1 files changed, 69 insertions, 0 deletions
diff --git a/src/Manager.php b/src/Manager.php
new file mode 100644
index 0000000..215ec50
--- /dev/null
+++ b/src/Manager.php
@@ -0,0 +1,69 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Zhineng\Snowflake;
+
+final class Manager
+{
+    /**
+     * The ID format.
+     */
+    private Structure $structure;
+
+    /**
+     * The last value except sequence.
+     */
+    private int $lastCombination = 0;
+
+    /**
+     * Set the ID format.
+     */
+    public function structureUsing(Structure $structure): self
+    {
+        $this->structure = $structure;
+        $this->lastCombination = 0;
+
+        return $this;
+    }
+
+    /**
+     * Generate the next Snowflake ID.
+     */
+    public function nextId(): int
+    {
+        if (! isset($this->structure)) {
+            throw new \RuntimeException('ID structure is not defined.');
+        }
+
+        $id = 0;
+        $sequence = null;
+
+        foreach ($this->structure->components() as $field) {
+            // Defer sequence until after detecting other-field changes
+            // so we can reset it if needed.
+            if ($field instanceof Sequence) {
+                $sequence = $field;
+
+                continue;
+            }
+
+            $current = $field->maxValue() & $field->value();
+            $id |= $current << $field->offset();
+        }
+
+        // The ID variable now holds the combination of all fields except
+        // sequence. Reset the sequence field if any other field has changed.
+        if ($this->lastCombination !== $id) {
+            $sequence?->reset();
+        }
+
+        $this->lastCombination = $id;
+
+        if ($sequence instanceof Sequence) {
+            $id |= ($sequence->maxValue() & $sequence->value()) << $sequence->offset();
+        }
+
+        return $id;
+    }
+}