly disable observer after construction
	on_construct = function(pos)
		local timer = minetest.get_node_timer(pos)
		-- 1 redstone tick = 0.1 seconds
		timer:start(0.1)
	end,
	on_timer = function(pos, elapsed)
		local node = minetest.get_node(pos)
		minetest.set_node(pos, {name = "mcl_observers:observer_down_off", param2 = node.param2})
		mesecon.receptor_off(pos, rules_down)
	end,
})

mesecon.register_node("mcl_observers:observer_up",
{
	is_ground_content = false,
	sounds = mcl_sounds.node_sound_stone_defaults(),
	groups = {pickaxey=1, material_stone=1, not_opaque=1, not_in_creative_inventory=1 },
	on_rotate = false,
	_mcl_blast_resistance = 17.5,
	_mcl_hardness = 3.5,
	drop = "mcl_observers:observer_off",
},
{
	tiles = {
		"mcl_observers_observer_front.png", "mcl_observers_observer_back.png",
		"mcl_observers_observer_side.png^[transformR270", "mcl_observers_observer_side.png^[transformR270",
		"mcl_observers_observer_top.png^[transformR180", "mcl_observers_observer_top.png^[transformR180",
	},
	mesecons = { receptor = {
		state = mesecon.state.off,
		rules = rules_up,
	}},
	on_construct = function(pos)
		observer_scan(pos, true)
	end,
},
{
	_doc_items_create_entry = false,
	tiles = {
		"mcl_observers_observer_front.png", "mcl_observers_observer_back_lit.png",
		"mcl_observers_observer_side.png^[transformR270", "mcl_observers_observer_side.png^[transformR270",
		"mcl_observers_observer_top.png^[transformR180", "mcl_observers_observer_top.png^[transformR180",
	},
	mesecons = { receptor = {
		state = mesecon.state.on,
		rules = rules_up,
	}},

	-- VERY quickly disable observer after construction
	on_construct = function(pos)
		local timer = minetest.get_node_timer(pos)
		-- 1 redstone tick = 0.1 seconds
		timer:start(0.1)
	end,
	on_timer = function(pos, elapsed)
		minetest.set_node(pos, {name = "mcl_observers:observer_up_off"})
		mesecon.receptor_off(pos, rules_up)
	end,
})




-- Regularily check the observer nodes.
-- TODO: This is rather slow and clunky. Find a more efficient way to do this.
minetest.register_abm({
	nodenames = {"mcl_observers:observer_off", "mcl_observers:observer_down_off", "mcl_observers:observer_up_off"},
	interval = 1,
	chance = 1,
	action = function(pos, node)
		observer_scan(pos)
	end,
})


minetest.register_craft({
	output = "mcl_observers:observer_off",
	recipe = {
		{ "mcl_core:cobble", "mcl_core:cobble", "mcl_core:cobble" },
		{ "mcl_nether:quartz", "mesecons:redstone", "mesecons:redstone" },
		{ "mcl_core:cobble", "mcl_core:cobble", "mcl_core:cobble" },
	}
})
minetest.register_craft({
	output = "mcl_observers:observer_off",
	recipe = {
		{ "mcl_core:cobble", "mcl_core:cobble", "mcl_core:cobble" },
		{ "mesecons:redstone", "mesecons:redstone", "mcl_nether:quartz" },
		{ "mcl_core:cobble", "mcl_core:cobble", "mcl_core:cobble" },
	}
})