<?php

namespace App\Services;

use App\Models\AuditLog;
use App\Models\DrawResult;
use App\Models\DrawSession;
use App\Models\Member;
use App\Models\Prize;
use App\Models\User;
use Illuminate\Database\QueryException;
use Illuminate\Database\UniqueConstraintViolationException;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\DB;
use RuntimeException;

class DrawService
{
    /**
     * Senarai anggota yang LAYAK masuk cabutan untuk sesi ini:
     *  - sudah hadir
     *  - belum menang & disahkan
     *  - (ikut setting) yang dibatalkan boleh kekal/dikeluarkan dari pool
     *
     * @return Collection<int, Member>
     */
    public function eligibleMembers(DrawSession $session): Collection
    {
        $query = Member::query()
            ->hadir()
            ->whereDoesntHave('drawResults', function ($q) {
                $q->where('status', DrawResult::STATUS_CONFIRMED);
            });

        if (! $session->return_cancelled_to_pool) {
            // Setting: keluarkan terus peserta yang pernah dibatalkan
            $query->whereDoesntHave('drawResults', function ($q) {
                $q->where('status', DrawResult::STATUS_CANCELLED);
            });
        }

        return $query->orderBy('id')->get();
    }

    /**
     * Pusing roda: pilih seorang anggota layak secara rawak & cipta rekod
     * pending_confirmation untuk hadiah yang dipilih.
     */
    public function spin(Prize $prize, DrawSession $session, User $user): DrawResult
    {
        if (! $prize->isAvailable()) {
            throw new RuntimeException('Hadiah ini sudah ada pemenang disahkan atau sedang diproses.');
        }

        $pool = $this->eligibleMembers($session);
        if ($pool->isEmpty()) {
            throw new RuntimeException('Tiada peserta layak yang masih ada dalam pool cabutan.');
        }

        return DB::transaction(function () use ($prize, $session, $user, $pool) {
            $prize = Prize::whereKey($prize->getKey())->lockForUpdate()->firstOrFail();

            if (! $prize->isAvailable()) {
                throw new RuntimeException('Hadiah ini sudah ada pemenang disahkan.');
            }

            // Tandakan sebarang pending sedia ada untuk hadiah ini sebagai redrawn
            DrawResult::where('prize_id', $prize->id)
                ->where('status', DrawResult::STATUS_PENDING)
                ->update([
                    'status' => DrawResult::STATUS_REDRAWN,
                    'updated_at' => now(),
                ]);

            $member = $pool->random();
            $attempt = DrawResult::where('prize_id', $prize->id)->count() + 1;

            $result = DrawResult::create([
                'draw_session_id' => $session->id,
                'prize_id' => $prize->id,
                'member_id' => $member->id,
                'status' => DrawResult::STATUS_PENDING,
                'attempt_number' => $attempt,
                'spun_at' => now(),
            ]);

            $prize->update(['status' => Prize::STATUS_SEDANG]);

            AuditLog::record('draw.spin', "Spin hadiah '{$prize->nama_hadiah}' -> {$member->nama}", $result, [
                'prize_id' => $prize->id,
                'member_id' => $member->id,
                'attempt' => $attempt,
            ]);

            return $result->load('member', 'prize');
        });
    }

    /**
     * Sahkan pemenang. Dilindungi unique index DB supaya tiada
     * double-confirm (race condition) walaupun dua operator tekan serentak.
     */
    public function confirm(DrawResult $result, User $user): DrawResult
    {
        return DB::transaction(function () use ($result, $user) {
            $result = DrawResult::whereKey($result->getKey())->lockForUpdate()->firstOrFail();

            if ($result->status === DrawResult::STATUS_CONFIRMED) {
                return $result; // idempotent
            }

            if ($result->status !== DrawResult::STATUS_PENDING) {
                throw new RuntimeException('Cabutan ini tidak lagi menunggu pengesahan.');
            }

            $member = Member::findOrFail($result->member_id);
            if ($member->hasConfirmedWin()) {
                throw new RuntimeException("{$member->nama} sudah pun memenangi hadiah lain dan disahkan.");
            }

            try {
                $result->update([
                    'status' => DrawResult::STATUS_CONFIRMED,
                    'confirmed_at' => now(),
                    'confirmed_by' => $user->id,
                    'confirmed_member_id' => $result->member_id,
                    'confirmed_prize_id' => $result->prize_id,
                ]);
            } catch (UniqueConstraintViolationException|QueryException $e) {
                // Unique index DB menghalang double winner / member menang dua kali
                throw new RuntimeException('Pengesahan gagal: pemenang atau hadiah ini sudah disahkan oleh operator lain.');
            }

            Prize::whereKey($result->prize_id)->update(['status' => Prize::STATUS_DISAHKAN]);

            AuditLog::record('draw.confirm', "Sahkan pemenang '{$member->nama}' untuk hadiah #{$result->prize_id}", $result, [
                'prize_id' => $result->prize_id,
                'member_id' => $result->member_id,
            ]);

            return $result->fresh(['member', 'prize']);
        });
    }

    /**
     * Batalkan pemenang (tiada di dewan). Hadiah jadi 'redraw_required'
     * dan boleh dicabut semula.
     */
    public function cancel(DrawResult $result, User $user, ?string $reason = null): DrawResult
    {
        return DB::transaction(function () use ($result, $user, $reason) {
            $result = DrawResult::whereKey($result->getKey())->lockForUpdate()->firstOrFail();

            if ($result->status !== DrawResult::STATUS_PENDING) {
                throw new RuntimeException('Hanya cabutan yang menunggu pengesahan boleh dibatalkan.');
            }

            $result->update([
                'status' => DrawResult::STATUS_CANCELLED,
                'cancelled_at' => now(),
                'cancelled_by' => $user->id,
                'sebab_batal' => $reason ?: 'Pemenang tiada di dewan',
            ]);

            $prize = Prize::findOrFail($result->prize_id);
            $prize->update([
                'status' => Prize::STATUS_REDRAW,
                'redraw_count' => $prize->redraw_count + 1,
            ]);

            AuditLog::record('draw.cancel', "Batal cabutan hadiah #{$result->prize_id} (member #{$result->member_id})", $result, [
                'prize_id' => $result->prize_id,
                'member_id' => $result->member_id,
                'sebab' => $result->sebab_batal,
            ]);

            return $result->fresh(['member', 'prize']);
        });
    }
}