-----------------------------------------------------------------------------
-- limits for trading: maximum and minimum stock to keep
-----------------------------------------------------------------------------
-- sometimes players may not want the NPC to sell *all* of their stock,
-- or not let the NPC buy endless amounts of something when only a limited
-- amount is needed
-----------------------------------------------------------------------------

-- helper function: make sure all necessary entries in the trades table exist
yl_speak_up.setup_trade_limits = function(dialog)
	if(not(dialog)) then
		dialog = {}
	end
	if(not(dialog.trades)) then
		dialog.trades = {}
	end
	if(not(dialog.trades.limits)) then
		dialog.trades.limits = {}
	end
	if(not(dialog.trades.limits.sell_if_more)) then
		dialog.trades.limits.sell_if_more = {}
	end
	if(not(dialog.trades.limits.buy_if_less)) then
		dialog.trades.limits.buy_if_less = {}
	end
	return dialog
end


-- helper function: count how many items the NPC has in his inventory
--   empty stacks are counted under the key "";
--   for other items, the amount of items of each type is counted
yl_speak_up.count_npc_inv = function(n_id)
	if(not(n_id)) then
		return {}
	end
	-- the NPC's inventory
	local npc_inv = minetest.get_inventory({type="detached", name="yl_speak_up_npc_"..tostring(n_id)})

	if(not(npc_inv)) then
		return {}
	end
	local anz = npc_inv:get_size('npc_main')
	local stored = {}
	for i=1, anz do
		local stack = npc_inv:get_stack('npc_main', i )
		local name = stack:get_name()
		local count = stack:get_count()
		-- count empty stacks 
		if(name=="") then
			count = 1
		end
		-- count how much of each item is there
		if(not(stored[ name ])) then
			stored[ name ] = count
		else
			stored[ name ] = stored[ name ] + count
		end
	end
	return stored
end


-- helper function: update the items table so that it reflects a limitation
-- items is a table (list) with these entries:
--   [1] 0 in stock;
--   [2] sell if more than 0;
--   [3] buy if less than 10000;
--   [4] item is part of a trade offer
yl_speak_up.insert_trade_item_limitation = function( items, k, i, v )
	if( i<1 or i>4) then
		return;
	end
	if( not( items[ k ] )) then
		-- 0 in stock; sell if more than 0; buy if less than 10000; item is part of a trade offer
		items[ k ] = { 0, 0, 10000, false, #items }
	end
	items[ k ][ i ] = v
end