1 files changed, 62 insertions, 0 deletions
diff --git a/src/Structure.php b/src/Structure.php
new file mode 100644
index 0000000..307397d
--- /dev/null
+++ b/src/Structure.php
@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Zhineng\Snowflake;
+
+final class Structure
+{
+    /**
+     * The ID components.
+     *
+     * @var \Zhineng\Snowflake\Component[]
+     */
+    private array $fields = [];
+
+    /**
+     * The current bit offset.
+     */
+    private int $currentOffset = 0;
+
+    /**
+     * The number of sequence fields added.
+     */
+    private int $sequenceCount = 0;
+
+    /**
+     * Add a field to the structure.
+     */
+    public function add(Component $field): self
+    {
+        if ($field instanceof Sequence && ++$this->sequenceCount > 1) {
+            throw new \LogicException('Only one sequence field is allowed in a structure.');
+        }
+
+        if ($this->currentOffset + $field->bits() > 63) {
+            throw new \OverflowException('Total structure size cannot exceed 63 bits.');
+        }
+
+        $this->fields[] = $field->setOffset($this->currentOffset);
+        $this->currentOffset += $field->bits();
+
+        return $this;
+    }
+
+    /**
+     * The ID components.
+     *
+     * @return \Zhineng\Snowflake\Component[]
+     */
+    public function components(): array
+    {
+        return $this->fields;
+    }
+
+    /**
+     * The total size in bits.
+     */
+    public function size(): int
+    {
+        return $this->currentOffset;
+    }
+}