<?php
/**
 * Abilities API: core functions for registering and managing abilities.
 *
 * The Abilities API provides a unified, extensible framework for registering
 * and executing discrete capabilities within WordPress. An "ability" is a
 * self-contained unit of functionality with defined inputs, outputs, permissions,
 * and execution logic.
 *
 * ## Overview
 *
 * The Abilities API enables developers to:
 *
 *  - Register custom abilities with standardized interfaces.
 *  - Define permission checks and execution callbacks.
 *  - Organize abilities into logical categories.
 *  - Validate inputs and outputs using JSON Schema.
 *  - Expose abilities to clients such as the REST API.
 *
 * ## Working with Abilities
 *
 * Abilities must be registered on the `wp_abilities_api_init` action hook.
 * Attempting to register an ability outside of this hook will fail and
 * trigger a `_doing_it_wrong()` notice.
 *
 * Example:
 *
 *     function my_plugin_register_abilities(): void {
 *         wp_register_ability(
 *             'my-plugin/export-users',
 *             array(
 *                 'label'                 => __( 'Export Users', 'my-plugin' ),
 *                 'description'           => __( 'Exports user data to CSV format.', 'my-plugin' ),
 *                 'category'              => 'data-export',
 *                 'execute_callback'      => 'my_plugin_export_users',
 *                 'required_capabilities' => array( 'export' ),
 *                 'input_schema'          => array(
 *                     'type'        => 'string',
 *                     'enum'        => array( 'subscriber', 'contributor', 'author', 'editor', 'administrator' ),
 *                     'description' => __( 'Limits the export to users with this role.', 'my-plugin' ),
 *                     'default'     => 'subscriber',
 *                 ),
 *                 'output_schema'         => array(
 *                     'type'        => 'string',
 *                     'description' => __( 'User data in CSV format.', 'my-plugin' ),
 *                 ),
 *                 'meta'                  => array(
 *                     'public' => true,
 *                 ),
 *             )
 *         );
 *     }
 *     add_action( 'wp_abilities_api_init', 'my_plugin_register_abilities' );
 *
 * Use a category to group related abilities and improve discoverability. The
 * `data-export` category must be registered first with `wp_register_ability_category()`
 * on `wp_abilities_api_categories_init`, or the ability registration fails.
 * Abilities that omit `category` fall back to the built-in `uncategorized` category.
 *
 * Once registered, abilities can be checked, retrieved, and managed:
 *
 *     // Checks if an ability is registered, and prints its label.
 *     if ( wp_has_ability( 'my-plugin/export-users' ) ) {
 *         $ability = wp_get_ability( 'my-plugin/export-users' );
 *
 *         echo $ability->get_label();
 *     }
 *
 *     // Gets all registered abilities.
 *     $all_abilities = wp_get_abilities();
 *
 *     // Unregisters when no longer needed.
 *     wp_unregister_ability( 'my-plugin/export-users' );
 *
 * ## Best Practices
 *
 *  - Always register abilities on the `wp_abilities_api_init` hook.
 *  - Use namespaced ability names to prevent conflicts.
 *  - Declare capabilities required for every execution in `required_capabilities`.
 *  - Check input-dependent permissions in `permission_callback`.
 *  - Provide an `input_schema` to ensure data integrity and document expected inputs.
 *  - Define an `output_schema` to describe return values and validate responses.
 *  - Return `WP_Error` objects for failures rather than throwing exceptions.
 *  - Use internationalization functions for all user-facing strings.
 *
 * @package WordPress
 * @subpackage Abilities_API
 * @since 6.9.0
 */

declare( strict_types = 1 );

/**
 * Registers a new ability using the Abilities API. It requires three steps:
 *
 *  1. Hook into the `wp_abilities_api_init` action.
 *  2. Call `wp_register_ability()` with a namespaced name and configuration.
 *  3. Provide an `execute_callback`. For permission checks, set `required_capabilities`,
 *     `permission_callback`, or both.
 *
 * Example:
 *
 *     function my_plugin_register_abilities(): void {
 *         wp_register_ability(
 *             'my-plugin/analyze-text',
 *             array(
 *                 'label'                 => __( 'Analyze Text', 'my-plugin' ),
 *                 'description'           => __( 'Performs sentiment analysis on provided text.', 'my-plugin' ),
 *                 'category'              => 'text-processing',
 *                 'input_schema'          => array(
 *                     'type'        => 'string',
 *                     'description' => __( 'The text to be analyzed.', 'my-plugin' ),
 *                     'minLength'   => 10,
 *                 ),
 *                 'output_schema'         => array(
 *                     'type'        => 'string',
 *                     'enum'        => array( 'positive', 'negative', 'neutral' ),
 *                     'description' => __( 'The sentiment result: positive, negative, or neutral.', 'my-plugin' ),
 *                 ),
 *                 'execute_callback'      => 'my_plugin_analyze_text',
 *                 'required_capabilities' => array( 'edit_posts' ),
 *                 'permission_callback'   => 'my_plugin_can_analyze_text',
 *                 'meta'                  => array(
 *                     'annotations' => array(
 *                         'readonly' => true,
 *                     ),
 *                     'public'      => true,
 *                 ),
 *             )
 *         );
 *     }
 *     add_action( 'wp_abilities_api_init', 'my_plugin_register_abilities' );
 *
 * The `text-processing` category must be registered first with
 * `wp_register_ability_category()`, or the registration fails.
 *
 * On failure, this function returns `null` and calls `_doing_it_wrong()` with the reason.
 * By default, the resulting notice is displayed when `WP_DEBUG` is enabled.
 *
 * ### Naming Conventions
 *
 * Ability names must follow these rules:
 *
 *  - Include exactly one namespace and one ability name, separated by a single slash
 *    (e.g., `my-plugin/my-ability`). Nested namespaces are not supported.
 *  - Use only lowercase alphanumeric characters, dashes, and forward slashes.
 *  - Use descriptive, action-oriented names (e.g., `process-payment`, `generate-report`).
 *
 * ### Categories
 *
 * Abilities can be organized into categories. If no category is provided, the ability is
 * assigned to the built-in `uncategorized` category. Custom categories must be registered
 * before the abilities that reference them:
 *
 *     function my_plugin_register_categories(): void {
 *         wp_register_ability_category(
 *             'text-processing',
 *             array(
 *                 'label'       => __( 'Text Processing', 'my-plugin' ),
 *                 'description' => __( 'Abilities for analyzing and transforming text.', 'my-plugin' ),
 *             )
 *         );
 *     }
 *     add_action( 'wp_abilities_api_categories_init', 'my_plugin_register_categories' );
 *
 * ### Input and Output Schemas
 *
 * Schemas define the expected structure, type, and constraints for ability inputs
 * and outputs using JSON Schema syntax. They serve two critical purposes: automatic
 * validation of data passed to and returned from abilities, and self-documenting
 * API contracts for developers.
 *
 * WordPress implements a validator based on a subset of the JSON Schema Version 4
 * specification (https://json-schema.org/specification-links.html#draft-4).
 * For details on supported JSON Schema properties and syntax, see the
 * related WordPress REST API Schema documentation:
 * https://developer.wordpress.org/rest-api/extending-the-rest-api/schema/#json-schema-basics
 *
 * An input schema is required when passing non-null input. Without one, only `null`
 * input is accepted and callbacks receive no arguments. When input is `null`, a
 * top-level `default` in the input schema is applied before validation.
 *
 * An output schema is optional. When omitted, output schema validation is skipped.
 * Define one to document and validate the result returned by the ability:
 *
 *     'input_schema'  => array(
 *         'type'        => 'string',
 *         'description' => __( 'The text to be analyzed.', 'my-plugin' ),
 *         'minLength'   => 10,
 *     ),
 *     'output_schema' => array(
 *         'type'        => 'string',
 *         'enum'        => array( 'positive', 'negative', 'neutral' ),
 *         'description' => __( 'The sentiment result: positive, negative, or neutral.', 'my-plugin' ),
 *     ),
 *
 * ### Callbacks
 *
 * #### Execute Callback
 *
 * The execute callback performs the ability's core functionality. It receives
 * the normalized, validated input when an input schema is defined, and no arguments
 * otherwise. It returns either a result or `WP_Error` on failure. Exceptions thrown
 * by execute or permission callbacks are caught and converted to a `WP_Error`.
 *
 *     function my_plugin_analyze_text( string $input ): string|WP_Error {
 *         $score = My_Plugin::perform_sentiment_analysis( $input );
 *         if ( is_wp_error( $score ) ) {
 *             return $score;
 *         }
 *         return My_Plugin::interpret_sentiment_score( $score );
 *     }
 *
 * #### Required Capabilities and Permission Callback
 *
 * Declare only the minimum capabilities required for every execution in
 * `required_capabilities`. Check additional capabilities that depend on the input
 * in `permission_callback`. Declaring capabilities needed only for particular inputs
 * can cause discovery to hide an ability the current user is allowed to execute
 * with other inputs.
 *
 * Each required capability is checked with `current_user_can()` before the
 * permission callback runs. The callback is optional when the list is non-empty.
 * For an ability that everyone may execute, use `__return_true` as the callback
 * with no required capabilities.
 *
 * The permission callback determines whether the ability can be executed.
 * It receives the same input as the execute callback and must return a
 * boolean or `WP_Error`. Common use cases include checking user capabilities,
 * validating API keys, or verifying system state. In the example above, every
 * execution requires `edit_posts`, and the callback only adds the check that
 * depends on the input:
 *
 *     function my_plugin_can_analyze_text( string $input ): bool|WP_Error {
 *         // Only administrators can analyze long texts.
 *         if ( mb_strlen( $input ) > 5000 ) {
 *             return current_user_can( 'manage_options' );
 *         }
 *         return true;
 *     }
 *
 * ### Execution Lifecycle
 *
 * Call `WP_Ability::execute()` to normalize and validate input, check permissions,
 * invoke the execute callback, and validate output. It returns the result or a
 * `WP_Error` on failure. Custom ability classes can override this behavior.
 *
 * Hooks run in this order, and processing stops at the first failure:
 *
 *  1. `wp_ability_invoked` action, with the raw input.
 *  2. `wp_pre_execute_ability` filter, which can short-circuit the rest of execution.
 *  3. `wp_ability_normalize_input`, `wp_ability_validate_input`, and
 *     `wp_ability_permission_result` filters. The input validation filter runs only
 *     when a non-empty input schema is defined.
 *  4. `wp_before_execute_ability` action.
 *  5. `wp_ability_execute_result` and `wp_ability_validate_output` filters.
 *  6. `wp_after_execute_ability` action.
 *
 * ### Client Exposure
 *
 * Exposure flags do not grant execution permission.
 *
 * Set the high-level `public` flag to make an ability available to clients
 * such as the REST API, MCP, or AI agents:
 *
 *     'meta' => array(
 *         'public' => true,
 *     ),
 *
 * The `public` flag seeds the default for each per-channel flag. For the REST
 * API it seeds `show_in_rest`, which lets the ability be invoked via HTTP
 * requests. Set a per-channel flag directly to override that default. For
 * example, keep a public ability out of the REST API:
 *
 *     'meta' => array(
 *         'public'       => true,
 *         'show_in_rest' => false,
 *     ),
 *
 * @since 6.9.0
 * @since 7.1.0 Added the `public` meta argument.
 * @since 7.2.0 The `category` argument is now optional and defaults to `uncategorized`.
 * @since 7.2.0 Added the `required_capabilities` argument.
 *
 * @see WP_Abilities_Registry::register()
 * @see WP_Ability::execute()
 * @see wp_register_ability_category()
 * @see wp_unregister_ability()
 *
 * @param string               $name The name of the ability. Must be a namespaced string containing
 *                                   a prefix, e.g., `my-plugin/my-ability`. Can only contain lowercase
 *                                   alphanumeric characters and dashes, with exactly one slash
 *                                   separating the namespace from the ability name.
 * @param array<string, mixed> $args {
 *     An associative array of arguments for configuring the ability.
 *
 *     @type string               $label                 Required. The human-readable label for the ability.
 *     @type string               $description           Required. A detailed description of what the ability does
 *                                                       and when it should be used.
 *     @type string               $category              Optional. The ability category slug this ability belongs to.
 *                                                       Defaults to `uncategorized`. Custom categories must be registered
 *                                                       via `wp_register_ability_category()` before registering the ability.
 *     @type callable             $execute_callback      Required. A callback function to execute when the ability is invoked.
 *                                                       Receives optional mixed input data and must return either a result
 *                                                       value (any type) or a `WP_Error` object on failure.
 *     @type callable             $permission_callback   Required unless `$required_capabilities` lists at least one capability.
 *                                                       A callback function to check permissions before execution.
 *                                                       Receives optional mixed input data (same as `execute_callback`) and
 *                                                       must return `true`/`false` for simple checks, or `WP_Error` for
 *                                                       detailed error responses. To let everyone run the ability,
 *                                                       use `__return_true` with no required capabilities. The `public`
 *                                                       meta flag doesn't affect this. It only controls where the
 *                                                       ability is shown.
 *     @type list<string>         $required_capabilities Optional. Minimum capabilities required for every execution of the
 *                                                       ability, regardless of input. Each one is checked with
 *                                                       `current_user_can()` before `permission_callback` runs.
 *                                                       Must be a list of non-empty strings. Check input-dependent
 *                                                       requirements in `permission_callback`. Default empty array.
 *     @type array<string, mixed> $input_schema          Optional. JSON Schema definition for validating the ability's input.
 *                                                       Must be a valid JSON Schema object defining the structure and
 *                                                       constraints for input data. Used for automatic validation and
 *                                                       API documentation.
 *     @type array<string, mixed> $output_schema         Optional. JSON Schema definition for the ability's output.
 *                                                       Describes the structure of successful return values from
 *                                                       `execute_callback`. Used for documentation and validation.
 *     @type array<string, mixed> $meta                  {
 *         Optional. Additional metadata for the ability.
 *
 *         @type array<string, bool|null> $annotations  {
 *             Optional. Semantic annotations describing the ability's behavioral characteristics.
 *             These annotations are hints for tooling and documentation, not enforced behavior.
 *             Each annotation defaults to null, indicating that its behavior is unspecified.
 *
 *             @type bool|null $readonly    Optional. If true, the ability does not modify its environment.
 *             @type bool|null $destructive Optional. If true, the ability may perform destructive updates to its environment.
 *                                          If false, the ability performs only additive updates.
 *             @type bool|null $idempotent  Optional. If true, calling the ability repeatedly with the same arguments
 *                                          will have no additional effect on its environment.
 *         }
 *         @type bool                     $public       Optional. Whether the ability is meant to be available to
 *                                                      clients such as the REST API, MCP, or AI agents. Seeds
 *                                                      the default for per-channel flags like `$show_in_rest`.
 *                                                      Defaults to false.
 *         @type bool                     $show_in_rest Optional. Whether to expose this ability in the REST API.
 *                                                      When true, the ability can be invoked via HTTP requests.
 *                                                      Default is the value of `$public` when set, false otherwise.
 *     }
 *     @type string               $ability_class       Optional. Fully-qualified custom class name to instantiate
 *                                                     instead of the default `WP_Ability` class. The custom class
 *                                                     must extend `WP_Ability`. Useful for advanced customization
 *                                                     of ability behavior, including callback handling. The default
 *                                                     execute and permission callback registration requirements
 *                                                     are not enforced for custom classes.
 * }
 * @return WP_Ability|null The registered ability instance on success, `null` on failure.
 *
 * @phpstan-param lowercase-string&non-falsy-string $name
 */
function wp_register_ability( string $name, array $args ): ?WP_Ability {
	if ( ! doing_action( 'wp_abilities_api_init' ) ) {
		_doing_it_wrong(
			__FUNCTION__,
			sprintf(
				/* translators: 1: wp_abilities_api_init, 2: string value of the ability name. */
				__( 'Abilities must be registered on the %1$s action. The ability %2$s was not registered.' ),
				'<code>wp_abilities_api_init</code>',
				'<code>' . esc_html( $name ) . '</code>'
			),
			'6.9.0'
		);
		return null;
	}

	$registry = WP_Abilities_Registry::get_instance();
	if ( null === $registry ) {
		return null;
	}

	return $registry->register( $name, $args );
}

/**
 * Unregisters an ability from the Abilities API.
 *
 * Removes a previously registered ability from the global registry. Use this to
 * disable abilities provided by other plugins or when an ability is no longer needed.
 *
 * Can be called at any time after the ability has been registered.
 *
 * Example:
 *
 *     if ( wp_has_ability( 'other-plugin/some-ability' ) ) {
 *         wp_unregister_ability( 'other-plugin/some-ability' );
 *     }
 *
 * @since 6.9.0
 *
 * @see WP_Abilities_Registry::unregister()
 * @see wp_register_ability()
 *
 * @param string $name The name of the ability to unregister, including namespace prefix
 *                     (e.g., 'my-plugin/my-ability').
 * @return WP_Ability|null The unregistered ability instance on success, `null` on failure.
 */
function wp_unregister_ability( string $name ): ?WP_Ability {
	$registry = WP_Abilities_Registry::get_instance();
	if ( null === $registry ) {
		return null;
	}

	return $registry->unregister( $name );
}

/**
 * Checks if an ability is registered.
 *
 * Use this for conditional logic and feature detection before attempting to
 * retrieve or use an ability.
 *
 * Example:
 *
 *     // Displays different UI based on available abilities.
 *     if ( wp_has_ability( 'premium-plugin/advanced-export' ) ) {
 *         echo 'Export with Premium Features';
 *     } else {
 *         echo 'Basic Export';
 *     }
 *
 * @since 6.9.0
 *
 * @see WP_Abilities_Registry::is_registered()
 * @see wp_get_ability()
 *
 * @param string $name The name of the ability to check, including namespace prefix
 *                     (e.g., 'my-plugin/my-ability').
 * @return bool `true` if the ability is registered, `false` otherwise.
 */
function wp_has_ability( string $name ): bool {
	$registry = WP_Abilities_Registry::get_instance();
	if ( null === $registry ) {
		return false;
	}

	return $registry->is_registered( $name );
}

/**
 * Retrieves a registered ability.
 *
 * Returns the ability instance for inspection or use. The instance provides access
 * to the ability's configuration, metadata, and execution methods.
 *
 * Example:
 *
 *     // Prints information about a registered ability.
 *     $ability = wp_get_ability( 'my-plugin/export-data' );
 *     if ( $ability ) {
 *         echo $ability->get_label() . ': ' . $ability->get_description();
 *     }
 *
 * @since 6.9.0
 *
 * @see WP_Abilities_Registry::get_registered()
 * @see wp_has_ability()
 *
 * @param string $name The name of the ability, including namespace prefix
 *                     (e.g., 'my-plugin/my-ability').
 * @return WP_Ability|null The registered ability instance, or `null` if not registered.
 */
function wp_get_ability( string $name ): ?WP_Ability {
	$registry = WP_Abilities_Registry::get_instance();
	if ( null === $registry ) {
		return null;
	}

	return $registry->get_registered( $name );
}

/**
 * Retrieves registered abilities, optionally filtered by the given arguments.
 *
 * When called without arguments, returns all registered abilities. When called
 * with an $args array, returns only abilities that match every specified condition.
 * In both cases, the callbacks and filters below can change the result.
 *
 * Filtering pipeline (executed in order):
 *
 * 1. Declarative filters (`category`, `namespace`, `meta`, `has_required_capabilities`) —
 *    per-item, AND logic between arg types.
 * 2. `item_include_callback` — per-item, caller-scoped. Return true to include, false to exclude.
 * 3. `wp_get_abilities_item_include` filter — per-item, ecosystem-scoped. Plugins can enforce
 *    inclusion rules for abilities that passed the declarative filters.
 * 4. `result_callback` — on the full matched array, caller-scoped. Sort, slice, or reshape.
 * 5. `wp_get_abilities_result` filter — on the full array, ecosystem-scoped.
 *
 * Steps 1–3 run inside a single loop over the registry — no extra iteration.
 *
 * Examples:
 *
 *     // All abilities.
 *     $abilities = wp_get_abilities();
 *
 *     // Filter by category.
 *     $abilities = wp_get_abilities( array( 'category' => 'content' ) );
 *
 *     // Filter by namespace.
 *     $abilities = wp_get_abilities( array( 'namespace' => 'woocommerce' ) );
 *
 *     // Filter by meta.
 *     $abilities = wp_get_abilities( array( 'meta' => array( 'show_in_rest' => true ) ) );
 *
 *     // Abilities whose declared minimum capabilities the current user has.
 *     // Input-dependent permission checks still run when executing an ability.
 *     $abilities = wp_get_abilities( array( 'has_required_capabilities' => true ) );
 *
 *     // Combine filters (AND logic between arg types).
 *     $abilities = wp_get_abilities( array(
 *         'category'  => 'content',
 *         'namespace' => 'core',
 *         'meta'      => array( 'show_in_rest' => true ),
 *     ) );
 *
 *     // Caller-scoped per-item callback.
 *     $abilities = wp_get_abilities( array(
 *         'item_include_callback' => function ( WP_Ability $ability ) {
 *             return current_user_can( 'manage_options' );
 *         },
 *     ) );
 *
 *     // Caller-scoped result callback (sort + paginate).
 *     $abilities = wp_get_abilities( array(
 *         'result_callback' => function ( array $abilities ) {
 *             uasort( $abilities, fn( $a, $b ) => strcasecmp( $a->get_label(), $b->get_label() ) );
 *             return array_slice( $abilities, 0, 10, true );
 *         },
 *     ) );
 *
 * The pipeline always runs, even when called with no arguments. This ensures that the
 * `wp_get_abilities_result` filter always fires, giving plugins a reliable place to
 * enforce universal shaping rules.
 * For raw, unfiltered registry data that bypasses the filter pipeline entirely, use
 * {@see WP_Abilities_Registry::get_all_registered()} directly.
 *
 * @since 6.9.0
 * @since 7.1.0 Added the `$args` parameter for filtering support.
 * @since 7.2.0 Added the `has_required_capabilities` argument.
 *
 * @see WP_Abilities_Registry::get_all_registered()
 *
 * @param array $args {
 *     Optional. Arguments to filter the returned abilities. Default empty array.
 *     Omitted filters do not restrict the results.
 *
 *     @type string          $category                  Optional. Filter by category slug. Only abilities whose category
 *                                                      exactly matches the given slug are included.
 *     @type string          $namespace                 Optional. Filter by ability namespace prefix. Pass the namespace
 *                                                      without a trailing slash, e.g. `'woocommerce'` matches
 *                                                      `'woocommerce/create-order'`.
 *     @type array           $meta                      Optional. Filter by meta key/value pairs. All keys must exist
 *                                                      and non-array values must match strictly, including their types.
 *                                                      Nested arrays are matched recursively as subsets, e.g.
 *                                                      `array( 'mcp' => array( 'public' => true ) )`.
 *     @type bool            $has_required_capabilities Optional. Whether to leave out abilities whose required capabilities
 *                                                      the current user doesn't have. Abilities without required
 *                                                      capabilities pass this check but remain subject to other filters.
 *                                                      Permission callbacks do not run, so inclusion does not guarantee
 *                                                      execution permission.
 *     @type callable        $item_include_callback     Optional. A callback invoked per ability after declarative
 *                                                      filters. Receives a WP_Ability instance, returns bool.
 *                                                      Return true to include, false to exclude.
 *     @type callable        $result_callback           Optional. A callback invoked once on the full matched
 *                                                      array. Receives WP_Ability[], must return WP_Ability[].
 *                                                      Use for sorting, slicing, or reshaping the result.
 * }
 * @return WP_Ability[] An array of registered WP_Ability instances, keyed by ability name
 *                      unless reshaped by a callback or filter. Returns an empty array if
 *                      the registry is unavailable.
 */
function wp_get_abilities( array $args = array() ): array {
	$registry = WP_Abilities_Registry::get_instance();
	if ( null === $registry ) {
		return array();
	}

	$abilities = $registry->get_all_registered();

	$category                  = isset( $args['category'] ) && is_string( $args['category'] ) ? $args['category'] : '';
	$namespace                 = isset( $args['namespace'] ) && is_string( $args['namespace'] ) ? rtrim( $args['namespace'], '/' ) . '/' : '';
	$meta                      = isset( $args['meta'] ) && is_array( $args['meta'] ) ? $args['meta'] : array();
	$has_required_capabilities = ! empty( $args['has_required_capabilities'] );
	$item_include_callback     = isset( $args['item_include_callback'] ) && is_callable( $args['item_include_callback'] ) ? $args['item_include_callback'] : null;
	$result_callback           = isset( $args['result_callback'] ) && is_callable( $args['result_callback'] ) ? $args['result_callback'] : null;

	$matched = array();

	foreach ( $abilities as $name => $ability ) {
		// Step 1a: Filter by category.
		if ( '' !== $category && $ability->get_category() !== $category ) {
			continue;
		}

		// Step 1b: Filter by namespace prefix.
		if ( '' !== $namespace && ! str_starts_with( $ability->get_name(), $namespace ) ) {
			continue;
		}

		// Step 1c: Filter by meta key/value pairs (AND logic, supports nested arrays).
		if ( ! empty( $meta ) && ! _wp_get_abilities_match_meta( $ability->get_meta(), $meta ) ) {
			continue;
		}

		// Step 1d: Leave out abilities whose required capabilities the current user doesn't have.
		if ( $has_required_capabilities ) {
			foreach ( $ability->get_required_capabilities() as $capability ) {
				if ( ! current_user_can( $capability ) ) {
					continue 2;
				}
			}
		}

		// Step 2: Caller-scoped per-item callback.
		$include = true;
		if ( null !== $item_include_callback ) {
			$include = (bool) call_user_func( $item_include_callback, $ability );
		}

		/**
		 * Filters whether an individual ability should be included in the result set.
		 *
		 * Fires after the declarative filters and the caller-scoped item_include_callback.
		 * Only abilities that pass the declarative filters reach this hook. It can override
		 * the caller-scoped callback's result.
		 *
		 * @since 7.1.0
		 *
		 * @param bool       $include The caller-scoped callback's result, or true when no callback is provided.
		 * @param WP_Ability $ability The ability instance being evaluated.
		 * @param array      $args    The full $args array passed to wp_get_abilities().
		 */
		$include = (bool) apply_filters( 'wp_get_abilities_item_include', $include, $ability, $args );

		if ( $include ) {
			$matched[ $name ] = $ability;
		}
	}

	// Step 4: Caller-scoped result callback.
	if ( null !== $result_callback ) {
		$matched = (array) call_user_func( $result_callback, $matched );
	}

	/**
	 * Filters the full list of matched abilities after all per-item filtering is complete.
	 *
	 * Fires after the caller-scoped result_callback. Plugins can use this to sort,
	 * paginate, or reshape the final result set universally.
	 *
	 * @since 7.1.0
	 *
	 * @param WP_Ability[] $matched The matched abilities after all filtering.
	 * @param array        $args    The full $args array passed to wp_get_abilities().
	 */
	return (array) apply_filters( 'wp_get_abilities_result', $matched, $args );
}

/**
 * Checks whether an ability's meta array matches a set of required key/value conditions.
 *
 * All conditions must match (AND logic). Supports nested arrays for structured meta,
 * e.g. `array( 'mcp' => array( 'public' => true ) )`. Every condition key must exist,
 * and non-array values are compared strictly, including their types. Extra meta keys
 * are allowed at any level.
 *
 * @since 7.1.0
 * @access private
 *
 * @param array $meta       The ability's meta array.
 * @param array $conditions The required key/value conditions to match against.
 * @return bool True if all conditions match, false otherwise.
 */
function _wp_get_abilities_match_meta( array $meta, array $conditions ): bool {
	foreach ( $conditions as $key => $value ) {
		if ( ! array_key_exists( $key, $meta ) ) {
			return false;
		}

		if ( is_array( $value ) ) {
			if ( ! is_array( $meta[ $key ] ) || ! _wp_get_abilities_match_meta( $meta[ $key ], $value ) ) {
				return false;
			}
		} elseif ( $meta[ $key ] !== $value ) {
			return false;
		}
	}

	return true;
}

/**
 * Registers a new ability category.
 *
 * Ability categories provide a way to organize and group related abilities for better
 * discoverability and management. Custom categories must be registered before abilities
 * that reference them. Abilities that omit a category are assigned to the built-in
 * `uncategorized` category, which is intended as an escape hatch for simple or transitional
 * registrations.
 *
 * Ability categories must be registered on the `wp_abilities_api_categories_init` action hook.
 *
 * Example:
 *
 *     function my_plugin_register_categories() {
 *         wp_register_ability_category(
 *             'content-management',
 *             array(
 *                 'label'       => __( 'Content Management', 'my-plugin' ),
 *                 'description' => __( 'Abilities for managing and organizing content.', 'my-plugin' ),
 *             )
 *         );
 *     }
 *     add_action( 'wp_abilities_api_categories_init', 'my_plugin_register_categories' );
 *
 * On failure, this function returns `null` and calls `_doing_it_wrong()` with the reason.
 * By default, the resulting notice is displayed when `WP_DEBUG` is enabled.
 *
 * @since 6.9.0
 *
 * @see WP_Ability_Categories_Registry::register()
 * @see wp_register_ability()
 * @see wp_unregister_ability_category()
 *
 * @param string               $slug The unique slug for the ability category. Must contain lowercase
 *                                   alphanumeric segments separated by single dashes (e.g., 'data-export'),
 *                                   with no leading or trailing dash.
 * @param array<string, mixed> $args {
 *     An associative array of arguments for the ability category.
 *
 *     @type string               $label       Required. The human-readable label for the ability category.
 *     @type string               $description Required. A description of what abilities in this category do.
 *     @type array<string, mixed> $meta        Optional. Additional metadata for the ability category.
 * }
 * @return WP_Ability_Category|null The registered ability category instance on success, `null` on failure.
 *
 * @phpstan-param lowercase-string&non-empty-string $slug
 */
function wp_register_ability_category( string $slug, array $args ): ?WP_Ability_Category {
	if ( ! doing_action( 'wp_abilities_api_categories_init' ) ) {
		_doing_it_wrong(
			__FUNCTION__,
			sprintf(
				/* translators: 1: wp_abilities_api_categories_init, 2: ability category slug. */
				__( 'Ability categories must be registered on the %1$s action. The ability category %2$s was not registered.' ),
				'<code>wp_abilities_api_categories_init</code>',
				'<code>' . esc_html( $slug ) . '</code>'
			),
			'6.9.0'
		);
		return null;
	}

	$registry = WP_Ability_Categories_Registry::get_instance();
	if ( null === $registry ) {
		return null;
	}

	return $registry->register( $slug, $args );
}

/**
 * Unregisters an ability category.
 *
 * Removes a previously registered ability category from the global registry. Use this to
 * disable ability categories that are no longer needed.
 *
 * Can be called at any time after the ability category has been registered.
 *
 * Example:
 *
 *     if ( wp_has_ability_category( 'deprecated-category' ) ) {
 *         wp_unregister_ability_category( 'deprecated-category' );
 *     }
 *
 * @since 6.9.0
 *
 * @see WP_Ability_Categories_Registry::unregister()
 * @see wp_register_ability_category()
 *
 * @param string $slug The slug of the ability category to unregister.
 * @return WP_Ability_Category|null The unregistered ability category instance on success, `null` on failure.
 */
function wp_unregister_ability_category( string $slug ): ?WP_Ability_Category {
	$registry = WP_Ability_Categories_Registry::get_instance();
	if ( null === $registry ) {
		return null;
	}

	return $registry->unregister( $slug );
}

/**
 * Checks if an ability category is registered.
 *
 * Use this for conditional logic and feature detection before attempting to
 * retrieve or use an ability category.
 *
 * Example:
 *
 *     // Displays different UI based on available ability categories.
 *     if ( wp_has_ability_category( 'premium-features' ) ) {
 *         echo 'Premium Features Available';
 *     } else {
 *         echo 'Standard Features';
 *     }
 *
 * @since 6.9.0
 *
 * @see WP_Ability_Categories_Registry::is_registered()
 * @see wp_get_ability_category()
 *
 * @param string $slug The slug of the ability category to check.
 * @return bool `true` if the ability category is registered, `false` otherwise.
 */
function wp_has_ability_category( string $slug ): bool {
	$registry = WP_Ability_Categories_Registry::get_instance();
	if ( null === $registry ) {
		return false;
	}

	return $registry->is_registered( $slug );
}

/**
 * Retrieves a registered ability category.
 *
 * Returns the ability category instance for inspection or use. The instance provides access
 * to the ability category's configuration and metadata.
 *
 * Example:
 *
 *     // Prints information about a registered ability category.
 *     $ability_category = wp_get_ability_category( 'content-management' );
 *     if ( $ability_category ) {
 *         echo $ability_category->get_label() . ': ' . $ability_category->get_description();
 *     }
 *
 * @since 6.9.0
 *
 * @see WP_Ability_Categories_Registry::get_registered()
 * @see wp_has_ability_category()
 * @see wp_get_ability_categories()
 *
 * @param string $slug The slug of the ability category.
 * @return WP_Ability_Category|null The ability category instance, or `null` if not registered.
 */
function wp_get_ability_category( string $slug ): ?WP_Ability_Category {
	$registry = WP_Ability_Categories_Registry::get_instance();
	if ( null === $registry ) {
		return null;
	}

	return $registry->get_registered( $slug );
}

/**
 * Retrieves all registered ability categories.
 *
 * Returns an array of all ability category instances currently registered in the system.
 * Use this for discovery, debugging, or building administrative interfaces.
 *
 * Example:
 *
 *     // Prints information about all available ability categories.
 *     $ability_categories = wp_get_ability_categories();
 *     foreach ( $ability_categories as $ability_category ) {
 *         echo $ability_category->get_label() . ': ' . $ability_category->get_description() . "\n";
 *     }
 *
 * @since 6.9.0
 *
 * @see WP_Ability_Categories_Registry::get_all_registered()
 * @see wp_get_ability_category()
 *
 * @return WP_Ability_Category[] An array of registered ability category instances,
 *                               keyed by category slug. Returns an empty array if no ability categories
 *                               are registered or if the registry is unavailable.
 */
function wp_get_ability_categories(): array {
	$registry = WP_Ability_Categories_Registry::get_instance();
	if ( null === $registry ) {
		return array();
	}

	return $registry->get_all_registered();
}