local class = require"common.class"
local Chunk = require"common.chunk".Chunk
local json = require"common.dkjson"
local db = require'db'

local ChunkS = class.extend(Chunk)
function ChunkS.make(cls,...)
	local self = Chunk.make(cls,...)
	self.dirty = false
	return self
end

function ChunkS.apply_migrations(self)
	-- if tile format has changed and format in db isn't up to date any more
	-- then perform updates here
	for i,t in ipairs(self.tiles) do
		if t == false then self.tiles[i] = 0
		elseif t == true then self.tiles[i] = 9 end
	end
end

function ChunkS.load_from_disk(cls,cp)
	-- tries to load from database. returns nil if not there.
	local txn,dbi = db.get_db('chunks')
	local d = dbi[tostring(cp)]
	txn:commit()

	if not d then return nil end
	local j = json.decode(d)

	local self = cls:from_packet_data(j)
	self:apply_migrations()

	return self
end

function ChunkS.save_if_dirty(self,txn)
	if self.dirty then
		print("saving chunk",self.cp)
		local dbi = txn:open'chunks'
		dbi[tostring(self.cp)] = self:data_packet()
		self.dirty = false
	end
end

function ChunkS.set_at(self,...)
	Chunk.set_at(self,...)
	self.dirty = true
end

return {ChunkS=ChunkS}