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<?php |
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/** |
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* SchemaTransformer class for converting flattened schemas to MCP-compatible object schemas. |
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* |
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* @package McpAdapter |
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*/ |
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|
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declare( strict_types=1 ); |
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|
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namespace WP\MCP\Domain\Utils; |
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|
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/** |
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* SchemaTransformer class. |
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* |
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* This class transforms flattened JSON schemas (e.g., type: string, number, boolean, array) |
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* into MCP-compatible object schemas. MCP requires all tool input schemas to be of type "object". |
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* |
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* @package McpAdapter |
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*/ |
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class SchemaTransformer { |
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/** |
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* Transform a schema to MCP-compatible object format. |
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* |
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* If the schema is already an object type, it is returned unchanged. |
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* If the schema is a flattened type (string, number, boolean, array), it is |
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* wrapped in an object structure with a single property (defaults to "input"). |
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* |
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* @param array<string,mixed>|null $schema The JSON schema to transform. |
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* @param string $wrapper_key Property name to use when wrapping non-object schemas. |
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* |
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* @return array<string,mixed> Array containing 'schema', 'was_transformed' (bool), and 'wrapper_property' when transformed. |
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*/ |
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public static function transform_to_object_schema( ?array $schema, string $wrapper_key = 'input' ): array { |
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// Convert any objects to arrays and strip empty properties. |
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// Abilities may contain objects from JSON decode cycles. Empty properties must be removed |
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// because MCP expects properties to be a JSON object, and PHP serializes empty arrays as []. |
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$schema = self::normalize( $schema ); |
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|
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// Handle null or empty schema - return minimal valid MCP object schema. |
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if ( empty( $schema ) ) { |
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return array( |
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'schema' => array( |
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'type' => 'object', |
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), |
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'was_transformed' => false, |
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'wrapper_property' => null, |
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); |
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} |
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|
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// If no type is specified, add 'object' type since MCP requires it. |
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if ( ! isset( $schema['type'] ) ) { |
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$schema['type'] = 'object'; |
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|
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return array( |
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'schema' => $schema, |
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'was_transformed' => false, |
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'wrapper_property' => null, |
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); |
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} |
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|
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// If already an object type, return as-is |
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if ( 'object' === $schema['type'] ) { |
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return array( |
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'schema' => $schema, |
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'was_transformed' => false, |
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'wrapper_property' => null, |
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); |
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} |
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|
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// Transform flattened schema to object format |
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return array( |
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'schema' => self::wrap_in_object( $schema, $wrapper_key ), |
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'was_transformed' => true, |
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'wrapper_property' => $wrapper_key, |
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); |
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} |
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|
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/** |
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* Wrap a flattened schema in an object structure. |
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* |
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* Creates an object schema with a single property (named by $wrapper_key) that |
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* contains the original flattened schema. |
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* |
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* @param array<string,mixed> $schema The flattened schema to wrap. |
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* @param string $wrapper_key Property name to wrap the value under. |
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* |
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* @return array<string,mixed> The wrapped object schema. |
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*/ |
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private static function wrap_in_object( array $schema, string $wrapper_key ): array { |
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return array( |
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'type' => 'object', |
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'properties' => array( |
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$wrapper_key => $schema, |
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), |
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'required' => array( $wrapper_key ), |
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); |
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} |
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|
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/** |
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* Convert objects to arrays and strip empty properties. |
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* |
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* @param array<string,mixed>|null $schema The schema to normalize. |
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* |
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* @return array<string,mixed>|null The normalized schema. |
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*/ |
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private static function normalize( ?array $schema ): ?array { |
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if ( null === $schema ) { |
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return null; |
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} |
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|
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$schema = self::convert_objects_to_arrays( $schema ); |
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|
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if ( array_key_exists( 'properties', $schema ) && is_array( $schema['properties'] ) && empty( $schema['properties'] ) ) { |
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unset( $schema['properties'] ); |
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} |
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|
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return $schema; |
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} |
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|
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/** |
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* Recursively convert objects to arrays. |
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* |
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* @param mixed $value The value to convert. |
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* |
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* @return mixed The converted value. |
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*/ |
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private static function convert_objects_to_arrays( $value ) { |
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if ( is_object( $value ) ) { |
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$value = (array) $value; |
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} |
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|
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if ( is_array( $value ) ) { |
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return array_map( array( self::class, 'convert_objects_to_arrays' ), $value ); |
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} |
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|
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return $value; |
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} |
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} |
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|
