2 files changed, 68 insertions, 0 deletions
diff --git a/src/RegionException.php b/src/RegionException.php
new file mode 100644
index 0000000..f33adec
--- /dev/null
+++ b/src/RegionException.php
@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Zhineng\Region;
+
+final class RegionException extends \Exception
+{
+    //
+}
diff --git a/src/RegionManager.php b/src/RegionManager.php
new file mode 100644
index 0000000..9b8b969
--- /dev/null
+++ b/src/RegionManager.php
@@ -0,0 +1,58 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Zhineng\Region;
+
+final class RegionManager
+{
+    /**
+     * @param  array<string, string>  $codeToName
+     * @param  array<string, int[]>  $relationships
+     * @param  array<int, int[]>  $topLevels
+     */
+    public function __construct(
+        private array $codeToName,
+        private array $relationships,
+        private array $topLevels
+    ) {
+        //
+    }
+
+    public static function createFromBuiltIn(): static
+    {
+        return new self(
+            require __DIR__.'/../resources/code-to-name.php',
+            require __DIR__.'/../resources/relationships.php',
+            require __DIR__.'/../resources/top-levels.php'
+        );
+    }
+
+    public function getName(int $code): string
+    {
+        return $this->codeToName[$this->groupKey($code)]
+            ?? throw new RegionException('The region code does not exist.');
+    }
+
+    /**
+     * @return int[]
+     */
+    public function getTopLevelNodes(): array
+    {
+        return $this->topLevels;
+    }
+
+    /**
+     * @return int[]
+     */
+    public function getNodes(int $code): array
+    {
+        return $this->relationships[$this->groupKey($code)]
+            ?? throw new RegionException('Could not find any nodes under the region code.');
+    }
+
+    private function groupKey(int $code): string
+    {
+        return '_'.$code;
+    }
+}