<?php

Prado::using('Application.dto.CalendarGridDayDTO');
Prado::using('Application.dto.GridEventDTO');

class CalendarGridDTO {

    public $DateFrom;
    public $DateTo;
    public $Weeks = [];

    public function __construct(array $events, DateTime $dateFrom, DateTime $dateTo) {
        $this->DateFrom = DateTimeImmutable::createFromMutable($dateFrom);
        $this->DateTo = DateTimeImmutable::createFromMutable($dateTo);
        $date = $this->DateFrom;
        $days = [];
        $previousDay = NULL;
        while ($date <= $this->DateTo) {
            $day = $this->_getGridDay($date, $events, $previousDay);
            $days[] = $day;
            $previousDay = $day;
            $date = $date->modify('+1 day');
        }
        $this->Weeks = array_chunk($days, 7);
    }

    private function _getContinuedEventGridPositions(
        CalendarGridDayDTO $day,
        CalendarGridDayDTO $previousDay = NULL) {
        $eventPositions = [];
        if ($previousDay) {
            foreach ($day->Events as $event) {
                if (in_array($event, $previousDay->Events)) {
                    $eventPositions[] = $event->GridPosition;
                }
            }
        }
        return $eventPositions;
    }

    private function _alignEvents(array $eventPositions, array $events) {
        $previousCount = count($eventPositions);
        foreach ($events as $event) {
            if ($event->GridPosition === NULL) {
                $event->GridPosition = min(
                    array_diff(
                        range(0, count($events) + $previousCount),
                        $eventPositions
                    )
                );
                $eventPositions[] = $event->GridPosition;
            }
        }
        usort($events, ['GridEventDTO', '__compare']);
        return $events;
    }

    private function _fillEventGrid(array $events) {
        $previousEvent = -1;
        foreach ($events as $event) {
            $eventStep = $event->GridPosition - $previousEvent;
            if ($eventStep > 1) {
                array_splice(
                    $events, $previousEvent + 1, 0, array_fill(0, $eventStep - 1, NULL)
                );
            }
            $previousEvent = $event->GridPosition;
        }
        return $events;
    }

    protected function _getGridDay(DateTimeImmutable $date,
                                 array $events,
                                 CalendarGridDayDTO $previousDay = NULL) {
        $day = new CalendarGridDayDTO($date, $events);
        $eventPositions = $this->_getContinuedEventGridPositions($day, $previousDay);
        $day->Events = $this->_alignEvents($eventPositions, $day->Events);
        $day->Events = $this->_fillEventGrid($day->Events);
        return $day;
    }

}

?>