<?php
namespace YOOtheme\GraphQL\Utils;

class BlockString {
    /**
     * Produces the value of a block string from its parsed raw value, similar to
     * Coffeescript's block string, Python's docstring trim or Ruby's strip_heredoc.
     *
     * This implements the GraphQL spec's BlockStringValue() static algorithm.
     */
    public static function value($rawString) {
        // Expand a block string's raw value into independent lines.
        $lines = preg_split("/\\r\\n|[\\n\\r]/", $rawString);
    
        // Remove common indentation from all lines but first.
        $commonIndent = null;
        $linesLength = count($lines);

        for ($i = 1; $i < $linesLength; $i++) {
            $line = $lines[$i];
            $indent = self::leadingWhitespace($line);
    
            if (
                $indent < mb_strlen($line) &&
                ($commonIndent === null || $indent < $commonIndent)
            ) {
                $commonIndent = $indent;
                if ($commonIndent === 0) {
                    break;
                }
            }
        }
    
        if ($commonIndent) {
            for ($i = 1; $i < $linesLength; $i++) {
                $line = $lines[$i];
                $lines[$i] = mb_substr($line, $commonIndent);
            }
        }
    
        // Remove leading and trailing blank lines.
        while (count($lines) > 0 && trim($lines[0], " \t") === '') {
            array_shift($lines);
        }
        while (count($lines) > 0 && trim($lines[count($lines) - 1], " \t") === '') {
            array_pop($lines);
        }

        // Return a string of the lines joined with U+000A.
        return implode("\n", $lines);
    }

    private static function leadingWhitespace($str) {
        $i = 0;
        while ($i < mb_strlen($str) && ($str[$i] === ' ' || $str[$i] === '\t')) {
          $i++;
        }

        return $i;
    }
}