<?php
Class DateRanges {

	private $dateFormat = "Y-m-d";
	private $rangeSeparator = ";";
	private $dateSeparator = ":";

	private function strToArr($str) {
		return array_map(function ($range) {
			$_range = array_combine(['from', 'to'], array_map(function ($date) {
				if (!$date) return '';
				return DateTime::createFromFormat('!' . $this->dateFormat, $date)->getTimestamp();
			}, explode($this->dateSeparator, $range)));
			if ($_range['to'] && $_range['to'] < $_range['from']) throw new Exception("Date 'to' before date 'from'");
			return $_range;
		}, explode($this->rangeSeparator, $str));
	}

	private function arrToStr($arr) {
		return implode($this->rangeSeparator, array_map(function ($range) {
			return implode($this->dateSeparator, array_map(function ($date) {
				if (!$date) return '';
				return date($this->dateFormat, $date);
			}, $range));
		}, $arr));
	}

	private static function sort(&$ranges) {
		uasort($ranges, function($a, $b) {
			if ($a['from'] == $b['from']) {
				if ($a['to'] == $b['to']) return 0;
				if (!$a['to']) return 1;
				if (!$b['to']) return -1;
				return ($a['to'] < $b['to']) ? -1 : 1;
			}
			return ($a['from'] < $b['from']) ? -1 : 1;
		});
	}

	private function implodeRanges($ranges) {
		if (is_array($ranges)) {
			$ranges = implode($this->rangeSeparator, array_filter($ranges, function($range) {
				if ($range) return true;
				return false;
			}));
		}
		return $ranges;
	}

	private function _merge($ranges) {
		$ranges = $this->implodeRanges($ranges);
		if (!$ranges) throw new Exception("DataRanges::_merges - bad ranges");
		$ranges = $this->strToArr($ranges);
		self::sort($ranges);

		$result = [];
		foreach ($ranges as $range) {
			if (!$result) $result[] = $range;
			else {
				if (!end($result)['to']) break;
				$k = key($result);
				if ($range['from'] == $result[$k]['from']) $result[$k]['to'] = $range['to'];
				elseif ((!$range['to']) || ($range['to'] > $result[$k]['to'])) {
					if ($range['from'] > $result[$k]['to']) $result[] = $range;
					else $result[$k]['to'] = $range['to'];
				}
			}
		}

		return $this->arrToStr($result);
	}

	private static function lt($date1, $date2) {
		if (!$date1) return false;
		if (!$date2) return true;
		return ($date1 < $date2);
	}

	private static function gt($date1, $date2) {
		if (!$date2) return false;
		if (!$date1) return true;
		return ($date1 > $date2);
	}

	private static function le($date1, $date2) {
		return (!self::gt($date1, $date2));
	}

	private static function ge($date1, $date2) {
		return (!self::lt($date1, $date2));
	}

	private static function min($dates) {
		if ((!is_array($dates)) || (!$dates)) throw new Exception("DateRanges::min - bad arguments");
		$min = null;
		foreach ($dates as $date) {
			if ($min === null) {
				$min = $date;
				continue;
			}
			if (self::lt($date, $min)) $min = $date;
		}
		return $min;
	}

	private static function max($dates) {
		if ((!is_array($dates)) || (!$dates)) throw new Exception("DateRanges::max - bad arguments");
		$max = null;
		foreach ($dates as $date) {
			if ($max === null) {
				$max = $date;
				continue;
			}
			if (self::gt($date, $max)) $max = $date;
		}
		return $max;
	}

	private function _common($rangesA, $rangesB) {
		$rangesA = $this->implodeRanges($rangesA);
		$rangesB = $this->implodeRanges($rangesB);
		if (!($rangesA && $rangesB)) throw new Exception("DataRanges::_common - bad ranges");
		$rangesA = $this->strToArr($rangesA);
		$rangesB = $this->strToArr($rangesB);
		self::sort($rangesA);
		self::sort($rangesB);
		$ranges = [];
		foreach ($rangesA as $rangeA) {
			foreach ($rangesB as $rangeB) {
//				if ($rangeA['from'] == $rangeB['from'] && $rangeA['to'] == $rangeB['to']) {
//					$ranges[] = $rangeA;
//					continue;
//				}
				$range = [
					'from' => self::max([$rangeA['from'], $rangeB['from']]),
					'to' => self::min([$rangeA['to'], $rangeB['to']]),
				];
//print_r($range);
				if (self::le($range['from'], $range['to'])) { // || ($range['from'] == $range['to'] && ($rangeA['from'] == $rangeB['from'] || $rangeA['to'] == $rangeB['to']))) {
					$ranges[] = $range;
				}
			}
		}
		if (!$ranges) return null;
		return $this->_merge($this->arrToStr($ranges));
	}

	private function _days($ranges) {
		$ranges = $this->implodeRanges($ranges);
		if (!$ranges) throw new Exception("DataRanges::_days - bad ranges ({$ranges})");
		$ranges = $this->strToArr($ranges);
		$result = (int) 0;
		foreach ($ranges as $range) {
			if (!$range['from']) throw new Exception("DataRanges::_days - bad date from");
			if (!$range['to']) return -1;
			if ($range['to'] < $range['from']) throw new Exception("DataRanges::_days - date to before date from");
			$result += round(($range['to'] - $range['from']) / 86400);
		}
		return round($result);
	}

	public function __construct($dateFormat = null, $rangeSeparator = null, $dateSeparator = null) {
		if ($dateFormat !== null) $this->dateFormat = $dateFormat;
		if ($rangeSeparator !== null) $this->rangeSeparator = $rangeSeparator;
		if ($dateSeparator !== null) $this->dateSeparator = $dateSeparator;
	}

	public static function merge($ranges, $dateFormat = null, $rangeSeparator = null, $dateSeparator = null) {
		$obj = new DateRanges($dateFormat, $rangeSeparator, $dateSeparator);
		return $obj->_merge($ranges);
	}

	public static function common($rangesA, $rangesB, $dateFormat = null, $rangeSeparator = null, $dateSeparator = null) {
		$obj = new DateRanges($dateFormat, $rangeSeparator, $dateSeparator);
		return $obj->_common($rangesA, $rangesB);
	}

	public static function days($ranges, $dateFormat = null, $rangeSeparator = null, $dateSeparator = null) {
		$obj = new DateRanges($dateFormat, $rangeSeparator, $dateSeparator);
		return $obj->_days($ranges);
	}
}

class DateRanges_debug extends DateRanges {
}