<?php

namespace Box\Spout\Writer\Common\Helper;

/**
 * Class CellHelper
 * This class provides helper functions when working with cells
 */
class CellHelper
{

<     /** @var array Cache containing the mapping column index => cell index */
<     private static $columnIndexToCellIndexCache = [];



>     /** @var array Cache containing the mapping column index => column letters */
>     private static $columnIndexToColumnLettersCache = [];



    /**

<      * Returns the cell index (base 26) associated to the base 10 column index.



>      * Returns the column letters (base 26) associated to the base 10 column index.


     * Excel uses A to Z letters for column indexing, where A is the 1st column,
     * Z is the 26th and AA is the 27th.
     * The mapping is zero based, so that 0 maps to A, B maps to 1, Z to 25 and AA to 26.
     *

<      * @param int $columnIndex The Excel column index (0, 42, ...)



>      * @param int $columnIndexZeroBased The Excel column index (0, 42, ...)
>      *


     * @return string The associated cell index ('A', 'BC', ...)
     */

<     public static function getCellIndexFromColumnIndex($columnIndex)



>     public static function getColumnLettersFromColumnIndex($columnIndexZeroBased)


    {

<         $originalColumnIndex = $columnIndex;



>         $originalColumnIndex = $columnIndexZeroBased;



        // Using isset here because it is way faster than array_key_exists...

<         if (!isset(self::$columnIndexToCellIndexCache[$originalColumnIndex])) {
<             $cellIndex = '';
<             $capitalAAsciiValue = ord('A');



>         if (!isset(self::$columnIndexToColumnLettersCache[$originalColumnIndex])) {
>             $columnLetters = '';
>             $capitalAAsciiValue = \ord('A');



            do {

<                 $modulus = $columnIndex % 26;
<                 $cellIndex = chr($capitalAAsciiValue + $modulus) . $cellIndex;



>                 $modulus = $columnIndexZeroBased % 26;
>                 $columnLetters = \chr($capitalAAsciiValue + $modulus) . $columnLetters;



                // substracting 1 because it's zero-based

<                 $columnIndex = (int) ($columnIndex / 26) - 1;
<             } while ($columnIndex >= 0);



>                 $columnIndexZeroBased = (int) ($columnIndexZeroBased / 26) - 1;
>             } while ($columnIndexZeroBased >= 0);




<             self::$columnIndexToCellIndexCache[$originalColumnIndex] = $cellIndex;



>             self::$columnIndexToColumnLettersCache[$originalColumnIndex] = $columnLetters;


        }


<         return self::$columnIndexToCellIndexCache[$originalColumnIndex];



>         return self::$columnIndexToColumnLettersCache[$originalColumnIndex];


    }
}