<?php

namespace DayTidy\Booking;

use DayTidy\Db;

class ResourceLocks
{
    private Db $db;

    /**
     * @var string[]
     */
    private array $locks = [];

    public function __construct(?Db $db = null)
    {
        $this->db = $db ?: new Db();
    }

    public function acquire(Draft $draft, int $timeout = 5, bool $preserve_existing_assignments = false): bool
    {
        $draft->lockResourceAssignments(!$preserve_existing_assignments);

        foreach ($this->resourceIds($draft) as $resource_id)
        {
            $key = $this->lockKey($resource_id);
            $locked = (int) $this->db->getVar(
                $this->db->prepare('SELECT GET_LOCK(%s, %d)', $key, $timeout)
            );

            if ($locked !== 1)
            {
                $this->release();

                return false;
            }

            $this->locks[] = $key;
        }

        return true;
    }

    public function release(): void
    {
        foreach (array_reverse($this->locks) as $key)
        {
            $this->db->getVar(
                $this->db->prepare('SELECT RELEASE_LOCK(%s)', $key)
            );
        }

        $this->locks = [];
    }

    /**
     * @return int[]
     */
    private function resourceIds(Draft $draft): array
    {
        $ids = array_map('absint', array_values($draft->getResources()));
        $ids = array_values(array_unique(array_filter($ids)));
        sort($ids);

        return $ids;
    }

    private function lockKey(int $resource_id): string
    {
        return 'daytidy_' . md5($this->db->wpdb()->prefix) . '_resource_' . $resource_id;
    }
}