<?php
/**
 * Full-site extraction in batches.
 *
 * @package Unbreak
 */

namespace Unbreak\Queue;

use Unbreak\Extract\Indexer;
use Unbreak\Support\Clock;
use Unbreak\Support\Settings;

defined( 'ABSPATH' ) || exit;

/**
 * Walks every eligible post in ID order, 50 per background job, then menus, widgets and (optionally) comments.
 */
final class FullScan {

	public const STATE_OPTION = 'unbreak_scan_state';
	public const HOOK_POSTS   = 'unbreak_scan_posts_batch';
	public const HOOK_COMMENT = 'unbreak_scan_comments_batch';
	public const BATCH_SIZE   = 50;

	/**
	 * Wall-clock budget per batch in seconds; a batch stops early and re-queues itself when exceeded.
	 */
	private const TIME_BUDGET = 20;

	/**
	 * Indexer.
	 *
	 * @var Indexer
	 */
	private $indexer;

	/**
	 * Constructor.
	 *
	 * @param Indexer|null $indexer Indexer.
	 */
	public function __construct( ?Indexer $indexer = null ) {
		$this->indexer = $indexer ?? new Indexer();
	}

	/**
	 * Register hooks.
	 */
	public function register(): void {
		add_action( 'unbreak_start_full_scan', array( $this, 'start' ) );
		add_action( self::HOOK_POSTS, array( $this, 'run_posts_batch' ) );
		add_action( self::HOOK_COMMENT, array( $this, 'run_comments_batch' ) );
	}

	/**
	 * Start (or restart) a full scan. Only counts rows and enqueues the first batch.
	 */
	public function start(): void {
		global $wpdb;
		$types = Indexer::post_types();
		$total = 0;
		if ( ! empty( $types ) ) {
			$in = implode( ',', array_fill( 0, count( $types ), '%s' ) );
			// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching,WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare -- Placeholders generated above.
			$total = (int) $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM {$wpdb->posts} WHERE post_type IN ({$in}) AND post_status IN ('publish','private')", $types ) );
		}

		self::save_state(
			array(
				'status'      => 'extracting',
				'started_at'  => Clock::now(),
				'finished_at' => null,
				'total'       => $total,
				'processed'   => 0,
			)
		);

		Jobs::cancel( self::HOOK_POSTS );
		Jobs::cancel( self::HOOK_COMMENT );
		Jobs::enqueue_unique( self::HOOK_POSTS, array( 0 ) );
	}

	/**
	 * Process up to BATCH_SIZE posts with ID greater than $after_id.
	 *
	 * @param int $after_id Last processed post ID.
	 */
	public function run_posts_batch( $after_id = 0 ): void {
		global $wpdb;
		$after_id = (int) $after_id;
		$types    = Indexer::post_types();
		$ids      = array();
		if ( ! empty( $types ) ) {
			$in     = implode( ',', array_fill( 0, count( $types ), '%s' ) );
			$params = array_merge( array( $after_id ), $types, array( self::BATCH_SIZE ) );
			// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching,WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare,WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber -- Placeholders generated above.
			$ids = array_map( 'intval', (array) $wpdb->get_col( $wpdb->prepare( "SELECT ID FROM {$wpdb->posts} WHERE ID > %d AND post_type IN ({$in}) AND post_status IN ('publish','private') ORDER BY ID ASC LIMIT %d", $params ) ) );
		}

		$started = microtime( true );
		$last    = $after_id;
		$done    = 0;
		foreach ( $ids as $id ) {
			$this->indexer->index_post( $id );
			$last = $id;
			++$done;
			if ( microtime( true ) - $started > self::TIME_BUDGET ) {
				break;
			}
		}
		self::release_memory();

		$state              = self::state();
		$state['processed'] = min( (int) $state['total'], (int) $state['processed'] + $done );
		self::save_state( $state );

		if ( count( $ids ) === self::BATCH_SIZE || $done < count( $ids ) ) {
			Jobs::enqueue_unique( self::HOOK_POSTS, array( $last ) );
			return;
		}

		$this->indexer->index_menus();
		$this->indexer->index_widgets();

		if ( Settings::source_enabled( 'comment' ) ) {
			Jobs::enqueue_unique( self::HOOK_COMMENT, array( 0 ) );
			return;
		}
		$this->finish();
	}

	/**
	 * Process up to BATCH_SIZE approved comments with ID greater than $after_id.
	 *
	 * @param int $after_id Last processed comment ID.
	 */
	public function run_comments_batch( $after_id = 0 ): void {
		global $wpdb;
		$after_id = (int) $after_id;
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching -- Batched background scan.
		$ids  = array_map( 'intval', (array) $wpdb->get_col( $wpdb->prepare( "SELECT comment_ID FROM {$wpdb->comments} WHERE comment_ID > %d AND comment_approved = '1' ORDER BY comment_ID ASC LIMIT %d", $after_id, self::BATCH_SIZE ) ) );
		$last = $after_id;
		foreach ( $ids as $id ) {
			$this->indexer->index_comment( $id );
			$last = $id;
		}
		self::release_memory();
		if ( count( $ids ) === self::BATCH_SIZE ) {
			Jobs::enqueue_unique( self::HOOK_COMMENT, array( $last ) );
			return;
		}
		$this->finish();
	}

	/**
	 * Mark extraction finished.
	 */
	private function finish(): void {
		$state                = self::state();
		$state['status']      = 'done';
		$state['finished_at'] = Clock::now();
		$state['processed']   = $state['total'];
		self::save_state( $state );
		/**
		 * Fires when a full extraction pass has finished.
		 */
		do_action( 'unbreak_extraction_done' );
	}

	/**
	 * Current scan state.
	 *
	 * @return array{status:string,started_at:int|null,finished_at:int|null,total:int,processed:int}
	 */
	public static function state(): array {
		$state = get_option( self::STATE_OPTION, array() );
		$state = is_array( $state ) ? $state : array();
		return array(
			'status'      => isset( $state['status'] ) ? (string) $state['status'] : 'idle',
			'started_at'  => isset( $state['started_at'] ) ? (int) $state['started_at'] : null,
			'finished_at' => isset( $state['finished_at'] ) ? (int) $state['finished_at'] : null,
			'total'       => isset( $state['total'] ) ? (int) $state['total'] : 0,
			'processed'   => isset( $state['processed'] ) ? (int) $state['processed'] : 0,
		);
	}

	/**
	 * Persist scan state.
	 *
	 * @param array<string,mixed> $state State.
	 */
	private static function save_state( array $state ): void {
		update_option( self::STATE_OPTION, $state, false );
	}

	/**
	 * Free per-request caches between batches so long queues stay under the memory budget.
	 */
	private static function release_memory(): void {
		if ( function_exists( 'wp_cache_flush_runtime' ) && ! wp_using_ext_object_cache() ) {
			wp_cache_flush_runtime();
		}
	}
}