local chest
for _,name in ipairs(peripheral.getNames()) do
	if name:match("chest") then chest = peripheral.wrap(name) break end
end
assert(chest,"couldn't find chest")
-- might not work if there are multiple modems but why would you do that
local localname = peripheral.find("modem").getNameLocal()

local function take_stock()
	-- if you do this in parallel, you avoid having to wait 1 tick for each
	-- slot of the chest. which is probably good.
	local out = {}
	local fns = {}
	for i=1,chest.size() do
		fns[i] = function() out[i] = chest.getItemDetail(i) end
	end
	parallel.waitForAll(unpack(fns))
	return out
end

local function item_desc_matches(idesc,itemdetail)
	-- idesc is an entry from ITEMS
	-- itemdetail is something returned from getItemDetail on the chest
	-- if you were wondering

	if idesc.itname == itemdetail.name then
		if idesc.check then return idesc.check(itemdetail) end
		return true
	end
	return false

end

local function amt_of(stockinfo,idesc)
	local total = 0
	for ix,itm in pairs(stockinfo) do
		if item_desc_matches(idesc,itm) then
			total = total + itm.count
		end
	end
	return total
end

local function give(stockinfo,idesc,amt)
	amt = amt or 1
	-- assumes that we have at least amt in stock already
	-- actually no, might as well double check this anyway
	assert(amt_of(stockinfo,idesc) >= amt)
	assert(amt>0)
	-- make sure current turtle inv slot is empty
	assert(turtle.getItemCount() == 0)

	for slotidx,idtl in pairs(stockinfo) do
		if item_desc_matches(idesc,idtl) then
			local a = math.min(amt,idtl.count)
			chest.pushItems(localname, slotidx, a, 1)
			turtle.drop(a)
			amt = amt - a
			if amt <= 0 then break end
		end
	end
end


return {take_stock=take_stock,amt_of=amt_of,give=give}