<?php
/**
 * Marker that a save was started by this plugin.
 *
 * @package Kordiam
 */

declare( strict_types=1 );

namespace Kordiam\Import;

use Kordiam\Support\MetaKeys;

// Exit if accessed directly.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Stops the export direction from reacting to the import direction's own writes.
 *
 * Without it, an import's save_post would export the still-unlinked post as a new story.
 * Uses an in-memory depth counter (nesting-safe) plus post meta (visible inside
 * wp_insert_post() via meta_input).
 */
final class PostStatusGuard {

	/**
	 * How many guarded operations are in progress, keyed by post ID.
	 *
	 * @var array<int, int>
	 */
	private static array $depth = array();

	/**
	 * Blocking instantiation: this class is a namespaced function group.
	 */
	private function __construct() {
	}

	/**
	 * Getting the meta key the marker is stored under.
	 *
	 * @return string Meta key.
	 */
	public static function meta_key(): string {
		return MetaKeys::INTERNAL_SAVE;
	}

	/**
	 * Adding the marker to post data about to be inserted.
	 *
	 * @param array<string, mixed> $post_data Post data being assembled.
	 *
	 * @return array<string, mixed> Post data carrying the marker.
	 */
	public static function mark( array $post_data ): array {
		if ( ! isset( $post_data['meta_input'] ) || ! is_array( $post_data['meta_input'] ) ) {
			$post_data['meta_input'] = array();
		}

		$post_data['meta_input'][ self::meta_key() ] = true;

		return $post_data;
	}

	/**
	 * Opening a guarded operation on an existing post.
	 *
	 * @param int $post_id Post ID.
	 */
	public static function begin( int $post_id ): void {
		if ( $post_id <= 0 ) {
			return;
		}

		self::$depth[ $post_id ] = ( self::$depth[ $post_id ] ?? 0 ) + 1;

		update_post_meta( $post_id, self::meta_key(), true );
	}

	/**
	 * Closing a guarded operation; the outermost one removes the marker.
	 *
	 * @param int $post_id Post ID.
	 */
	public static function end( int $post_id ): void {
		if ( $post_id <= 0 || ! isset( self::$depth[ $post_id ] ) ) {
			return;
		}

		--self::$depth[ $post_id ];

		if ( self::$depth[ $post_id ] > 0 ) {
			return;
		}

		unset( self::$depth[ $post_id ] );

		delete_post_meta( $post_id, self::meta_key() );
	}

	/**
	 * Checking whether a save is one of this plugin's own.
	 *
	 * @param int $post_id Post ID.
	 *
	 * @return bool Whether the export direction should stay out of it.
	 */
	public static function is_active( int $post_id ): bool {
		if ( $post_id <= 0 ) {
			return false;
		}

		if ( ( self::$depth[ $post_id ] ?? 0 ) > 0 ) {
			return true;
		}

		if ( self::meta_is_set( $post_id, self::meta_key() ) ) {
			return true;
		}

		return self::meta_is_set( $post_id, MetaKeys::legacy_post_meta()[ MetaKeys::INTERNAL_SAVE ] );
	}

	/**
	 * Running an operation with the guard held, released even if it throws.
	 *
	 * @param int      $post_id   Post ID.
	 * @param callable $operation Operation to run.
	 *
	 * @return mixed Whatever the operation returned.
	 */
	public static function guarded( int $post_id, callable $operation ) {
		self::begin( $post_id );

		try {
			return $operation();
		} finally {
			self::end( $post_id );
		}
	}

	/**
	 * Clearing every in-memory marker (for tests).
	 */
	public static function reset(): void {
		self::$depth = array();
	}

	/**
	 * Checking whether a meta key holds a truthy value.
	 *
	 * @param int    $post_id  Post ID.
	 * @param string $meta_key Meta key.
	 *
	 * @return bool Whether the marker is set.
	 */
	private static function meta_is_set( int $post_id, string $meta_key ): bool {
		$value = get_post_meta( $post_id, $meta_key, true );

		return '' !== $value && false !== $value && '0' !== $value && 0 !== $value && null !== $value;
	}
}