<?php
namespace TYPO3\CMS\Scheduler\CronCommand;

/**
 * This file is part of the TYPO3 CMS project.
 *
 * It is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License, either version 2
 * of the License, or any later version.
 *
 * For the full copyright and license information, please read the
 * LICENSE.txt file that was distributed with this source code.
 *
 * The TYPO3 project - inspiring people to share!
 */
use TYPO3\CMS\Core\Utility\MathUtility;

/**
 * Validate and normalize a cron command.
 *
 * Special fields like three letter weekdays, ranges and steps are substituted
 * to a comma separated list of integers. Example:
 * '2-4 10-40/10 * mar * fri'  will be normalized to '2,4 10,20,30,40 * * 3 1,2'
 *
 * @author Christian Kuhn <lolli@schwarzbu.ch>
 */
class NormalizeCommand {

	/**
	 * Main API method: Get the cron command and normalize it.
	 *
	 * If no exception is thrown, the resulting cron command is validated
	 * and consists of five whitespace separated fields, which are either
	 * the letter '*' or a sorted, unique comma separated list of integers.
	 *
	 * @api
	 * @throws \InvalidArgumentException cron command is invalid or out of bounds
	 * @param string $cronCommand The cron command to normalize
	 * @return string Normalized cron command
	 */
	static public function normalize($cronCommand) {
		$cronCommand = trim($cronCommand);
		$cronCommand = self::convertKeywordsToCronCommand($cronCommand);
		$cronCommand = self::normalizeFields($cronCommand);
		return $cronCommand;
	}

	/**
	 * Accept special cron command keywords and convert to standard cron syntax.
	 * Allowed keywords: @yearly, @annually, @monthly, @weekly, @daily, @midnight, @hourly
	 *
	 * @param string $cronCommand Cron command
	 * @return string Normalized cron command if keyword was found, else unchanged cron command
	 */
	static protected function convertKeywordsToCronCommand($cronCommand) {
		switch ($cronCommand) {
			case '@yearly':

			case '@annually':
				$cronCommand = '0 0 1 1 *';
				break;
			case '@monthly':
				$cronCommand = '0 0 1 * *';
				break;
			case '@weekly':
				$cronCommand = '0 0 * * 0';
				break;
			case '@daily':

			case '@midnight':
				$cronCommand = '0 0 * * *';
				break;
			case '@hourly':
				$cronCommand = '0 * * * *';
				break;
		}
		return $cronCommand;
	}

	/**
	 * Normalize cron command field to list of integers or *
	 *
	 * @param string $cronCommand cron command
	 * @return string Normalized cron command
	 */
	static protected function normalizeFields($cronCommand) {
		$fieldArray = self::splitFields($cronCommand);
		$fieldArray[0] = self::normalizeIntegerField($fieldArray[0], 0, 59);
		$fieldArray[1] = self::normalizeIntegerField($fieldArray[1], 0, 23);
		$fieldArray[2] = self::normalizeIntegerField($fieldArray[2], 1, 31);
		$fieldArray[3] = self::normalizeMonthAndWeekdayField($fieldArray[3], TRUE);
		$fieldArray[4] = self::normalizeMonthAndWeekdayField($fieldArray[4], FALSE);
		$normalizedCronCommand = implode(' ', $fieldArray);
		return $normalizedCronCommand;
	}

	/**
	 * Split a given cron command like '23 * * * *' to an array with five fields.
	 *
	 * @throws \InvalidArgumentException If splitted array does not contain five entries
	 * @param string $cronCommand cron command
	 * @return array
	 */
	static protected function splitFields($cronCommand) {
		$fields = explode(' ', $cronCommand);
		if (count($fields) !== 5) {
			throw new \InvalidArgumentException('Unable to split given cron command to five fields.', 1291227373);
		}
		return $fields;
	}

	/**
	 * Normalize month field.
	 *
	 * @param string $expression Month field expression
	 * @param boolean $isMonthField TRUE if month field is handled, FALSE for weekday field
	 * @return string Normalized expression
	 */
	static protected function normalizeMonthAndWeekdayField($expression, $isMonthField = TRUE) {
		if ((string) $expression === '*') {
			$fieldValues = '*';
		} else {
			// Fragment expression by , / and - and substitute three letter code of month and weekday to numbers
			$listOfCommaValues = explode(',', $expression);
			$fieldArray = array();
			foreach ($listOfCommaValues as $listElement) {
				if (strpos($listElement, '/') !== FALSE) {
					list($left, $right) = explode('/', $listElement);
					if (strpos($left, '-') !== FALSE) {
						list($leftBound, $rightBound) = explode('-', $left);
						$leftBound = self::normalizeMonthAndWeekday($leftBound, $isMonthField);
						$rightBound = self::normalizeMonthAndWeekday($rightBound, $isMonthField);
						$left = $leftBound . '-' . $rightBound;
					} else {
						if ((string) $left !== '*') {
							$left = self::normalizeMonthAndWeekday($left, $isMonthField);
						}
					}
					$fieldArray[] = $left . '/' . $right;
				} elseif (strpos($listElement, '-') !== FALSE) {
					list($left, $right) = explode('-', $listElement);
					$left = self::normalizeMonthAndWeekday($left, $isMonthField);
					$right = self::normalizeMonthAndWeekday($right, $isMonthField);
					$fieldArray[] = $left . '-' . $right;
				} else {
					$fieldArray[] = self::normalizeMonthAndWeekday($listElement, $isMonthField);
				}
			}
			$fieldValues = implode(',', $fieldArray);
		}
		return $isMonthField ? self::normalizeIntegerField($fieldValues, 1, 12) : self::normalizeIntegerField($fieldValues, 1, 7);
	}

	/**
	 * Normalize integer field.
	 *
	 * @throws \InvalidArgumentException If field is invalid or out of bounds
	 * @param string $expression Expression
	 * @param integer $lowerBound Lower limit of result list
	 * @param integer $upperBound Upper limit of result list
	 * @return string Normalized expression
	 */
	static protected function normalizeIntegerField($expression, $lowerBound = 0, $upperBound = 59) {
		if ((string) $expression === '*') {
			$fieldValues = '*';
		} else {
			$listOfCommaValues = explode(',', $expression);
			$fieldArray = array();
			foreach ($listOfCommaValues as $listElement) {
				if (strpos($listElement, '/') !== FALSE) {
					list($left, $right) = explode('/', $listElement);
					if ((string) $left === '*') {
						$leftList = self::convertRangeToListOfValues($lowerBound . '-' . $upperBound);
					} else {
						$leftList = self::convertRangeToListOfValues($left);
					}
					$fieldArray[] = self::reduceListOfValuesByStepValue($leftList . '/' . $right);
				} elseif (strpos($listElement, '-') !== FALSE) {
					$fieldArray[] = self::convertRangeToListOfValues($listElement);
				} elseif (MathUtility::canBeInterpretedAsInteger($listElement)) {
					$fieldArray[] = $listElement;
				} else {
					throw new \InvalidArgumentException('Unable to normalize integer field.', 1291429389);
				}
			}
			$fieldValues = implode(',', $fieldArray);
		}
		if (strlen($fieldValues) === 0) {
			throw new \InvalidArgumentException('Unable to convert integer field to list of values: Result list empty.', 1291422012);
		}
		if ((string) $fieldValues !== '*') {
			$fieldList = explode(',', $fieldValues);
			sort($fieldList);
			$fieldList = array_unique($fieldList);
			if (current($fieldList) < $lowerBound) {
				throw new \InvalidArgumentException('Lowest element in list is smaller than allowed.', 1291470084);
			}
			if (end($fieldList) > $upperBound) {
				throw new \InvalidArgumentException('An element in the list is higher than allowed.', 1291470170);
			}
			$fieldValues = implode(',', $fieldList);
		}
		return (string) $fieldValues;
	}

	/**
	 * Convert a range of integers to a list: 4-6 results in a string '4,5,6'
	 *
	 * @throws \InvalidArgumentException If range can not be converted to list
	 * @param string $range Integer-integer
	 * @return array
	 */
	static protected function convertRangeToListOfValues($range) {
		if (strlen($range) === 0) {
			throw new \InvalidArgumentException('Unable to convert range to list of values with empty string.', 1291234985);
		}
		$rangeArray = explode('-', $range);
		// Sanitize fields and cast to integer
		foreach ($rangeArray as $fieldNumber => $fieldValue) {
			if (!MathUtility::canBeInterpretedAsInteger($fieldValue)) {
				throw new \InvalidArgumentException('Unable to convert value to integer.', 1291237668);
			}
			$rangeArray[$fieldNumber] = (int)$fieldValue;
		}
		$resultList = '';
		if (count($rangeArray) === 1) {
			$resultList = $rangeArray[0];
		} elseif (count($rangeArray) === 2) {
			$left = $rangeArray[0];
			$right = $rangeArray[1];
			if ($left > $right) {
				throw new \InvalidArgumentException('Unable to convert range to list: Left integer must not be greater than right integer.', 1291237145);
			}
			$resultListArray = array();
			for ($i = $left; $i <= $right; $i++) {
				$resultListArray[] = $i;
			}
			$resultList = implode(',', $resultListArray);
		} else {
			throw new \InvalidArgumentException('Unable to convert range to list of values.', 1291234986);
		}
		return (string) $resultList;
	}

	/**
	 * Reduce a given list of values by step value.
	 * Following a range with ``/<number>'' specifies skips of the number's value through the range.
	 * 1-5/2 -> 1,3,5
	 * 2-10/3 -> 2,5,8
	 *
	 * @throws \InvalidArgumentException if step value is invalid or if resulting list is empty
	 * @param string $stepExpression Step value expression
	 * @return string Comma separated list of valid values
	 */
	static protected function reduceListOfValuesByStepValue($stepExpression) {
		if (strlen($stepExpression) === 0) {
			throw new \InvalidArgumentException('Unable to convert step values.', 1291234987);
		}
		$stepValuesAndStepArray = explode('/', $stepExpression);
		if (count($stepValuesAndStepArray) < 1 || count($stepValuesAndStepArray) > 2) {
			throw new \InvalidArgumentException('Unable to convert step values: Multiple slashes found.', 1291242168);
		}
		$left = $stepValuesAndStepArray[0];
		$right = $stepValuesAndStepArray[1];
		if (strlen($stepValuesAndStepArray[0]) === 0) {
			throw new \InvalidArgumentException('Unable to convert step values: Left part of / is empty.', 1291414955);
		}
		if (strlen($stepValuesAndStepArray[1]) === 0) {
			throw new \InvalidArgumentException('Unable to convert step values: Right part of / is empty.', 1291414956);
		}
		if (!MathUtility::canBeInterpretedAsInteger($right)) {
			throw new \InvalidArgumentException('Unable to convert step values: Right part must be a single integer.', 1291414957);
		}
		$right = (int)$right;
		$leftArray = explode(',', $left);
		$validValues = array();
		$currentStep = $right;
		foreach ($leftArray as $leftValue) {
			if (!MathUtility::canBeInterpretedAsInteger($leftValue)) {
				throw new \InvalidArgumentException('Unable to convert step values: Left part must be a single integer or comma separated list of integers.', 1291414958);
			}
			if ($currentStep === 0) {
				$currentStep = $right;
			}
			if ($currentStep === $right) {
				$validValues[] = (int)$leftValue;
			}
			$currentStep--;
		}
		if (count($validValues) === 0) {
			throw new \InvalidArgumentException('Unable to convert step values: Result value list is empty.', 1291414959);
		}
		return implode(',', $validValues);
	}

	/**
	 * Dispatcher method for normalizeMonth and normalizeWeekday
	 *
	 * @param string $expression Month or weekday to be normalized
	 * @param boolean $isMonth TRUE if a month is handled, FALSE for weekday
	 * @return string normalized month or weekday
	 */
	static protected function normalizeMonthAndWeekday($expression, $isMonth = TRUE) {
		$expression = $isMonth ? self::normalizeMonth($expression) : self::normalizeWeekday($expression);
		return (string) $expression;
	}

	/**
	 * Accept a string representation or integer number of a month like
	 * 'jan', 'February', 01, ... and convert to normalized integer value 1 .. 12
	 *
	 * @throws \InvalidArgumentException If month string can not be converted to integer
	 * @param string $month Month representation
	 * @return integer month integer representation between 1 and 12
	 */
	static protected function normalizeMonth($month) {
		$timestamp = strtotime('2010-' . $month . '-01');
		// timestamp must be >= 2010-01-01 and <= 2010-12-01
		if (!$timestamp || $timestamp < strtotime('2010-01-01') || $timestamp > strtotime('2010-12-01')) {
			throw new \InvalidArgumentException('Unable to convert given month name.', 1291083486);
		}
		return (int)date('n', $timestamp);
	}

	/**
	 * Accept a string representation or integer number of a weekday like
	 * 'mon', 'Friday', 3, ... and convert to normalized integer value 1 .. 7
	 *
	 * @throws \InvalidArgumentException If weekday string can not be converted
	 * @param string $weekday Weekday representation
	 * @return integer weekday integer representation between 1 and 7
	 */
	static protected function normalizeWeekday($weekday) {
		$normalizedWeekday = FALSE;
		// 0 (sunday) -> 7
		if ((string) $weekday === '0') {
			$weekday = 7;
		}
		if ($weekday >= 1 && $weekday <= 7) {
			$normalizedWeekday = (int)$weekday;
		}
		if (!$normalizedWeekday) {
			// Convert string representation like 'sun' to integer
			$timestamp = strtotime('next ' . $weekday, mktime(0, 0, 0, 1, 1, 2010));
			if (!$timestamp || $timestamp < strtotime('2010-01-01') || $timestamp > strtotime('2010-01-08')) {
				throw new \InvalidArgumentException('Unable to convert given weekday name.', 1291163589);
			}
			$normalizedWeekday = (int)date('N', $timestamp);
		}
		return $normalizedWeekday;
	}

}
