local json = require"common.dkjson"
local class = require"common.class"

local CHUNK_SIZE = 64

-- for now tiles shall be booleans

local function index_ok(offq,offr)
	return 0<=offq and 0<=offr and offq<CHUNK_SIZE and offr<CHUNK_SIZE
end

local function index(offq,offr)
	-- indexes start at 0
	-- and go up to (CHUNK_SIZE^2)-1
	assert(index_ok(offq,offr), "chunk hex offset out of bounds")
	return CHUNK_SIZE*offq + offr + 1
end

local Chunk = class()
function Chunk.make(cls,tiles)
	return setmetatable({tiles=tiles},cls)
end
function Chunk.at(self,hoffs)
	if not index_ok(hoffs.q,hoffs.r) then return nil end
	return self.tiles[index(hoffs.q,hoffs.r)]
end
function Chunk.set_at(self,hoffs,tile)
	if not index_ok(hoffs.q,hoffs.r) then return end
	self.tiles[index(hoffs.q,hoffs.r)] = tile
end

function Chunk.data_packet(self)
	return json.encode{t="chunk",tiles=self.tiles}
end
function Chunk.from_packet_data(packet)
	-- assuming packet has already been json.decoded
	-- since otherwise how would we know it's a chunk packet
	return Chunk:make(packet.tiles)
end

return {
	Chunk=Chunk,
	SIZE=CHUNK_SIZE,
	index=index,
	index_ok=index_ok,
}