<?php

namespace App\Http\Controllers\Api;

use App\Http\Controllers\Controller;
use App\Services\ExamPdfExportService;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Log;
use Illuminate\Support\Facades\Validator;

class QuestionPdfController extends Controller
{
    protected ExamPdfExportService $pdfService;

    public function __construct(ExamPdfExportService $pdfService)
    {
        $this->pdfService = $pdfService;
    }

    /**
     * Generate PDF for specified questions
     *
     * POST /api/questions/pdf
     *
     * Request body:
     * {
     *   "question_ids": [19903, 17766, ...],
     *   "student_id": "123456",
     *   "student_name": "张三",        // optional
     *   "student_grade": "初二",       // optional
     *   "teacher_name": "李老师",      // optional
     *   "paper_name": "专项练习",      // optional
     *   "include_grading": false       // optional, whether to generate grading PDF
     * }
     */
    public function generate(Request $request)
    {
        $validator = Validator::make($request->all(), [
            'question_ids' => 'required|array|min:1|max:100',
            'question_ids.*' => 'required|integer',
            'student_id' => 'required|string',
            'student_name' => 'nullable|string|max:50',
            'student_grade' => 'nullable|string|max:20',
            'teacher_name' => 'nullable|string|max:50',
            'paper_name' => 'nullable|string|max:100',
            'include_grading' => 'nullable|boolean',
        ]);

        if ($validator->fails()) {
            return response()->json([
                'success' => false,
                'message' => '参数验证失败',
                'errors' => $validator->errors(),
            ], 422);
        }

        $questionIds = $request->input('question_ids');
        $studentId = $request->input('student_id');
        $studentName = $request->input('student_name', '');
        $studentGrade = $request->input('student_grade', '');
        $teacherName = $request->input('teacher_name', '');
        $paperName = $request->input('paper_name', '专项练习');
        $includeGrading = $request->input('include_grading', false);

        Log::info('生成指定题目PDF', [
            'question_ids' => $questionIds,
            'student_id' => $studentId,
            'count' => count($questionIds),
        ]);

        try {
            // 1. Fetch questions from database
            $questions = DB::connection('remote_mysql')
                ->table('questions')
                ->whereIn('id', $questionIds)
                ->get();

            if ($questions->isEmpty()) {
                return response()->json([
                    'success' => false,
                    'message' => '未找到指定的题目',
                ], 404);
            }

            // 2. Group questions by type
            $groupedQuestions = $this->groupQuestionsByType($questions, $questionIds);

            // 3. Build virtual paper structure
            $paper = $this->buildVirtualPaper($paperName, $studentId, $groupedQuestions);

            // 4. Generate PDF
            $result = $this->pdfService->generateByQuestions(
                $paper,
                $groupedQuestions,
                [
                    'name' => $studentName,
                    'grade' => $studentGrade,
                ],
                [
                    'name' => $teacherName,
                ],
                $includeGrading
            );

            Log::info('指定题目PDF生成成功', [
                'student_id' => $studentId,
                'question_count' => count($questionIds),
                'pdf_url' => $result['pdf_url'] ?? null,
            ]);

            return response()->json([
                'success' => true,
                'message' => 'PDF生成成功',
                'data' => $result,
            ]);

        } catch (\Exception $e) {
            Log::error('生成指定题目PDF失败', [
                'error' => $e->getMessage(),
                'trace' => $e->getTraceAsString(),
            ]);

            return response()->json([
                'success' => false,
                'message' => '生成PDF失败: ' . $e->getMessage(),
            ], 500);
        }
    }

    /**
     * Group questions by type and maintain order
     */
    private function groupQuestionsByType($questions, array $originalOrder): array
    {
        // Create a map for quick lookup and preserve original order
        $questionMap = [];
        foreach ($questions as $q) {
            $questionMap[$q->id] = $q;
        }

        $grouped = [
            'choice' => [],
            'fill' => [],
            'answer' => [],
        ];

        $questionNumber = 1;

        // Process in original order
        foreach ($originalOrder as $id) {
            if (!isset($questionMap[$id])) {
                continue;
            }

            $q = $questionMap[$id];
            $type = $this->normalizeQuestionType($q->question_type);

            // Build question object for template
            $questionObj = (object) [
                'id' => $q->id,
                'question_number' => $questionNumber++,
                'content' => $q->stem,
                'options' => is_string($q->options) ? json_decode($q->options, true) : ($q->options ?? []),
                'answer' => $q->answer,
                'solution' => $q->solution,
                'score' => $this->getDefaultScore($type),
                'difficulty' => $q->difficulty,
                'kp_code' => $q->kp_code,
            ];

            $grouped[$type][] = $questionObj;
        }

        return $grouped;
    }

    /**
     * Normalize question type to standard format
     */
    private function normalizeQuestionType(?string $type): string
    {
        if (!$type) {
            return 'answer';
        }

        $type = strtolower(trim($type));

        $typeMap = [
            'choice' => 'choice',
            '选择题' => 'choice',
            'single_choice' => 'choice',
            'multiple_choice' => 'choice',
            'fill' => 'fill',
            '填空题' => 'fill',
            'blank' => 'fill',
            'answer' => 'answer',
            '解答题' => 'answer',
            'subjective' => 'answer',
            'calculation' => 'answer',
            'proof' => 'answer',
        ];

        return $typeMap[$type] ?? 'answer';
    }

    /**
     * Get default score by question type
     */
    private function getDefaultScore(string $type): int
    {
        return match ($type) {
            'choice' => 5,
            'fill' => 5,
            'answer' => 10,
            default => 5,
        };
    }

    /**
     * Build virtual paper structure
     */
    private function buildVirtualPaper(string $paperName, string $studentId, array $groupedQuestions): object
    {
        $totalScore = 0;
        $totalQuestions = 0;

        foreach ($groupedQuestions as $type => $questions) {
            foreach ($questions as $q) {
                $totalScore += $q->score;
                $totalQuestions++;
            }
        }

        // Generate unique paper ID
        $paperId = 'custom_' . $studentId . '_' . time() . '_' . uniqid();

        return (object) [
            'paper_id' => $paperId,
            'paper_name' => $paperName,
            'total_score' => $totalScore,
            'total_questions' => $totalQuestions,
            'created_at' => now()->toDateTimeString(),
        ];
    }
}