improve how world spawn is located

TerraForgedCore/src/main/java/com/terraforged/core/world/rivermap/river/River.java

@@ -163,9 +163,8 @@ public class River extends TerrainPopulator {
         // lerp the position's height to the riverbank height
         if (cell.value > bankHeight) {
             cell.value = NoiseUtil.lerp(cell.value, bankHeight, valleyAlpha);
-            return true;
         }
-        return false;
+        return true;
     }
 
     private boolean carveBanks(Cell<Terrain> cell, float banksAlpha, float bedHeight) {

TerraForgedMod/src/main/java/com/terraforged/mod/biome/provider/BiomeProvider.java

@@ -63,10 +63,22 @@ public class BiomeProvider extends AbstractBiomeProvider {
         this.modifierManager = SetupHooks.setup(new BiomeModifierManager(context, biomeMap), context.copy());
     }
 
+    public TerraContext getContext() {
+        return context;
+    }
+
+    public void lookupPos(int x, int z, Cell<Terrain> cell) {
+        worldLookup.applyCell(cell, x, z);
+    }
+
     public Cell<Terrain> lookupPos(int x, int z) {
         return worldLookup.getCell(x, z);
     }
 
+    public boolean canSpawnAt(Cell<Terrain> cell) {
+        return cell.tag != context.terrain.ocean && cell.tag != context.terrain.deepOcean && cell.value > context.levels.ground;
+    }
+
     @Override
     public Biome getNoiseBiome(int x, int y, int z) {
         x = (x << 2);

TerraForgedMod/src/main/java/com/terraforged/mod/biome/spawn/SpawnHandler.java

@@ -0,0 +1,43 @@
+package com.terraforged.mod.biome.spawn;
+
+import com.terraforged.mod.Log;
+import com.terraforged.mod.biome.provider.BiomeProvider;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.world.gen.feature.ConfiguredFeature;
+import net.minecraft.world.gen.feature.Feature;
+import net.minecraft.world.gen.feature.IFeatureConfig;
+import net.minecraft.world.server.ServerWorld;
+import net.minecraftforge.event.world.WorldEvent;
+import net.minecraftforge.eventbus.api.SubscribeEvent;
+import net.minecraftforge.fml.common.Mod;
+
+@Mod.EventBusSubscriber(bus = Mod.EventBusSubscriber.Bus.FORGE)
+public class SpawnHandler {
+
+    @SubscribeEvent
+    public static void createSpawn(WorldEvent.CreateSpawnPosition event) {
+        if (event.getWorld() instanceof ServerWorld) {
+            ServerWorld world =(ServerWorld) event.getWorld();
+            if (world.getChunkProvider().getChunkGenerator().getBiomeProvider() instanceof BiomeProvider) {
+                Log.info("Searching for world spawn position");
+                BiomeProvider provider = (BiomeProvider) world.getChunkProvider().getChunkGenerator().getBiomeProvider();
+                SpawnSearch search = new SpawnSearch(BlockPos.ZERO, provider);
+                BlockPos spawn = search.get();
+
+                Log.info("Setting world spawn: {}", spawn);
+                event.setCanceled(true);
+                event.getWorld().getWorldInfo().setSpawn(spawn);
+
+                if (event.getSettings().isBonusChestEnabled()) {
+                    Log.info("Generating bonus chest");
+                    createBonusChest(world, spawn);
+                }
+            }
+        }
+    }
+
+    private static void createBonusChest(ServerWorld world, BlockPos pos) {
+        ConfiguredFeature<?, ?> chest = Feature.BONUS_CHEST.withConfiguration(IFeatureConfig.NO_FEATURE_CONFIG);
+        chest.place(world, world.getChunkProvider().getChunkGenerator(), world.rand, pos);
+    }
+}

TerraForgedMod/src/main/java/com/terraforged/mod/biome/spawn/SpawnSearch.java

@@ -0,0 +1,43 @@
+package com.terraforged.mod.biome.spawn;
+
+import com.terraforged.core.cell.Cell;
+import com.terraforged.core.world.terrain.Terrain;
+import com.terraforged.mod.Log;
+import com.terraforged.mod.biome.provider.BiomeProvider;
+import com.terraforged.mod.command.search.Search;
+import net.minecraft.util.math.BlockPos;
+
+public class SpawnSearch extends Search {
+
+    private final BiomeProvider biomeProvider;
+    private final Cell<Terrain> cell = new Cell<>();
+
+    public SpawnSearch(BlockPos center, BiomeProvider biomeProvider) {
+        super(center, 0, 2048);
+        this.biomeProvider = biomeProvider;
+    }
+
+    @Override
+    public int getSpacing() {
+        return 64;
+    }
+
+    @Override
+    public boolean test(BlockPos pos) {
+        biomeProvider.lookupPos(pos.getX(), pos.getZ(), cell);
+        return biomeProvider.canSpawnAt(cell);
+    }
+
+    @Override
+    protected BlockPos success(BlockPos.Mutable pos) {
+        pos.setY(biomeProvider.getContext().levels.scale(cell.value));
+        Log.info("Found valid spawn position: {}", pos);
+        return super.success(pos);
+    }
+
+    @Override
+    protected BlockPos fail(BlockPos pos) {
+        Log.info("Unable to find valid spawn position, defaulting x=0, z=0");
+        return new BlockPos(0, biomeProvider.getContext().levels.groundLevel, 0);
+    }
+}

TerraForgedMod/src/main/java/com/terraforged/mod/command/arg/TerrainArgType.java

@@ -41,7 +41,6 @@ import net.minecraft.command.arguments.IArgumentSerializer;
 import net.minecraft.network.PacketBuffer;
 import net.minecraft.util.text.StringTextComponent;
 
-import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import java.util.stream.Collectors;

TerraForgedMod/src/main/java/com/terraforged/mod/command/search/Search.java

@@ -38,6 +38,14 @@ public abstract class Search implements Supplier<BlockPos> {
         return 16;
     }
 
+    protected BlockPos success(BlockPos.Mutable pos) {
+        return pos.toImmutable();
+    }
+
+    protected BlockPos fail(BlockPos pos) {
+        return pos;
+    }
+
     @Override
     public BlockPos get() {
         int radius = maxRadius;
@@ -60,7 +68,7 @@ public abstract class Search implements Supplier<BlockPos> {
                 pos.setPos(center.getX() + (x * getSpacing()), center.getY(), center.getZ() + (z * getSpacing()));
                 if (center.distanceSq(pos) >= minRadius2) {
                     if (test(pos)) {
-                        return pos.toImmutable();
+                        return success(pos);
                     }
                 }
             }
@@ -75,7 +83,7 @@ public abstract class Search implements Supplier<BlockPos> {
             z += dz;
         }
 
-        return BlockPos.ZERO;
+        return fail(BlockPos.ZERO);
     }
 
     public abstract boolean test(BlockPos pos);