<?php

namespace App\Event;

use DateTime;
use Exception;

/**
 * @property \DateTime $start
 * @property \DateTime $end
 */
class Range
{
    const MODE_MONTH     = 'month';
    const MODE_CAL_MONTH = 'calMonth';
    const MODE_CAL42     = 'cal42';

    const FIRST_DAY = 7;    // 1..7     ISO-8601 "N"

    protected static $mode = self::MODE_CAL42;

    /** @var \DateTime */
    protected $start;

    /** @var \DateTime */
    protected $end;

    public function __construct($start, $end)
    {
        $this->start = $start instanceof DateTime ? $start : new DateTime($start);
        $this->end = $end instanceof DateTime ? $end : new DateTime($end);
        return $this;
    }

    public function __get($name)
    {
        switch ($name) {
            case 'start':
                $date = clone $this->start;
                return $date;

            case 'end':
                $date = clone $this->end;
                return $date;
        }

        throw new Exception('Unknown property ' . get_class($this) . '->' . $name);
    }

    public static function createMonthRange(DateTime $date)
    {
        switch (self::$mode) {
            case self::MODE_MONTH:
                $range = self::getMonthRange($date);
                break;

            case self::MODE_CAL_MONTH:
                $range = self::getCalMonthRange($date);
                break;

            case self::MODE_CAL42:
                $range = self::getCal42Range($date);
                break;

            default:
                throw new Exception('Wrong mode "' . self::$mode . '"');
        }

        return new self($range[0], $range[1]);
    }

    protected static function getMonthRange(DateTime $date)
    {
        $start = clone $date;
        $end = clone $date;
        $start = $start->modify('first day of this month');
        $end = $end->modify('last day of this month');
        return [$start, $end];
    }

    protected static function getCalMonthRange(DateTime $date)
    {
        /** @var DateTime $start */
        /** @var DateTime $end */
        $range = self::getMonthRange($date);
        $start = $range[0];
        $end = $range[1];
        if (1 === self::FIRST_DAY) {
            $start->modify('-' . ($start->format('N') - 1) . ' day');
            $end->modify('+' . (7 - $end->format('N')) . ' day');
        } else if (7 === self::FIRST_DAY) {
            $start->modify('-' . $start->format('w') . ' day');
            $end->modify('+' . (6 - $end->format('w')) . ' day');
        } else {
            throw new \Exception('Wrong first day of week "' . self::FIRST_DAY . '"');
        }
        return [$start, $end];
    }

    protected static function getCal42Range(DateTime $date)
    {
        /** @var DateTime $start */
        /** @var DateTime $end */
        $range = self::getCalMonthRange($date);
        $start = $range[0];
        $end = $range[1];

        $end->modify('+' . (42 - $end->diff($start)->days) . ' day');
        return [$start, $end];
    }

}