<?php

namespace Box\Spout\Writer\Common\Helper;

/**
 * Class CellHelper
 * This class provides helper functions when working with cells
 *
 * @package Box\Spout\Writer\Common\Helper
 */
class CellHelper {

	/** @var array Cache containing the mapping column index => cell index */
	private static $columnIndexToCellIndexCache = array();

	/**
	 * Returns the cell index (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, ...)
	 * @return string The associated cell index ('A', 'BC', ...)
	 */
	public static function getCellIndexFromColumnIndex( $columnIndex ) {
		$originalColumnIndex = $columnIndex;

		// Using isset here because it is way faster than array_key_exists...
		if ( ! isset( self::$columnIndexToCellIndexCache[ $originalColumnIndex ] ) ) {
			$cellIndex          = '';
			$capitalAAsciiValue = ord( 'A' );

			do {
				$modulus   = $columnIndex % 26;
				$cellIndex = chr( $capitalAAsciiValue + $modulus ) . $cellIndex;

				// substracting 1 because it's zero-based
				$columnIndex = intval( $columnIndex / 26 ) - 1;

			} while ( $columnIndex >= 0 );

			self::$columnIndexToCellIndexCache[ $originalColumnIndex ] = $cellIndex;
		}

		return self::$columnIndexToCellIndexCache[ $originalColumnIndex ];
	}

	/**
	 * @param $value
	 * @return bool Whether the given value is considered "empty"
	 */
	public static function isEmpty( $value ) {
		return ( $value === null || $value === '' );
	}

	/**
	 * @param $value
	 * @return bool Whether the given value is a non empty string
	 */
	public static function isNonEmptyString( $value ) {
		 return ( gettype( $value ) === 'string' && $value !== '' );
	}

	/**
	 * Returns whether the given value is numeric.
	 * A numeric value is from type "integer" or "double" ("float" is not returned by gettype).
	 *
	 * @param $value
	 * @return bool Whether the given value is numeric
	 */
	public static function isNumeric( $value ) {
		$valueType = gettype( $value );
		return ( $valueType === 'integer' || $valueType === 'double' );
	}

	/**
	 * Returns whether the given value is boolean.
	 * "true"/"false" and 0/1 are not booleans.
	 *
	 * @param $value
	 * @return bool Whether the given value is boolean
	 */
	public static function isBoolean( $value ) {
		return gettype( $value ) === 'boolean';
	}
}