<?php

namespace Box\Spout\Reader\XLSX\Helper;

use Box\Spout\Common\Exception\InvalidArgumentException;

/**
 * Class CellHelper
 * This class provides helper functions when working with cells
 *
 * @package Box\Spout\Reader\XLSX\Helper
 */
class CellHelper {

	// Using ord() is super slow... Using a pre-computed hash table instead.
	private static $columnLetterToIndexMapping = array(
		'A' => 0,
		'B' => 1,
		'C' => 2,
		'D' => 3,
		'E' => 4,
		'F' => 5,
		'G' => 6,
		'H' => 7,
		'I' => 8,
		'J' => 9,
		'K' => 10,
		'L' => 11,
		'M' => 12,
		'N' => 13,
		'O' => 14,
		'P' => 15,
		'Q' => 16,
		'R' => 17,
		'S' => 18,
		'T' => 19,
		'U' => 20,
		'V' => 21,
		'W' => 22,
		'X' => 23,
		'Y' => 24,
		'Z' => 25,
	);

	/**
	 * Fills the missing indexes of an array with a given value.
	 * For instance, $dataArray = []; $a[1] = 1; $a[3] = 3;
	 * Calling fillMissingArrayIndexes($dataArray, 'FILL') will return this array: ['FILL', 1, 'FILL', 3]
	 *
	 * @param array $dataArray The array to fill
	 * @param string|void $fillValue optional
	 * @return array
	 */
	public static function fillMissingArrayIndexes( $dataArray, $fillValue = '' ) {
		if ( empty( $dataArray ) ) {
			return array();
		}
		$existingIndexes = array_keys( $dataArray );

		$newIndexes = array_fill_keys( range( 0, max( $existingIndexes ) ), $fillValue );
		$dataArray += $newIndexes;

		ksort( $dataArray );

		return $dataArray;
	}

	/**
	 * Returns the base 10 column index associated to the cell index (base 26).
	 * 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 A1 maps to 0, B2 maps to 1, Z13 to 25 and AA4 to 26.
	 *
	 * @param string $cellIndex The Excel cell index ('A1', 'BC13', ...)
	 * @return int
	 * @throws \Box\Spout\Common\Exception\InvalidArgumentException When the given cell index is invalid
	 */
	public static function getColumnIndexFromCellIndex( $cellIndex ) {
		if ( ! self::isValidCellIndex( $cellIndex ) ) {
			throw new InvalidArgumentException( 'Cannot get column index from an invalid cell index.' );
		}

		$columnIndex = 0;

		// Remove row information
		$columnLetters = preg_replace( '/\d/', '', $cellIndex );

		// strlen() is super slow too... Using isset() is way faster and not too unreadable,
		// since we checked before that there are between 1 and 3 letters.
		$columnLength = isset( $columnLetters[1] ) ? ( isset( $columnLetters[2] ) ? 3 : 2 ) : 1;

		// Looping over the different letters of the column is slower than this method.
		// Also, not using the pow() function because it's slooooow...
		switch ( $columnLength ) {
			case 1:
				$columnIndex = ( self::$columnLetterToIndexMapping[ $columnLetters ] );
				break;
			case 2:
				$firstLetterIndex  = ( self::$columnLetterToIndexMapping[ $columnLetters[0] ] + 1 ) * 26;
				$secondLetterIndex = self::$columnLetterToIndexMapping[ $columnLetters[1] ];
				$columnIndex       = $firstLetterIndex + $secondLetterIndex;
				break;
			case 3:
				$firstLetterIndex  = ( self::$columnLetterToIndexMapping[ $columnLetters[0] ] + 1 ) * 676;
				$secondLetterIndex = ( self::$columnLetterToIndexMapping[ $columnLetters[1] ] + 1 ) * 26;
				$thirdLetterIndex  = self::$columnLetterToIndexMapping[ $columnLetters[2] ];
				$columnIndex       = $firstLetterIndex + $secondLetterIndex + $thirdLetterIndex;
				break;
		}

		return $columnIndex;
	}

	/**
	 * Returns whether a cell index is valid, in an Excel world.
	 * To be valid, the cell index should start with capital letters and be followed by numbers.
	 * There can only be 3 letters, as there can only be 16,384 rows, which is equivalent to 'XFE'.
	 *
	 * @param string $cellIndex The Excel cell index ('A1', 'BC13', ...)
	 * @return bool
	 */
	protected static function isValidCellIndex( $cellIndex ) {
		return ( preg_match( '/^[A-Z]{1,3}\d+$/', $cellIndex ) === 1 );
	}
}