<?php
/**
 * Background batch orchestration for product sync
 *
 * Splits the WooCommerce-first product sync into small chunks processed via
 * Action Scheduler (bundled with WooCommerce), so neither the "Sync Now"
 * AJAX request nor the WP-Cron event has to process the entire catalog in a
 * single PHP execution. At real catalog sizes (tens of thousands of SKUs)
 * that single-request approach exceeds PHP's max_execution_time and the
 * webserver/proxy's read timeout, surfacing as a 502 Bad Gateway.
 *
 * @package WooBusinessCentral
 */

// Prevent direct access
if ( ! defined( 'ABSPATH' ) ) {
    exit;
}

/**
 * Class WBC_Batch_Sync
 */
class WBC_Batch_Sync {

    /**
     * Number of products processed per background action
     */
    const BATCH_SIZE = 25;

    /**
     * Option name storing the current/last run's progress
     */
    const RUN_OPTION = 'wbc_sync_run';

    /**
     * Transient used as a simple "a sync is already running" guard
     */
    const LOCK_TRANSIENT = 'wbc_sync_lock';

    /**
     * Action Scheduler hook processed per batch
     */
    const ACTION_HOOK = 'wbc_process_sync_batch';

    /**
     * Action Scheduler group name
     */
    const ACTION_GROUP = 'wbc_product_sync';

    /**
     * Register the Action Scheduler batch handler
     */
    public function register_hooks() {
        add_action( self::ACTION_HOOK, array( $this, 'process_batch' ), 10, 1 );
    }

    /**
     * Kick off a full catalog sync in the background
     *
     * Gathers WooCommerce product IDs with a SKU (ID-only query - never
     * loads full product objects for the whole catalog into memory), splits
     * them into batches, and enqueues one background action per batch.
     * Returns immediately; actual work happens asynchronously.
     *
     * @return array Result with 'success' and 'message'.
     */
    public static function queue_full_sync() {
        if ( get_transient( self::LOCK_TRANSIENT ) ) {
            $run = get_option( self::RUN_OPTION, array() );
            return array(
                'success' => true,
                'started' => false,
                'message' => __( 'A sync is already running.', 'woo-business-central' ),
                'run'     => $run,
            );
        }

        if ( get_option( 'wbc_enable_stock_sync', 'yes' ) !== 'yes' && get_option( 'wbc_enable_price_sync', 'yes' ) !== 'yes' ) {
            WBC_Logger::info( 'BatchSync', 'Sync skipped - both stock and price sync are disabled' );
            return array(
                'success' => true,
                'message' => __( 'Sync skipped - both stock and price sync are disabled.', 'woo-business-central' ),
            );
        }

        if ( ! WBC_OAuth::is_configured() ) {
            WBC_Logger::error( 'BatchSync', 'Sync failed - API credentials not configured' );
            return array(
                'success' => false,
                'message' => __( 'Sync failed - API credentials not configured.', 'woo-business-central' ),
            );
        }

        if ( ! function_exists( 'as_enqueue_async_action' ) ) {
            WBC_Logger::error( 'BatchSync', 'Action Scheduler not available (ships with WooCommerce)' );
            return array(
                'success' => false,
                'message' => __( 'Background task runner is not available.', 'woo-business-central' ),
            );
        }

        // ID-only query with a meta filter, so 60k+ catalogs don't get loaded
        // as full WC_Product objects just to check for a SKU.
        $product_ids = wc_get_products( array(
            'limit'      => -1,
            'status'     => 'publish',
            'return'     => 'ids',
            'meta_query' => array( // phpcs:ignore WooCommerce.Commenting -- deliberate, avoids full-object load at scale.
                array(
                    'key'     => '_sku',
                    'value'   => '',
                    'compare' => '!=',
                ),
            ),
        ) );

        if ( empty( $product_ids ) ) {
            WBC_Logger::info( 'BatchSync', 'No WooCommerce products with SKU found' );
            return array(
                'success' => true,
                'message' => __( 'No WooCommerce products with SKU found.', 'woo-business-central' ),
            );
        }

        $run_id = uniqid( 'wbc_', true );
        $batches = array_chunk( $product_ids, self::BATCH_SIZE );

        update_option( self::RUN_OPTION, array(
            'run_id'        => $run_id,
            'status'        => 'running',
            'total'         => count( $product_ids ),
            'total_batches' => count( $batches ),
            'batches_done'  => 0,
            'success'       => 0,
            'failed'        => 0,
            'skipped'       => 0,
            'started_at'    => current_time( 'mysql' ),
            'finished_at'   => '',
        ), false );

        // Safety-net expiry in case a batch throws and never reports back;
        // prevents the lock from wedging the sync button forever.
        set_transient( self::LOCK_TRANSIENT, $run_id, 4 * HOUR_IN_SECONDS );

        foreach ( $batches as $batch ) {
            as_enqueue_async_action( self::ACTION_HOOK, array(
                'run_id'      => $run_id,
                'product_ids' => $batch,
            ), self::ACTION_GROUP );
        }

        WBC_Logger::info( 'BatchSync', 'Queued background sync', array(
            'run_id'         => $run_id,
            'total_products' => count( $product_ids ),
            'total_batches'  => count( $batches ),
        ) );

        return array(
            'success' => true,
            'started' => true,
            'message' => sprintf(
                /* translators: %d: number of products */
                __( 'Sync started in the background for %d product(s).', 'woo-business-central' ),
                count( $product_ids )
            ),
        );
    }

    /**
     * Process a single batch (called by Action Scheduler)
     *
     * @param array $args Action args: run_id, product_ids.
     */
    public function process_batch( $args ) {
        $run_id = $args['run_id'] ?? '';
        $product_ids = $args['product_ids'] ?? array();

        $run = get_option( self::RUN_OPTION, array() );

        // A newer sync superseded this run (e.g. re-triggered manually) - drop it.
        if ( empty( $run ) || ( $run['run_id'] ?? '' ) !== $run_id ) {
            return;
        }

        $sync = new WBC_Product_Sync();
        $sync->run_sync_for_ids( $product_ids );
        $batch_results = $sync->get_results();

        // Progress counters are best-effort: Action Scheduler can run batches
        // concurrently, and update_option() read-modify-write isn't atomic.
        // Good enough for a progress indicator; not used for anything
        // correctness-critical.
        $run = get_option( self::RUN_OPTION, $run );
        if ( ( $run['run_id'] ?? '' ) !== $run_id ) {
            return;
        }

        $run['batches_done'] = (int) ( $run['batches_done'] ?? 0 ) + 1;
        $run['success'] = (int) ( $run['success'] ?? 0 ) + $batch_results['success'];
        $run['failed'] = (int) ( $run['failed'] ?? 0 ) + $batch_results['failed'];
        $run['skipped'] = (int) ( $run['skipped'] ?? 0 ) + $batch_results['skipped'];

        if ( $run['batches_done'] >= $run['total_batches'] ) {
            $run['status'] = 'completed';
            $run['finished_at'] = current_time( 'mysql' );
            WBC_Cron::update_last_sync_time();
            delete_transient( self::LOCK_TRANSIENT );

            WBC_Logger::info( 'BatchSync', 'Background sync completed', $run );
        }

        update_option( self::RUN_OPTION, $run, false );
    }

    /**
     * Get the current/last sync run status
     *
     * @return array Run status, or array('status' => 'none') if never run.
     */
    public static function get_status() {
        $run = get_option( self::RUN_OPTION, array() );

        if ( empty( $run ) ) {
            return array( 'status' => 'none' );
        }

        return $run;
    }
}