<?php

namespace App\Service\Assignment;

use App\Entity\Assignment;
use App\Model\TimelineItem;
use Carbon\CarbonPeriod;
use function Symfony\Component\String\b;

/**
 * Service for processing assignments into timeline visualization data.
 * Organizes assignments and dispositions by hotel in a timeline format,
 * handling overlapping dates by distributing items across multiple rows.
 */
class TimelineService
{
    /**
     * Preprocesses assignments into a timeline structure organized by hotel.
     * Creates timeline items for both vacant assignment slots and actual dispositions,
     * distributing them across multiple rows to avoid date overlaps.
     *
     * @param Assignment[] $assignments Array of assignments to process
     * @return array Multi-dimensional array: [hotelCode][rowIndex][itemKey] => TimelineItem
     */
    public function preprocess(array $assignments): array
    {
        $rows = [];

        foreach ($assignments as $assignment) {
            // exclude called off assignments
            // TODO: refactor filtering to do this on database level
            if (Assignment::STATUS_CALLED_OFF === $assignment->getStatus()) {
                continue;
            }
            $destination = $assignment->getDestination();
            $hotelCode = $destination->getHotelCodeNormalized();

            // add first row for current hotel unless existing
            if (false === isset($rows[$hotelCode])) {
                $rows[$hotelCode] = [[]];
            }

            $dispositionsCount = $assignment->getDispositions()->count();
            $dispositionsAvailable = $assignment->getAvailableDispositions();

            // Handle assignments with no dispositions - create items for all available slots
            if (0 === $dispositionsCount) {
                $item = TimelineItem::fromAssignment($assignment);
                for ($i = 1; $i <= $assignment->getAvailableDispositions(); $i++) {
                    $this->addItem($rows[$hotelCode], $item);
                }
            } else {
                // Create items for remaining vacant slots if any
                if ($dispositionsCount < $dispositionsAvailable) {
                    $item = TimelineItem::fromAssignment($assignment);
                    for ($i = 1; $i <= $dispositionsAvailable - $dispositionsCount; $i++) {
                        $this->addItem($rows[$hotelCode], $item);
                    }
                }
                // Create items for actual dispositions
                foreach ($assignment->getDispositions() as $disposition) {
                    $item = TimelineItem::fromDisposition($disposition);
                    $this->addItem($rows[$hotelCode], $item);
                }
            }
        }

        return $rows;
    }

    /**
     * Adds a timeline item to the appropriate row, ensuring no date overlaps.
     * Finds the first available row where the item doesn't overlap with existing items,
     * or creates a new row if necessary.
     *
     * @param array $rows Reference to the rows array for a specific hotel
     * @param TimelineItem $item The timeline item to add
     */
    private function addItem(array &$rows, TimelineItem $item): void
    {
        $rowIndex = 0;
        $fitsRow = false;

        // Find first row where item doesn't overlap with existing items
        foreach ($rows as $index => $row) {
            $fitsRow = true;
            foreach ($row as $entry) {
                /** @var TimelineItem $entry */
                // Check for date overlap: item overlaps if its end >= entry start AND item start <= entry end
                if ($entry->getDateTo() >= $item->getDateFrom() && $entry->getDateFrom() <= $item->getDateTo()) {
                    $fitsRow = false;
                }
            }
            $rowIndex = $index;
            if (true === $fitsRow) {
                break;
            }
        }

        // If no existing row fits, create a new row
        if (false === $fitsRow) {
            ++$rowIndex;
        }

        $rows[$rowIndex][$item->getKey()] = $item;
    }

    /**
     * Creates a time window for timeline visualization.
     * Returns a period from 6 weeks ago to 6 months in the future,
     * providing context for both recent and upcoming assignments.
     *
     * @return CarbonPeriod The active time window for timeline display
     */
    public function getActiveWindow(): CarbonPeriod
    {
        $dateFrom = (new \DateTimeImmutable())->modify('-6 weeks');
        $dateTo = (new \DateTimeImmutable())->modify('+6 months');

        return CarbonPeriod::create($dateFrom, $dateTo);
    }
}