--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/style-engine/class-wp-style-engine-processor.php	Fri Sep 05 18:40:08 2025 +0200
@@ -0,0 +1,181 @@
+<?php
+/**
+ * Style Engine: WP_Style_Engine_Processor class
+ *
+ * @package WordPress
+ * @subpackage StyleEngine
+ * @since 6.1.0
+ */
+
+/**
+ * Core class used to compile styles from stores or collection of CSS rules.
+ *
+ * @since 6.1.0
+ */
+#[AllowDynamicProperties]
+class WP_Style_Engine_Processor {
+
+	/**
+	 * A collection of Style Engine Store objects.
+	 *
+	 * @since 6.1.0
+	 * @var WP_Style_Engine_CSS_Rules_Store[]
+	 */
+	protected $stores = array();
+
+	/**
+	 * The set of CSS rules that this processor will work on.
+	 *
+	 * @since 6.1.0
+	 * @var WP_Style_Engine_CSS_Rule[]
+	 */
+	protected $css_rules = array();
+
+	/**
+	 * Adds a store to the processor.
+	 *
+	 * @since 6.1.0
+	 *
+	 * @param WP_Style_Engine_CSS_Rules_Store $store The store to add.
+	 * @return WP_Style_Engine_Processor Returns the object to allow chaining methods.
+	 */
+	public function add_store( $store ) {
+		if ( ! $store instanceof WP_Style_Engine_CSS_Rules_Store ) {
+			_doing_it_wrong(
+				__METHOD__,
+				__( '$store must be an instance of WP_Style_Engine_CSS_Rules_Store' ),
+				'6.1.0'
+			);
+			return $this;
+		}
+
+		$this->stores[ $store->get_name() ] = $store;
+
+		return $this;
+	}
+
+	/**
+	 * Adds rules to be processed.
+	 *
+	 * @since 6.1.0
+	 * @since 6.6.0 Added support for rules_group.
+	 *
+	 * @param WP_Style_Engine_CSS_Rule|WP_Style_Engine_CSS_Rule[] $css_rules A single, or an array of,
+	 *                                                                       WP_Style_Engine_CSS_Rule objects
+	 *                                                                       from a store or otherwise.
+	 * @return WP_Style_Engine_Processor Returns the object to allow chaining methods.
+	 */
+	public function add_rules( $css_rules ) {
+		if ( ! is_array( $css_rules ) ) {
+			$css_rules = array( $css_rules );
+		}
+
+		foreach ( $css_rules as $rule ) {
+			$selector    = $rule->get_selector();
+			$rules_group = $rule->get_rules_group();
+
+			/**
+			 * If there is a rules_group and it already exists in the css_rules array,
+			 * add the rule to it.
+			 * Otherwise, create a new entry for the rules_group.
+			 */
+			if ( ! empty( $rules_group ) ) {
+				if ( isset( $this->css_rules[ "$rules_group $selector" ] ) ) {
+					$this->css_rules[ "$rules_group $selector" ]->add_declarations( $rule->get_declarations() );
+					continue;
+				}
+				$this->css_rules[ "$rules_group $selector" ] = $rule;
+				continue;
+			}
+
+			// If the selector already exists, add the declarations to it.
+			if ( isset( $this->css_rules[ $selector ] ) ) {
+				$this->css_rules[ $selector ]->add_declarations( $rule->get_declarations() );
+				continue;
+			}
+			$this->css_rules[ $rule->get_selector() ] = $rule;
+		}
+
+		return $this;
+	}
+
+	/**
+	 * Gets the CSS rules as a string.
+	 *
+	 * @since 6.1.0
+	 * @since 6.4.0 The Optimization is no longer the default.
+	 *
+	 * @param array $options   {
+	 *     Optional. An array of options. Default empty array.
+	 *
+	 *     @type bool $optimize Whether to optimize the CSS output, e.g. combine rules.
+	 *                          Default false.
+	 *     @type bool $prettify Whether to add new lines and indents to output.
+	 *                          Defaults to whether the `SCRIPT_DEBUG` constant is defined.
+	 * }
+	 * @return string The computed CSS.
+	 */
+	public function get_css( $options = array() ) {
+		$defaults = array(
+			'optimize' => false,
+			'prettify' => defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG,
+		);
+		$options  = wp_parse_args( $options, $defaults );
+
+		// If we have stores, get the rules from them.
+		foreach ( $this->stores as $store ) {
+			$this->add_rules( $store->get_all_rules() );
+		}
+
+		// Combine CSS selectors that have identical declarations.
+		if ( true === $options['optimize'] ) {
+			$this->combine_rules_selectors();
+		}
+
+		// Build the CSS.
+		$css = '';
+		foreach ( $this->css_rules as $rule ) {
+			// See class WP_Style_Engine_CSS_Rule for the get_css method.
+			$css .= $rule->get_css( $options['prettify'] );
+			$css .= $options['prettify'] ? "\n" : '';
+		}
+		return $css;
+	}
+
+	/**
+	 * Combines selectors from the rules store when they have the same styles.
+	 *
+	 * @since 6.1.0
+	 */
+	private function combine_rules_selectors() {
+		// Build an array of selectors along with the JSON-ified styles to make comparisons easier.
+		$selectors_json = array();
+		foreach ( $this->css_rules as $rule ) {
+			$declarations = $rule->get_declarations()->get_declarations();
+			ksort( $declarations );
+			$selectors_json[ $rule->get_selector() ] = wp_json_encode( $declarations );
+		}
+
+		// Combine selectors that have the same styles.
+		foreach ( $selectors_json as $selector => $json ) {
+			// Get selectors that use the same styles.
+			$duplicates = array_keys( $selectors_json, $json, true );
+			// Skip if there are no duplicates.
+			if ( 1 >= count( $duplicates ) ) {
+				continue;
+			}
+
+			$declarations = $this->css_rules[ $selector ]->get_declarations();
+
+			foreach ( $duplicates as $key ) {
+				// Unset the duplicates from the $selectors_json array to avoid looping through them as well.
+				unset( $selectors_json[ $key ] );
+				// Remove the rules from the rules collection.
+				unset( $this->css_rules[ $key ] );
+			}
+			// Create a new rule with the combined selectors.
+			$duplicate_selectors                     = implode( ',', $duplicates );
+			$this->css_rules[ $duplicate_selectors ] = new WP_Style_Engine_CSS_Rule( $duplicate_selectors, $declarations );
+		}
+	}
+}