--[[

	Hyperloop Mod
	=============

	Copyright (C) 2017 Joachim Stolberg

	LGPLv2.1+
	See LICENSE.txt for more information

	History:
	see init.lua

]]--

-- Block arrangement:  [0]    [1][2][1]  [S][1][2][2][1][S]
-- Scan all 8 neighbor positions for tube nodes.
-- Return:
--  0, nodes    - no node available
--  1, nodes    - one tube1 available
--  3, nodes    - two tube1 available
--  4, nodes    - one tube2 available
--  5, nodes    - invalid position
function hyperloop.scan_neighbours(pos)
	local nodes = {}
	local node, npos, idx
	local res = 0
	for _,dir in ipairs(hyperloop.NeighborPos) do
		npos = vector.add(pos, dir)
		node = minetest.get_node(npos)
		if string.find(node.name, "hyperloop:tube") then
			node.pos = npos
			table.insert(nodes, node)
			idx = string.byte(node.name, -1) - 48
			if idx == 0 then        -- starter tube node?
				idx = 1
			elseif idx == 2 then    -- normal tube node?
				return 4, nodes
			end
			res = res * 2 + idx
		end
	end
	if res > 3 then
		res = 5
	end
	return res, nodes
end

-- Degrade one node.
-- Needed when a new node is placed nearby.
local function degrade_tupe_node(node)
	if node.name == "hyperloop:tube0" then
		node.name = "hyperloop:tube1"
	elseif node.name == "hyperloop:tube1" then
		node.name = "hyperloop:tube2"
		node.diggable = false
	else
		return
	end
	minetest.swap_node(node.pos, node)
end

-- Upgrade one node.
-- Needed when a tube node is digged.
local function upgrade_node(pos, node)
	local meta_local = minetest.get_meta(pos)
	local meta_head = minetest.get_meta(node.pos)
	meta_head:set_string("other", meta_local:get_string("other"))
	meta_head:set_string("me", minetest.pos_to_string(node.pos))
	node.diggable = true
	if node.name == "hyperloop:tube2" then          -- 2 connections?
		node.name = "hyperloop:tube1"
	elseif node.name == "hyperloop:tube1" then      -- 1 connection?
		node.name = "hyperloop:tube0"
	end
	minetest.swap_node(node.pos, node)
end

-- Place a node without neighbours
local function starter_node(node)
	local meta = minetest.get_meta(node.pos)
	meta:set_string("local", minetest.pos_to_string(node.pos))
	meta:set_string("remote", minetest.pos_to_string(node.pos))
	-- upgrade self to starter node
	node.name = "hyperloop:tube0"
	minetest.swap_node(node.pos, node)
end

-- Place a node with one neighbor
local function head_node(node, node1)
	local meta_local = minetest.get_meta(node.pos)
	local meta_head  = minetest.get_meta(node1.pos)
	-- set local data
	meta_local:set_string("local", minetest.pos_to_string(node.pos))
	meta_local:set_string("remote", meta_head:get_string("remote"))
	-- set remote data
	local rpos = minetest.string_to_pos(meta_head:get_string("remote"))
	local rmeta = minetest.get_meta(rpos)
	rmeta:set_string("remote", minetest.pos_to_string(node.pos))
	print("rmeta:get_string(remote) = " .. rmeta:get_string("remote"))
	-- punch remote node
	minetest.punch_node(rpos)
	-- upgrade self
	node.name = "hyperloop:tube1"
	minetest.swap_node(node.pos, node)
	-- degrade old head
	degrade_tupe_node(node1)
end

local function link_node(node, node1, node2)
	-- determine the meta data from both remote heads
	local meta_head1 = minetest.get_meta(node1.pos)
	local meta_head2 = minetest.get_meta(node2.pos)
	local pos1 = minetest.string_to_pos(meta_head1:get_string("remote"))
	local pos2 = minetest.string_to_pos(meta_head2:get_string("remote"))
	local meta_rmt1 = minetest.get_meta(pos1)
	local meta_rmt2 = minetest.get_meta(pos2)
	-- exchange position data
	meta_rmt2:set_string("remote", meta_rmt1:get_string("local"))
	meta_rmt1:set_string("remote", meta_rmt2:get_string("local"))
	-- punch remote nodes
	minetest.punch_node(pos1)
	minetest.punch_node(pos2)
	-- set to tube2
	node.name = "hyperloop:tube2"
	node.diggable = true
	minetest.swap_node(node.pos, node)
	-- degrade both nodes
	degrade_tupe_node(node1)
	degrade_tupe_node(node2)
end

local function remove_node(pos, node)
	---minetest.remove_node(pos)   can't call because "on_destruct" will then be called, too
	node.name = "air"
	node.diggable = true
	minetest.swap_node(pos, node)
end

-- simple tube without logic or "memory"
minetest.register_node("hyperloop:tube2", {
		description = "Hyperloop Tube",
		tiles = {
			{
				name = "hyperloop_tube_locked.png",
				animation = {
					type = "vertical_frames",
					aspect_w = 32,
					aspect_h = 32,
					length = 2.0,
				},
			},
		},

		diggable = false,
		paramtype2 = "facedir",
		groups = {cracky=1, not_in_creative_inventory=1},
		is_ground_content = false,
	})

-- single-node and head-node with meta info about the counter part node
for idx = 0,1 do
	minetest.register_node("hyperloop:tube"..idx, {
			description = "Hyperloop Tube",
			inventory_image = "hyperloop_tube_inventury.png",
			drawtype = "nodebox",
			tiles = {
				-- up, down, right, left, back, front
				'hyperloop_tube_closed.png',
				'hyperloop_tube_closed.png',
				'hyperloop_tube_closed.png',
				'hyperloop_tube_closed.png',
				'hyperloop_tube_open.png',
				'hyperloop_tube_open.png',
			},

			after_place_node = function(pos, placer, itemstack, pointed_thing)
				local res, nodes = hyperloop.scan_neighbours(pos)
				local node = minetest.get_node(pos)
				node.pos = pos
				if res == 0 then            -- no neighbor available?
					starter_node(node)
				elseif res == 1 then        -- one neighbor available?
					head_node(node, nodes[1])
				elseif res == 3 then        -- two neighbours available?
					--minetest.chat_send_player(placer:get_player_name(), "two neighbours")
					link_node(node, nodes[1], nodes[2])
				else                        -- invalid position
					minetest.chat_send_player(placer:get_player_name(), "Error: Invalid tube block position!")
					remove_node(pos, node)
					return itemstack
				end
				-- for debugging purposes
				local meta = minetest.get_meta(pos)
				meta:set_string("infotext", meta:get_string("local").." => "..meta:get_string("remote"))
			end,

			on_destruct = function(pos)
				local res, nodes = hyperloop.scan_neighbours(pos)
				if res == 4 then
					upgrade_node(pos, nodes[1])
				end
			end,

			-- wake up station node so that it updates its dataset
			on_punch = function(pos, node, puncher, pointed_thing)
				print("Tube punched")
				local res, nodes = hyperloop.scan_for_nodes(pos, "hyperloop:junction")
				for _,node in ipairs(nodes) do
					print(dump(node.pos))
					minetest.punch_node(node.pos)
				-- for debugging purposes
				local meta = minetest.get_meta(pos)
				meta:set_string("infotext", meta:get_string("local").." => "..meta:get_string("remote"))
				end
			end,

			paramtype2 = "facedir",
			groups = {cracky=2, not_in_creative_inventory=idx},
			is_ground_content = false,
			drop = "hyperloop:tube0",
		})
end