<?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\Casing;

use PhpCsFixer\AbstractFixer;
use PhpCsFixer\FixerDefinition\CodeSample;
use PhpCsFixer\FixerDefinition\FixerDefinition;
use PhpCsFixer\FixerDefinition\FixerDefinitionInterface;
use PhpCsFixer\Tokenizer\Analyzer\Analysis\NamespaceAnalysis;
use PhpCsFixer\Tokenizer\Analyzer\NamespacesAnalyzer;
use PhpCsFixer\Tokenizer\CT;
use PhpCsFixer\Tokenizer\Token;
use PhpCsFixer\Tokenizer\Tokens;

final class ClassReferenceNameCasingFixer extends AbstractFixer
{
    /**
     * {@inheritdoc}
     */
    public function getDefinition(): FixerDefinitionInterface
    {
        return new FixerDefinition(
            'When referencing a class it must be written using the correct casing.',
            [
                new CodeSample("<?php\nthrow new \\exception();\n"),
            ]
        );
    }

    /**
     * {@inheritdoc}
     */
    public function isCandidate(Tokens $tokens): bool
    {
        return $tokens->isTokenKindFound(T_STRING);
    }

    /**
     * {@inheritdoc}
     */
    protected function applyFix(\SplFileInfo $file, Tokens $tokens): void
    {
        $namespacesAnalyzer = new NamespacesAnalyzer();
        $classNames = $this->getClassNames();

        foreach ($namespacesAnalyzer->getDeclarations($tokens) as $namespace) {
            foreach ($this->getClassReference($tokens, $namespace) as $reference) {
                $currentContent = $tokens[$reference]->getContent();
                $lowerCurrentContent = strtolower($currentContent);

                if (isset($classNames[$lowerCurrentContent]) && $currentContent !== $classNames[$lowerCurrentContent]) {
                    $tokens[$reference] = new Token([T_STRING, $classNames[$lowerCurrentContent]]);
                }
            }
        }
    }

    private function getClassReference(Tokens $tokens, NamespaceAnalysis $namespace): \Generator
    {
        static $notBeforeKinds;

        if (null === $notBeforeKinds) {
            $notBeforeKinds = [
                CT::T_USE_TRAIT,
                T_AS,
                T_CASE, // PHP 8.1 trait enum-case
                T_CLASS,
                T_CONST,
                T_DOUBLE_COLON,
                T_FUNCTION,
                T_INTERFACE,
                T_OBJECT_OPERATOR,
                T_TRAIT,
            ];

            if (\defined('T_ENUM')) { // @TODO: drop condition when PHP 8.1+ is required
                $notBeforeKinds[] = T_ENUM;
            }
        }

        $namespaceIsGlobal = $namespace->isGlobalNamespace();

        for ($index = $namespace->getScopeStartIndex(); $index < $namespace->getScopeEndIndex(); ++$index) {
            if (!$tokens[$index]->isGivenKind(T_STRING)) {
                continue;
            }

            $nextIndex = $tokens->getNextMeaningfulToken($index);

            if ($tokens[$nextIndex]->isGivenKind(T_NS_SEPARATOR)) {
                continue;
            }

            $prevIndex = $tokens->getPrevMeaningfulToken($index);
            $isNamespaceSeparator = $tokens[$prevIndex]->isGivenKind(T_NS_SEPARATOR);

            if (!$isNamespaceSeparator && !$namespaceIsGlobal) {
                continue;
            }

            if ($isNamespaceSeparator) {
                $prevIndex = $tokens->getPrevMeaningfulToken($prevIndex);

                if ($tokens[$prevIndex]->isGivenKind(T_STRING)) {
                    continue;
                }
            } elseif ($tokens[$prevIndex]->isGivenKind($notBeforeKinds)) {
                continue;
            }

            if (!$tokens[$prevIndex]->isGivenKind([T_NEW]) && $tokens[$nextIndex]->equals('(')) {
                continue;
            }

            yield $index;
        }
    }

    private function getClassNames(): array
    {
        static $classes = null;

        if (null === $classes) {
            $classes = [];

            foreach (get_declared_classes() as $class) {
                if ((new \ReflectionClass($class))->isInternal()) {
                    $classes[strtolower($class)] = $class;
                }
            }
        }

        return $classes;
    }
}
