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<?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 SebastianBergmann\Diff;

use const PHP_INT_SIZE;

use const PREG_SPLIT_DELIM_CAPTURE;

use const PREG_SPLIT_NO_EMPTY;

use function array_shift;

use function array_unshift;

use function array_values;

use function count;

use function current;

use function end;

use function get_class;

use function gettype;

use function is_array;

use function is_object;

use function is_string;

use function key;

use function min;

use function preg_split;

use function prev;

use function reset;

use function sprintf;

use function substr;

use SebastianBergmann\Diff\Output\DiffOutputBuilderInterface;

use SebastianBergmann\Diff\Output\UnifiedDiffOutputBuilder;

final class Differ

{

    public const OLD                     = 0;

    public const ADDED                   = 1;

    public const REMOVED                 = 2;

    public const DIFF_LINE_END_WARNING   = 3;

    public const NO_LINE_END_EOF_WARNING = 4;

    /**

     * @var DiffOutputBuilderInterface

     */

    private $outputBuilder;

    /**

     * @param DiffOutputBuilderInterface $outputBuilder

     *

     * @throws InvalidArgumentException

     */

    public function __construct($outputBuilder = null)

    {

        if ($outputBuilder instanceof DiffOutputBuilderInterface) {

            $this->outputBuilder = $outputBuilder;

        } elseif (null === $outputBuilder) {

            $this->outputBuilder = new UnifiedDiffOutputBuilder;

        } elseif (is_string($outputBuilder)) {

            // PHPUnit 6.1.4, 6.2.0, 6.2.1, 6.2.2, and 6.2.3 support

            // @see https://github.com/sebastianbergmann/phpunit/issues/2734#issuecomment-314514056

            // @deprecated

            $this->outputBuilder = new UnifiedDiffOutputBuilder($outputBuilder);

        } else {

            throw new InvalidArgumentException(

                sprintf(

                    'Expected builder to be an instance of DiffOutputBuilderInterface, <null> or a string, got %s.',

                    is_object($outputBuilder) ? 'instance of "' . get_class($outputBuilder) . '"' : gettype($outputBuilder) . ' "' . $outputBuilder . '"'

                )

            );

        }

    }

    /**

     * Returns the diff between two arrays or strings as string.

     *

     * @param array|string $from

     * @param array|string $to

     */

    public function diff($from, $to, LongestCommonSubsequenceCalculator $lcs = null): string

    {

        $diff = $this->diffToArray(

            $this->normalizeDiffInput($from),

            $this->normalizeDiffInput($to),

            $lcs

        );

        return $this->outputBuilder->getDiff($diff);

    }

    /**

     * Returns the diff between two arrays or strings as array.

     *

     * Each array element contains two elements:

     *   - [0] => mixed $token

     *   - [1] => 2|1|0

     *

     * - 2: REMOVED: $token was removed from $from

     * - 1: ADDED: $token was added to $from

     * - 0: OLD: $token is not changed in $to

     *

     * @param array|string                       $from

     * @param array|string                       $to

     * @param LongestCommonSubsequenceCalculator $lcs

     */

    public function diffToArray($from, $to, LongestCommonSubsequenceCalculator $lcs = null): array

    {

        if (is_string($from)) {

            $from = $this->splitStringByLines($from);

        } elseif (!is_array($from)) {

            throw new InvalidArgumentException('"from" must be an array or string.');

        }

        if (is_string($to)) {

            $to = $this->splitStringByLines($to);

        } elseif (!is_array($to)) {

            throw new InvalidArgumentException('"to" must be an array or string.');

        }

        [$from, $to, $start, $end] = self::getArrayDiffParted($from, $to);

        if ($lcs === null) {

            $lcs = $this->selectLcsImplementation($from, $to);

        }

        $common = $lcs->calculate(array_values($from), array_values($to));

        $diff   = [];

        foreach ($start as $token) {

            $diff[] = [$token, self::OLD];

        }

        reset($from);

        reset($to);

        foreach ($common as $token) {

            while (($fromToken = reset($from)) !== $token) {

                $diff[] = [array_shift($from), self::REMOVED];

            }

            while (($toToken = reset($to)) !== $token) {

                $diff[] = [array_shift($to), self::ADDED];

            }

            $diff[] = [$token, self::OLD];

            array_shift($from);

            array_shift($to);

        }

        while (($token = array_shift($from)) !== null) {

            $diff[] = [$token, self::REMOVED];

        }

        while (($token = array_shift($to)) !== null) {

            $diff[] = [$token, self::ADDED];

        }

        foreach ($end as $token) {

            $diff[] = [$token, self::OLD];

        }

        if ($this->detectUnmatchedLineEndings($diff)) {

            array_unshift($diff, ["#Warning: Strings contain different line endings!\n", self::DIFF_LINE_END_WARNING]);

        }

        return $diff;

    }

    /**

     * Casts variable to string if it is not a string or array.

     *

     * @return array|string

     */

    private function normalizeDiffInput($input)

    {

        if (!is_array($input) && !is_string($input)) {

            return (string) $input;

        }

        return $input;

    }

    /**

     * Checks if input is string, if so it will split it line-by-line.

     */

    private function splitStringByLines(string $input): array

    {

        return preg_split('/(.*\R)/', $input, -1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);

    }

    private function selectLcsImplementation(array $from, array $to): LongestCommonSubsequenceCalculator

    {

        // We do not want to use the time-efficient implementation if its memory

        // footprint will probably exceed this value. Note that the footprint

        // calculation is only an estimation for the matrix and the LCS method

        // will typically allocate a bit more memory than this.

        $memoryLimit = 100 * 1024 * 1024;

        if ($this->calculateEstimatedFootprint($from, $to) > $memoryLimit) {

            return new MemoryEfficientLongestCommonSubsequenceCalculator;

        }

        return new TimeEfficientLongestCommonSubsequenceCalculator;

    }

    /**

     * Calculates the estimated memory footprint for the DP-based method.

     *

     * @return float|int

     */

    private function calculateEstimatedFootprint(array $from, array $to)

    {

        $itemSize = PHP_INT_SIZE === 4 ? 76 : 144;

        return $itemSize * min(count($from), count($to)) ** 2;

    }

    /**

     * Returns true if line ends don't match in a diff.

     */

    private function detectUnmatchedLineEndings(array $diff): bool

    {

        $newLineBreaks = ['' => true];

        $oldLineBreaks = ['' => true];

        foreach ($diff as $entry) {

            if (self::OLD === $entry[1]) {

                $ln                 = $this->getLinebreak($entry[0]);

                $oldLineBreaks[$ln] = true;

                $newLineBreaks[$ln] = true;

            } elseif (self::ADDED === $entry[1]) {

                $newLineBreaks[$this->getLinebreak($entry[0])] = true;

            } elseif (self::REMOVED === $entry[1]) {

                $oldLineBreaks[$this->getLinebreak($entry[0])] = true;

            }

        }

        // if either input or output is a single line without breaks than no warning should be raised

        if (['' => true] === $newLineBreaks || ['' => true] === $oldLineBreaks) {

            return false;

        }

        // two way compare

        foreach ($newLineBreaks as $break => $set) {

            if (!isset($oldLineBreaks[$break])) {

                return true;

            }

        }

        foreach ($oldLineBreaks as $break => $set) {

            if (!isset($newLineBreaks[$break])) {

                return true;

            }

        }

        return false;

    }

    private function getLinebreak($line): string

    {

        if (!is_string($line)) {

            return '';

        }

        $lc = substr($line, -1);

        if ("\r" === $lc) {

            return "\r";

        }

        if ("\n" !== $lc) {

            return '';

        }

        if ("\r\n" === substr($line, -2)) {

            return "\r\n";

        }

        return "\n";

    }

    private static function getArrayDiffParted(array &$from, array &$to): array

    {

        $start = [];

        $end   = [];

        reset($to);

        foreach ($from as $k => $v) {

            $toK = key($to);

            if ($toK === $k && $v === $to[$k]) {

                $start[$k] = $v;

                unset($from[$k], $to[$k]);

            } else {

                break;

            }

        }

        end($from);

        end($to);

        do {

            $fromK = key($from);

            $toK   = key($to);

            if (null === $fromK || null === $toK || current($from) !== current($to)) {

                break;

            }

            prev($from);

            prev($to);

            $end = [$fromK => $from[$fromK]] + $end;

            unset($from[$fromK], $to[$toK]);

        } while (true);

        return [$from, $to, $start, $end];

    }

}