
local S = minetest.get_translator("pipeworks")
local filename = minetest.get_worldpath().."/teleport_tubes"  -- Only used for backward-compat
local storage = minetest.get_mod_storage()

local has_digilines = minetest.get_modpath("digilines")

-- V1: Serialized text file indexed by vector position.
-- V2: Serialized text file indexed by hash position.
-- V3: Mod storage using serialized tables.
-- V4: Mod storage using "<can_receive>:<channel>" format.
local tube_db_version = 4
local tube_db = {}
local receiver_cache = {}

local function hash_pos(pos)
	vector.round(pos)
	return string.format("%.0f", minetest.hash_node_position(pos))
end

local function serialize_tube(tube)
	return string.format("%d:%s", tube.cr, tube.channel)
end

local function deserialize_tube(hash, str)
	local sep = str:sub(2, 2) == ":"
	local cr = tonumber(str:sub(1, 1))
	local channel = str:sub(3)
	if sep and cr and channel then
		local pos = minetest.get_position_from_hash(tonumber(hash))
		return {x = pos.x, y = pos.y, z = pos.z, cr = cr, channel = channel}
	end
end

local function save_tube_db()
	receiver_cache = {}
	local fields = {version = tube_db_version}
	for key, val in pairs(tube_db) do
		fields[key] = serialize_tube(val)
	end
	storage:from_table({fields = fields})
end

local function save_tube(hash)
	local tube = tube_db[hash]
	receiver_cache[tube.channel] = nil
	storage:set_string(hash, serialize_tube(tube))
end

local function remove_tube(pos)
	local hash = hash_pos(pos)
	if tube_db[hash] then
		receiver_cache[tube_db[hash].channel] = nil
		tube_db[hash] = nil
		storage:set_string(hash, "")
	end
end

local function migrate_tube_db()
	if storage:get_int("version") == 3 then
		for key, val in pairs(storage:to_table().fields) do
			if tonumber(key) then
				tube_db[key] = minetest.deserialize(val)
			elseif key ~= "version" then
				error("Unknown field in teleport tube database: "..key)
			end
		end
		save_tube_db()
		return
	end
	local file = io.open(filename, "r")
	if file then
		local content = file:read("*all")
		io.close(file)
		if content and content ~= "" then
			tube_db = minetest.deserialize(content)
		end
	end
	local version = tube_db.version or 0
	tube_db.version = nil
	if version < 2 then
		local tmp_db = {}
		for _, val in pairs(tube_db) do
			if val.channel ~= "" then  -- Skip unconfigured tubes
				tmp_db[hash_pos(val)] = val
			end
		end
		tube_db = tmp_db
	end
	save_tube_db()
end

local function read_tube_db()
	local version = storage:get_int("version")
	if version < tube_db_version then
		migrate_tube_db()
	elseif version > tube_db_version then
		error("Cannot read teleport tube database of version "..version)
	else
		for key, val in pairs(storage:to_table().fields) do
			if tonumber(key) then
				tube_db[key] = deserialize_tube(key, val)
			elseif key ~= "version" then
				error("Unknown field in teleport tube database: "..key)
			end
		end
	end
	tube_db.version = nil
end

local function set_tube(pos, channel, cr)
	local hash = hash_pos(pos)
	local tube = tube_db[hash]
	if tube then
		if tube.channel ~= channel or tube.cr ~= cr then
			tube.channel = channel
			tube.cr = cr
			save_tube(hash)
		end
	else
		tube_db[hash] = {x = pos.x, y = pos.y, z = pos.z, channel = channel, cr = cr}
		save_tube(hash)
	end
end

local function get_receivers(pos, channel)
	local hash = hash_pos(pos)
	local cache = receiver_cache[channel] or {}
	if cache[hash] then
		return cache[hash]
	end
	local receivers = {}
	for key, val in pairs(tube_db) do
		if val.cr == 1 and val.channel == channel and not vector.equals(val, pos) then
			minetest.load_area(val)
			local node_name = minetest.get_node(val).name
			if node_name:find("pipeworks:teleport_tube") then
				table.insert(receivers, val)
			else
				remove_tube(val)
			end
		end
	end
	cache[hash] = receivers
	receiver_cache[channel] = cache
	return receivers
end

local help_text = S("Channels are public by default").."\n"..
	S("Use <player>:<channel> for fully private channels").."\n"..
	S("Use <player>\\;<channel> for private receivers")

local size = has_digilines and "8,5.9" or "8,4.4"

local formspec = "formspec_version[2]size["..size.."]"..
	pipeworks.fs_helpers.get_prepends(size)..
	"image[0.5,0.3;1,1;pipeworks_teleport_tube_inv.png]"..
	"label[1.75,0.8;"..S("Teleporting Tube").."]"..
	"field[0.5,1.7;5,0.8;channel;"..S("Channel")..";${channel}]"..
	"button_exit[5.5,1.7;2,0.8;save;"..S("Save").."]"..
	"label[6.5,0.6;"..S("Receive").."]"..
	"label[0.5,2.8;"..help_text.."]"

if has_digilines then
	formspec = formspec..
		"field[0.5,4.6;5,0.8;digiline_channel;"..S("Digiline Channel")..";${digiline_channel}]"..
		"button_exit[5.5,4.6;2,0.8;save;"..S("Save").."]"
end

local function update_meta(meta)
	local channel = meta:get_string("channel")
	local cr = meta:get_int("can_receive") == 1
	if channel == "" then
		meta:set_string("infotext", S("Unconfigured Teleportation Tube"))
	else
		local desc = cr and "sending and receiving" or "sending"
		meta:set_string("infotext", S("Teleportation Tube @1 on '@2'", desc, channel))
	end
	local state = cr and "on" or "off"
	meta:set_string("formspec", formspec..
		"image_button[6.4,0.8;1,0.6;pipeworks_button_"..state..
		".png;cr_"..state..";;;false;pipeworks_button_interm.png]")
end

local function update_tube(pos, channel, cr, player_name)
	local meta = minetest.get_meta(pos)
	if meta:get_string("channel") == channel and meta:get_int("can_receive") == cr then
		return
	end
	if channel == "" then
		meta:set_string("channel", "")
		meta:set_int("can_receive", cr)
		remove_tube(pos)
		return
	end
	local name, mode = channel:match("^([^:;]+)([:;])")
	if name and mode and name ~= player_name then
		if mode == ":" then
			minetest.chat_send_player(player_name,
				S("Sorry, channel '@1' is reserved for exclusive use by @2", channel, name))
			return
		elseif mode == ";" and cr ~= 0 then
			minetest.chat_send_player(player_name,
				S("Sorry, receiving from channel '@1' is reserved for @2", channel, name))
			return
		end
	end
	meta:set_string("channel", channel)
	meta:set_int("can_receive", cr)
	set_tube(pos, channel, cr)
end

local function receive_fields(pos, _, fields, sender)
	if not fields.channel or not pipeworks.may_configure(pos, sender) then
		return
	end
	local meta = minetest.get_meta(pos)
	local channel = fields.channel:trim()
	local cr = meta:get_int("can_receive")
	if fields.cr_on then
		cr = 0
	elseif fields.cr_off then
		cr = 1
	end
	if has_digilines and fields.digiline_channel then
		meta:set_string("digiline_channel", fields.digiline_channel)
	end
	update_tube(pos, channel, cr, sender:get_player_name())
	update_meta(meta)
end

local function can_go(pos, node, velocity, stack)
	velocity.x = 0
	velocity.y = 0
	velocity.z = 0
	local channel = minetest.get_meta(pos):get_string("channel")
	if channel == "" then
		return {}
	end
	local receivers = get_receivers(pos, channel)
	if #receivers == 0 then
		return {}
	end
	local target = receivers[math.random(1, #receivers)]
	pos.x = target.x
	pos.y = target.y
	pos.z = target.z
	return pipeworks.meseadjlist
end

local function repair_tube(pos, node)
	minetest.swap_node(pos, {name = node.name, param2 = node.param2})
	pipeworks.scan_for_tube_objects(pos)
	local meta = minetest.get_meta(pos)
	local channel = meta:get_string("channel")
	if channel ~= "" then
		set_tube(pos, channel, meta:get_int("can_receive"))
	end
	update_meta(meta)
end

local function digiline_action(pos, _, channel, msg)
	local meta = minetest.get_meta(pos)
	if channel ~= meta:get_string("digiline_channel") or type(msg) ~= "string" then
		return
	end
	local name = meta:get_string("owner")
	local cr = meta:get_int("can_receive")
	update_tube(pos, msg, cr, name)
	update_meta(meta)
end

local def = {
	tube = {
		can_go = can_go,
		on_repair = repair_tube,
	},
	on_construct = function(pos)
		local meta = minetest.get_meta(pos)
		meta:set_int("can_receive", 1)  -- Enabled by default
		update_meta(meta)
	end,
	on_receive_fields = receive_fields,
	on_destruct = remove_tube,
}

if has_digilines then
	def.after_place_node = function(pos, placer)
		-- Set owner for digilines
		minetest.get_meta(pos):set_string("owner", placer:get_player_name())
		pipeworks.after_place(pos)
	end
	def.digiline = {
		receptor = {
			rules = pipeworks.digilines_rules,
		},
		effector = {
			rules = pipeworks.digilines_rules,
			action = digiline_action,
		}
	}
end

pipeworks.register_tube("pipeworks:teleport_tube", {
	description = S("Teleporting Pneumatic Tube Segment"),
	inventory_image = "pipeworks_teleport_tube_inv.png",
	noctr = { "pipeworks_teleport_tube_noctr.png" },
	plain = { "pipeworks_teleport_tube_plain.png" },
	ends = { "pipeworks_teleport_tube_end.png" },
	short = "pipeworks_teleport_tube_short.png",
	node_def = def,
})

if minetest.get_modpath("mesecons_mvps") then
	-- Update tubes when moved by pistons
	mesecon.register_on_mvps_move(function(moved_nodes)
		for _, n in ipairs(moved_nodes) do
			if n.node.name:find("pipeworks:teleport_tube") then
				local meta = minetest.get_meta(n.pos)
				set_tube(n.pos, meta:get_string("channel"), meta:get_int("can_receive"))
			end
		end
	end)
end

-- Expose teleport tube database API for other mods
pipeworks.tptube = {
	version = tube_db_version,
	hash = hash_pos,
	get_db = function() return tube_db end,
	save_tube_db = save_tube_db,
	set_tube = set_tube,
	save_tube = save_tube,
	update_tube = update_tube,
	update_meta = function(meta, cr)
		-- Legacy behaviour
		if cr ~= nil then
			meta:set_int("can_receive", cr and 1 or 0)
		end
		update_meta(meta)
	end,
}

-- Load the database
read_tube_db()
