<?php

namespace App\Services;

use App\Models\MarkdownImport;
use App\Models\PaperPart;
use App\Models\PaperQuestionRef;
use App\Models\PreQuestionCandidate;
use App\Models\SourcePaper;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Str;

class QuestionExtractorService
{
    /**
     * 使用严格题号正则拆分题目，写入候选表与绑定表。
     */
    public function extractAndPersist(PaperPart $part, ?MarkdownImport $import = null, int &$sequenceStart = 1): Collection
    {
        $paper = $part->paper;
        $file = $paper->file;
        $import = $import ?? $this->ensureSyntheticImport($paper);

        $blocks = app(\App\Services\AsyncMarkdownSplitter::class)->split($part->raw_markdown);

        return DB::transaction(function () use ($blocks, $part, $paper, $file, $import, &$sequenceStart) {
            $created = collect();

            foreach ($blocks as $i => $block) {
                $questionNumber = (string) ($block['question_number'] ?? ($i + 1));
                $order = $i + 1;
                $raw = $block['raw_markdown'];
                $clean = $this->cleanMarkdown($raw);
                $sequence = $sequenceStart++;
                $reuse = $this->findReusableCandidate($raw, $clean);
                $reuseConfidence = $reuse?->confidence ?? $reuse?->ai_confidence;

                $candidate = PreQuestionCandidate::updateOrCreate(
                    [
                        'import_id' => $import->id,
                        'sequence' => $sequence,
                    ],
                    [
                        'source_file_id' => $file?->id,
                        'source_paper_id' => $paper?->id,
                        'part_id' => $part?->id,
                        'index' => (int) $questionNumber,
                        'question_number' => $questionNumber,
                        'order' => $order,
                        'sequence' => $sequence,
                        'raw_markdown' => $raw,
                        'clean_markdown' => $clean,
                        'structured_json' => $reuse?->structured_json,
                        'stem' => $reuse?->stem,
                        'options' => $reuse?->options,
                        'images' => !empty($reuse?->images) ? $reuse->images : ($block['images'] ?? []),
                        'tables' => !empty($reuse?->tables) ? $reuse->tables : ($block['tables'] ?? []),
                        'is_question_candidate' => $reuse?->is_question_candidate ?? true,
                        'ai_confidence' => $reuse?->ai_confidence,
                        'confidence' => $reuseConfidence,
                        'formula_detected' => $this->detectFormula($raw),
                        'is_valid_question' => $reuse?->is_valid_question ?? true,
                        'status' => PreQuestionCandidate::STATUS_PENDING,
                    ]
                );

                PaperQuestionRef::updateOrCreate(
                    [
                        'source_paper_id' => $paper->id,
                        'part_id' => $part->id,
                        'candidate_id' => $candidate->id,
                    ],
                    [
                        'question_number' => $questionNumber,
                        'order' => $order,
                        'raw_markdown' => $raw,
                        'metadata' => [
                            'source_file_uuid' => $file?->uuid,
                            'paper_uuid' => $paper?->uuid,
                            'part_order' => $part?->order,
                        ],
                    ]
                );

                $created->push($candidate);
            }

            $part->update(['question_count' => $created->count()]);

            return $created;
        });
    }

    /**
     * 严格按题号拆分，题号正则：^\s*(\d+)(\.|、|\)|）|\]|】)?\s+
     */
    public function splitQuestions(string $markdown): array
    {
        $pattern = '/^\s*(\d+)(?:[\\.、\\)）\\]】])?\s+/m';
        preg_match_all($pattern, $markdown, $matches, PREG_OFFSET_CAPTURE);

        if (empty($matches[0])) {
            return [[
                'question_number' => 1,
                'raw_markdown' => trim($markdown),
            ]];
        }

        $blocks = [];
        $positions = array_map(fn($m) => $m[1], $matches[0]);
        $numbers = array_map(fn($m) => $m[0], $matches[1]);

        foreach ($positions as $idx => $start) {
            $end = $positions[$idx + 1] ?? strlen($markdown);
            $slice = substr($markdown, $start, $end - $start);
            $blocks[] = [
                'question_number' => $numbers[$idx] ?? ($idx + 1),
                'raw_markdown' => trim($slice),
            ];
        }

        return $blocks;
    }

    protected function detectFormula(string $markdown): bool
    {
        return (bool) preg_match('/\\$\\$.*?\\$\\$|\\$[^$]+\\$|\\\\frac|\\\\sum|\\\\int|\\\\sqrt/u', $markdown);
    }

    protected function cleanMarkdown(string $markdown): string
    {
        return trim(Str::of($markdown)->replace("\r", '')->toString());
    }

    /**
     * 查找可复用的高置信度候选题，避免重复 AI 解析。
     */
    protected function findReusableCandidate(string $raw, string $clean): ?PreQuestionCandidate
    {
        return PreQuestionCandidate::query()
            ->where(function ($query) use ($raw, $clean) {
                $query->where('raw_markdown', $raw)
                    ->orWhere('clean_markdown', $clean);
            })
            ->where(function ($query) {
                $query->where('confidence', '>=', 0.85)
                    ->orWhere('ai_confidence', '>=', 0.85);
            })
            ->orderByDesc('confidence')
            ->orderByDesc('ai_confidence')
            ->first();
    }

    protected function ensureSyntheticImport(SourcePaper $paper): MarkdownImport
    {
        return MarkdownImport::firstOrCreate(
            [
                'file_name' => $paper->file?->original_filename ?? ('paper-' . $paper->id),
                'source_name' => $paper->title,
            ],
            [
                'original_markdown' => $paper->raw_markdown,
                'status' => MarkdownImport::STATUS_PARSED,
                'progress_stage' => MarkdownImport::STAGE_PARSED,
                'progress_message' => 'Auto generated from source_papers',
                'progress_current' => 0,
                'progress_total' => 0,
                'progress_updated_at' => now(),
            ]
        );
    }
}