<?php
namespace App\Services;

use App\Models\Participant;
use Illuminate\Support\Collection;

class MatcherService
{
    public function match(): void
    {
        $participants = Participant::all();

        if ($participants->count() < 2) {
            return;
        }

        $assignments = [];

        $newParticipantIds = $participants
            ->filter(fn($p) => $p->is_unmatched)
            ->pluck('id')
            ->shuffle()
            ->all();

        $desperateGiverIds = $participants
            ->filter(fn($p) => $p->is_desperate && !$p->hasReceiver())
            ->pluck('id')
            ->shuffle()
            ->all();

        $desperateReceiverIds = $participants
            ->filter(fn($p) => $p->is_desperate && !$p->hasGiver())
            ->pluck('id')
            ->shuffle()
            ->all();

        while (!empty($desperateGiverIds) && !empty($desperateReceiverIds)) {

            $giverId = array_shift($desperateGiverIds);
            $receiverId = array_shift($desperateReceiverIds);

            if ($giverId === $receiverId) {
                array_unshift($desperateReceiverIds, $receiverId);
                continue;
            }

            $assignments[$giverId] = $receiverId;
        }

        $newCount = count($newParticipantIds);
        if ($newCount >= 2) {

            for ($i = 0; $i < $newCount; $i++) {

                $currentId = $newParticipantIds[$i];

                $nextId = $newParticipantIds[($i + 1) % $newCount];

                $assignments[$currentId] = $nextId;
            }
        }


        foreach ($assignments as $giverId => $receiverId) {
            Participant::where('id', $giverId)->update([
                'giving_id' => $receiverId,
            ]);
        }
    }
}