<?php

namespace App\Services;

use App\Models\SourceFile;
use App\Models\SourcePaper;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Str;

class SourcePaperExtractorService
{
    /**
     * 从单个 Markdown 文件中切出多套卷子，并持久化。
     */
    public function extract(SourceFile $sourceFile): Collection
    {
        $segments = $this->splitIntoPapers($sourceFile->raw_markdown);

        return DB::transaction(function () use ($sourceFile, $segments) {
            $sourceFile->papers()->delete();

            $papers = collect();
            foreach ($segments as $idx => $segment) {
                $papers->push(
                    SourcePaper::create([
                        'uuid' => (string) Str::uuid(),
                        'source_file_id' => $sourceFile->id,
                        'order' => $idx + 1,
                        'title' => $segment['title'] ?? null,
                        'full_title' => $segment['full_title'] ?? null,
                        'chapter' => $segment['chapter'] ?? $sourceFile->extracted_metadata['chapter'] ?? null,
                        'grade' => $segment['grade'] ?? $sourceFile->extracted_metadata['grade'] ?? null,
                        'term' => $segment['term'] ?? $sourceFile->extracted_metadata['term'] ?? null,
                        'edition' => $segment['edition'] ?? $sourceFile->extracted_metadata['edition'] ?? null,
                        'textbook_series' => $segment['textbook_series'] ?? $sourceFile->extracted_metadata['textbook_series'] ?? null,
                        'source_type' => $segment['source_type'] ?? null,
                        'source_year' => $segment['source_year'] ?? $sourceFile->extracted_metadata['year'] ?? null,
                        'raw_markdown' => $segment['raw'],
                        'detected_metadata' => $segment['meta'] ?? [],
                    ])
                );
            }

            return $papers;
        });
    }

    /**
     * 基于 Markdown 标题拆分卷子。
     */
    public function splitIntoPapers(string $markdown): array
    {
        $lines = preg_split('/\r\n|\r|\n/', $markdown);
        $segments = [];
        $current = ['title' => null, 'buffer' => []];

        $paperPattern = '/^(#{1,2})\s*(.+卷|期中|期末|专项|模拟|基础卷|提升卷|练习卷)/u';

        foreach ($lines as $line) {
            if (preg_match($paperPattern, $line, $m)) {
                if (!empty($current['buffer'])) {
                    $segments[] = [
                        'title' => $current['title'],
                        'full_title' => $current['title'],
                        'raw' => trim(implode("\n", $current['buffer'])),
                        'meta' => $this->detectMetaFromTitle($current['title']),
                    ];
                }
                $current = [
                    'title' => trim($m[2]),
                    'buffer' => [$line],
                ];
            } else {
                $current['buffer'][] = $line;
            }
        }

        if (!empty($current['buffer'])) {
            $segments[] = [
                'title' => $current['title'],
                'full_title' => $current['title'],
                'raw' => trim(implode("\n", $current['buffer'])),
                'meta' => $this->detectMetaFromTitle($current['title']),
            ];
        }

        if (empty($segments)) {
            return [[
                'title' => null,
                'full_title' => null,
                'raw' => trim($markdown),
                'meta' => [],
            ]];
        }

        return $segments;
    }

    protected function detectMetaFromTitle(?string $title): array
    {
        if (!$title) {
            return [];
        }

        $meta = [];
        if (preg_match('/第[一二三四五六七八九十0-9]+章/u', $title, $m)) {
            $meta['chapter'] = $m[0];
        }
        if (preg_match('/20[0-9]{2}/', $title, $m)) {
            $meta['source_year'] = $m[0];
        }
        if (Str::contains($title, '期中')) {
            $meta['source_type'] = 'midterm';
        } elseif (Str::contains($title, '期末')) {
            $meta['source_type'] = 'final';
        } elseif (Str::contains($title, '模拟')) {
            $meta['source_type'] = 'mock';
        }

        return $meta;
    }
}