--[[

  ITB (insidethebox) minetest game - Copyright (C) 2017-2018 sofar & nore

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public License
  as published by the Free Software Foundation; either version 2.1
  of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free
  Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  MA 02111-1307 USA

]]--

-- Functions to handle binary data encoding the boxes, to save and load them

local function bytes_to_string(bytes)
	local s = {}
	for i = 1, #bytes do
		s[i] = string.char(bytes[i])
	end
	return table.concat(s)
end

function boxes.save(minp, maxp)
	local t1 = os.clock()
	--[[ TODO: save the box in incremental steps to avoid stalling the server. The
		problem is that we have to iterate over all positions since there is no way
		to get the metadata of all nodes in an area, although the engine can.
		However, we still use a voxelmanip to load node bulk data.
	]]
	local vm = minetest.get_voxel_manip(minp, maxp)
	local emin, emax = vm:get_emerged_area()
	local data = vm:get_data()
	local param2 = vm:get_param2_data()
	local flat_data = {}
	local flat_index = 1
	local function add_u8(x)
		flat_data[flat_index] = x
		flat_index = flat_index + 1
	end
	local function add_u16(x)
		add_u8(math.floor(x / 256))
		add_u8(x % 256)
	end
	local function add_string(s)
		add_u16(string.len(s))
		for i = 1, string.len(s) do
			add_u8(string.byte(s, i))
		end
	end

	-- Version
	add_u8(2)

	local sx = maxp.x - minp.x + 1
	local sy = maxp.y - minp.y + 1
	local sz = maxp.z - minp.z + 1
	-- Size
	add_u16(sx)
	add_u16(sy)
	add_u16(sz)

	local cid_mapping = {}
	local cid_index = 0
	local cid_rmapping = {}
	local va = VoxelArea:new{MinEdge=emin,MaxEdge=emax}

	for z = minp.z, maxp.z do
		for y = minp.y, maxp.y do
			local index = va:index(minp.x, y, z)
			for x = minp.x, maxp.x do
				local cid = data[index]
				if cid_rmapping[cid] == nil then
					cid_rmapping[cid] = cid_index
					cid_mapping[cid_index] = minetest.get_name_from_content_id(cid)
					cid_index = cid_index + 1
				end
				index = index + 1
			end
		end
	end

	-- Write cid mapping
	add_u16(cid_index)
	for i = 0, cid_index - 1 do
		add_string(cid_mapping[i])
	end

	-- Write bulk node data
	for z = minp.z, maxp.z do
		for y = minp.y, maxp.y do
			local index = va:index(minp.x, y, z)
			for x = minp.x, maxp.x do
				add_u16(cid_rmapping[data[index]])
				add_u8(param2[index])
				index = index + 1
			end
		end
	end

	local meta_at_pos = {}
	for _, v in pairs(minetest.find_nodes_with_meta(minp, maxp)) do
		meta_at_pos[minetest.pos_to_string(v)] = 1
	end

	local meta_to_save = {}
	local meta_save_index = 1
	for z = minp.z, maxp.z do
		for y = minp.y, maxp.y do
			for x = minp.x, maxp.x do
				--FIXME don't save meta if cid==air
				local meta_table
				if meta_at_pos[minetest.pos_to_string({x = x, y = y, z = z})] then
					local meta = minetest.get_meta({x = x, y = y, z = z})
					meta_table = meta:to_table()
				else
					meta_table = {fields = {}, inventory = {}}
				end
				local nodetimer = minetest.get_node_timer({x = x, y = y, z = z})
				if next(meta_table.fields) ~= nil or next(meta_table.inventory) ~= nil or nodetimer:is_started() then
					local inv = {}
					for inv_name, inv_list in pairs(meta_table.inventory) do
						local inv_list_2 = {}
						for i, stack in ipairs(inv_list) do
							inv_list_2[i] = stack:to_string()
						end
						inv[inv_name] = inv_list_2
					end
					local sv = {x = x - minp.x, y = y - minp.y, z = z - minp.z}
					if next(meta_table.fields) ~= nil then
						sv.fields = meta_table.fields
					end
					if next(inv) ~= nil then
						sv.inventory = inv
					end
					if nodetimer:is_started() then
						sv.timer = {to = nodetimer:get_timeout(), el = nodetimer:get_elapsed()}
					end

					meta_to_save[meta_save_index] = sv
					meta_save_index = meta_save_index + 1
				end
			end
		end
	end

	add_u16(meta_save_index - 1)
	for i = 1, meta_save_index - 1 do
		local m = meta_to_save[i]
		add_u16(m.x)
		add_u16(m.y)
		add_u16(m.z)
		if m.fields then
			add_string(minetest.serialize(m.fields))
		else
			add_string("")
		end
		if m.inventory then
			add_string(minetest.serialize(m.inventory))
		else
			add_string("")
		end
		if m.timer then
			add_string(minetest.serialize(m.timer))
		else
			add_string("")
		end
	end

	local raw_data = bytes_to_string(flat_data)

	local t2 = os.clock()

	local cc = minetest.compress(raw_data, "deflate")

	local t3 = os.clock()
	minetest.log("action", "boxes.save: " .. (t2 - t1) .. ", " .. (t3 - t2))

	return cc
end

function boxes.load(minp, box_id, player)
	local compressed = db.box_get_data(box_id)
	local raw_data = minetest.decompress(compressed, "deflate")
	local raw_data_index = 1
	local function read_u8()
		local c = string.byte(raw_data, raw_data_index)
		raw_data_index = raw_data_index + 1
		return c
	end
	local function read_u16()
		local a = read_u8()
		local b = read_u8()
		return 256 * a + b
	end
	local function read_string()
		local len = read_u16()
		local r = string.sub(raw_data, raw_data_index, raw_data_index + len - 1)
		raw_data_index = raw_data_index + len
		return r
	end

	local version = read_u8()
	assert (version <= 2)

	local sx = read_u16()
	local sy = read_u16()
	local sz = read_u16()

	-- Read cid mapping
	local cid_mapping = {}
	local callbacks = {}
	local cid_index = read_u16()
	for i = 0, cid_index - 1 do
		local name = read_string()
		callbacks[i] = minetest.registered_nodes[name].after_box_construct
		cid_mapping[i] = minetest.get_content_id(name)
	end

	local maxp = {x = minp.x + sx - 1, y = minp.y + sy - 1, z = minp.z + sz - 1}
	local vm = minetest.get_voxel_manip(minp, maxp)
	local emin, emax = vm:get_emerged_area()
	local va = VoxelArea:new{MinEdge=emin,MaxEdge=emax}
	local vmdata = vm:get_data()
	local param2 = vm:get_param2_data()

	local to_call = {}
	local to_call_index = 1
	-- Read bulk node data
	for z = minp.z, maxp.z do
		for y = minp.y, maxp.y do
			local index = va:index(minp.x, y, z)
			for x = minp.x, maxp.x do
				local cid = read_u16()
				vmdata[index] = cid_mapping[cid]
				param2[index] = read_u8()
				index = index + 1
				if callbacks[cid] then
					to_call[to_call_index] = {x = x, y = y, z = z, callback = callbacks[cid]}
					to_call_index = to_call_index + 1
				end
			end
		end
	end
	vm:set_data(vmdata)
	vm:set_param2_data(param2)
	vm:update_liquids()
	vm:write_to_map()
	vm:update_map()
	minetest.after(0.2, function()
		minetest.fix_light(vector.add(minp, -16), vector.add(maxp, 16))
	end)

	-- Clear existing metadata
	local meta_positions = minetest.find_nodes_with_meta(minp, maxp)
	for _, pos in ipairs(meta_positions) do
		minetest.get_meta(pos):from_table()
	end

	-- Finally, read metadata
	local nmeta = read_u16()
	for _ = 1, nmeta do
		local x = read_u16()
		local y = read_u16()
		local z = read_u16()
		local p = {x = minp.x + x, y = minp.y + y, z = minp.z + z}
		local meta = minetest.get_meta(p)
		local fields = minetest.deserialize(read_string()) or {}
		local inv = minetest.deserialize(read_string()) or {}
		if version >= 2 then
			local timer = minetest.deserialize(read_string()) or {}
			if timer.to then
				minetest.get_node_timer(p):set(timer.to, timer.el)
			end
		end
		for inv_name, inv_list in pairs(inv) do
			for i, stack in ipairs(inv_list) do
				inv_list[i] = ItemStack(inv_list[i])
			end
		end
		meta:from_table({fields = fields, inventory = inv})
	end

	-- And call callbacks for nodes which define them
	for i = 1, to_call_index - 1 do
		local tc = to_call[i]
		tc.callback({x = tc.x, y = tc.y, z = tc.z}, box_id, player)
	end
end

-- Although that function can be quite useful in some cases,
-- it implies decompressing the whole compressed data just to
-- know the extent of a box. Thus, it is commented out and while
-- it can be useful for quick prototyping, it should be avoided to
-- use it in production code.

--[[
function boxes.extent(compressed)
	local raw_data = minetest.decompress(compressed, "deflate")
	local raw_data_index = 1
	local function read_u8()
		local c = string.byte(raw_data, raw_data_index)
		raw_data_index = raw_data_index + 1
		return c
	end
	local function read_u16()
		local a = read_u8()
		local b = read_u8()
		return 256 * a + b
	end

	local version = read_u8()
	assert (version == 1)

	local sx = read_u16()
	local sy = read_u16()
	local sz = read_u16()

	return {x = sx, y = sy, z = sz}
end
]]