Make sure chainsaw drops appear above ground

A fix for https://github.com/minetest-technic/technic/issues/137
Chainsaw drops are forced to pop above ground. Also, as asl suggested,
they must not end up too high on a ledge or a pillar.

This also cleans up the code style of chainsaw.lua.

technic/tools/chainsaw.lua

@@ -132,7 +132,6 @@ local produced = nil
 -- items sawed down so that we can drop them i an nice single stack
 local function chainsaw_handle_node_drops(pos, drops, digger)
 	-- Add dropped items to list of collected nodes
-        local _, dropped_item
 	for _, dropped_item in ipairs(drops) do
 		if produced[dropped_item] == nil then
 			produced[dropped_item] = 1
@@ -204,6 +203,36 @@ local function recursive_dig(pos, remaining_charge, player)
 	return remaining_charge
 end
 
+-- Function to randomize positions for new node drops
+local function get_drop_pos(pos)
+	local drop_pos = {}
+
+	for i = 0, 8 do
+		-- Randomize position for a new drop
+		drop_pos.x = pos.x + math.random(-3, 3)
+		drop_pos.y = pos.y - 1
+		drop_pos.z = pos.z + math.random(-3, 3)
+
+		-- Move the randomized position upwards until
+		-- the node is air or unloaded.
+		for y = drop_pos.y, drop_pos.y + 5 do
+			drop_pos.y = y
+			local node = minetest.get_node_or_nil(drop_pos)
+
+			if not node then
+				-- If the node is not loaded yet simply drop
+				-- the item at the original digging position.
+				return pos
+			elseif node.name == "air" then
+				return drop_pos
+			end
+		end
+	end
+
+	-- Return the original position if this takes too long
+	return pos
+end
+
 -- Saw down trees entry point
 local function chainsaw_dig_it(pos, player,current_charge)
 	if minetest.is_protected(pos, player:get_player_name()) then
@@ -232,18 +261,10 @@ local function chainsaw_dig_it(pos, player,current_charge)
 		for produced_item,number in pairs(produced) do
 				--print("ADDING ITEM: " .. produced_item .. " " .. number)
 				-- Drop stacks of 99 or less
-                p = {
-                        x = pos.x + math.random()*4,
-                        y = pos.y,
-                        z = pos.z + math.random()*4
-                }
+				p = get_drop_pos(pos)
 				while number > 99 do
 						minetest.env:add_item(p, produced_item .. " 99")
-                        p = {
-                                x = pos.x + math.random()*4,
-                                y = pos.y,
-                                z = pos.z + math.random()*4
-                        }
+						p = get_drop_pos(pos)
 						number = number - 99
 				end
 				minetest.env:add_item(p, produced_item .. " " .. number)
@@ -287,4 +308,3 @@ minetest.register_craft({
 		{'',                               '',                             'default:copper_ingot'},
 	}
 })
-