build: compile against Paper API 1.21.10

pom.xml

@@ -18,15 +18,21 @@
 
   <repositories>
     <repository>
-      <id>spigot-repo</id>
-      <url>https://hub.spigotmc.org/nexus/content/repositories/snapshots/</url>
+      <id>papermc</id>
+      <url>https://repo.papermc.io/repository/maven-public/</url>
     </repository>
   </repositories>
 
   <dependencies>
     <dependency>
-      <groupId>org.spigotmc</groupId>
-      <artifactId>spigot-api</artifactId>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>4.13.2</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>io.papermc.paper</groupId>
+      <artifactId>paper-api</artifactId>
       <version>1.21.10-R0.1-SNAPSHOT</version>
       <scope>provided</scope>
     </dependency>

src/main/java/net/tfminecraft/archaeo/museum/MuseumListener.java

@@ -9,6 +9,7 @@
 import net.tfminecraft.archaeo.site.SiteRepository;
 import org.bukkit.Material;
 import org.bukkit.block.Block;
+import org.bukkit.block.BlockFace;
 import org.bukkit.block.BlockState;
 import org.bukkit.block.Lectern;
 import org.bukkit.block.Shelf;
@@ -200,7 +201,7 @@ private static List<ItemStack> displayedOnBlock(BlockState state, Vector click)
                 }
                 return stacks;
             }
-            int slot = shelf.getSlot(click);
+            int slot = shelfSlot(((org.bukkit.block.data.type.Shelf) shelf.getBlockData()).getFacing(), click);
             if (slot >= 0) {
                 stacks.add(shelf.getInventory().getItem(slot));
             }
@@ -209,6 +210,27 @@ private static List<ItemStack> displayedOnBlock(BlockState state, Vector click)
         return stacks;
     }
 
+    // Paper 1.21.10 has no Shelf#getSlot. Match vanilla's three equal columns,
+    // ordered left to right when looking at the shelf's front.
+    static int shelfSlot(BlockFace facing, Vector click) {
+        if (click == null || !(click.getX() >= 0 && click.getX() <= 1
+                && click.getY() >= 0 && click.getY() <= 1
+                && click.getZ() >= 0 && click.getZ() <= 1)) {
+            return -1;
+        }
+        float horizontal = (float) switch (facing) {
+            case NORTH -> 1 - click.getX();
+            case SOUTH -> click.getX();
+            case WEST -> click.getZ();
+            case EAST -> 1 - click.getZ();
+            default -> -1;
+        };
+        if (horizontal < 0) {
+            return -1;
+        }
+        return Math.min(2, (int) Math.floor(horizontal * 16.0f / (16.0f / 3)));
+    }
+
     /**
      * @param entity frame, display, armor stand, or furniture root
      * @return stacks that entity is showing

src/test/java/net/tfminecraft/archaeo/museum/MuseumListenerTest.java

@@ -0,0 +1,40 @@
+package net.tfminecraft.archaeo.museum;
+
+import org.bukkit.block.BlockFace;
+import org.bukkit.util.Vector;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class MuseumListenerTest {
+    @Test
+    public void selectsAllThreeSlotsFromEachFacing() {
+        for (int slot = 0; slot < 3; slot++) {
+            double horizontal = (slot + 0.5) / 3;
+            assertEquals(slot, MuseumListener.shelfSlot(BlockFace.NORTH, new Vector(1 - horizontal, 0.5, 0)));
+            assertEquals(slot, MuseumListener.shelfSlot(BlockFace.SOUTH, new Vector(horizontal, 0.5, 1)));
+            assertEquals(slot, MuseumListener.shelfSlot(BlockFace.WEST, new Vector(0, 0.5, horizontal)));
+            assertEquals(slot, MuseumListener.shelfSlot(BlockFace.EAST, new Vector(1, 0.5, 1 - horizontal)));
+        }
+    }
+
+    @Test
+    public void keepsEdgesInsideTheInventoryAndSplitsAtThirds() {
+        double[] positions = {0, 1.0 / 3 - 0.001, 1.0 / 3, 2.0 / 3 - 0.001, 2.0 / 3, 1};
+        int[] slots = {0, 0, 1, 1, 2, 2};
+        for (int i = 0; i < positions.length; i++) {
+            assertEquals(slots[i], MuseumListener.shelfSlot(BlockFace.SOUTH, new Vector(positions[i], 0, 1)));
+        }
+    }
+
+    @Test
+    public void rejectsPositionsOutsideTheBlock() {
+        assertEquals(-1, MuseumListener.shelfSlot(BlockFace.SOUTH, null));
+        assertEquals(-1, MuseumListener.shelfSlot(BlockFace.UP, new Vector(0.5, 0.5, 0.5)));
+        for (double invalid : new double[] {-0.01, 1.01, Double.NaN, Double.POSITIVE_INFINITY}) {
+            assertEquals(-1, MuseumListener.shelfSlot(BlockFace.SOUTH, new Vector(invalid, 0.5, 0.5)));
+            assertEquals(-1, MuseumListener.shelfSlot(BlockFace.SOUTH, new Vector(0.5, invalid, 0.5)));
+            assertEquals(-1, MuseumListener.shelfSlot(BlockFace.SOUTH, new Vector(0.5, 0.5, invalid)));
+        }
+    }
+}