<?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\FunctionNotation;

use PhpCsFixer\AbstractFixer;
use PhpCsFixer\FixerDefinition\CodeSample;
use PhpCsFixer\FixerDefinition\FixerDefinition;
use PhpCsFixer\FixerDefinition\FixerDefinitionInterface;
use PhpCsFixer\Tokenizer\CT;
use PhpCsFixer\Tokenizer\Token;
use PhpCsFixer\Tokenizer\Tokens;
use PhpCsFixer\Tokenizer\TokensAnalyzer;

/**
 * @no-named-arguments Parameter names are not covered by the backward compatibility promise.
 */
final class StaticLambdaFixer extends AbstractFixer
{
    public function getDefinition(): FixerDefinitionInterface
    {
        return new FixerDefinition(
            'Lambdas not (indirectly) referencing `$this` must be declared `static`.',
            [
                new CodeSample(
                    <<<'PHP'
                        <?php
                        $a = function () {
                            echo $b;
                        };

                        $b = (function () {
                            \assert($this !== null); // approach you can use to instruct PHP CS Fixer to not convert this lambda to static, e.g. when you see "Cannot bind an instance to a static closure" error caused by lambda handling outside of your control
                        })->bindTo(new stdClass());

                        PHP,
                ),
            ],
            null,
            'Risky when using `->bindTo` on lambdas without referencing to `$this`.',
        );
    }

    public function isCandidate(Tokens $tokens): bool
    {
        return $tokens->isAnyTokenKindsFound([\T_FUNCTION, \T_FN]);
    }

    public function isRisky(): bool
    {
        return true;
    }

    /**
     * {@inheritdoc}
     *
     * Must run after StaticPrivateMethodFixer.
     */
    public function getPriority(): int
    {
        return parent::getPriority();
    }

    protected function applyFix(\SplFileInfo $file, Tokens $tokens): void
    {
        $analyzer = new TokensAnalyzer($tokens);
        $expectedFunctionKinds = [\T_FUNCTION, \T_FN];

        for ($index = $tokens->count() - 4; $index > 0; --$index) {
            if (!$tokens[$index]->isGivenKind($expectedFunctionKinds) || !$analyzer->isLambda($index)) {
                continue;
            }

            $prev = $tokens->getPrevMeaningfulToken($index);

            if ($tokens[$prev]->isGivenKind(\T_STATIC)) {
                continue; // lambda is already 'static'
            }

            $argumentsStartIndex = $tokens->getNextTokenOfKind($index, ['(']);
            $argumentsEndIndex = $tokens->findBlockEnd(Tokens::BLOCK_TYPE_PARENTHESIS, $argumentsStartIndex);

            // figure out where the lambda starts and ends

            if ($tokens[$index]->isGivenKind(\T_FUNCTION)) {
                $lambdaOpenIndex = $tokens->getNextTokenOfKind($argumentsEndIndex, ['{']);
                $lambdaEndIndex = $tokens->findBlockEnd(Tokens::BLOCK_TYPE_BRACE, $lambdaOpenIndex);
            } else { // T_FN
                $lambdaOpenIndex = $tokens->getNextTokenOfKind($argumentsEndIndex, [[\T_DOUBLE_ARROW]]);
                $lambdaEndIndex = $analyzer->getLastTokenIndexOfArrowFunction($index);
            }

            if ($this->hasPossibleReferenceToThis($tokens, $lambdaOpenIndex, $lambdaEndIndex)) {
                continue;
            }

            // make the lambda static
            $tokens->insertAt(
                $index,
                [
                    new Token([\T_STATIC, 'static']),
                    new Token([\T_WHITESPACE, ' ']),
                ],
            );

            $index -= 4; // fixed after a lambda, closes candidate is at least 4 tokens before that
        }
    }

    /**
     * Returns 'true' if there is a possible reference to '$this' within the given tokens index range.
     */
    private function hasPossibleReferenceToThis(Tokens $tokens, int $startIndex, int $endIndex): bool
    {
        for ($i = $startIndex; $i <= $endIndex; ++$i) {
            if ($tokens[$i]->isGivenKind(\T_VARIABLE) && '$this' === strtolower($tokens[$i]->getContent())) {
                return true; // directly accessing '$this'
            }

            if ($tokens[$i]->isGivenKind([
                \T_INCLUDE,                    // loading additional symbols we cannot analyse here
                \T_INCLUDE_ONCE,               // "
                \T_REQUIRE,                    // "
                \T_REQUIRE_ONCE,               // "
                CT::T_DYNAMIC_VAR_BRACE_OPEN, // "$h = ${$g};" case
                \T_EVAL,                       // "$c = eval('return $this;');" case
            ])) {
                return true;
            }

            if ($tokens[$i]->isClassy()) {
                $openBraceIndex = $tokens->getNextTokenOfKind($i, ['{']);
                $i = $tokens->getNextMeaningfulToken($i);
                if ($i <= $openBraceIndex && $this->hasPossibleReferenceToThis(
                    $tokens,
                    $i,
                    $openBraceIndex,
                )) {
                    return true;
                }
                $i = $tokens->findBlockEnd(Tokens::BLOCK_TYPE_BRACE, $openBraceIndex);

                continue;
            }

            if ($tokens[$i]->equals('$')) {
                $nextIndex = $tokens->getNextMeaningfulToken($i);

                if ($tokens[$nextIndex]->isGivenKind(\T_VARIABLE)) {
                    return true; // "$$a" case
                }
            }

            if ($tokens[$i]->equals([\T_STRING, 'parent'], false)) {
                return true; // parent:: case
            }
        }

        return false;
    }
}
