Further refactors to prepare for y=-64 lower limit

src/world/format/Chunk.php

@@ -131,17 +131,17 @@ class Chunk{
 	 * @param int $x 0-15
 	 * @param int $z 0-15
 	 *
-	 * @return int 0-255, or -1 if there are no blocks in the column
+	 * @return int|null 0-255, or null if there are no blocks in the column
 	 */
-	public function getHighestBlockAt(int $x, int $z) : int{
+	public function getHighestBlockAt(int $x, int $z) : ?int{
 		for($y = $this->subChunks->count() - 1; $y >= 0; --$y){
-			$height = $this->getSubChunk($y)->getHighestBlockAt($x, $z) | ($y << 4);
-			if($height !== -1){
-				return $height;
+			$height = $this->getSubChunk($y)->getHighestBlockAt($x, $z);
+			if($height !== null){
+				return $height | ($y << 4);
 			}
 		}
 
-		return -1;
+		return null;
 	}
 
 	/**

src/world/format/SubChunk.php

@@ -96,9 +96,9 @@ class SubChunk{
 		return $this->blockLayers;
 	}
 
-	public function getHighestBlockAt(int $x, int $z) : int{
+	public function getHighestBlockAt(int $x, int $z) : ?int{
 		if(count($this->blockLayers) === 0){
-			return -1;
+			return null;
 		}
 		for($y = 15; $y >= 0; --$y){
 			if($this->blockLayers[0]->get($x, $y, $z) !== $this->emptyBlockId){
@@ -106,7 +106,7 @@ class SubChunk{
 			}
 		}
 
-		return -1; //highest block not in this subchunk
+		return null; //highest block not in this subchunk
 	}
 
 	public function getBlockSkyLightArray() : LightArray{

src/world/format/io/WorldProvider.php

@@ -36,10 +36,15 @@ interface WorldProvider{
 	 */
 	public function __construct(string $path);
 
+	/**
+	 * Returns the lowest buildable Y coordinate of this world
+	 */
+	public function getWorldMinY() : int;
+
 	/**
 	 * Gets the build height limit of this world
 	 */
-	public function getWorldHeight() : int;
+	public function getWorldMaxY() : int;
 
 	public function getPath() : string;
 

src/world/format/io/leveldb/LevelDB.php

@@ -132,7 +132,11 @@ class LevelDB extends BaseWorldProvider implements WritableWorldProvider{
 		return new BedrockWorldData($this->getPath() . DIRECTORY_SEPARATOR . "level.dat");
 	}
 
-	public function getWorldHeight() : int{
+	public function getWorldMinY() : int{
+		return 0;
+	}
+
+	public function getWorldMaxY() : int{
 		return 256;
 	}
 

src/world/format/io/region/Anvil.php

@@ -51,7 +51,11 @@ class Anvil extends RegionWorldProvider{
 		return 19133;
 	}
 
-	public function getWorldHeight() : int{
+	public function getWorldMinY() : int{
+		return 0;
+	}
+
+	public function getWorldMaxY() : int{
 		//TODO: add world height options
 		return 256;
 	}

src/world/format/io/region/McRegion.php

@@ -106,7 +106,11 @@ class McRegion extends RegionWorldProvider{
 		return 19132;
 	}
 
-	public function getWorldHeight() : int{
+	public function getWorldMinY() : int{
+		return 0;
+	}
+
+	public function getWorldMaxY() : int{
 		//TODO: add world height options
 		return 128;
 	}

src/world/format/io/region/PMAnvil.php

@@ -50,7 +50,11 @@ class PMAnvil extends RegionWorldProvider{
 		return -1; //Not a PC format, only PocketMine-MP
 	}
 
-	public function getWorldHeight() : int{
+	public function getWorldMinY() : int{
+		return 0;
+	}
+
+	public function getWorldMaxY() : int{
 		return 256;
 	}
 }