<?php

declare(strict_types=1);

namespace MeshVault\Indexer;

use Closure;
use InvalidArgumentException;
use Throwable;

/** Advisory preflight only: free space may change immediately after checking. */
final readonly class SpaceChecker
{
    private Closure $freeSpace;

    /** Margin is a fraction of payload bytes, not a fraction of disk capacity. */
    public function __construct(private float $margin = 0.05, ?callable $freeSpace = null)
    {
        if (!is_finite($margin) || $margin < 0) {
            throw new InvalidArgumentException('Space margin must be finite and nonnegative.');
        }
        $this->freeSpace = $freeSpace === null
            ? static fn (string $path): float|false => @disk_free_space($path)
            : Closure::fromCallable($freeSpace);
    }

    /** Require ceil(bytes * (1 + margin)) available bytes on an existing destination directory. */
    public function check(string $directory, int $bytes): void
    {
        if ($bytes < 0) {
            throw new InvalidArgumentException('Payload size must be nonnegative.');
        }
        try {
            $free = ($this->freeSpace)($directory);
        } catch (Throwable $error) {
            throw new ImportException('SPACE_CHECK_FAILED', 'Cannot query destination free space.', $error);
        }
        if ((!is_float($free) && !is_int($free)) || !is_finite((float) $free) || $free < 0) {
            throw new ImportException('SPACE_CHECK_FAILED', 'Cannot determine destination free space.');
        }
        $required = ceil($bytes + $bytes * $this->margin);
        if (!is_finite($required) || $free < $required) {
            throw new ImportException('DISK_FULL', 'Insufficient free space including the safety margin.');
        }
    }
}