<?php

namespace App\Services;

use App\Http\Controllers\ExamPdfController;
use App\Models\Paper;
use App\Models\PaperQuestion;
use App\Models\User;
use Illuminate\Support\Facades\Auth;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Schema;
use Illuminate\Support\Str;

/**
 * 待入库题目加入组卷队列（不写 questions 表），生成临时试卷以走判卷 PDF 链路验版式
 */
class QuestionsTemAssemblyService
{
    public function tableExists(): bool
    {
        return Schema::hasTable('questions_tem_assembly_queue');
    }

    public function queueForUser(int $userId): array
    {
        if (! $this->tableExists() || ! Schema::hasTable('questions_tem')) {
            return [];
        }

        $rows = DB::table('questions_tem as q')
            ->join('questions_tem_assembly_queue as aq', 'q.id', '=', 'aq.questions_tem_id')
            ->where('aq.user_id', $userId)
            ->orderBy('aq.sort_order')
            ->orderBy('aq.id')
            ->select('q.*')
            ->get();

        return $rows->all();
    }

    public function add(int $userId, int $temId): void
    {
        if (! $this->tableExists() || ! Schema::hasTable('questions_tem')) {
            return;
        }

        if (! DB::table('questions_tem')->where('id', $temId)->exists()) {
            return;
        }

        if (DB::table('questions_tem_assembly_queue')
            ->where('user_id', $userId)
            ->where('questions_tem_id', $temId)
            ->exists()) {
            return;
        }

        $max = (int) DB::table('questions_tem_assembly_queue')->where('user_id', $userId)->max('sort_order');

        DB::table('questions_tem_assembly_queue')->insert([
            'user_id' => $userId,
            'questions_tem_id' => $temId,
            'sort_order' => $max + 1,
            'created_at' => now(),
            'updated_at' => now(),
        ]);
    }

    public function remove(int $userId, int $temId): void
    {
        if (! $this->tableExists()) {
            return;
        }

        DB::table('questions_tem_assembly_queue')
            ->where('user_id', $userId)
            ->where('questions_tem_id', $temId)
            ->delete();
    }

    public function clear(int $userId): void
    {
        if (! $this->tableExists()) {
            return;
        }

        DB::table('questions_tem_assembly_queue')->where('user_id', $userId)->delete();
    }

    /**
     * 创建临时试卷并写入 paper_questions（question_bank_id 为负 tem id，判卷页会从 questions_tem 还原选项）
     */
    public function createTrialPaperForQueue(int $userId): ?string
    {
        $rows = $this->queueForUser($userId);
        if ($rows === []) {
            return null;
        }

        $user = User::query()->find($userId);
        $studentKey = (string) ($user?->username ?? 'preview');
        $teacherKey = (string) ($user?->username ?? 'preview');

        $paperId = 'TEMQ-'.Str::upper(Str::random(12));

        $pdf = app(ExamPdfController::class);
        $questionsData = $pdf->prepareQuestionsDataFromTemRows($rows);
        $grouped = $pdf->buildGroupedQuestionsForPaperBody($questionsData, null);

        $order = 1;
        $totalScore = 0.0;
        $flat = array_merge($grouped['choice'], $grouped['fill'], $grouped['answer']);
        usort($flat, fn ($a, $b) => ($a->question_number ?? 0) <=> ($b->question_number ?? 0));

        foreach ($flat as $obj) {
            $totalScore += (float) ($obj->score ?? 5);
        }

        Paper::query()->create([
            'paper_id' => $paperId,
            'student_id' => (string) $studentKey,
            'teacher_id' => (string) $teacherKey,
            'paper_name' => '待入库组卷验真',
            'paper_type' => 0,
            'total_questions' => count($flat),
            'total_score' => $totalScore,
            'status' => 'tem_preview',
            'difficulty_category' => '中等',
        ]);

        foreach ($flat as $obj) {
            $type = (string) ($obj->question_type ?? 'answer');
            $stem = (string) ($obj->stem ?? $obj->content ?? '');
            $bankId = (int) ($obj->id ?? 0);
            PaperQuestion::query()->create([
                'paper_id' => $paperId,
                'question_bank_id' => $bankId,
                'question_id' => 'tem-'.$order,
                'knowledge_point' => (string) ($obj->kp_code ?? ''),
                'question_type' => $type,
                'question_text' => $stem,
                'correct_answer' => (string) ($obj->answer ?? ''),
                'solution' => (string) ($obj->solution ?? ''),
                'difficulty' => (float) ($obj->difficulty ?? 0.5),
                'score' => (float) ($obj->score ?? 5),
                'question_number' => (int) ($obj->question_number ?? $order),
            ]);
            $order++;
        }

        return $paperId;
    }

    public static function currentUserId(): ?int
    {
        $u = Auth::user();
        if ($u instanceof User) {
            return (int) $u->id;
        }

        return null;
    }
}