class UnnecessaryStringConcatSniff

class UnnecessaryStringConcatSniff implements Sniff {
    
    /**
     * A list of tokenizers this sniff supports.
     *
     * @var array
     */
    public $supportedTokenizers = [
        'PHP',
        'JS',
    ];
    
    /**
     * If true, an error will be thrown; otherwise a warning.
     *
     * @var boolean
     */
    public $error = true;
    
    /**
     * If true, strings concatenated over multiple lines are allowed.
     *
     * Useful if you break strings over multiple lines to work
     * within a max line length.
     *
     * @var boolean
     */
    public $allowMultiline = false;
    
    /**
     * Returns an array of tokens this test wants to listen for.
     *
     * @return array<int|string>
     */
    public function register() {
        return [
            T_STRING_CONCAT,
            T_PLUS,
        ];
    }
    
    //end register()
    
    /**
     * Processes this sniff, when one of its tokens is encountered.
     *
     * @param \PHP_CodeSniffer\Files\File $phpcsFile The file being scanned.
     * @param int                         $stackPtr  The position of the current token
     *                                               in the stack passed in $tokens.
     *
     * @return void
     */
    public function process(File $phpcsFile, $stackPtr) {
        $tokens = $phpcsFile->getTokens();
        if ($tokens[$stackPtr]['code'] === T_STRING_CONCAT && $phpcsFile->tokenizerType === 'JS') {
            // JS uses T_PLUS for string concatenation, not T_STRING_CONCAT.
            return;
        }
        else {
            if ($tokens[$stackPtr]['code'] === T_PLUS && $phpcsFile->tokenizerType === 'PHP') {
                // PHP uses T_STRING_CONCAT for string concatenation, not T_PLUS.
                return;
            }
        }
        $prev = $phpcsFile->findPrevious(T_WHITESPACE, $stackPtr - 1, null, true);
        $next = $phpcsFile->findNext(T_WHITESPACE, $stackPtr + 1, null, true);
        if ($next === false) {
            return;
        }
        if (isset(Tokens::$stringTokens[$tokens[$prev]['code']]) === false || isset(Tokens::$stringTokens[$tokens[$next]['code']]) === false) {
            // Bow out as at least one of the two tokens being concatenated is not a string.
            return;
        }
        if ($tokens[$prev]['content'][0] !== $tokens[$next]['content'][0]) {
            // Bow out as the two strings are not of the same type.
            return;
        }
        // Before we throw an error for PHP, allow strings to be
        // combined if they would have < and ? next to each other because
        // this trick is sometimes required in PHP strings.
        if ($phpcsFile->tokenizerType === 'PHP') {
            $prevChar = substr($tokens[$prev]['content'], -2, 1);
            $nextChar = $tokens[$next]['content'][1];
            $combined = $prevChar . $nextChar;
            if ($combined === '?' . '>' || $combined === '<' . '?') {
                return;
            }
        }
        if ($this->allowMultiline === true && $tokens[$prev]['line'] !== $tokens[$next]['line']) {
            return;
        }
        $error = 'String concat is not required here; use a single string instead';
        if ($this->error === true) {
            $phpcsFile->addError($error, $stackPtr, 'Found');
        }
        else {
            $phpcsFile->addWarning($error, $stackPtr, 'Found');
        }
    }
    
    //end process()

}