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<?php
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declare(strict_types=1);
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namespace OpenSpout\Writer\Common\Helper;
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/**
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 * @internal
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 */
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final class CellHelper
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{
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    /** @var array<int, string> Cache containing the mapping column index => column letters */
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    private static array $columnIndexToColumnLettersCache = [];
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    /**
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     * Returns the column letters (base 26) associated to the base 10 column index.
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     * Excel uses A to Z letters for column indexing, where A is the 1st column,
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     * Z is the 26th and AA is the 27th.
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     * The mapping is zero based, so that 0 maps to A, B maps to 1, Z to 25 and AA to 26.
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     *
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     * @param int $columnIndexZeroBased The Excel column index (0, 42, ...)
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     *
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     * @return string The associated cell index ('A', 'BC', ...)
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     */
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    public static function getColumnLettersFromColumnIndex(int $columnIndexZeroBased): string
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    {
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        $originalColumnIndex = $columnIndexZeroBased;
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        // Using isset here because it is way faster than array_key_exists...
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        if (!isset(self::$columnIndexToColumnLettersCache[$originalColumnIndex])) {
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            $columnLetters = '';
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            $capitalAAsciiValue = \ord('A');
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            do {
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                $modulus = $columnIndexZeroBased % 26;
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                $columnLetters = \chr($capitalAAsciiValue + $modulus).$columnLetters;
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                // substracting 1 because it's zero-based
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                $columnIndexZeroBased = (int) ($columnIndexZeroBased / 26) - 1;
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            } while ($columnIndexZeroBased >= 0);
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            self::$columnIndexToColumnLettersCache[$originalColumnIndex] = $columnLetters;
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        }
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        return self::$columnIndexToColumnLettersCache[$originalColumnIndex];
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    }
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}