<?php
/**
 * Inventory reservation for agent checkout sessions.
 *
 * Temporarily reduces WooCommerce stock during agent checkout sessions
 * to prevent overselling. Stock is released on expiry/failure, kept on completion.
 *
 * @package AICommerce\Agentic
 */

declare(strict_types=1);

namespace AICommerce\Agentic;

/**
 * Manages 10-minute inventory holds for agent checkout sessions.
 */
class InventoryReservation {

	/**
	 * Reservation TTL in seconds (10 minutes).
	 */
	private const RESERVATION_TTL = 600;

	/**
	 * Cron hook for cleanup.
	 */
	public const CLEANUP_HOOK = 'aicommerce_cleanup_reservations';

	/**
	 * Reserve stock for a checkout session.
	 *
	 * Temporarily reduces WC stock. Uses WC's own stock management — does
	 * NOT bypass WC inventory. All reservations are atomic: if any item
	 * fails, previously reserved items are rolled back.
	 *
	 * @param string $session_id The agent session UUID.
	 * @param array  $cart_items Validated cart items.
	 *
	 * @return bool True if all items reserved.
	 *
	 * @throws \RuntimeException If stock is insufficient for any item.
	 */
	public function reserve( string $session_id, array $cart_items ): bool {
		$reservations = array();

		foreach ( $cart_items as $item ) {
			$product_id   = (int) $item['product_id'];
			$variation_id = (int) ( $item['variation_id'] ?? 0 );
			$quantity     = (int) $item['quantity'];

			$product = $variation_id ? wc_get_product( $variation_id ) : wc_get_product( $product_id );

			if ( ! $product || ! $product->managing_stock() ) {
				continue;
			}

			$current_stock = $product->get_stock_quantity();

			if ( null === $current_stock || $current_stock < $quantity ) {
				$this->release_multiple( $reservations );
				throw new \RuntimeException(
					esc_html(
						sprintf(
							'Insufficient stock for product %s (available: %d, requested: %d)',
							$product->get_name(),
							$current_stock ?? 0,
							$quantity
						)
					)
				);
			}

			wc_update_product_stock( $product, -$quantity, 'decrease' );

			$reservations[] = array(
				'product_id'   => $product_id,
				'variation_id' => $variation_id,
				'quantity'     => $quantity,
			);
		}

		if ( empty( $reservations ) ) {
			return true;
		}

		set_transient( 'aicommerce_reservation_' . $session_id, $reservations, self::RESERVATION_TTL );

		$active                = get_option( 'aicommerce_active_reservations', array() );
		$active[ $session_id ] = array(
			'expires' => time() + self::RESERVATION_TTL,
			'items'   => $reservations,
		);
		update_option( 'aicommerce_active_reservations', $active, false );

		return true;
	}

	/**
	 * Release a reservation — restore stock for a specific session.
	 *
	 * Called when a session expires or fails. NOT called on completion
	 * (items are sold, stock stays reduced).
	 *
	 * @param string $session_id The agent session UUID.
	 *
	 * @return void
	 */
	public function release( string $session_id ): void {
		$reservations = get_transient( 'aicommerce_reservation_' . $session_id );

		if ( ! $reservations || ! is_array( $reservations ) ) {
			// Fall back to active_reservations option.
			$active = get_option( 'aicommerce_active_reservations', array() );
			if ( isset( $active[ $session_id ] ) ) {
				$reservations = $active[ $session_id ]['items'] ?? array();
			}
		}

		if ( ! empty( $reservations ) ) {
			$this->release_multiple( $reservations );
		}

		delete_transient( 'aicommerce_reservation_' . $session_id );

		$active = get_option( 'aicommerce_active_reservations', array() );
		unset( $active[ $session_id ] );
		update_option( 'aicommerce_active_reservations', $active, false );
	}

	/**
	 * Mark a reservation as completed (items sold — do NOT restore stock).
	 *
	 * Simply removes the reservation tracking without restoring stock.
	 *
	 * @param string $session_id The agent session UUID.
	 *
	 * @return void
	 */
	public function mark_completed( string $session_id ): void {
		delete_transient( 'aicommerce_reservation_' . $session_id );

		$active = get_option( 'aicommerce_active_reservations', array() );
		unset( $active[ $session_id ] );
		update_option( 'aicommerce_active_reservations', $active, false );
	}

	/**
	 * Release stock for multiple reservation items.
	 *
	 * @param array $reservations Array of reservation items.
	 *
	 * @return void
	 */
	public function release_multiple( array $reservations ): void {
		foreach ( $reservations as $item ) {
			$vid     = (int) ( $item['variation_id'] ?? 0 );
			$product = $vid ? wc_get_product( $vid ) : wc_get_product( (int) $item['product_id'] );

			if ( $product && $product->managing_stock() ) {
				wc_update_product_stock( $product, (int) $item['quantity'], 'increase' );
			}
		}
	}

	/**
	 * Clean up expired reservations — restore stock and expire sessions.
	 *
	 * Called by WP Cron every 15 minutes.
	 *
	 * @return void
	 */
	public function cleanup_expired_reservations(): void {
		$active = get_option( 'aicommerce_active_reservations', array() );
		$now    = time();

		if ( empty( $active ) ) {
			return;
		}

		$changed = false;

		foreach ( $active as $session_id => $data ) {
			if ( $data['expires'] >= $now ) {
				continue;
			}

			// Restore stock.
			if ( ! empty( $data['items'] ) ) {
				$this->release_multiple( $data['items'] );
			}

			unset( $active[ $session_id ] );
			$changed = true;

			// Update session status in DB.
			global $wpdb;
			// Safe: internal $wpdb->prefix table names; user values use placeholders.
			// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
			$wpdb->update(
				$wpdb->prefix . 'aicommerce_agent_sessions',
				array( 'status' => 'expired' ),
				array(
					'session_id' => $session_id,
					'status'     => 'pending',
				),
				array( '%s' ),
				array( '%s', '%s' )
			);
			// phpcs:enable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter

			delete_transient( 'aicommerce_reservation_' . $session_id );
		}

		if ( $changed ) {
			update_option( 'aicommerce_active_reservations', $active, false );
		}
	}

	/**
	 * Prune old session and log records (90+ days).
	 *
	 * @return void
	 */
	public function prune_old_records(): void {
		global $wpdb;

		// Safe: internal $wpdb->prefix table names; user values use placeholders.
		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
		$wpdb->query(
			"DELETE FROM {$wpdb->prefix}aicommerce_agent_sessions WHERE status IN ('expired','failed','completed') AND created_at < DATE_SUB(NOW(), INTERVAL 90 DAY)"
		);
		// phpcs:enable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter

		// Safe: internal $wpdb->prefix table names; user values use placeholders.
		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
		$wpdb->query(
			"DELETE FROM {$wpdb->prefix}aicommerce_agent_log WHERE created_at < DATE_SUB(NOW(), INTERVAL 90 DAY)"
		);
		// phpcs:enable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
	}
}