<?php
/**
 * Application-layer availability handler with generation-counter cache.
 *
 * @package Bookline
 */

declare( strict_types=1 );

namespace Bookline\Application\Availability;

use Bookline\Domain\Availability\AvailabilityEngine;
use Bookline\Domain\Availability\AvailabilityQuery;
use Bookline\Domain\Availability\SlotCollection;
use Closure;

/**
 * Wraps the pure engine with an optional cache backend.
 */
final class GetAvailabilityHandler {

	/**
	 * Constructor.
	 *
	 * @param AvailabilityEngine $engine      Availability engine.
	 * @param Closure            $cache_get   Get cached slots by key.
	 * @param Closure            $cache_set   Store slots with TTL seconds.
	 * @param Closure            $generation  Current global generation counter.
	 * @param int                $ttl_seconds Cache TTL in seconds.
	 */
	public function __construct(
		private readonly AvailabilityEngine $engine,
		private readonly Closure $cache_get,
		private readonly Closure $cache_set,
		private readonly Closure $generation,
		private readonly int $ttl_seconds = 300,
	) {}

	/**
	 * Resolve availability, bypassing cache when a booking is excluded.
	 *
	 * @param AvailabilityQuery         $query  Availability query.
	 * @param list<array<string,mixed>> $agents Agent payloads for the engine.
	 */
	public function handle( AvailabilityQuery $query, array $agents ): SlotCollection {
		if ( null !== $query->exclude_booking_id ) {
			return $this->engine->generate( $query, $agents );
		}

		$key = $this->cache_key( $query );
		$hit = ( $this->cache_get )( $key );
		if ( $hit instanceof SlotCollection ) {
			return $hit;
		}

		$result = $this->engine->generate( $query, $agents );
		( $this->cache_set )( $key, $result, $this->ttl_seconds );
		return $result;
	}

	/**
	 * Build a cache key including the generation counter.
	 *
	 * @param AvailabilityQuery $query Availability query.
	 */
	private function cache_key( AvailabilityQuery $query ): string {
		$extras = [];
		foreach ( $query->selected_extras as $row ) {
			$extras[] = $row['extraId'] . 'x' . $row['quantity'];
		}
		sort( $extras );
		$day = $query->range_start_utc->format( 'Y-m-d' );
		return sprintf(
			'bookline_avail_g%d_%d_%d_%s_%s_%s_%d_%s',
			( $this->generation )(),
			$query->service_id,
			$query->duration_id,
			null === $query->agent_id ? 'any' : (string) $query->agent_id,
			null === $query->location_id ? 'any' : (string) $query->location_id,
			$day,
			$query->attendees,
			implode( ',', $extras )
		);
	}
}