Further refactors to prepare for y=-64 lower limit

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;
 	}
 }