<?php
/**
 * Background rebuild and live refresh.
 *
 * A full rebuild walks every customer in pages, using WooCommerce's Action Scheduler so
 * nothing runs during a page load. After that, each order change refreshes just the
 * customer it belongs to.
 *
 * @package Statbird
 */

namespace Statbird;

defined( 'ABSPATH' ) || exit;

/**
 * Rebuild state machine and order hooks.
 */
class Rebuild {

	const GROUP      = 'statbird';
	const BATCH_HOOK = 'statbird_rebuild_batch';
	const REFRESH    = 'statbird_refresh_customer';
	const STATE      = 'statbird_rebuild';
	const BATCH_SIZE = 500;

	/**
	 * Hooks.
	 */
	public static function init() {
		add_action( self::BATCH_HOOK, array( __CLASS__, 'run_batch' ) );
		add_action( self::REFRESH, array( __CLASS__, 'refresh' ) );

		// Any change that can alter a customer's totals or dates.
		add_action( 'woocommerce_order_status_changed', array( __CLASS__, 'order_changed' ), 20, 1 );
		add_action( 'woocommerce_order_refunded', array( __CLASS__, 'order_changed' ), 20, 1 );
		add_action( 'woocommerce_refund_deleted', array( __CLASS__, 'refund_deleted' ), 20, 2 );
		add_action( 'woocommerce_before_delete_order', array( __CLASS__, 'order_changed' ), 20, 1 );
		add_action( 'woocommerce_before_trash_order', array( __CLASS__, 'order_changed' ), 20, 1 );
		add_action( 'woocommerce_untrash_order', array( __CLASS__, 'order_changed' ), 20, 1 );
	}

	/**
	 * Current state.
	 *
	 * @return array{status:string,cursor:string,done:int,started:string,finished:string,total:int}
	 */
	public static function state() {
		$s = get_option( self::STATE, array() );
		return wp_parse_args(
			is_array( $s ) ? $s : array(),
			array(
				'status'   => 'idle',
				'cursor'   => '',
				'done'     => 0,
				'total'    => 0,
				'started'  => '',
				'finished' => '',
				'run'      => 0,
			)
		);
	}

	/**
	 * Starts a full rebuild in the background (or restarts one that is running).
	 *
	 * @return bool False when WooCommerce's scheduler is not available.
	 */
	public static function start() {
		if ( ! function_exists( 'as_enqueue_async_action' ) ) {
			return false;
		}
		as_unschedule_all_actions( self::BATCH_HOOK, array(), self::GROUP );
		$run = (int) self::state()['run'] + 1;
		update_option(
			self::STATE,
			array(
				'run'      => $run,
				'status'   => 'running',
				'cursor'   => '',
				'done'     => 0,
				'total'    => 0,
				'started'  => gmdate( 'Y-m-d H:i:s' ),
				'finished' => '',
			),
			false
		);
		as_enqueue_async_action( self::BATCH_HOOK, array(), self::GROUP );
		return true;
	}

	/**
	 * Processes one page of customers and queues the next.
	 *
	 * @return array State after the batch.
	 */
	public static function run_batch() {
		$s = self::state();
		if ( 'running' !== $s['status'] ) {
			return $s;
		}
		$rows = Orders::customers_page( $s['cursor'], self::BATCH_SIZE );
		Store::upsert( $rows, gmdate( 'Y-m-d H:i:s' ), (int) $s['run'] );

		if ( count( $rows ) < self::BATCH_SIZE ) {
			Store::prune_except( (int) $s['run'] );
			$s['status']   = 'complete';
			$s['finished'] = gmdate( 'Y-m-d H:i:s' );
		} else {
			$s['cursor'] = end( $rows )['customer_key'];
		}
		$s['done'] += count( $rows );
		update_option( self::STATE, $s, false );

		/**
		 * Fires after each rebuild batch. Scoring hooks in here once the rebuild completes.
		 *
		 * @param array $state Rebuild state.
		 */
		do_action( 'statbird_rebuild_batch_done', $s );

		if ( 'running' === $s['status'] && function_exists( 'as_enqueue_async_action' ) && ! self::running_in_cli() ) {
			as_enqueue_async_action( self::BATCH_HOOK, array(), self::GROUP );
		}
		return $s;
	}

	/**
	 * WP-CLI drives batches itself in a loop, without the queue.
	 *
	 * @return bool
	 */
	private static function running_in_cli() {
		return defined( 'WP_CLI' ) && WP_CLI && ! doing_action( self::BATCH_HOOK );
	}

	/**
	 * Queues a refresh for the customer an order belongs to. Several changes to the same
	 * customer in one request (status change, then refund) become one refresh.
	 *
	 * @param int|\WC_Order $order Order or order ID.
	 */
	public static function order_changed( $order ) {
		$order = is_object( $order ) ? $order : wc_get_order( $order );
		if ( ! $order || 'shop_order' !== $order->get_type() ) {
			return;
		}
		$key = Orders::key_for_order( $order );
		if ( '' === $key ) {
			return;
		}
		if ( function_exists( 'as_enqueue_async_action' ) ) {
			if ( ! as_has_scheduled_action( self::REFRESH, array( $key ), self::GROUP ) ) {
				as_enqueue_async_action( self::REFRESH, array( $key ), self::GROUP );
			}
		} else {
			self::refresh( $key );
		}
	}

	/**
	 * After a refund is deleted, refresh its parent order's customer.
	 *
	 * @param int $refund_id Refund ID.
	 * @param int $order_id  Parent order ID.
	 */
	public static function refund_deleted( $refund_id, $order_id ) {
		self::order_changed( (int) $order_id );
	}

	/**
	 * Recomputes one customer from their orders.
	 *
	 * @param string $key Identity key from Orders::key_for_order().
	 */
	public static function refresh( $key ) {
		$row = Orders::customer( $key );
		if ( $row ) {
			Store::upsert( array( $row ), gmdate( 'Y-m-d H:i:s' ), (int) self::state()['run'] );
		} else {
			Store::delete( md5( $key ) );
		}
		// A guest who has since registered: their guest orders now belong to the account.
		if ( 0 === strpos( $key, 'u' ) ) {
			$user = get_userdata( (int) substr( $key, 1 ) );
			if ( $user && $user->user_email ) {
				Store::delete( md5( 'e' . strtolower( trim( $user->user_email ) ) ) );
			}
		}
		/**
		 * Fires after one customer's purchase facts are refreshed.
		 *
		 * @param string     $customer_key MD5 key.
		 * @param array|null $row          New aggregate, or null when removed.
		 */
		do_action( 'statbird_customer_refreshed', md5( $key ), $row );
	}
}