<?php

namespace App\Domains\Event\Services;

use App\Domains\Event\Enums\EventDateChangeType;
use App\Domains\Event\Models\EventDate;
use App\Domains\Event\Models\EventDateChange;
use Illuminate\Support\Collection;

class EventDateInfoFormatter
{
    /** @param Collection<int, EventDateChange> $changes */
    public function format(EventDate $eventDate, Collection $changes): ?string
    {
        $messages = collect();

        if ($eventDate->suspended_at !== null) {
            $messages->push('Esta fecha fue cancelada.');
        }

        $sourceDates = $this->reschedulesEndingAt($eventDate, $changes)
            ->pluck('previous_date')
            ->filter()
            ->map(fn ($date): string => $date->format('d/m/Y'))
            ->unique()
            ->values();

        if ($sourceDates->isNotEmpty()) {
            $verb = $sourceDates->count() === 1 ? 'se reprogramó' : 'se reprogramaron';
            $messages->push("{$sourceDates->join(', ', ' y ')} {$verb} para este día.");
        }

        return $messages->isEmpty() ? null : $messages->join(' ');
    }

    /**
     * Includes direct and intermediate reschedules that ultimately end at the
     * displayed event date, while preserving the original change order.
     *
     * @param  Collection<int, EventDateChange>  $changes
     * @return Collection<int, EventDateChange>
     */
    private function reschedulesEndingAt(EventDate $eventDate, Collection $changes): Collection
    {
        $eventDateId = $eventDate->getKey();
        $reschedules = $changes->where('change_type', EventDateChangeType::Rescheduled);

        if ($eventDateId === null) {
            return $reschedules->where('destination_event_date_id', null);
        }

        $destinationIds = [(int) $eventDateId => true];

        do {
            $foundAncestor = false;

            foreach ($reschedules as $change) {
                $destinationId = $change->destination_event_date_id;
                $sourceId = $change->source_event_date_id;

                if ($destinationId === null || $sourceId === null) {
                    continue;
                }

                if (isset($destinationIds[(int) $destinationId]) && ! isset($destinationIds[(int) $sourceId])) {
                    $destinationIds[(int) $sourceId] = true;
                    $foundAncestor = true;
                }
            }
        } while ($foundAncestor);

        return $reschedules
            ->filter(fn (EventDateChange $change): bool => $change->destination_event_date_id !== null
                && isset($destinationIds[(int) $change->destination_event_date_id]));
    }
}