From 79f5afe0f6da6cf830c28e0c21a58f3561ca5458 Mon Sep 17 00:00:00 2001
From: cora <coradelamouche@gmx.ch>
Date: Sun, 11 Sep 2022 19:40:16 +0200
Subject: [PATCH] Implement shulker teleportation

---
 mods/ENTITIES/mobs_mc/shulker.lua | 81 ++++++++++++++++++++++++++++++-
 1 file changed, 80 insertions(+), 1 deletion(-)

diff --git a/mods/ENTITIES/mobs_mc/shulker.lua b/mods/ENTITIES/mobs_mc/shulker.lua
index 6e12146f2..01712f03d 100644
--- a/mods/ENTITIES/mobs_mc/shulker.lua
+++ b/mods/ENTITIES/mobs_mc/shulker.lua
@@ -9,8 +9,26 @@ local S = minetest.get_translator("mobs_mc")
 --################### SHULKER
 --###################
 
+local adjacents = {
+	vector.new(1,0,0),
+	vector.new(-1,0,0),
+	vector.new(0,1,0),
+	vector.new(0,-1,0),
+	vector.new(0,0,1),
+	vector.new(0,0,-1),
+}
+local function check_spot(pos)
+	local n = minetest.get_node(pos)
+	if n.name~="air" then return false end
+	for _,a in pairs(adjacents) do
+		local p = vector.add(pos,a)
+		local pn = minetest.get_node(p)
+		if minetest.get_item_group(pn.name,"solid") > 0 then return true end
+	end
+	return false
+end
+local pr = PseudoRandom(os.time()*(-334))
 -- animation 45-80 is transition between passive and attack stance
-
 mcl_mobs:register_mob("mobs_mc:shulker", {
 	description = S("Shulker"),
 	type = "monster",
@@ -35,6 +53,8 @@ mcl_mobs:register_mob("mobs_mc:shulker", {
 	walk_chance = 0,
 	knock_back = false,
 	jump = false,
+	can_despawn = false,
+	fall_speed = 0,
 	drops = {
 		{name = "mcl_mobitems:shulker_shell",
 		chance = 2,
@@ -55,6 +75,7 @@ mcl_mobs:register_mob("mobs_mc:shulker", {
 	fear_height = 0,
 	noyaw = true,
 	do_custom = function(self,dtime)
+		local pos = self.object:get_pos()
 		if math.floor(self.object:get_yaw()) ~=0 then
 			self.object:set_yaw(0)
 			mcl_mobs:yaw(self, 0, 0, dtime)
@@ -68,6 +89,64 @@ mcl_mobs:register_mob("mobs_mc:shulker", {
 		end
 		self.path.way = false
 		self.look_at_players = false
+		if not check_spot(pos) then
+			self:teleport(nil)
+		end
+	end,
+	do_punch = function(self, puncher, time_from_last_punch, tool_capabilities, dir, damage)
+		self:teleport(puncher)
+	end,
+	do_teleport = function(self, target)
+		if target ~= nil then
+			local target_pos = target:get_pos()
+			-- Find all solid nodes below air in a 10×10×10 cuboid centered on the target
+			local nodes = minetest.find_nodes_in_area_under_air(vector.subtract(target_pos, 5), vector.add(target_pos, 5), {"group:solid", "group:cracky", "group:crumbly"})
+			local telepos
+			if nodes ~= nil then
+				if #nodes > 0 then
+					-- Up to 64 attempts to teleport
+					for n=1, math.min(64, #nodes) do
+						local r = pr:next(1, #nodes)
+						local nodepos = nodes[r]
+						local tg = vector.offset(nodepos,0,1,0)
+						if check_spot(tg) then
+							telepos = tg
+							node_ok = true
+						end
+					end
+					if telepos then
+						self.object:set_pos(telepos)
+					end
+				end
+			end
+		else
+			local pos = self.object:get_pos()
+			-- Up to 8 top-level attempts to teleport
+			for n=1, 8 do
+				local node_ok = false
+				-- We need to add (or subtract) different random numbers to each vector component, so it couldn't be done with a nice single vector.add() or .subtract():
+				local randomCube = vector.new( pos.x + 8*(pr:next(0,16)-8), pos.y + 8*(pr:next(0,16)-8), pos.z + 8*(pr:next(0,16)-8) )
+				local nodes = minetest.find_nodes_in_area_under_air(vector.subtract(randomCube, 4), vector.add(randomCube, 4), {"group:solid", "group:cracky", "group:crumbly"})
+				if nodes ~= nil then
+					if #nodes > 0 then
+						-- Up to 8 low-level (in total up to 8*8 = 64) attempts to teleport
+						for n=1, math.min(8, #nodes) do
+							local r = pr:next(1, #nodes)
+							local nodepos = nodes[r]
+							local tg = vector.offset(nodepos,0,1,0)
+							if check_spot(tg) then
+								self.object:set_pos(tg)
+								node_ok = true
+								break
+							end
+						end
+					end
+				end
+				if node_ok then
+					 break
+				end
+			end
+		end
 	end,
 })