math_cms/app/Services/QuestionLocalService.php

<?php

namespace App\Services;

use App\Models\KnowledgePoint;
use App\Models\Question;
use App\Services\KnowledgeServiceApi;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\Cache;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Log;
use Illuminate\Support\Str;

class QuestionLocalService
{
    private DifficultyDistributionService $difficultyDistributionService;
    private QuestionDifficultyResolver $questionDifficultyResolver;

    public function __construct(
        ?DifficultyDistributionService $difficultyDistributionService = null,
        ?QuestionDifficultyResolver $questionDifficultyResolver = null
    )
    {
        $this->difficultyDistributionService = $difficultyDistributionService
            ?? app(DifficultyDistributionService::class);
        $this->questionDifficultyResolver = $questionDifficultyResolver
            ?? app(QuestionDifficultyResolver::class);
    }

    public function listQuestions(int $page = 1, int $perPage = 50, array $filters = []): array
    {
        $query = $this->applyFilters(Question::query(), $filters);
        $paginator = $query->orderByDesc('id')->paginate($perPage, ['*'], 'page', $page);

        $data = $this->mapQuestions(collect($paginator->items()));

        return [
            'data' => $data,
            'meta' => [
                'page' => $paginator->currentPage(),
                'per_page' => $paginator->perPage(),
                'total' => $paginator->total(),
                'total_pages' => $paginator->lastPage(),
            ],
        ];
    }

    public function getQuestionById(int $id): ?array
    {
        $question = Question::find($id);
        if (!$question) {
            return null;
        }

        return $this->mapQuestion($question);
    }

    public function getQuestionByCode(string $questionCode): ?array
    {
        $question = Question::where('question_code', $questionCode)->first();
        if (!$question) {
            return null;
        }

        return $this->mapQuestion($question);
    }

    public function updateQuestionByCode(string $questionCode, array $payload): bool
    {
        $question = Question::where('question_code', $questionCode)->first();
        if (!$question) {
            return false;
        }

        $question->fill($this->normalizePayload($payload));
        $question->save();

        return true;
    }

    public function deleteQuestionByCode(string $questionCode): bool
    {
        $question = Question::where('question_code', $questionCode)->first();
        if (!$question) {
            return false;
        }

        $question->delete();
        return true;
    }

    public function deleteQuestionById(int $id): bool
    {
        $question = Question::find($id);
        if (!$question) {
            return false;
        }

        $question->delete();
        return true;
    }

    public function searchQuestions(string $query, int $limit = 20): array
    {
        $questions = Question::query()
            ->search($query)
            ->orderByDesc('id')
            ->limit($limit)
            ->get();

        return [
            'data' => $this->mapQuestions($questions),
        ];
    }

    public function getQuestionsByIds(array $ids): array
    {
        if (empty($ids)) {
            return ['data' => []];
        }

        $questions = Question::query()
            ->whereIn('id', $ids)
            ->orderByDesc('id')
            ->get();

        return [
            'data' => $this->mapQuestions($questions),
        ];
    }

    public function getQuestionsByKpCode(string $kpCode, int $limit = 100): array
    {
        $kpCode = trim($kpCode);
        $query = Question::query()->where(function ($q) use ($kpCode): void {
            $q->where('kp_code', $kpCode);
            if ($kpCode !== '' && Schema::hasTable('question_kp_relations')) {
                $q->orWhereIn('id', function ($sub) use ($kpCode): void {
                    $sub->select('question_id')
                        ->from('question_kp_relations')
                        ->where('kp_code', $kpCode);
                });
            }
        });

        $questions = $query->orderByDesc('id')->limit($limit)->get();

        return [
            'data' => $this->mapQuestions($questions),
        ];
    }

    /**
     * 按 kp 统计正式库题目数：主表 kp_code 与 question_kp_relations 合并，同一题同一 kp 只计一次。
     *
     * @param  list<string>|null  $onlyKpCodes  非空时仅返回这些 kp 的计数
     * @return array<string, int>
     */
    public function questionCountsGroupedByKp(?array $onlyKpCodes = null): array
    {
        if (! Schema::hasTable('questions')) {
            return [];
        }

        $onlyKpCodes = $onlyKpCodes !== null
            ? array_values(array_unique(array_filter(array_map('strval', $onlyKpCodes))))
            : null;

        if ($onlyKpCodes === []) {
            return [];
        }

        $relationUnion = '';
        if (Schema::hasTable('question_kp_relations')) {
            $relationUnion = " UNION ALL SELECT question_id AS qid, kp_code FROM question_kp_relations WHERE kp_code IS NOT NULL AND kp_code != ''";
        }

        $sql = "SELECT kp_code, COUNT(DISTINCT qid) AS c FROM (
            SELECT id AS qid, kp_code FROM questions WHERE kp_code IS NOT NULL AND kp_code != ''
            {$relationUnion}
        ) merged";

        $bindings = [];
        if ($onlyKpCodes !== null) {
            $placeholders = implode(',', array_fill(0, count($onlyKpCodes), '?'));
            $sql .= " WHERE kp_code IN ({$placeholders})";
            $bindings = $onlyKpCodes;
        }

        $sql .= ' GROUP BY kp_code';

        $out = [];
        foreach (DB::select($sql, $bindings) as $row) {
            $k = (string) ($row->kp_code ?? '');
            if ($k !== '') {
                $out[$k] = (int) ($row->c ?? 0);
            }
        }

        return $out;
    }

    public function getStatistics(array $filters = []): array
    {
        $baseQuery = $this->applyFilters(Question::query(), $filters);
        $total = (clone $baseQuery)->count();

        $byDifficulty = (clone $baseQuery)
            ->selectRaw('difficulty, COUNT(*) as total')
            ->groupBy('difficulty')
            ->pluck('total', 'difficulty')
            ->toArray();

        $byTypeRaw = (clone $baseQuery)
            ->selectRaw('question_type, COUNT(*) as total')
            ->groupBy('question_type')
            ->pluck('total', 'question_type')
            ->toArray();

        $byType = [];
        foreach ($byTypeRaw as $type => $count) {
            $label = $this->mapQuestionTypeLabel((string) $type);
            $byType[$label] = ($byType[$label] ?? 0) + $count;
        }

        $byKp = (clone $baseQuery)
            ->selectRaw('kp_code, COUNT(*) as total')
            ->groupBy('kp_code')
            ->pluck('total', 'kp_code')
            ->toArray();

        $bySource = (clone $baseQuery)
            ->selectRaw('source, COUNT(*) as total')
            ->groupBy('source')
            ->pluck('total', 'source')
            ->toArray();

        return [
            'total' => $total,
            'by_difficulty' => $byDifficulty,
            'by_type' => $byType,
            'by_kp' => $byKp,
            'by_source' => $bySource,
        ];
    }

    public function generateQuestions(array $params): array
    {
        $kpCode = $params['kp_code'] ?? null;
        // 允许 kp_code 为空，此时从所有可用题目中选择
        if (!$kpCode) {
            // 从 params 中获取 kp_codes 数组
            $kpCodes = $params['kp_codes'] ?? [];
            if (is_string($kpCodes)) {
                $kpCodes = array_map('trim', explode(',', $kpCodes));
            }
            if (is_array($kpCodes) && !empty($kpCodes)) {
                $kpCode = $kpCodes[0]; // 使用第一个知识点
            } else {
                // 如果没有指定知识点，从数据库中随机选择一个可用的知识点
                $availableKp = Question::query()
                    ->whereNotNull('kp_code')
                    ->where('kp_code', '!=', '')
                    ->distinct()
                    ->pluck('kp_code')
                    ->first();

                if ($availableKp) {
                    $kpCode = $availableKp;
                } else {
                    return [
                        'success' => false,
                        'message' => '系统中没有可用的题目，请先添加题目数据',
                    ];
                }
            }
        }

        $count = max(1, (int) ($params['count'] ?? 1));
        $keyword = (string) ($params['keyword'] ?? '');
        $type = $params['type'] ?? null;
        $difficulty = $params['difficulty'] ?? null;
        $skills = $params['skills'] ?? [];

        $solutionService = app(AiSolutionService::class);

        $created = [];

        DB::transaction(function () use (
            $count,
            $kpCode,
            $keyword,
            $type,
            $difficulty,
            $skills,
            $solutionService,
            &$created,
            $params
        ) {
            for ($i = 1; $i <= $count; $i++) {
                $questionCode = $this->generateQuestionCode();
                $stemSuffix = $keyword ? "（{$keyword}）" : '';
                $stem = "【AI生成】{$kpCode} 题目 {$i}{$stemSuffix}";

                $options = null;
                $answer = null;
                $questionType = $type ?? 'CALCULATION';

                if (in_array($questionType, ['CHOICE', 'MULTIPLE_CHOICE'], true)) {
                    $options = [
                        ['label' => 'A', 'text' => '选项 A'],
                        ['label' => 'B', 'text' => '选项 B'],
                        ['label' => 'C', 'text' => '选项 C'],
                        ['label' => 'D', 'text' => '选项 D'],
                    ];
                    $answer = 'A';
                }

                $solution = $solutionService->generateSolution($stem, [
                    'kp_code' => $kpCode,
                    'difficulty' => $difficulty,
                    'question_type' => $questionType,
                ]);

                $question = Question::create([
                    'question_code' => $questionCode,
                    'kp_code' => $kpCode,
                    'stem' => $stem,
                    'options' => $options,
                    'answer' => $answer,
                    'solution' => $solution['solution'] ?? null,
                    'difficulty' => $difficulty,
                    'source' => 'ai::local',
                    'question_type' => $questionType,
                    'meta' => [
                        'skills' => $skills,
                        'prompt_template' => $params['prompt_template'] ?? null,
                        'strategy' => $params['strategy'] ?? null,
                        'generated_at' => now()->toDateTimeString(),
                        'solution_steps' => $solution['steps'] ?? [],
                    ],
                ]);

                $created[] = $this->mapQuestion($question);
            }
        });

        return [
            'success' => true,
            'message' => '生成完成',
            'count' => count($created),
            'data' => $created,
        ];
    }

    public function importQuestions(array $questions): array
    {
        if (empty($questions)) {
            return [
                'success' => false,
                'message' => '题目为空',
                'count' => 0,
            ];
        }

        $created = 0;

        DB::transaction(function () use ($questions, &$created) {
            foreach ($questions as $payload) {
                $questionCode = $payload['question_code'] ?? $this->generateQuestionCode();
                $question = Question::firstOrNew(['question_code' => $questionCode]);
                $question->fill($this->normalizePayload($payload));
                $question->save();
                $created++;
            }
        });

        return [
            'success' => true,
            'message' => '导入完成',
            'count' => $created,
        ];
    }

    public function selectQuestionsForExam(int $totalQuestions, array $filters): array
    {
        $query = Question::query();

        // 【新增】只获取审核通过的题目（audit_status = 0 表示合格）
        $query->where('audit_status', 0);

        if (!empty($filters['kp_codes'])) {
            $query->whereIn('kp_code', $filters['kp_codes']);
        }

        if (!empty($filters['skills'])) {
            $skills = array_values(array_filter($filters['skills']));
            if (!empty($skills)) {
                $query->where(function ($q) use ($skills) {
                    foreach ($skills as $skill) {
                        $q->orWhereJsonContains('meta->skills', $skill);
                    }
                });
            }
        }

        if (!empty($filters['grade'])) {
            $stageGrade = $this->normalizeStageGrade((int) $filters['grade']);
            if ($stageGrade !== null) {
                $query->where('grade', $stageGrade);
            }
        }

        $questions = $query->get();

        $selected = $this->applyRatioSelection($questions, $totalQuestions, $filters);

        return $this->mapQuestions(collect($selected));
    }

    public function getKnowledgePointOptions(): array
    {
        return KnowledgePoint::query()
            ->orderBy('kp_code')
            ->pluck('name', 'kp_code')
            ->toArray();
    }

    public function getSkillNameMapping(?string $kpCode = null): array
    {
        return [];
    }

    private function applyFilters($query, array $filters)
    {
        if (!empty($filters['kp_code'])) {
            $query->where('kp_code', $filters['kp_code']);
        }

        if (!empty($filters['difficulty'])) {
            $query->where('difficulty', $filters['difficulty']);
        }

        if (!empty($filters['type'])) {
            $query->where('question_type', $filters['type']);
        }

        if (!empty($filters['search'])) {
            $query->search($filters['search']);
        }

        if (!empty($filters['grade'])) {
            $stageGrade = $this->normalizeStageGrade((int) $filters['grade']);
            if ($stageGrade !== null) {
                $query->where('grade', $stageGrade);
            }
        }

        return $query;
    }

    private function normalizeStageGrade(int $grade): ?int
    {
        if ($grade <= 0) {
            return null;
        }

        return $grade <= 9 ? 2 : 3;
    }

    private function normalizePayload(array $payload): array
    {
        $normalized = [
            'question_code' => $payload['question_code'] ?? null,
            'kp_code' => $payload['kp_code'] ?? null,
            'stem' => $payload['stem'] ?? ($payload['content'] ?? ''),
            'options' => $payload['options'] ?? null,
            'answer' => $payload['answer'] ?? null,
            'solution' => $payload['solution'] ?? null,
            'difficulty' => $payload['difficulty'] ?? null,
            'source' => $payload['source'] ?? null,
            'tags' => $payload['tags'] ?? null,
            'question_type' => $payload['question_type'] ?? ($payload['type'] ?? null),
            'meta' => $payload['meta'] ?? null,
        ];

        if (isset($payload['skills'])) {
            $meta = $normalized['meta'] ?? [];
            $meta['skills'] = is_array($payload['skills'])
                ? $payload['skills']
                : array_filter(array_map('trim', explode(',', (string) $payload['skills'])));
            $normalized['meta'] = $meta;
        }

        return array_filter($normalized, static fn ($value) => $value !== null);
    }

    private function mapQuestions(Collection $questions): array
    {
        $kpCodes = $questions->pluck('kp_code')->filter()->unique()->values();
        $kpMap = $this->resolveKnowledgePointNames($kpCodes->all());

        return $questions->map(function (Question $question) use ($kpMap) {
            $data = $this->mapQuestion($question);
            $data['kp_name'] = $kpMap[$question->kp_code] ?? null;
            return $data;
        })->values()->all();
    }

    private function mapQuestion(Question $question): array
    {
        $meta = $question->meta ?? [];

        $data = [
            'id' => $question->id,
            'question_code' => $question->question_code,
            'kp_code' => $question->kp_code,
            'stem' => $question->stem,
            'options' => $question->options,
            'answer' => $question->answer,
            'solution' => $question->solution,
            'difficulty' => $question->difficulty,
            'source' => $question->source,
            'tags' => $question->tags,
            'type' => $question->question_type,
            'question_type' => $question->question_type,
            'skills' => $meta['skills'] ?? [],
            'meta' => $meta,
            'created_at' => $question->created_at?->toDateTimeString(),
            'updated_at' => $question->updated_at?->toDateTimeString(),
        ];

        return MathFormulaProcessor::processQuestionData($data);
    }

    private function generateQuestionCode(): string
    {
        return 'Q' . Str::upper(Str::random(10));
    }

    private function mapQuestionTypeLabel(string $type): string
    {
        return match (strtoupper($type)) {
            'CHOICE' => '选择题',
            'MULTIPLE_CHOICE' => '多选题',
            'FILL_IN_THE_BLANK', 'FILL' => '填空题',
            'CALCULATION', 'WORD_PROBLEM', 'ANSWER' => '解答题',
            'PROOF' => '证明题',
            default => '其他',
        };
    }

    private function applyRatioSelection(Collection $questions, int $totalQuestions, array $filters): array
    {
        $questionsByType = $questions->groupBy(fn (Question $q) => $q->question_type ?? 'CALCULATION');
        $questionsByDifficulty = $questions->groupBy(function (Question $q) {
            $difficulty = (float) ($q->difficulty ?? 0);
            if ($difficulty <= 0.4) {
                return 'easy';
            }
            if ($difficulty <= 0.7) {
                return 'medium';
            }
            return 'hard';
        });

        $typeRatio = $filters['question_type_ratio'] ?? [];
        $difficultyRatio = $filters['difficulty_ratio'] ?? [];

        $selected = collect();

        if (!empty($typeRatio)) {
            foreach ($typeRatio as $type => $ratio) {
                $bucket = $questionsByType->get($type, collect());
                $count = (int) round($totalQuestions * (float) $ratio);
                $selected = $selected->merge($bucket->shuffle()->take($count));
            }
        }

        if (!empty($difficultyRatio)) {
            foreach ($difficultyRatio as $key => $ratio) {
                $bucketKey = $this->normalizeDifficultyKey($key);
                $bucket = $questionsByDifficulty->get($bucketKey, collect());
                $count = (int) round($totalQuestions * (float) $ratio);
                $selected = $selected->merge($bucket->shuffle()->take($count));
            }
        }

        if ($selected->isEmpty()) {
            return $questions->shuffle()->take($totalQuestions)->values()->all();
        }

        if ($selected->count() < $totalQuestions) {
            $missing = $totalQuestions - $selected->count();
            $fill = $questions->diff($selected)->shuffle()->take($missing);
            $selected = $selected->merge($fill);
        }

        return $selected->values()->all();
    }

    private function normalizeDifficultyKey(string $key): string
    {
        if (in_array($key, ['easy', 'medium', 'hard'], true)) {
            return $key;
        }

        $value = (float) $key;
        if ($value <= 0.4) {
            return 'easy';
        }
        if ($value <= 0.7) {
            return 'medium';
        }
        return 'hard';
    }

    private function resolveKnowledgePointNames(array $kpCodes): array
    {
        $kpCodes = array_values(array_filter(array_unique($kpCodes)));
        if (empty($kpCodes)) {
            return [];
        }

        $cacheKey = 'kp-name-map-' . md5(implode('|', $kpCodes));
        return Cache::remember($cacheKey, now()->addMinutes(30), function () use ($kpCodes) {
            $kpMap = KnowledgePoint::query()
                ->whereIn('kp_code', $kpCodes)
                ->pluck('name', 'kp_code')
                ->toArray();

            $missing = array_values(array_filter($kpCodes, fn ($code) => empty($kpMap[$code])));
            if (empty($missing)) {
                return $kpMap;
            }

            try {
                $api = app(KnowledgeServiceApi::class);
                $all = $api->listKnowledgePoints();
                foreach ($all as $kp) {
                    $code = $kp['kp_code'] ?? null;
                    $name = $kp['cn_name'] ?? $kp['name'] ?? null;
                    if ($code && $name && in_array($code, $missing, true)) {
                        $kpMap[$code] = $name;
                    }
                }
            } catch (\Throwable $e) {
                // Fallback: keep existing mapping
            }

            return $kpMap;
        });
    }

    /**
     * 根据难度系数分布选择题目
     *
     * @param array $questions 候选题目数组
     * @param int $totalQuestions 总题目数
     * @param int $difficultyCategory 难度类别 (0-4)
     *   - 0: 0-0.1占90%，0.1-0.25占10%
     *   - 1: 0-0.25占90%，0.25-1占10%
     *   - 2: 0.25-0.5范围占50%，<0.25占25%，>0.5占25%
     *   - 3: 0.5-0.75范围占50%，<0.5占25%，>0.75占25%
     *   - 4: 0.75-1范围占50%，其他占50%
     * @param array $filters 其他筛选条件
     * @return array 分布后的题目
     */
    public function selectQuestionsByDifficultyDistribution(array $questions, int $totalQuestions, int $difficultyCategory = 1, array $filters = []): array
    {
        Log::info('QuestionLocalService: 根据难度系数分布选择题目', [
            'total_questions' => $totalQuestions,
            'difficulty_category' => $difficultyCategory,
        ]);

        if (empty($questions)) {
            Log::warning('QuestionLocalService: 输入题目为空');
            return [];
        }

        $questions = $this->questionDifficultyResolver->applyCalibratedDifficulty($questions);
        $calibratedCount = count(array_filter($questions, fn ($q) => ($q['difficulty_source'] ?? null) === 'calibrated'));
        $servedBlendCount = count(array_filter($questions, fn ($q) => ($q['difficulty_source'] ?? null) === 'served_blend'));
        Log::info('QuestionLocalService: 组卷前应用校准难度', [
            'total_candidates' => count($questions),
            'calibrated_candidates' => $calibratedCount,
            'served_blend_candidates' => $servedBlendCount,
        ]);

        $resolveQuestionId = static function (array $question): string {
            return (string) ($question['id'] ?? $question['question_id'] ?? $question['question_bank_id'] ?? '');
        };

        // 【恢复】简化逻辑，避免复杂处理
        $distribution = $this->difficultyDistributionService->calculateDistribution($difficultyCategory, $totalQuestions);

        // 按难度范围分桶
        $buckets = $this->difficultyDistributionService->groupQuestionsByDifficultyRange($questions, $difficultyCategory);

        Log::info('QuestionLocalService: 题目分桶', [
            'buckets' => array_map(fn($bucket) => count($bucket), $buckets),
            'total_input' => count($questions),
            'distribution' => $distribution
        ]);

        // 根据分布选择题目
        $selected = [];
        $usedIds = [];

        foreach ($distribution as $level => $config) {
            $targetCount = $config['count'];
            if ($targetCount <= 0) {
                Log::debug('QuestionLocalService: 跳过难度层级', [
                    'level' => $level,
                    'target_count' => $targetCount
                ]);
                continue;
            }

            $rangeKey = $this->difficultyDistributionService->mapDifficultyLevelToRangeKey($level, $difficultyCategory);
            $bucket = $buckets[$rangeKey] ?? [];

            // 随机打乱
            shuffle($bucket);

            // 选择题目
            $taken = 0;
            foreach ($bucket as $question) {
                if ($taken >= $targetCount) break;

                $questionId = $resolveQuestionId($question);
                if ($questionId !== '' && !in_array($questionId, $usedIds, true)) {
                    $selected[] = $question;
                    $usedIds[] = $questionId;
                    $taken++;
                }
            }

            // 【修复】如果某个难度范围题目不足，记录日志但不截断
            if ($taken < $targetCount) {
                Log::warning('QuestionLocalService: 难度范围题目不足，允许后续补充', [
                    'level' => $level,
                    'range_key' => $rangeKey,
                    'target' => $targetCount,
                    'actual' => $taken,
                    'bucket_size' => count($bucket)
                ]);
            }
        }

        // 如果数量不足，从剩余题目中补充
        if (count($selected) < $totalQuestions) {
            Log::warning('QuestionLocalService: 开始补充题目（难度分布无法满足要求）', [
                'need_more' => $totalQuestions - count($selected),
                'selected_count' => count($selected),
                'difficulty_category' => $difficultyCategory,
                'note' => '优先从次级桶补充，不足再放宽'
            ]);

            $needMore = $totalQuestions - count($selected);
            $supplemented = 0;
            $supplementOrder = $this->difficultyDistributionService->getSupplementOrder($difficultyCategory);

            foreach ($supplementOrder as $bucketKey) {
                if ($supplemented >= $needMore) {
                    break;
                }

                $bucket = $buckets[$bucketKey] ?? [];
                if (empty($bucket)) {
                    continue;
                }

                shuffle($bucket);
                foreach ($bucket as $q) {
                    if ($supplemented >= $needMore) {
                        break;
                    }

                    $id = $resolveQuestionId($q);
                    if ($id !== '' && !in_array($id, $usedIds, true)) {
                        $selected[] = $q;
                        $usedIds[] = $id;
                        $supplemented++;
                    }
                }
            }

            if ($supplemented < $needMore) {
                $remaining = [];
                foreach ($questions as $q) {
                    $id = $resolveQuestionId($q);
                    if ($id !== '' && !in_array($id, $usedIds, true)) {
                        $remaining[] = $q;
                    }
                }

                shuffle($remaining);
                $supplementCount = min($needMore - $supplemented, count($remaining));
                $selected = array_merge($selected, array_slice($remaining, 0, $supplementCount));
                $supplemented += $supplementCount;
            }

            Log::warning('QuestionLocalService: 补充完成', [
                'supplement_added' => $supplemented,
                'final_count_before_truncate' => count($selected),
                'remaining_unused' => max(0, count($questions) - count($selected))
            ]);
        }

        // 截断至目标数量
        $selected = array_slice($selected, 0, $totalQuestions);

        $finalBuckets = $this->difficultyDistributionService->groupQuestionsByDifficultyRange($selected, $difficultyCategory);
        $finalTotal = max(1, count($selected));
        $distributionStats = array_map(static function ($bucket) use ($finalTotal) {
            $count = count($bucket);
            return [
                'count' => $count,
                'ratio' => round(($count / $finalTotal) * 100, 2),
            ];
        }, $finalBuckets);

        Log::info('QuestionLocalService: 难度分布选择完成', [
            'final_count' => count($selected),
            'target_count' => $totalQuestions,
            'success' => count($selected) === $totalQuestions,
            'input_count' => count($questions),
            'distribution_applied' => true,
            'final_distribution' => $distributionStats
        ]);

        return $selected;
    }

}