diff -r 48c4eec2b7e6 -r 8c2e4d02f4ef wp/wp-includes/class-wp-speculation-rules.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/class-wp-speculation-rules.php	Fri Sep 05 18:52:52 2025 +0200
@@ -0,0 +1,293 @@
+<?php
+/**
+ * Class 'WP_Speculation_Rules'.
+ *
+ * @package WordPress
+ * @subpackage Speculative Loading
+ * @since 6.8.0
+ */
+
+/**
+ * Class representing a set of speculation rules.
+ *
+ * @since 6.8.0
+ * @access private
+ */
+final class WP_Speculation_Rules implements JsonSerializable {
+
+	/**
+	 * Stored rules, as a map of `$mode => $rules` pairs.
+	 *
+	 * Every `$rules` value is a map of `$id => $rule` pairs.
+	 *
+	 * @since 6.8.0
+	 * @var array<string, array<string, mixed>>
+	 */
+	private $rules_by_mode = array();
+
+	/**
+	 * The allowed speculation rules modes as a map, used for validation.
+	 *
+	 * @since 6.8.0
+	 * @var array<string, bool>
+	 */
+	private static $mode_allowlist = array(
+		'prefetch'  => true,
+		'prerender' => true,
+	);
+
+	/**
+	 * The allowed speculation rules eagerness levels as a map, used for validation.
+	 *
+	 * @since 6.8.0
+	 * @var array<string, bool>
+	 */
+	private static $eagerness_allowlist = array(
+		'immediate'    => true,
+		'eager'        => true,
+		'moderate'     => true,
+		'conservative' => true,
+	);
+
+	/**
+	 * The allowed speculation rules sources as a map, used for validation.
+	 *
+	 * @since 6.8.0
+	 * @var array<string, bool>
+	 */
+	private static $source_allowlist = array(
+		'list'     => true,
+		'document' => true,
+	);
+
+	/**
+	 * Adds a speculation rule to the speculation rules to consider.
+	 *
+	 * @since 6.8.0
+	 *
+	 * @param string               $mode Speculative loading mode. Either 'prefetch' or 'prerender'.
+	 * @param string               $id   Unique string identifier for the speculation rule.
+	 * @param array<string, mixed> $rule Associative array of rule arguments.
+	 * @return bool True on success, false if invalid parameters are provided.
+	 */
+	public function add_rule( string $mode, string $id, array $rule ): bool {
+		if ( ! self::is_valid_mode( $mode ) ) {
+			_doing_it_wrong(
+				__METHOD__,
+				sprintf(
+					/* translators: %s: invalid mode value */
+					__( 'The value "%s" is not a valid speculation rules mode.' ),
+					esc_html( $mode )
+				),
+				'6.8.0'
+			);
+			return false;
+		}
+
+		if ( ! $this->is_valid_id( $id ) ) {
+			_doing_it_wrong(
+				__METHOD__,
+				sprintf(
+					/* translators: %s: invalid ID value */
+					__( 'The value "%s" is not a valid ID for a speculation rule.' ),
+					esc_html( $id )
+				),
+				'6.8.0'
+			);
+			return false;
+		}
+
+		if ( $this->has_rule( $mode, $id ) ) {
+			_doing_it_wrong(
+				__METHOD__,
+				sprintf(
+					/* translators: %s: invalid ID value */
+					__( 'A speculation rule with ID "%s" already exists.' ),
+					esc_html( $id )
+				),
+				'6.8.0'
+			);
+			return false;
+		}
+
+		/*
+		 * Perform some basic speculation rule validation.
+		 * Every rule must have either a 'where' key or a 'urls' key, but not both.
+		 * The presence of a 'where' key implies a 'source' of 'document', while the presence of a 'urls' key implies
+		 * a 'source' of 'list'.
+		 */
+		if (
+			( ! isset( $rule['where'] ) && ! isset( $rule['urls'] ) ) ||
+			( isset( $rule['where'] ) && isset( $rule['urls'] ) )
+		) {
+			_doing_it_wrong(
+				__METHOD__,
+				sprintf(
+					/* translators: 1: allowed key, 2: alternative allowed key */
+					__( 'A speculation rule must include either a "%1$s" key or a "%2$s" key, but not both.' ),
+					'where',
+					'urls'
+				),
+				'6.8.0'
+			);
+			return false;
+		}
+		if ( isset( $rule['source'] ) ) {
+			if ( ! self::is_valid_source( $rule['source'] ) ) {
+				_doing_it_wrong(
+					__METHOD__,
+					sprintf(
+						/* translators: %s: invalid source value */
+						__( 'The value "%s" is not a valid source for a speculation rule.' ),
+						esc_html( $rule['source'] )
+					),
+					'6.8.0'
+				);
+				return false;
+			}
+
+			if ( 'list' === $rule['source'] && isset( $rule['where'] ) ) {
+				_doing_it_wrong(
+					__METHOD__,
+					sprintf(
+						/* translators: 1: source value, 2: forbidden key */
+						__( 'A speculation rule of source "%1$s" must not include a "%2$s" key.' ),
+						'list',
+						'where'
+					),
+					'6.8.0'
+				);
+				return false;
+			}
+
+			if ( 'document' === $rule['source'] && isset( $rule['urls'] ) ) {
+				_doing_it_wrong(
+					__METHOD__,
+					sprintf(
+						/* translators: 1: source value, 2: forbidden key */
+						__( 'A speculation rule of source "%1$s" must not include a "%2$s" key.' ),
+						'document',
+						'urls'
+					),
+					'6.8.0'
+				);
+				return false;
+			}
+		}
+
+		// If there is an 'eagerness' key specified, make sure it's valid.
+		if ( isset( $rule['eagerness'] ) ) {
+			if ( ! self::is_valid_eagerness( $rule['eagerness'] ) ) {
+				_doing_it_wrong(
+					__METHOD__,
+					sprintf(
+						/* translators: %s: invalid eagerness value */
+						__( 'The value "%s" is not a valid eagerness for a speculation rule.' ),
+						esc_html( $rule['eagerness'] )
+					),
+					'6.8.0'
+				);
+				return false;
+			}
+
+			if ( isset( $rule['where'] ) && 'immediate' === $rule['eagerness'] ) {
+				_doing_it_wrong(
+					__METHOD__,
+					sprintf(
+						/* translators: %s: forbidden eagerness value */
+						__( 'The eagerness value "%s" is forbidden for document-level speculation rules.' ),
+						'immediate'
+					),
+					'6.8.0'
+				);
+				return false;
+			}
+		}
+
+		if ( ! isset( $this->rules_by_mode[ $mode ] ) ) {
+			$this->rules_by_mode[ $mode ] = array();
+		}
+
+		$this->rules_by_mode[ $mode ][ $id ] = $rule;
+		return true;
+	}
+
+	/**
+	 * Checks whether a speculation rule for the given mode and ID already exists.
+	 *
+	 * @since 6.8.0
+	 *
+	 * @param string $mode Speculative loading mode. Either 'prefetch' or 'prerender'.
+	 * @param string $id   Unique string identifier for the speculation rule.
+	 * @return bool True if the rule already exists, false otherwise.
+	 */
+	public function has_rule( string $mode, string $id ): bool {
+		return isset( $this->rules_by_mode[ $mode ][ $id ] );
+	}
+
+	/**
+	 * Returns the speculation rules data ready to be JSON-encoded.
+	 *
+	 * @since 6.8.0
+	 *
+	 * @return array<string, array<string, mixed>> Speculation rules data.
+	 */
+	#[ReturnTypeWillChange]
+	public function jsonSerialize() {
+		// Strip the IDs for JSON output, since they are not relevant for the Speculation Rules API.
+		return array_map(
+			static function ( array $rules ) {
+				return array_values( $rules );
+			},
+			array_filter( $this->rules_by_mode )
+		);
+	}
+
+	/**
+	 * Checks whether the given ID is valid.
+	 *
+	 * @since 6.8.0
+	 *
+	 * @param string $id Unique string identifier for the speculation rule.
+	 * @return bool True if the ID is valid, false otherwise.
+	 */
+	private function is_valid_id( string $id ): bool {
+		return (bool) preg_match( '/^[a-z][a-z0-9_-]+$/', $id );
+	}
+
+	/**
+	 * Checks whether the given speculation rules mode is valid.
+	 *
+	 * @since 6.8.0
+	 *
+	 * @param string $mode Speculation rules mode.
+	 * @return bool True if valid, false otherwise.
+	 */
+	public static function is_valid_mode( string $mode ): bool {
+		return isset( self::$mode_allowlist[ $mode ] );
+	}
+
+	/**
+	 * Checks whether the given speculation rules eagerness is valid.
+	 *
+	 * @since 6.8.0
+	 *
+	 * @param string $eagerness Speculation rules eagerness.
+	 * @return bool True if valid, false otherwise.
+	 */
+	public static function is_valid_eagerness( string $eagerness ): bool {
+		return isset( self::$eagerness_allowlist[ $eagerness ] );
+	}
+
+	/**
+	 * Checks whether the given speculation rules source is valid.
+	 *
+	 * @since 6.8.0
+	 *
+	 * @param string $source Speculation rules source.
+	 * @return bool True if valid, false otherwise.
+	 */
+	public static function is_valid_source( string $source ): bool {
+		return isset( self::$source_allowlist[ $source ] );
+	}
+}