<?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 SebastianBergmann\Diff\Output\DiffOutputBuilderInterface;
use SebastianBergmann\Diff\Output\UnifiedDiffOutputBuilder;

/**
 * Diff implementation.
 */
final class Differ
{

    /**
     *
     * @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
     * @param LongestCommonSubsequenceCalculator|null $lcs
     *
     * @return string
     */
    public function diff($from, $to, LongestCommonSubsequenceCalculator $lcs = null): string
    {
        $from = $this->validateDiffInput($from);
        $to = $this->validateDiffInput($to);
        $diff = $this->diffToArray($from, $to, $lcs);
        
        return $this->outputBuilder->getDiff($diff);
    }

    /**
     * Casts variable to string if it is not a string or array.
     *
     * @param mixed $input
     *
     * @return string
     */
    private function validateDiffInput($input): string
    {
        if (! \is_array($input) && ! \is_string($input)) {
            return (string) $input;
        }
        
        return $input;
    }

    /**
     * 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 $lcs
     *
     * @return array
     */
    public function diffToArray($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.');
        }
        
        list ($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,
                0 /* OLD */
            ];
        }
        
        \reset($from);
        \reset($to);
        
        foreach ($common as $token) {
            while (($fromToken = \reset($from)) !== $token) {
                $diff[] = [
                    \array_shift($from),
                    2 /* REMOVED */
                ];
            }
            
            while (($toToken = \reset($to)) !== $token) {
                $diff[] = [
                    \array_shift($to),
                    1 /* ADDED */
                ];
            }
            
            $diff[] = [
                $token,
                0 /* OLD */
            ];
            
            \array_shift($from);
            \array_shift($to);
        }
        
        while (($token = \array_shift($from)) !== null) {
            $diff[] = [
                $token,
                2 /* REMOVED */
            ];
        }
        
        while (($token = \array_shift($to)) !== null) {
            $diff[] = [
                $token,
                1 /* ADDED */
            ];
        }
        
        foreach ($end as $token) {
            $diff[] = [
                $token,
                0 /* OLD */
            ];
        }
        
        if ($this->detectUnmatchedLineEndings($diff)) {
            \array_unshift($diff, [
                "#Warning: Strings contain different line endings!\n",
                3
            ]);
        }
        
        return $diff;
    }

    /**
     * Checks if input is string, if so it will split it line-by-line.
     *
     * @param string $input
     *
     * @return array
     */
    private function splitStringByLines(string $input): array
    {
        return \preg_split('/(.*\R)/', $input, - 1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);
    }

    /**
     *
     * @param array $from
     * @param array $to
     *
     * @return LongestCommonSubsequenceCalculator
     */
    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.
     *
     * @param array $from
     * @param array $to
     *
     * @return int|float
     */
    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.
     *
     * @param array $diff
     *
     * @return bool
     */
    private function detectUnmatchedLineEndings(array $diff): bool
    {
        $newLineBreaks = [
            '' => true
        ];
        $oldLineBreaks = [
            '' => true
        ];
        
        foreach ($diff as $entry) {
            if (0 === $entry[1]) { /* OLD */
                $ln = $this->getLinebreak($entry[0]);
                $oldLineBreaks[$ln] = true;
                $newLineBreaks[$ln] = true;
            } elseif (1 === $entry[1]) { /* ADDED */
                $newLineBreaks[$this->getLinebreak($entry[0])] = true;
            } elseif (2 === $entry[1]) { /* REMOVED */
                $oldLineBreaks[$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
        ];
    }
}
