More "rational" tunneling behavior

This adds a tunneling function that can be used for any dungeon-building
mob. It's tweaked to slow the tunneling down to a reasonable level, but
that can be changed by adjusting the chances of state change at the end
of the function. I also temporarily corrected a default setting for
def.replace_rate_secondary that causes the current master to crash. This
isn't a complete fix. Checking for a bad value at the math.random call
would be better. My change may result in crashes at long intervals, but
it's better than the current state.

api.lua

@@ -78,7 +78,14 @@ function mobs_goblins:register_mob(name, def)
 		replace_what = def.replace_what,
 		replace_with = def.replace_with,
 		-- or maybe something different?
-		replace_rate_secondary = def.replace_rate_secondary or 0,
+		--
+		-- Zero is a BAD default, as random will not take a 1,0 range.
+		--  The mod fails with an error in the current master.
+		--  I recommend replacing with an unreasonably large number, or
+		--  nil (and changing the random call to check for nil).
+		-- replace_rate_secondary = def.replace_rate_secondary or 0,
+		replace_rate_secondary = def.replace_rate_secondary or 1000000,
+		--
 		replace_with_secondary = def.replace_with_secondary or def.replace_with,
 		timer = 0,
 		env_damage_timer = 0, -- only if state = "attack"
@@ -1731,4 +1738,4 @@ function mobs_goblins:feed_tame(self, clicker, feed_count, breed)
 	else
 		return false
 	end
-end
+end

goblins.lua

@@ -1,6 +1,96 @@
  
 -- Npc by TenPlus1 converted for FLG Goblins :D
 
+mobs_goblins.goblin_tunneling = function(self, type)
+	-- Types are available for fine-tuning.
+	if type == nil then
+		type = "digger"
+	end
+
+	-- He destroys everything diggable in his path. It's too much trouble
+	--  to fudge around with particulars. Besides, I don't want them to
+	--  mine for me.
+	local diggable_nodes = {"group:stone", "group:sand", "group:soil", "group:cracky", "group:crumbly", "group:choppy", "group:plant"}
+	-- This translates yaw into vectors.
+	local cardinals = {{x=0,y=0,z=0.75}, {x=-0.75,y=0,z=0}, {x=0,y=0,z=-0.75}, {x=0.75,y=0,z=0}}
+	local pos = self.object:getpos()
+
+	if self.state == "tunnel" then
+		-- Yaw is stored as one of the four cardinal directions.
+		if not self.digging_dir then
+			self.digging_dir = math.random(0,3)
+		end
+
+		-- Turn him roughly in the right direction.
+		-- self.object:setyaw(self.digging_dir * math.pi * 0.5 + math.random() * 0.5 - 0.25)
+		self.object:setyaw(self.digging_dir * math.pi * 0.5)
+
+		-- Get a pair of coordinates that should cover what's in front of him.
+		local p = vector.add(pos, cardinals[self.digging_dir+1])
+		p.y = p.y - 0.5  -- What's this about?
+		local p1 = vector.add(p, -0.3)
+		local p2 = vector.add(p, 0.3)
+
+		-- Get any diggable nodes in that area.
+		local np_list = minetest.find_nodes_in_area(p1, p2, diggable_nodes)
+
+		if #np_list > 0 then
+			-- Dig it.
+			for _, np in pairs(np_list) do
+				minetest.remove_node(np)
+			end
+		end
+
+		if math.random() < 0.2 then
+			local d = {-1,1}
+			self.digging_dir = (self.digging_dir + d[math.random(2)]) % 4
+		end
+
+		self:set_animation("walk")
+		self.set_velocity(self, self.walk_velocity)
+	elseif self.state == "room" then  -- Dig a room.
+		if not self.room_radius then
+			self.room_radius = 1
+		end
+
+		self:set_animation("stand")
+		self.set_velocity(self, 0)
+
+		-- Work from the inside, out.
+		for r = 1,self.room_radius do
+			-- Get a pair of coordinates that form a room.
+			local p1 = vector.add(pos, -r)
+			local p2 = vector.add(pos, r)
+			-- But not below him.
+			p1.y = pos.y
+
+			local np_list = minetest.find_nodes_in_area(p1, p2, diggable_nodes)
+
+			-- I wanted to leave the outer layer incomplete, but this
+			--  actually tends to make it look worse.
+			if r >= self.room_radius and #np_list == 0 then
+				self.room_radius = math.random(1,2) + math.random(0,1)
+				self.state = "stand"
+				break
+			end
+
+			if #np_list > 0 then
+				-- Dig it.
+				minetest.remove_node(np_list[math.random(#np_list)])
+				break
+			end
+		end
+	end
+
+	if self.state == "stand" and math.random() < 0.05 then
+		self.state = "tunnel"
+	elseif self.state == "tunnel" and math.random() < 0.05 then
+		self.state = "room"
+	elseif self.state == "tunnel" and math.random() < 0.1 then
+		self.state = "stand"
+	end
+end
+
 mobs_goblins.goblin_drops = {
 	"default:pick_steel",  "default:sword_steel",
 	"default:shovel_steel", "farming:bread", "bucket:bucket_water"
@@ -179,7 +269,7 @@ mobs_goblins:register_mob("mobs_goblins:goblin_digger", {
 	search_offset_below = 1.1,
 	search_offset_above = 1,
 	replace_rate = 4,
-	replace_what = {"group:soil","group:sand","default:gravel","default:stone","default:desert_stone","default:torch"},
+	replace_what = {"default:torch"},
 	replace_with = "air",
 
 	view_range = 15,
@@ -246,6 +336,13 @@ mobs_goblins:register_mob("mobs_goblins:goblin_digger", {
 		mobs_goblins:capture_mob(self, clicker, 0, 5, 80, false, nil)
 	end,
 		
+	do_custom = function(self)
+		mobs_goblins.goblin_tunneling(self, "digger")
+
+		-- mobs_goblins.search_replace(self.object:getpos(), 5, {"default:torch"}, "air")
+		-- mobs_goblins.search_replace(self.object:getpos(), 10, {"group:stone"}, "default:mossycobble")
+		-- mobs_goblins.search_replace(self.object:getpos(), 50, {"group:stone"}, "mobs_goblins:mossycobble_trap")
+	end,
 })
 
 mobs_goblins:register_mob("mobs_goblins:goblin_coal", {