<?php

declare (strict_types=1);
/*
 * This file is part of sebastian/diff.
 *
 * (c) Sebastian Bergmann <sebastian@phpunit.de>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */
namespace RectorPrefix20210808\SebastianBergmann\Diff;

use function array_fill;
use function array_merge;
use function array_reverse;
use function array_slice;
use function count;
use function in_array;
use function max;
final class MemoryEfficientLongestCommonSubsequenceCalculator implements \RectorPrefix20210808\SebastianBergmann\Diff\LongestCommonSubsequenceCalculator
{
    /**
     * {@inheritdoc}
     * @param mixed[] $from
     * @param mixed[] $to
     */
    public function calculate($from, $to) : array
    {
        $cFrom = \count($from);
        $cTo = \count($to);
        if ($cFrom === 0) {
            return [];
        }
        if ($cFrom === 1) {
            if (\in_array($from[0], $to, \true)) {
                return [$from[0]];
            }
            return [];
        }
        $i = (int) ($cFrom / 2);
        $fromStart = \array_slice($from, 0, $i);
        $fromEnd = \array_slice($from, $i);
        $llB = $this->length($fromStart, $to);
        $llE = $this->length(\array_reverse($fromEnd), \array_reverse($to));
        $jMax = 0;
        $max = 0;
        for ($j = 0; $j <= $cTo; $j++) {
            $m = $llB[$j] + $llE[$cTo - $j];
            if ($m >= $max) {
                $max = $m;
                $jMax = $j;
            }
        }
        $toStart = \array_slice($to, 0, $jMax);
        $toEnd = \array_slice($to, $jMax);
        return \array_merge($this->calculate($fromStart, $toStart), $this->calculate($fromEnd, $toEnd));
    }
    private function length(array $from, array $to) : array
    {
        $current = \array_fill(0, \count($to) + 1, 0);
        $cFrom = \count($from);
        $cTo = \count($to);
        for ($i = 0; $i < $cFrom; $i++) {
            $prev = $current;
            for ($j = 0; $j < $cTo; $j++) {
                if ($from[$i] === $to[$j]) {
                    $current[$j + 1] = $prev[$j] + 1;
                } else {
                    $current[$j + 1] = \max($current[$j], $prev[$j + 1]);
                }
            }
        }
        return $current;
    }
}
