class UselessVariableSniff

class UselessVariableSniff implements Sniff {
    public const CODE_USELESS_VARIABLE = 'UselessVariable';
    
    /**
     * @return array<int, (int|string)>
     */
    public function register() : array {
        return [
            T_RETURN,
        ];
    }
    
    /**
     * @phpcsSuppress SlevomatCodingStandard.TypeHints.ParameterTypeHint.MissingNativeTypeHint
     * @param int $returnPointer
     */
    public function process(File $phpcsFile, $returnPointer) : void {
        $tokens = $phpcsFile->getTokens();
        
        /** @var int $variablePointer */
        $variablePointer = TokenHelper::findNextEffective($phpcsFile, $returnPointer + 1);
        if ($tokens[$variablePointer]['code'] !== T_VARIABLE) {
            return;
        }
        $returnSemicolonPointer = TokenHelper::findNextEffective($phpcsFile, $variablePointer + 1);
        if ($tokens[$returnSemicolonPointer]['code'] !== T_SEMICOLON) {
            return;
        }
        $variableName = $tokens[$variablePointer]['content'];
        $functionPointer = $this->findFunctionPointer($phpcsFile, $variablePointer);
        if ($functionPointer !== null) {
            if ($this->isReturnedByReference($phpcsFile, $functionPointer)) {
                return;
            }
            if ($this->isStaticVariable($phpcsFile, $functionPointer, $variablePointer, $variableName)) {
                return;
            }
            if ($this->isFunctionParameter($phpcsFile, $functionPointer, $variableName)) {
                return;
            }
        }
        $previousVariablePointer = $this->findPreviousVariablePointer($phpcsFile, $returnPointer, $variableName);
        if ($previousVariablePointer === null) {
            return;
        }
        if (!$this->isAssignmentToVariable($phpcsFile, $previousVariablePointer)) {
            return;
        }
        if ($this->isAssignedInControlStructure($phpcsFile, $previousVariablePointer)) {
            return;
        }
        if ($this->isAssignedInFunctionCall($phpcsFile, $previousVariablePointer)) {
            return;
        }
        if ($this->hasVariableVarAnnotation($phpcsFile, $previousVariablePointer)) {
            return;
        }
        if ($this->hasAnotherAssignmentBefore($phpcsFile, $previousVariablePointer, $variableName)) {
            return;
        }
        if (!$this->areBothPointersNearby($phpcsFile, $previousVariablePointer, $returnPointer)) {
            return;
        }
        $errorParameters = [
            sprintf('Useless variable %s.', $variableName),
            $previousVariablePointer,
            self::CODE_USELESS_VARIABLE,
        ];
        $pointerBeforePreviousVariable = TokenHelper::findPreviousEffective($phpcsFile, $previousVariablePointer - 1);
        if (!in_array($tokens[$pointerBeforePreviousVariable]['code'], [
            T_SEMICOLON,
            T_OPEN_CURLY_BRACKET,
            T_CLOSE_CURLY_BRACKET,
        ], true) && TokenHelper::findNextEffective($phpcsFile, $returnSemicolonPointer + 1) !== null) {
            $phpcsFile->addError(...$errorParameters);
            return;
        }
        $fix = $phpcsFile->addFixableError(...$errorParameters);
        if (!$fix) {
            return;
        }
        
        /** @var int $assignmentPointer */
        $assignmentPointer = TokenHelper::findNextEffective($phpcsFile, $previousVariablePointer + 1);
        $assignmentFixerMapping = [
            T_PLUS_EQUAL => '+',
            T_MINUS_EQUAL => '-',
            T_MUL_EQUAL => '*',
            T_DIV_EQUAL => '/',
            T_POW_EQUAL => '**',
            T_MOD_EQUAL => '%',
            T_AND_EQUAL => '&',
            T_OR_EQUAL => '|',
            T_XOR_EQUAL => '^',
            T_SL_EQUAL => '<<',
            T_SR_EQUAL => '>>',
            T_CONCAT_EQUAL => '.',
        ];
        $previousVariableSemicolonPointer = $this->findSemicolon($phpcsFile, $previousVariablePointer);
        $phpcsFile->fixer
            ->beginChangeset();
        if ($tokens[$assignmentPointer]['code'] === T_EQUAL) {
            FixerHelper::change($phpcsFile, $previousVariablePointer, $assignmentPointer, 'return');
        }
        else {
            $phpcsFile->fixer
                ->addContentBefore($previousVariablePointer, 'return ');
            $phpcsFile->fixer
                ->replaceToken($assignmentPointer, $assignmentFixerMapping[$tokens[$assignmentPointer]['code']]);
        }
        FixerHelper::removeBetweenIncluding($phpcsFile, $previousVariableSemicolonPointer + 1, $returnSemicolonPointer);
        $phpcsFile->fixer
            ->endChangeset();
    }
    private function findPreviousVariablePointer(File $phpcsFile, int $pointer, string $variableName) : ?int {
        $tokens = $phpcsFile->getTokens();
        for ($i = $pointer - 1; $i >= 0; $i--) {
            if (in_array($tokens[$i]['code'], TokenHelper::$functionTokenCodes, true) && ScopeHelper::isInSameScope($phpcsFile, $tokens[$i]['scope_opener'] + 1, $pointer)) {
                return null;
            }
            if ($tokens[$i]['code'] !== T_VARIABLE) {
                continue;
            }
            if ($tokens[$i]['content'] !== $variableName) {
                continue;
            }
            $previousPointer = TokenHelper::findPreviousEffective($phpcsFile, $i - 1);
            if ($tokens[$previousPointer]['code'] === T_DOUBLE_COLON) {
                continue;
            }
            if (!ScopeHelper::isInSameScope($phpcsFile, $i, $pointer)) {
                continue;
            }
            return $i;
        }
        return null;
    }
    private function isAssignedInControlStructure(File $phpcsFile, int $pointer) : bool {
        $controlStructure = TokenHelper::findPrevious($phpcsFile, [
            T_WHILE,
            T_FOR,
            T_FOREACH,
            T_SWITCH,
            T_IF,
            T_ELSEIF,
        ], $pointer - 1);
        if ($controlStructure === null) {
            return false;
        }
        $tokens = $phpcsFile->getTokens();
        return $tokens[$controlStructure]['parenthesis_opener'] < $pointer && $pointer < $tokens[$controlStructure]['parenthesis_closer'];
    }
    private function isAssignedInFunctionCall(File $phpcsFile, int $pointer) : bool {
        $possibleFunctionNamePointer = TokenHelper::findPrevious($phpcsFile, T_STRING, $pointer - 1);
        if ($possibleFunctionNamePointer === null) {
            return false;
        }
        $tokens = $phpcsFile->getTokens();
        $parenthesisOpenerPointer = TokenHelper::findNextEffective($phpcsFile, $possibleFunctionNamePointer + 1);
        if ($tokens[$parenthesisOpenerPointer]['code'] !== T_OPEN_PARENTHESIS) {
            return false;
        }
        return $parenthesisOpenerPointer < $pointer && $pointer < $tokens[$parenthesisOpenerPointer]['parenthesis_closer'];
    }
    private function isAssignmentToVariable(File $phpcsFile, int $pointer) : bool {
        $assignmentPointer = TokenHelper::findNextEffective($phpcsFile, $pointer + 1);
        return in_array($phpcsFile->getTokens()[$assignmentPointer]['code'], [
            T_EQUAL,
            T_PLUS_EQUAL,
            T_MINUS_EQUAL,
            T_MUL_EQUAL,
            T_DIV_EQUAL,
            T_POW_EQUAL,
            T_MOD_EQUAL,
            T_AND_EQUAL,
            T_OR_EQUAL,
            T_XOR_EQUAL,
            T_SL_EQUAL,
            T_SR_EQUAL,
            T_CONCAT_EQUAL,
        ], true);
    }
    private function findFunctionPointer(File $phpcsFile, int $pointer) : ?int {
        $tokens = $phpcsFile->getTokens();
        foreach (array_reverse($tokens[$pointer]['conditions'], true) as $conditionPointer => $conditionTokenCode) {
            if (in_array($conditionTokenCode, TokenHelper::$functionTokenCodes, true)) {
                return $conditionPointer;
            }
        }
        return null;
    }
    private function isStaticVariable(File $phpcsFile, int $functionPointer, int $variablePointer, string $variableName) : bool {
        $tokens = $phpcsFile->getTokens();
        for ($i = $tokens[$functionPointer]['scope_opener'] + 1; $i < $variablePointer; $i++) {
            if ($tokens[$i]['code'] !== T_VARIABLE) {
                continue;
            }
            if ($tokens[$i]['content'] !== $variableName) {
                continue;
            }
            $pointerBeforeParameter = TokenHelper::findPreviousEffective($phpcsFile, $i - 1);
            if ($tokens[$pointerBeforeParameter]['code'] === T_STATIC) {
                return true;
            }
        }
        return false;
    }
    private function isFunctionParameter(File $phpcsFile, int $functionPointer, string $variableName) : bool {
        $tokens = $phpcsFile->getTokens();
        for ($i = $tokens[$functionPointer]['parenthesis_opener'] + 1; $i < $tokens[$functionPointer]['parenthesis_closer']; $i++) {
            if ($tokens[$i]['code'] !== T_VARIABLE) {
                continue;
            }
            if ($tokens[$i]['content'] !== $variableName) {
                continue;
            }
            return true;
        }
        return false;
    }
    private function isReturnedByReference(File $phpcsFile, int $functionPointer) : bool {
        $tokens = $phpcsFile->getTokens();
        $referencePointer = TokenHelper::findNextEffective($phpcsFile, $functionPointer + 1);
        return $tokens[$referencePointer]['code'] === T_BITWISE_AND;
    }
    private function hasVariableVarAnnotation(File $phpcsFile, int $variablePointer) : bool {
        $tokens = $phpcsFile->getTokens();
        $pointerBeforeVariable = TokenHelper::findPreviousNonWhitespace($phpcsFile, $variablePointer - 1);
        if ($tokens[$pointerBeforeVariable]['code'] !== T_DOC_COMMENT_CLOSE_TAG) {
            return false;
        }
        $docCommentContent = TokenHelper::getContent($phpcsFile, $tokens[$pointerBeforeVariable]['comment_opener'], $pointerBeforeVariable);
        return preg_match('~@(?:(?:phpstan|psalm)-)?var\\s+.+\\s+' . preg_quote($tokens[$variablePointer]['content'], '~') . '(?:\\s|$)~', $docCommentContent) !== 0;
    }
    private function hasAnotherAssignmentBefore(File $phpcsFile, int $variablePointer, string $variableName) : bool {
        $previousVariablePointer = $this->findPreviousVariablePointer($phpcsFile, $variablePointer, $variableName);
        if ($previousVariablePointer === null) {
            return false;
        }
        if (!$this->isAssignmentToVariable($phpcsFile, $previousVariablePointer)) {
            return false;
        }
        return $this->areBothVariablesNearby($phpcsFile, $previousVariablePointer, $variablePointer);
    }
    private function areBothPointersNearby(File $phpcsFile, int $firstPointer, int $secondPointer) : bool {
        $firstVariableSemicolonPointer = $this->findSemicolon($phpcsFile, $firstPointer);
        $pointerAfterFirstVariableSemicolon = TokenHelper::findNextEffective($phpcsFile, $firstVariableSemicolonPointer + 1);
        return $pointerAfterFirstVariableSemicolon === $secondPointer;
    }
    private function areBothVariablesNearby(File $phpcsFile, int $firstVariablePointer, int $secondVariablePointer) : bool {
        if ($this->areBothPointersNearby($phpcsFile, $firstVariablePointer, $secondVariablePointer)) {
            return true;
        }
        $tokens = $phpcsFile->getTokens();
        $lastConditionPointer = array_reverse(array_keys($tokens[$firstVariablePointer]['conditions']))[0];
        $lastConditionScopeCloserPointer = $tokens[$lastConditionPointer]['scope_closer'];
        if ($tokens[$lastConditionPointer]['code'] === T_DO) {
            $lastConditionScopeCloserPointer = TokenHelper::findNext($phpcsFile, T_SEMICOLON, $lastConditionScopeCloserPointer + 1);
        }
        return TokenHelper::findNextEffective($phpcsFile, $lastConditionScopeCloserPointer + 1) === $secondVariablePointer;
    }
    private function findSemicolon(File $phpcsFile, int $pointer) : int {
        $tokens = $phpcsFile->getTokens();
        $semicolonPointer = null;
        for ($i = $pointer + 1; $i < count($tokens) - 1; $i++) {
            if ($tokens[$i]['code'] !== T_SEMICOLON) {
                continue;
            }
            if (!ScopeHelper::isInSameScope($phpcsFile, $pointer, $i)) {
                continue;
            }
            $semicolonPointer = $i;
            break;
        }
        
        /** @var int $semicolonPointer */
        $semicolonPointer = $semicolonPointer;
        return $semicolonPointer;
    }

}