<?php

namespace App\Services;

use App\Exceptions\TabulationException;
use App\Models\Entry;
use App\Models\Event;
use App\Models\Student;
use Illuminate\Support\Facades\Cache;

/**
 * returns a collection of doublers for the event in the form of
 * [studentId => [student=>student, entries=>[entries]]
 */
class DoublerService
{
    public function doublersForEvent(Event $event, string $mode = 'seating')
    {
        $cacheKey = 'event'.$event->id.'doublers-'.$mode;
        return Cache::remember($cacheKey, 60, function () use ($event, $mode) {
            return $this->findDoublersForEvent($event, $mode);
        });
    }

    /**
     * @throws TabulationException
     */
    protected function findDoublersForEvent(Event $event, string $mode): array
    {
        $this->validateEvent($event);
        $entries = $event->entries;
        $entries = match ($mode) {
            'seating' => $entries->filter(fn ($entry) => $entry->for_seating === 1),
            'advancement' => $entries->filter(fn ($entry) => $entry->for_advance === 1),
        };
        $entries->load('student.school');
        $entries->load('audition');
        $grouped = $entries->groupBy('student_id');
        // Filter out student groups with only one entry in the event
        $grouped = $grouped->filter(fn ($s) => $s->count() > 1);
        $doubler_array = [];
        foreach ($grouped as $student_id => $entries) {
            $doubler_array[$student_id] = [
                'student' => $entries[0]->student,
                'entries' => $entries,
            ];
        }

        return $doubler_array;
    }

    /**
     * @throws TabulationException
     */
    protected function validateEvent(Event $event)
    {
        if (! $event->exists) {
            throw new TabulationException('Invalid event provided');
        }
    }
}