Add Cast for JSON

README.md

@@ -89,7 +89,6 @@ Please note that the following are not required, but are strongly recommended fo
 ## Unsupported features
 
 - STRUCT data types
-- Inserting/Updating JSON data types
 
 ## Limitations
 
@@ -235,6 +234,18 @@ When fetching rows, the library coverts the following column types
 
 Note that if you execute a query without QueryBuilder, it will not have these conversions.
 
+### JSON Type
+
+In order to use JSON columns, use the provided Cast on your model as below
+
+```php
+use Colopl\Spanner\Casts\SpannerJson;
+
+protected $casts = [
+    'json_column_name' => SpannerJson::class,
+]
+```
+
 
 ### Partitioned DML
 You can run partitioned DML as below.

src/Casts/SpannerJson.php

@@ -0,0 +1,55 @@
+<?php
+
+namespace Colopl\Spanner\Casts;
+
+use Google\Cloud\Spanner\PgJsonb;
+use Google\Cloud\Spanner\V1\TypeAnnotationCode;
+use Illuminate\Contracts\Database\Eloquent\CastsAttributes;
+use Illuminate\Database\Eloquent\Model;
+use JsonSerializable;
+
+/** 
+ * @implements CastsAttributes<mixed, mixed> 
+ * */
+class SpannerJson implements CastsAttributes
+{
+    public function get(Model $model, string $key, mixed $value, array $attributes)
+    {
+        if ($value === null) {
+            return null;
+        }
+
+        if (is_array($value)) {
+            return $value;
+        }
+
+        if (!is_string($value)) {
+            throw new \InvalidArgumentException('The given value must be an array, string or null.');
+        }
+
+        return json_decode($value, true);
+    }
+
+    public function set(Model $model, string $key, mixed $value, array $attributes)
+    {
+        if (
+            !is_array($value) && 
+            !$value instanceof JsonSerializable && 
+            $value !== null && 
+            !is_string($value)
+        ) {
+            throw new \InvalidArgumentException('The given value must be an array, JsonSerializable, string or null.');
+        }
+
+        return [$key => new SpannerJsonType($value)];
+    }
+}
+
+
+class SpannerJsonType extends PgJsonb
+{
+    public function typeAnnotation(): int
+    {
+        return TypeAnnotationCode::TYPE_ANNOTATION_CODE_UNSPECIFIED;
+    }
+}