<?php
/**
 * Copyright (C) 2011-2017 by Lars Strojny <lstrojny@php.net>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
namespace Functional;

use Functional\Exceptions\InvalidArgumentException;
use Traversable;

/**
 * Returns all items from $collection except first element (head). Preserves $collection keys.
 * Takes an optional callback for filtering the collection.
 *
 * @param Traversable|array $collection
 * @param callable $callback
 * @return array
 */
function tail($collection, callable $callback = null)
{
    InvalidArgumentException::assertCollection($collection, __FUNCTION__, 1);

    $tail = [];
    $isHead = true;

    foreach ($collection as $index => $element) {
        if ($isHead) {
            $isHead = false;
            continue;
        }

        if (!$callback || $callback($element, $index, $collection)) {
            $tail[$index] = $element;
        }
    }

    return $tail;
}