<?php
/**
 * Copyright 2026 Kacper Donat
 *
 * @author Kacper "Kadet" Donat <kacper@kadet.net>
 *
 * Full license available in separate LICENSE file
 */

namespace Kadet\Functional\Collections\Internal;

use function Kadet\Functional\compile;

/**
 * Compiles a collection callback, adapted to its arity.
 *
 * The returned closure is called with ($value, $key). Internal functions (including first-class callables like
 * `trim(...)`) and non-variadic closures declaring exactly one parameter receive only the value, so the key is
 * never mistaken for an optional argument.
 *
 * @internal
 */
function callback(callable $callable): \Closure
{
    $compiled   = compile($callable);
    $reflection = new \ReflectionFunction($compiled);

    if ($reflection->isInternal() || (!$reflection->isVariadic() && $reflection->getNumberOfParameters() === 1)) {
        return static fn ($value) => $compiled($value);
    }

    return $compiled;
}