Require footing for descriptive book travel

src/main/java/net/dnorberg/rivencraft/book/LinkingService.java

@@ -4,6 +4,7 @@ import java.util.Comparator;
 import java.util.Optional;
 import java.util.stream.Stream;
 import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.tags.BlockTags;
@@ -19,12 +20,21 @@ public final class LinkingService {
     }
 
     public static LinkResult travel(ServerPlayer player, LinkTarget target) {
+        return travel(player, target, false);
+    }
+
+    /** Travels to an Age-style destination, which must have solid footing. */
+    public static LinkResult travelWithFooting(ServerPlayer player, LinkTarget target) {
+        return travel(player, target, true);
+    }
+
+    private static LinkResult travel(ServerPlayer player, LinkTarget target, boolean requiresFooting) {
         ServerLevel destinationLevel = player.getServer().getLevel(target.location().dimension());
         if (destinationLevel == null) {
             return LinkResult.MISSING_DIMENSION;
         }
 
-        Optional<Vec3> destination = findSafeDestination(destinationLevel, target.location().pos());
+        Optional<Vec3> destination = findSafeDestination(destinationLevel, target.location().pos(), requiresFooting);
         if (destination.isEmpty()) {
             return LinkResult.NO_SAFE_DESTINATION;
         }
@@ -43,11 +53,15 @@ public final class LinkingService {
     }
 
     static Optional<Vec3> findSafeDestination(ServerLevel level, BlockPos origin) {
+        return findSafeDestination(level, origin, false);
+    }
+
+    private static Optional<Vec3> findSafeDestination(ServerLevel level, BlockPos origin, boolean requiresFooting) {
         WorldBorder border = level.getWorldBorder();
         return candidates(origin)
                 .filter(level::isInWorldBounds)
                 .filter(border::isWithinBounds)
-                .filter(position -> isSafe(level, position))
+                .filter(position -> isSafe(level, position, requiresFooting))
                 .map(position -> Vec3.atBottomCenterOf(position))
                 .findFirst();
     }
@@ -61,9 +75,11 @@ public final class LinkingService {
                 .sorted(Comparator.comparingDouble(position -> position.distSqr(origin)));
     }
 
-    private static boolean isSafe(ServerLevel level, BlockPos feet) {
+    private static boolean isSafe(ServerLevel level, BlockPos feet, boolean requiresFooting) {
         BlockPos head = feet.above();
-        return isPassableSpawnSpace(level, feet) && isPassableSpawnSpace(level, head);
+        return isPassableSpawnSpace(level, feet)
+                && isPassableSpawnSpace(level, head)
+                && (!requiresFooting || level.getBlockState(feet.below()).isFaceSturdy(level, feet.below(), Direction.UP));
     }
 
     private static boolean isPassableSpawnSpace(ServerLevel level, BlockPos position) {

src/main/java/net/dnorberg/rivencraft/gametest/LinkingGameTests.java

@@ -83,6 +83,22 @@ public final class LinkingGameTests {
         helper.succeed();
     }
 
+    @GameTest(template = "empty")
+    public static void descriptiveTravelRequiresFooting(GameTestHelper helper) {
+        BlockPos absoluteOrigin = helper.absolutePos(ORIGIN);
+        for (BlockPos position : BlockPos.betweenClosed(
+                absoluteOrigin.offset(-4, -3, -4), absoluteOrigin.offset(4, 3, 4))) {
+            helper.getLevel().setBlock(position, Blocks.AIR.defaultBlockState(), 2);
+        }
+
+        ServerPlayer player = helper.makeMockServerPlayerInLevel();
+        LinkTarget target = new LinkTarget(GlobalPos.of(helper.getLevel().dimension(), absoluteOrigin), 0.0F, 0.0F);
+
+        helper.assertValueEqual(LinkingService.travelWithFooting(player, target), LinkingService.LinkResult.NO_SAFE_DESTINATION,
+                "Descriptive Book travel must not place players without solid footing");
+        helper.succeed();
+    }
+
     @GameTest(template = "empty")
     public static void travelRejectsBlockedDestination(GameTestHelper helper) {
         BlockPos absoluteOrigin = helper.absolutePos(ORIGIN);

src/main/java/net/dnorberg/rivencraft/item/DescriptiveBookItem.java

@@ -49,7 +49,7 @@ public final class DescriptiveBookItem extends Item {
             return false;
         }
 
-        LinkingService.LinkResult result = LinkingService.travel(player, ageTarget);
+        LinkingService.LinkResult result = LinkingService.travelWithFooting(player, ageTarget);
         if (result != LinkingService.LinkResult.SUCCESS) {
             player.displayClientMessage(Component.translatable("message.rivencraft.descriptive_book.unsafe"), true);
             return false;