From ea08fee9ba572287f4aad42b0afa07a7ace7369b Mon Sep 17 00:00:00 2001
From: Elias Fleckenstein <eliasfleckenstein@web.de>
Date: Tue, 6 Apr 2021 16:38:23 +0200
Subject: [PATCH] Make the dragon stay within a 50 blocks range of the portal

---
 mods/ENTITIES/mobs_mc/ender_dragon.lua | 18 +++++++++++++++---
 mods/ITEMS/mcl_end/end_crystal.lua     |  2 +-
 mods/MAPGEN/mcl_mapgen_core/init.lua   |  2 +-
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/mods/ENTITIES/mobs_mc/ender_dragon.lua b/mods/ENTITIES/mobs_mc/ender_dragon.lua
index 50aaacd4b..fbdaf2bc9 100644
--- a/mods/ENTITIES/mobs_mc/ender_dragon.lua
+++ b/mods/ENTITIES/mobs_mc/ender_dragon.lua
@@ -61,14 +61,26 @@ mobs:register_mob("mobs_mc:enderdragon", {
 	ignores_nametag = true,
 	do_custom = function(self)
 		mcl_bossbars.update_boss(self, "Ender Dragon", "light_purple")
+		if self._portal_pos then
+			-- migrate old format
+			if type(self._portal_pos) == "string" then
+				self._portal_pos = minetest.string_to_pos(self._portal_pos)
+			end
+			local portal_center = vector.add(self._portal_pos, vector.new(3, 11, 3))
+			local pos = self.object:get_pos()
+			if vector.distance(pos, portal_center) > 50 then
+				self.object:set_pos(self._last_good_pos or portal_center)
+			else
+				self._last_good_pos = pos
+			end
+		end
 	end,
 	on_die = function(self, pos)
 		if self._portal_pos then
-			local portal_pos = minetest.string_to_pos(self._portal_pos)
-			mcl_structures.call_struct(portal_pos, "end_exit_portal_open")
+			mcl_structures.call_struct(self._portal_pos, "end_exit_portal_open")
 			if self._initial then
 				mcl_experience.throw_experience(pos, 11500) -- 500 + 11500 = 12000
-				minetest.set_node(vector.add(portal_pos, vector.new(3, 5, 3)), {name = mobs_mc.items.dragon_egg})
+				minetest.set_node(vector.add(self._portal_pos, vector.new(3, 5, 3)), {name = mobs_mc.items.dragon_egg})
 			end
 		end
 	end,
diff --git a/mods/ITEMS/mcl_end/end_crystal.lua b/mods/ITEMS/mcl_end/end_crystal.lua
index 63a37d3c6..772776a1c 100644
--- a/mods/ITEMS/mcl_end/end_crystal.lua
+++ b/mods/ITEMS/mcl_end/end_crystal.lua
@@ -60,7 +60,7 @@ local function spawn_crystal(pos)
 	end
 	local portal_pos = vector.add(portal_center, vector.new(-3, -1, -3))
 	mcl_structures.call_struct(portal_pos, "end_exit_portal")
-	minetest.add_entity(vector.add(portal_pos, vector.new(3, 11, 3)), "mobs_mc:enderdragon"):get_luaentity()._portal_pos = minetest.pos_to_string(portal_pos)
+	minetest.add_entity(vector.add(portal_pos, vector.new(3, 11, 3)), "mobs_mc:enderdragon"):get_luaentity()._portal_pos = portal_pos
 end
 
 minetest.register_entity("mcl_end:crystal", {
diff --git a/mods/MAPGEN/mcl_mapgen_core/init.lua b/mods/MAPGEN/mcl_mapgen_core/init.lua
index 237579dbe..e9d9368ad 100644
--- a/mods/MAPGEN/mcl_mapgen_core/init.lua
+++ b/mods/MAPGEN/mcl_mapgen_core/init.lua
@@ -1253,7 +1253,7 @@ end
 local function generate_end_exit_portal(pos)
 	local dragon_entity = minetest.add_entity(vector.add(pos, vector.new(3, 11, 3)), "mobs_mc:enderdragon"):get_luaentity()
 	dragon_entity._initial = true
-	dragon_entity._portal_pos = minetest.pos_to_string(pos)
+	dragon_entity._portal_pos = pos
 	mcl_structures.call_struct(pos, "end_exit_portal")
 end