<?php

namespace App\Services;

use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Schema;

class QuestionDifficultyResolver
{
    private const TABLE = 'question_difficulty_calibrations';

    private ?bool $tableReady = null;

    /**
     * @param  array<int, int|string>  $questionIds
     * @return array<int, float> question_bank_id => calibrated_difficulty
     */
    public function mapCalibratedDifficulty(array $questionIds): array
    {
        if (! $this->isReady()) {
            return [];
        }

        $questionIds = collect($questionIds)
            ->map(fn ($id) => (int) $id)
            ->filter(fn ($id) => $id > 0)
            ->unique()
            ->values()
            ->all();
        if ($questionIds === []) {
            return [];
        }

        return DB::table(self::TABLE)
            ->whereIn('question_bank_id', $questionIds)
            ->pluck('calibrated_difficulty', 'question_bank_id')
            ->map(fn ($v) => (float) $v)
            ->all();
    }

    /**
     * 批量给题目数组覆盖 difficulty（校准值优先，原始值兜底）
     *
     * @param  array<int, array<string, mixed>>  $questions
     * @return array<int, array<string, mixed>>
     */
    public function applyCalibratedDifficulty(array $questions): array
    {
        if ($questions === []) {
            return $questions;
        }

        $ids = [];
        foreach ($questions as $q) {
            $id = (int) ($q['id'] ?? $q['question_id'] ?? $q['question_bank_id'] ?? 0);
            if ($id > 0) {
                $ids[] = $id;
            }
        }
        $map = $this->mapCalibratedDifficulty($ids);
        if ($map === []) {
            return $questions;
        }

        foreach ($questions as &$q) {
            $id = (int) ($q['id'] ?? $q['question_id'] ?? $q['question_bank_id'] ?? 0);
            if ($id > 0 && array_key_exists($id, $map)) {
                $q['difficulty'] = (float) $map[$id];
                $q['difficulty_source'] = 'calibrated';
            }
        }
        unset($q);

        return $questions;
    }

    private function isReady(): bool
    {
        if ($this->tableReady !== null) {
            return $this->tableReady;
        }

        $this->tableReady = Schema::hasTable(self::TABLE);

        return $this->tableReady;
    }
}