<?php

declare(strict_types=1);

/*
 * This file is part of PHP CS Fixer.
 *
 * (c) Fabien Potencier <fabien@symfony.com>
 *     Dariusz Rumiński <dariusz.ruminski@gmail.com>
 *
 * This source file is subject to the MIT license that is bundled
 * with this source code in the file LICENSE.
 */

namespace PhpCsFixer\Fixer\Alias;

use PhpCsFixer\AbstractFixer;
use PhpCsFixer\FixerDefinition\CodeSample;
use PhpCsFixer\FixerDefinition\FixerDefinition;
use PhpCsFixer\FixerDefinition\FixerDefinitionInterface;
use PhpCsFixer\Preg;
use PhpCsFixer\Tokenizer\Token;
use PhpCsFixer\Tokenizer\Tokens;

/**
 * @author Filippo Tessarotto <zoeslam@gmail.com>
 */
final class BacktickToShellExecFixer extends AbstractFixer
{
    /**
     * {@inheritdoc}
     */
    public function isCandidate(Tokens $tokens): bool
    {
        return $tokens->isTokenKindFound('`');
    }

    /**
     * {@inheritdoc}
     */
    public function getDefinition(): FixerDefinitionInterface
    {
        return new FixerDefinition(
            'Converts backtick operators to `shell_exec` calls.',
            [
                new CodeSample(
                    <<<'EOT'
<?php
$plain = `ls -lah`;
$withVar = `ls -lah $var1 ${var2} {$var3} {$var4[0]} {$var5->call()}`;

EOT
                ),
            ],
            'Conversion is done only when it is non risky, so when special chars like single-quotes, double-quotes and backticks are not used inside the command.'
        );
    }

    /**
     * {@inheritdoc}
     *
     * Must run before EscapeImplicitBackslashesFixer, ExplicitStringVariableFixer, NativeFunctionInvocationFixer, SingleQuoteFixer.
     */
    public function getPriority(): int
    {
        return 2;
    }

    /**
     * {@inheritdoc}
     */
    protected function applyFix(\SplFileInfo $file, Tokens $tokens): void
    {
        $backtickStarted = false;
        $backtickTokens = [];
        for ($index = $tokens->count() - 1; $index > 0; --$index) {
            $token = $tokens[$index];

            if (!$token->equals('`')) {
                if ($backtickStarted) {
                    $backtickTokens[$index] = $token;
                }

                continue;
            }

            $backtickTokens[$index] = $token;

            if ($backtickStarted) {
                $this->fixBackticks($tokens, $backtickTokens);
                $backtickTokens = [];
            }

            $backtickStarted = !$backtickStarted;
        }
    }

    /**
     * Override backtick code with corresponding double-quoted string.
     *
     * @param array<int, Token> $backtickTokens
     */
    private function fixBackticks(Tokens $tokens, array $backtickTokens): void
    {
        // Track indices for final override
        ksort($backtickTokens);
        $openingBacktickIndex = key($backtickTokens);
        end($backtickTokens);
        $closingBacktickIndex = key($backtickTokens);

        // Strip enclosing backticks
        array_shift($backtickTokens);
        array_pop($backtickTokens);

        // Double-quoted strings are parsed differently if they contain
        // variables or not, so we need to build the new token array accordingly
        $count = \count($backtickTokens);

        $newTokens = [
            new Token([T_STRING, 'shell_exec']),
            new Token('('),
        ];

        if (1 !== $count) {
            $newTokens[] = new Token('"');
        }

        foreach ($backtickTokens as $token) {
            if (!$token->isGivenKind(T_ENCAPSED_AND_WHITESPACE)) {
                $newTokens[] = $token;

                continue;
            }

            $content = $token->getContent();
            // Escaping special chars depends on the context: too tricky
            if (Preg::match('/[`"\']/u', $content)) {
                return;
            }

            $kind = T_ENCAPSED_AND_WHITESPACE;

            if (1 === $count) {
                $content = '"'.$content.'"';
                $kind = T_CONSTANT_ENCAPSED_STRING;
            }

            $newTokens[] = new Token([$kind, $content]);
        }

        if (1 !== $count) {
            $newTokens[] = new Token('"');
        }

        $newTokens[] = new Token(')');

        $tokens->overrideRange($openingBacktickIndex, $closingBacktickIndex, $newTokens);
    }
}
