From f4c68bb0c307588016c3a099757f69372cc6a7dc Mon Sep 17 00:00:00 2001
From: Sollace <sollacea@gmail.com>
Date: Wed, 30 Aug 2023 21:34:50 +0100
Subject: [PATCH] Change pillar height for the altar from 3 to 4, check for sky
 visibility on the pillars, and allow the altar to fix itself if the current
 placement is determined to be valid

---
 .../unicopia/entity/SpellbookEntity.java         | 13 +++++++++++--
 .../unicopia/server/world/Altar.java             | 16 ++++++++++------
 2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/src/main/java/com/minelittlepony/unicopia/entity/SpellbookEntity.java b/src/main/java/com/minelittlepony/unicopia/entity/SpellbookEntity.java
index bc781209..7032448c 100644
--- a/src/main/java/com/minelittlepony/unicopia/entity/SpellbookEntity.java
+++ b/src/main/java/com/minelittlepony/unicopia/entity/SpellbookEntity.java
@@ -190,11 +190,18 @@ public class SpellbookEntity extends MobEntity implements MagicImmune {
         }
 
         if (!getWorld().isClient && age % 15 == 0) {
-            altar.ifPresent(altar -> {
 
+            if (altar.isEmpty()) {
+                altar = Altar.locateAltar(getWorld(), getBlockPos()).map(altar -> {
+                    altar.generateDecorations(getWorld());
+                    return altar;
+                });
+            }
+
+            altar = altar.filter(altar -> {
                 if (!altar.isValid(getWorld())) {
                     altar.tearDown(null, getWorld());
-                    return;
+                    return false;
                 }
 
                 altar.pillars().forEach(pillar -> {
@@ -229,6 +236,8 @@ public class SpellbookEntity extends MobEntity implements MagicImmune {
                         getWorld().setBlockState(pillar, Blocks.CRYING_OBSIDIAN.getDefaultState());
                     }
                 });
+
+                return true;
             });
         }
     }
diff --git a/src/main/java/com/minelittlepony/unicopia/server/world/Altar.java b/src/main/java/com/minelittlepony/unicopia/server/world/Altar.java
index 6830c358..70325717 100644
--- a/src/main/java/com/minelittlepony/unicopia/server/world/Altar.java
+++ b/src/main/java/com/minelittlepony/unicopia/server/world/Altar.java
@@ -123,8 +123,10 @@ public record Altar(BlockPos origin, Set<BlockPos> pillars) {
 
         if (isObsidian(world, pos.move(pillarPos))
             && isObsidian(world, pos.move(Direction.UP))
-            && isObsidian(world, pos.move(Direction.UP))) {
-            pillarPosCollector.accept(pos.toImmutable());
+            && isObsidian(world, pos.move(Direction.UP))
+            && isObsidian(world, pos.move(Direction.UP))
+            && world.isSkyVisible(pos.move(Direction.UP))) {
+            pillarPosCollector.accept(pos.move(Direction.DOWN).toImmutable());
             pos.set(x, y, z);
             return true;
         }
@@ -155,9 +157,6 @@ public record Altar(BlockPos origin, Set<BlockPos> pillars) {
     }
 
     public void tearDown(@Nullable Entity except, World world) {
-        if (!(except instanceof SpellbookEntity)) {
-            world.getOtherEntities(except, new Box(origin).expand(3), IS_PARTICIPANT).forEach(Entity::kill);
-        }
         pillars.forEach(pillar -> removeExisting(except, world, pillar));
     }
 
@@ -169,6 +168,11 @@ public record Altar(BlockPos origin, Set<BlockPos> pillars) {
         return checkState(world, origin, Blocks.SOUL_FIRE)
                 && checkState(world, origin.down(), Blocks.SOUL_SAND)
                 && checkSlab(world, origin.down())
-                && pillars.stream().allMatch(pillar -> isObsidian(world, pillar) && isObsidian(world, pillar.down()) && isObsidian(world, pillar.down(2)));
+                && pillars.stream().allMatch(pillar ->
+                           isObsidian(world, pillar)
+                        && world.isSkyVisible(pillar.up())
+                        && isObsidian(world, pillar.down())
+                        && isObsidian(world, pillar.down(2))
+                        && isObsidian(world, pillar.down(3)));
     }
 }