<?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\StringNotation;

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;

/**
 * @author Filippo Tessarotto <zoeslam@gmail.com>
 */
final class ExplicitStringVariableFixer extends AbstractFixer
{
    /**
     * {@inheritdoc}
     */
    public function getDefinition(): FixerDefinitionInterface
    {
        return new FixerDefinition(
            'Converts implicit variables into explicit ones in double-quoted strings or heredoc syntax.',
            [new CodeSample(
                <<<'EOT'
<?php
$a = "My name is $name !";
$b = "I live in $state->country !";
$c = "I have $farm[0] chickens !";

EOT
            )],
            'The reasoning behind this rule is the following:'
                ."\n".'- When there are two valid ways of doing the same thing, using both is confusing, there should be a coding standard to follow'
                ."\n".'- PHP manual marks `"$var"` syntax as implicit and `"${var}"` syntax as explicit: explicit code should always be preferred'
                ."\n".'- Explicit syntax allows word concatenation inside strings, e.g. `"${var}IsAVar"`, implicit doesn\'t'
                ."\n".'- Explicit syntax is easier to detect for IDE/editors and therefore has colors/highlight with higher contrast, which is easier to read'
            ."\n".'Backtick operator is skipped because it is harder to handle; you can use `backtick_to_shell_exec` fixer to normalize backticks to strings'
        );
    }

    /**
     * {@inheritdoc}
     *
     * Must run after BacktickToShellExecFixer.
     */
    public function getPriority(): int
    {
        return 0;
    }

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

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

            if ($token->equals('`')) {
                $backtickStarted = !$backtickStarted;

                continue;
            }

            if ($backtickStarted || !$token->isGivenKind(T_VARIABLE)) {
                continue;
            }

            $prevToken = $tokens[$index - 1];

            if (!$this->isStringPartToken($prevToken)) {
                continue;
            }

            $distinctVariableIndex = $index;
            $variableTokens = [
                $distinctVariableIndex => [
                    'tokens' => [$index => $token],
                    'firstVariableTokenIndex' => $index,
                    'lastVariableTokenIndex' => $index,
                ],
            ];

            $nextIndex = $index + 1;
            $squareBracketCount = 0;

            while (!$this->isStringPartToken($tokens[$nextIndex])) {
                if ($tokens[$nextIndex]->isGivenKind(T_CURLY_OPEN)) {
                    $nextIndex = $tokens->getNextTokenOfKind($nextIndex, [[CT::T_CURLY_CLOSE]]);
                } elseif ($tokens[$nextIndex]->isGivenKind(T_VARIABLE) && 1 !== $squareBracketCount) {
                    $distinctVariableIndex = $nextIndex;
                    $variableTokens[$distinctVariableIndex] = [
                        'tokens' => [$nextIndex => $tokens[$nextIndex]],
                        'firstVariableTokenIndex' => $nextIndex,
                        'lastVariableTokenIndex' => $nextIndex,
                    ];
                } else {
                    $variableTokens[$distinctVariableIndex]['tokens'][$nextIndex] = $tokens[$nextIndex];
                    $variableTokens[$distinctVariableIndex]['lastVariableTokenIndex'] = $nextIndex;

                    if ($tokens[$nextIndex]->equalsAny(['[', ']'])) {
                        ++$squareBracketCount;
                    }
                }

                ++$nextIndex;
            }
            krsort($variableTokens, SORT_NUMERIC);

            foreach ($variableTokens as $distinctVariableSet) {
                if (1 === \count($distinctVariableSet['tokens'])) {
                    $singleVariableIndex = key($distinctVariableSet['tokens']);
                    $singleVariableToken = current($distinctVariableSet['tokens']);
                    $tokens->overrideRange($singleVariableIndex, $singleVariableIndex, [
                        new Token([T_CURLY_OPEN, '{']),
                        new Token([T_VARIABLE, $singleVariableToken->getContent()]),
                        new Token([CT::T_CURLY_CLOSE, '}']),
                    ]);
                } else {
                    foreach ($distinctVariableSet['tokens'] as $variablePartIndex => $variablePartToken) {
                        if ($variablePartToken->isGivenKind(T_NUM_STRING)) {
                            $tokens[$variablePartIndex] = new Token([T_LNUMBER, $variablePartToken->getContent()]);

                            continue;
                        }

                        if ($variablePartToken->isGivenKind(T_STRING) && $tokens[$variablePartIndex + 1]->equals(']')) {
                            $tokens[$variablePartIndex] = new Token([T_CONSTANT_ENCAPSED_STRING, "'".$variablePartToken->getContent()."'"]);
                        }
                    }

                    $tokens->insertAt($distinctVariableSet['lastVariableTokenIndex'] + 1, new Token([CT::T_CURLY_CLOSE, '}']));
                    $tokens->insertAt($distinctVariableSet['firstVariableTokenIndex'], new Token([T_CURLY_OPEN, '{']));
                }
            }
        }
    }

    /**
     * Check if token is a part of a string.
     *
     * @param Token $token The token to check
     */
    private function isStringPartToken(Token $token): bool
    {
        return $token->isGivenKind(T_ENCAPSED_AND_WHITESPACE)
            || $token->isGivenKind(T_START_HEREDOC)
            || '"' === $token->getContent()
            || 'b"' === strtolower($token->getContent())
        ;
    }
}
