<?php

namespace App\Services;

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

/**
 * 题目质检服务
 *
 * 校验规则：题干、答案、解析、选项、公式、PDF 呈现
 * 自动质检 + 人工质检结果分别记录到 question_qc_results
 */
class QuestionQualityCheckService
{
    public const RULES = [
        'STEM_EMPTY' => ['name' => '题干为空', 'severity' => 'error'],
        'ANSWER_EMPTY' => ['name' => '答案为空', 'severity' => 'error'],
        'SOLUTION_EMPTY' => ['name' => '解析为空', 'severity' => 'warning'],
        'CHOICE_OPTIONS_MISSING' => ['name' => '选择题缺选项', 'severity' => 'error'],
        'FORMULA_INVALID' => ['name' => '公式异常', 'severity' => 'error'],
        'CONTENT_TOO_SHORT' => ['name' => '题干过短', 'severity' => 'warning'],
    ];

    /**
     * 对单道题目执行自动质检
     *
     * @param array $question 题目数据，需包含 stem, answer, solution, question_type, options
     * @param int|null $questionTemId question_tem 表 ID
     * @param int|null $questionId questions 表 ID
     * @return array ['passed' => bool, 'results' => array, 'errors' => array]
     */
    public function runAutoCheck(array $question, ?int $questionTemId = null, ?int $questionId = null): array
    {
        $stem = $question['stem'] ?? $question['content'] ?? '';
        $answer = $question['answer'] ?? '';
        $solution = $question['solution'] ?? '';
        $questionType = $question['question_type'] ?? ($question['tags'] ?? '');
        $options = $question['options'] ?? null;

        $results = [];
        $errors = [];

        // STEM_EMPTY / CONTENT_TOO_SHORT
        $stemLen = mb_strlen(trim((string) $stem));
        if ($stemLen === 0) {
            $results[] = $this->recordCheck('STEM_EMPTY', false, '题干为空');
            $errors[] = 'STEM_EMPTY';
        } elseif ($stemLen < 5) {
            $results[] = $this->recordCheck('CONTENT_TOO_SHORT', false, "题干过短({$stemLen}字)");
            $errors[] = 'CONTENT_TOO_SHORT';
        } else {
            $results[] = $this->recordCheck('STEM_EMPTY', true);
        }

        // ANSWER_EMPTY
        if (trim((string) $answer) === '') {
            $results[] = $this->recordCheck('ANSWER_EMPTY', false, '答案为空');
            $errors[] = 'ANSWER_EMPTY';
        } else {
            $results[] = $this->recordCheck('ANSWER_EMPTY', true);
        }

        // SOLUTION_EMPTY（解答题强校验）
        $isAnswerType = in_array(strtolower((string) $questionType), ['answer', '解答题', '解答'], true);
        if ($isAnswerType && trim((string) $solution) === '') {
            $results[] = $this->recordCheck('SOLUTION_EMPTY', false, '解答题解析为空');
            $errors[] = 'SOLUTION_EMPTY';
        } else {
            $results[] = $this->recordCheck('SOLUTION_EMPTY', true);
        }

        // CHOICE_OPTIONS_MISSING
        $isChoice = in_array(strtolower((string) $questionType), ['choice', '选择题', 'select'], true);
        if ($isChoice) {
            $optsOk = is_array($options) && count($options) >= 2;
            if (!$optsOk) {
                $results[] = $this->recordCheck('CHOICE_OPTIONS_MISSING', false, '选择题选项为空或不足2个');
                $errors[] = 'CHOICE_OPTIONS_MISSING';
            } else {
                $results[] = $this->recordCheck('CHOICE_OPTIONS_MISSING', true);
            }
        } else {
            $results[] = $this->recordCheck('CHOICE_OPTIONS_MISSING', true, null, 'skip');
        }

        // FORMULA_INVALID（尝试处理公式，捕获异常）
        try {
            $processed = MathFormulaProcessor::processFormulas($stem);
            $processedAnswer = MathFormulaProcessor::processFormulas($answer);
            $processedSolution = MathFormulaProcessor::processFormulas($solution);

            $hasError = $this->detectFormulaError($processed)
                || $this->detectFormulaError($processedAnswer)
                || $this->detectFormulaError($processedSolution);

            if ($hasError) {
                $results[] = $this->recordCheck('FORMULA_INVALID', false, '公式定界符不匹配或存在异常');
                $errors[] = 'FORMULA_INVALID';
            } else {
                $results[] = $this->recordCheck('FORMULA_INVALID', true);
            }
        } catch (\Throwable $e) {
            $results[] = $this->recordCheck('FORMULA_INVALID', false, $e->getMessage());
            $errors[] = 'FORMULA_INVALID';
        }

        $passed = empty($errors);

        foreach ($results as $r) {
            $this->saveQcResult($r, $questionTemId, $questionId, 'auto');
        }

        return [
            'passed' => $passed,
            'results' => $results,
            'errors' => $errors,
        ];
    }

    /**
     * 检测公式处理后的内容是否仍有明显错误（如未闭合的 $）
     */
    private function detectFormulaError(string $content): bool
    {
        $len = strlen($content);
        $dollarCount = 0;
        $inEscape = false;
        for ($i = 0; $i < $len; $i++) {
            $c = $content[$i];
            if ($c === '\\' && !$inEscape) {
                $inEscape = true;
                continue;
            }
            if ($c === '$') {
                $dollarCount++;
            }
            $inEscape = false;
        }
        return ($dollarCount % 2) !== 0;
    }

    private function recordCheck(string $ruleCode, bool $passed, ?string $detail = null, string $result = 'pass'): array
    {
        $info = self::RULES[$ruleCode] ?? ['name' => $ruleCode, 'severity' => 'error'];
        return [
            'rule_code' => $ruleCode,
            'rule_name' => $info['name'],
            'passed' => $passed,
            'auto_result' => $passed ? 'pass' : ($result === 'skip' ? 'skip' : 'fail'),
            'detail' => $detail,
        ];
    }

    private function saveQcResult(array $r, ?int $questionTemId, ?int $questionId, string $source): void
    {
        if (!Schema::hasTable('question_qc_results')) {
            return;
        }
        try {
            DB::table('question_qc_results')->insert([
                'question_tem_id' => $questionTemId,
                'question_id' => $questionId,
                'rule_code' => $r['rule_code'],
                'rule_name' => $r['rule_name'] ?? null,
                'passed' => $r['passed'],
                'auto_result' => $r['auto_result'] ?? ($r['passed'] ? 'pass' : 'fail'),
                'manual_result' => null,
                'pdf_render_ok' => null,
                'detail' => $r['detail'] ?? null,
                'source' => $source,
                'created_at' => now(),
                'updated_at' => now(),
            ]);
        } catch (\Throwable $e) {
            Log::warning('QuestionQualityCheckService: 保存质检结果失败', [
                'rule_code' => $r['rule_code'],
                'error' => $e->getMessage(),
            ]);
        }
    }

    /**
     * 记录人工质检结果（更新已有自动质检记录）
     */
    public function recordManualResult(int $questionTemId, string $ruleCode, string $manualResult, ?bool $pdfRenderOk = null): void
    {
        if (!Schema::hasTable('question_qc_results')) {
            return;
        }
        DB::table('question_qc_results')
            ->where('question_tem_id', $questionTemId)
            ->where('rule_code', $ruleCode)
            ->update([
                'manual_result' => $manualResult,
                'pdf_render_ok' => $pdfRenderOk,
                'updated_at' => now(),
            ]);
    }

    /**
     * 获取下学期章节关联的、题少的 KP 列表（用于筛选 question_tem）
     *
     * @param int|null $textbookId 教材 ID，null 则取默认教材
     * @param int $semesterCode 学期 1=上 2=下
     * @param int $limit 返回前 N 个题少的 KP
     * @return array [['kp_code' => string, 'question_count' => int], ...]
     */
    public function getKpsWithFewQuestions(?int $textbookId = null, int $semesterCode = 2, int $limit = 50): array
    {
        $textbooksQuery = DB::table('textbooks')->where('is_deleted', 0);
        if ($textbookId) {
            $textbooksQuery->where('id', $textbookId);
        }
        if (Schema::hasColumn('textbooks', 'semester_code')) {
            $textbooksQuery->where('semester_code', $semesterCode);
        }

        $textbookIds = $textbooksQuery->pluck('id')->toArray();
        if (empty($textbookIds)) {
            Log::warning('QuestionQualityCheckService: 未找到下学期教材');
            return [];
        }

        $kpCodes = DB::table('textbook_chapter_knowledge_relation as tckr')
            ->join('textbook_catalog_nodes as tcn', 'tckr.catalog_chapter_id', '=', 'tcn.id')
            ->whereIn('tcn.textbook_id', $textbookIds)
            ->where(function ($q) {
                $q->where('tckr.is_deleted', 0)->orWhereNull('tckr.is_deleted');
            })
            ->distinct()
            ->pluck('tckr.kp_code')
            ->toArray();

        if (empty($kpCodes)) {
            return [];
        }

        $counts = DB::table('questions')
            ->whereIn('kp_code', $kpCodes)
            ->where('audit_status', 0)
            ->selectRaw('kp_code, count(*) as cnt')
            ->groupBy('kp_code')
            ->pluck('cnt', 'kp_code')
            ->toArray();

        $result = [];
        foreach ($kpCodes as $kp) {
            $result[] = [
                'kp_code' => $kp,
                'question_count' => $counts[$kp] ?? 0,
            ];
        }

        usort($result, fn ($a, $b) => $a['question_count'] <=> $b['question_count']);
        return array_slice($result, 0, $limit);
    }
}