<?php

namespace app\common;

/**
 * 图书元数据反查：按 书名 + 作者 + 年份 + 版次 检索 ISBN / 出版社 / 出版年。
 *
 * 背景：绝大多数图书参考文献既没有 DOI（拿不到 Crossref 的 ISBN 数组），
 * 原文里也不会写 ISBN，所以只靠"抽取"永远拿不到，必须按书目信息去反查。
 *
 * 数据源：
 * - Open Library（主源，免密钥可直连）：先检索 work，再拉 editions 按年份/版次/出版社挑具体版本
 * - Google Books（备源，需 .env 配 google_books_api_key，无密钥时该 IP 会被 429）
 *
 * 环境变量：
 * - book_isbn_lookup      0 关闭反查，默认开启
 * - book_lookup_timeout   单次请求超时秒数，默认 8
 * - google_books_api_key  配置后启用 Google Books 备源
 */
class BookMetadataService
{
    /** @var int */
    private $timeout = 8;

    /** @var bool */
    private $enabled = true;

    /** @var string */
    private $googleKey = '';

    /** @var int 单条文献反查的总耗时上限（秒），防止队列被慢请求拖住 */
    private $budget = 20;

    /** @var float */
    private $deadline = 0;

    public function __construct(array $config = [])
    {
        $this->enabled = $this->envGet('book_isbn_lookup', '1') !== '0';
        $this->googleKey = trim((string)$this->envGet('google_books_api_key', ''));
        $timeout = intval($this->envGet('book_lookup_timeout', 0));
        if ($timeout > 0) {
            $this->timeout = max(3, $timeout);
        }

        $budget = intval($this->envGet('book_lookup_budget', 0));
        if ($budget > 0) {
            $this->budget = max(5, $budget);
        }

        if (isset($config['timeout'])) $this->timeout = max(3, intval($config['timeout']));
        if (isset($config['enabled'])) $this->enabled = (bool)$config['enabled'];
        if (isset($config['google_key'])) $this->googleKey = (string)$config['google_key'];
        if (isset($config['budget'])) $this->budget = max(5, intval($config['budget']));
    }

    private function outOfBudget()
    {
        return $this->deadline > 0 && microtime(true) >= $this->deadline;
    }

    /**
     * 反查 ISBN
     *
     * @param array $hints title / author / year / publisher / edition / content
     * @return array ['isbn'=>'','publisher'=>'','year'=>'','title'=>'','source'=>'']
     */
    public function resolve(array $hints)
    {
        $empty = ['isbn' => '', 'publisher' => '', 'year' => '', 'title' => '', 'source' => ''];
        if (!$this->enabled) {
            return $empty;
        }

        $hints = $this->normalizeHints($hints);
        if ($hints['title'] === '') {
            return $empty;
        }

        // 原文里直接写了 ISBN 的，优先采信，不用外网
        $inText = $this->extractIsbnFromText($hints['content']);
        if ($inText !== '') {
            return array_merge($empty, ['isbn' => $inText, 'source' => 'text']);
        }

        $cacheKey = 'book_' . sha1(strtolower($hints['title'] . '|' . $hints['author'] . '|' . $hints['year'] . '|' . $hints['edition']));
        $cached = $this->cacheGet($cacheKey, 30 * 86400);
        if (is_array($cached) && array_key_exists('isbn', $cached)) {
            return array_merge($empty, $cached);
        }

        $this->deadline = microtime(true) + $this->budget;
        $result = $this->searchOpenLibrary($hints);
        if ($result['isbn'] === '' && $this->googleKey !== '' && !$this->outOfBudget()) {
            $result = $this->searchGoogleBooks($hints);
        }
        $this->deadline = 0;

        $this->cacheSet($cacheKey, $result);

        return $result;
    }

    /**
     * 从参考文献原文抽取书目线索（书名 / 作者 / 年份 / 版次 / 出版社）
     */
    public function extractHints($content, array $known = [])
    {
        $content = trim((string)$content);
        $hints = [
            'title'     => trim((string)($known['title'] ?? '')),
            'author'    => trim((string)($known['author'] ?? '')),
            'year'      => trim((string)($known['year'] ?? '')),
            'publisher' => trim((string)($known['publisher'] ?? '')),
            'edition'   => '',
            'content'   => $content,
        ];

        if ($content === '') {
            return $hints;
        }

        // 反查用规则解析即可，不为了取个 ISBN 再多花一次大模型调用
        $parsed = (new BookCitationParser(['use_llm' => false]))->parse($content);

        // 章节引用反查的是书，不是章节
        if ($parsed['container'] !== '') {
            $hints['title'] = $parsed['container'];
        } elseif ($hints['title'] === '') {
            $hints['title'] = $parsed['title'];
        }

        foreach (['author', 'publisher', 'edition'] as $field) {
            if ($hints[$field] === '' && $parsed[$field] !== '') {
                $hints[$field] = $parsed[$field];
            }
        }
        if ($hints['year'] === '') {
            $hints['year'] = $parsed['year'];
        }

        return $hints;
    }

    // ------------------------------------------------------------------
    // Open Library
    // ------------------------------------------------------------------

    private function searchOpenLibrary(array $hints)
    {
        $empty = ['isbn' => '', 'publisher' => '', 'year' => '', 'title' => '', 'source' => ''];

        $q = 'title:"' . $this->escapeSolr($hints['title']) . '"';
        $surnames = $this->authorSurnames($hints['author']);
        if (!empty($surnames)) {
            $q .= ' author:' . $this->escapeSolr($surnames[0]);
        }

        $url = 'https://openlibrary.org/search.json?' . http_build_query([
            'q'      => $q,
            'limit'  => 5,
            'fields' => 'key,title,author_name,first_publish_year,edition_count,isbn,publisher',
        ]);
        $docs = $this->getJson($url);
        $docs = isset($docs['docs']) && is_array($docs['docs']) ? $docs['docs'] : [];
        if (empty($docs) && !empty($surnames) && !$this->outOfBudget()) {
            // 作者写法不一致时（编者、机构作者）退回只按书名检索
            $url = 'https://openlibrary.org/search.json?' . http_build_query([
                'q'      => 'title:"' . $this->escapeSolr($hints['title']) . '"',
                'limit'  => 5,
                'fields' => 'key,title,author_name,first_publish_year,edition_count,isbn,publisher',
            ]);
            $docs = $this->getJson($url);
            $docs = isset($docs['docs']) && is_array($docs['docs']) ? $docs['docs'] : [];
        }

        // 同一本书常被拆成多个 work（书名带不带副标题、换了出版社），
        // 只看第一个命中的 work 会漏掉真正对得上版次的那一版，所以候选放在一起比
        $best = null;
        $bestScore = -1;
        $checked = 0;
        foreach ($docs as $doc) {
            if ($checked >= 3 || $this->outOfBudget()) {
                break;
            }
            $docTitle = trim((string)($doc['title'] ?? ''));
            if (!$this->titlesMatch($hints['title'], $docTitle)) {
                continue;
            }
            // 章节引用里"作者"是章节作者、编者写法也各式各样，对不上时不直接放弃，
            // 改为要求出版年精确命中且另有版次或出版社佐证才采信
            $authorOk = $this->authorsMatch($surnames, $doc['author_name'] ?? []);

            $key = trim((string)($doc['key'] ?? ''));
            if ($key === '') {
                continue;
            }
            $checked++;
            $edition = $this->pickEdition($key, $hints);
            if (!$authorOk && $edition['score'] < 70) {
                continue;
            }
            if ($edition['isbn'] !== '' && $edition['score'] > $bestScore) {
                $bestScore = $edition['score'];
                $best = [
                    'isbn'      => $edition['isbn'],
                    'publisher' => $edition['publisher'],
                    'year'      => $edition['year'],
                    'title'     => $docTitle,
                    'source'    => 'openlibrary',
                ];
            }
            // 年份与版次都对上了，没有更好的可能，不用再翻其他 work
            if ($bestScore >= 100) {
                break;
            }
        }

        return $best === null ? $empty : $best;
    }

    /**
     * 在 work 的版本列表里挑最贴合引文的那一版。
     * 年份与版次是硬条件（对不上直接淘汰），出版社和 ISBN-13 只作同分时的取舍，
     * 否则会出现"出版社对上了就把 2020 年第 14 版当成 2006 年第 11 版"的错配。
     *
     * @return array 附带 score，供跨 work 比较
     */
    private function pickEdition($workKey, array $hints)
    {
        $empty = ['isbn' => '', 'publisher' => '', 'year' => '', 'score' => -1];

        $entries = [];
        for ($page = 0; $page < 2; $page++) {
            $url = 'https://openlibrary.org' . $workKey . '/editions.json?limit=100&offset=' . ($page * 100);
            $data = $this->getJson($url);
            $batch = isset($data['entries']) && is_array($data['entries']) ? $data['entries'] : [];
            if (empty($batch)) {
                break;
            }
            $entries = array_merge($entries, $batch);
            if (count($batch) < 100 || count($entries) >= intval($data['size'] ?? 0) || $this->outOfBudget()) {
                break;
            }
        }
        if (empty($entries)) {
            return $empty;
        }

        $wantYear = intval($hints['year']);
        $wantEdition = $this->editionOrdinal($hints['edition']);
        $wantPublisher = $this->normalizeToken($hints['publisher']);
        $hasConstraint = ($wantYear > 0 || $wantEdition > 0);

        $best = null;
        $bestScore = -1;
        foreach ($entries as $entry) {
            $isbn = $this->pickBestIsbn(array_merge(
                is_array($entry['isbn_13'] ?? null) ? $entry['isbn_13'] : [],
                is_array($entry['isbn_10'] ?? null) ? $entry['isbn_10'] : []
            ));
            if ($isbn === '') {
                continue;
            }

            $year = $this->parseYear((string)($entry['publish_date'] ?? ''));
            $entryEdition = $this->editionOrdinal((string)($entry['edition_name'] ?? ''));

            // 版次写明且不一致，一定不是同一版
            if ($wantEdition > 0 && $entryEdition > 0 && $wantEdition !== $entryEdition) {
                continue;
            }
            $editionMatched = ($wantEdition > 0 && $wantEdition === $entryEdition);

            $score = 0;
            if ($wantYear > 0) {
                if ($year > 0) {
                    $diff = abs($wantYear - $year);
                    if ($diff === 0) {
                        $score += 60;
                    } elseif ($diff === 1) {
                        // 版权年与实际发行年常差一年
                        $score += 40;
                    } elseif ($diff <= 2 && $editionMatched) {
                        $score += 20;
                    } else {
                        continue;
                    }
                } elseif (!$editionMatched) {
                    // 年份对不上又没有版次佐证，不敢认
                    continue;
                }
            }
            if ($editionMatched) {
                $score += 40;
            }

            if ($wantPublisher !== '') {
                foreach ((array)($entry['publishers'] ?? []) as $p) {
                    if ($this->tokensOverlap($wantPublisher, $this->normalizeToken($p))) {
                        $score += 10;
                        break;
                    }
                }
            }
            if (strlen($isbn) === 13) {
                $score += 3;
            }

            if ($score > $bestScore) {
                $bestScore = $score;
                $best = [
                    'isbn'      => $isbn,
                    'publisher' => $this->firstString($entry['publishers'] ?? []),
                    'year'      => $year > 0 ? (string)$year : '',
                    'score'     => $score,
                ];
            }
        }

        if ($best === null) {
            return $empty;
        }
        // 引文给了年份/版次，就必须真的对上其中之一
        if ($hasConstraint && $bestScore < 40) {
            return $empty;
        }
        // 引文什么线索都没给：只有单一版本的书才敢直接给 ISBN
        if (!$hasConstraint && count($entries) > 3) {
            return $empty;
        }

        return $best;
    }

    // ------------------------------------------------------------------
    // Google Books（备源）
    // ------------------------------------------------------------------

    private function searchGoogleBooks(array $hints)
    {
        $empty = ['isbn' => '', 'publisher' => '', 'year' => '', 'title' => '', 'source' => ''];

        $q = 'intitle:"' . $hints['title'] . '"';
        $surnames = $this->authorSurnames($hints['author']);
        if (!empty($surnames)) {
            $q .= ' inauthor:' . $surnames[0];
        }

        $url = 'https://www.googleapis.com/books/v1/volumes?' . http_build_query([
            'q'          => $q,
            'maxResults' => 5,
            'key'        => $this->googleKey,
        ]);
        $data = $this->getJson($url);
        $items = isset($data['items']) && is_array($data['items']) ? $data['items'] : [];

        foreach ($items as $item) {
            $info = isset($item['volumeInfo']) && is_array($item['volumeInfo']) ? $item['volumeInfo'] : [];
            $title = trim((string)($info['title'] ?? ''));
            if (!$this->titlesMatch($hints['title'], $title)) {
                continue;
            }
            if (!$this->authorsMatch($surnames, $info['authors'] ?? [])) {
                continue;
            }

            $year = $this->parseYear((string)($info['publishedDate'] ?? ''));
            $wantYear = intval($hints['year']);
            if ($wantYear > 0 && $year > 0 && abs($wantYear - $year) > 3) {
                continue;
            }

            $candidates = [];
            foreach ((array)($info['industryIdentifiers'] ?? []) as $id) {
                $type = strtoupper((string)($id['type'] ?? ''));
                if ($type === 'ISBN_13' || $type === 'ISBN_10') {
                    $candidates[] = (string)($id['identifier'] ?? '');
                }
            }
            $isbn = $this->pickBestIsbn($candidates);
            if ($isbn !== '') {
                return [
                    'isbn'      => $isbn,
                    'publisher' => trim((string)($info['publisher'] ?? '')),
                    'year'      => $year > 0 ? (string)$year : '',
                    'title'     => $title,
                    'source'    => 'googlebooks',
                ];
            }
        }

        return $empty;
    }

    // ------------------------------------------------------------------
    // 解析与校验
    // ------------------------------------------------------------------

    private function normalizeHints(array $hints)
    {
        $out = [
            'title'     => trim((string)($hints['title'] ?? '')),
            'author'    => trim((string)($hints['author'] ?? '')),
            'year'      => trim((string)($hints['year'] ?? '')),
            'publisher' => trim((string)($hints['publisher'] ?? '')),
            'edition'   => trim((string)($hints['edition'] ?? '')),
            'content'   => trim((string)($hints['content'] ?? '')),
        ];
        $out['title'] = $this->cleanTitle($out['title']);
        if (mb_strlen($out['title'], 'UTF-8') < 4) {
            $out['title'] = '';
        }

        return $out;
    }

    private function cleanTitle($title)
    {
        $title = trim((string)$title);
        $title = preg_replace('/\s+/u', ' ', $title);
        // 去掉粘在书名后的版次、卷次、出版地
        $title = preg_replace('/[\.,;]?\s*\b\d{1,2}(?:st|nd|rd|th)?\s*(?:ed\.?|edition|版)\b.*$/iu', '', $title);
        $title = preg_replace('/[\.,;]?\s*\b(?:first|second|third|fourth|fifth|sixth|seventh|eighth|ninth|tenth)\s+(?:ed\.?|edition)\b.*$/iu', '', $title);

        return trim($title, " .,;:");
    }

    private function editionOrdinal($edition)
    {
        $edition = strtolower(trim((string)$edition));
        if ($edition === '') {
            return 0;
        }
        if (preg_match('/\d{1,2}/', $edition, $m)) {
            return intval($m[0]);
        }
        $words = [
            'first' => 1, 'second' => 2, 'third' => 3, 'fourth' => 4, 'fifth' => 5,
            'sixth' => 6, 'seventh' => 7, 'eighth' => 8, 'ninth' => 9, 'tenth' => 10,
        ];
        foreach ($words as $word => $num) {
            if (strpos($edition, $word) !== false) {
                return $num;
            }
        }

        return 0;
    }

    private function parseYear($date)
    {
        return preg_match('/\b(1[5-9]\d{2}|20\d{2})\b/', (string)$date, $m) ? intval($m[1]) : 0;
    }

    /**
     * @return string[]
     */
    private function authorSurnames($author)
    {
        $author = trim((string)$author);
        if ($author === '') {
            return [];
        }
        $surnames = [];
        foreach (preg_split('/[,;]+/u', $author) as $chunk) {
            $chunk = trim(preg_replace('/\b(et al\.?|eds?\.?|editors?)\b/i', '', $chunk));
            if (preg_match_all('/[A-Za-z][A-Za-z\'\-]{2,}/u', $chunk, $m)) {
                $surnames[] = $m[0][0];
            }
        }

        return array_values(array_unique($surnames));
    }

    private function authorsMatch(array $surnames, $candidates)
    {
        if (empty($surnames)) {
            return true;
        }
        $blob = strtolower(is_array($candidates) ? implode(' ', $candidates) : (string)$candidates);
        if ($blob === '') {
            return true;
        }
        foreach ($surnames as $surname) {
            if (strpos($blob, strtolower($surname)) !== false) {
                return true;
            }
        }

        return false;
    }

    private function titlesMatch($expected, $found)
    {
        $a = $this->normalizeToken($expected);
        $b = $this->normalizeToken($found);
        if ($a === '' || $b === '') {
            return false;
        }
        if ($a === $b || strpos($a, $b) !== false || strpos($b, $a) !== false) {
            return true;
        }
        // 中日韩书名逐字比较不可靠，只认包含关系
        if (preg_match('/[\x{4e00}-\x{9fff}]/u', $expected . $found)) {
            return false;
        }
        similar_text($a, $b, $pct);

        return $pct >= 80;
    }

    private function normalizeToken($text)
    {
        $text = strtolower(trim((string)$text));
        $text = preg_replace('/[^a-z0-9\x{4e00}-\x{9fff}\s]+/u', ' ', $text);

        return trim(preg_replace('/\s+/u', ' ', $text));
    }

    private function tokensOverlap($a, $b)
    {
        if ($a === '' || $b === '') {
            return false;
        }
        if (strpos($a, $b) !== false || strpos($b, $a) !== false) {
            return true;
        }
        $wordsA = array_filter(explode(' ', $a), function ($w) {
            return strlen($w) > 3;
        });
        foreach ($wordsA as $word) {
            if (strpos($b, $word) !== false) {
                return true;
            }
        }

        return false;
    }

    /**
     * ISBN-13 优先，且必须通过校验位；只有 ISBN-10 时换算成等价的 ISBN-13
     */
    private function pickBestIsbn($list)
    {
        $list = is_array($list) ? $list : [$list];
        $isbn10 = '';
        foreach ($list as $raw) {
            $isbn = strtoupper(preg_replace('/[^0-9Xx]/', '', (string)$raw));
            if (!$this->isValidIsbn($isbn)) {
                continue;
            }
            if (strlen($isbn) === 13) {
                return $isbn;
            }
            if ($isbn10 === '') {
                $isbn10 = $isbn;
            }
        }

        return $isbn10 === '' ? '' : $this->isbn10To13($isbn10);
    }

    private function isbn10To13($isbn10)
    {
        $body = '978' . substr($isbn10, 0, 9);
        $sum = 0;
        for ($i = 0; $i < 12; $i++) {
            $sum += intval($body[$i]) * (($i % 2 === 0) ? 1 : 3);
        }

        return $body . ((10 - $sum % 10) % 10);
    }

    private function isValidIsbn($isbn)
    {
        $len = strlen($isbn);
        if ($len === 13) {
            if (!preg_match('/^\d{13}$/', $isbn)) {
                return false;
            }
            $sum = 0;
            for ($i = 0; $i < 12; $i++) {
                $sum += intval($isbn[$i]) * (($i % 2 === 0) ? 1 : 3);
            }

            return ((10 - $sum % 10) % 10) === intval($isbn[12]);
        }
        if ($len === 10) {
            if (!preg_match('/^\d{9}[\dX]$/', $isbn)) {
                return false;
            }
            $sum = 0;
            for ($i = 0; $i < 9; $i++) {
                $sum += intval($isbn[$i]) * (10 - $i);
            }
            $sum += ($isbn[9] === 'X') ? 10 : intval($isbn[9]);

            return $sum % 11 === 0;
        }

        return false;
    }

    private function extractIsbnFromText($content)
    {
        if (!preg_match_all('/\bISBN(?:-1[03])?[:\s]*([0-9][0-9\-\s]{8,20}[0-9Xx])/i', (string)$content, $m)) {
            return '';
        }

        return $this->pickBestIsbn($m[1]);
    }

    private function firstString($list)
    {
        foreach ((array)$list as $item) {
            $item = trim((string)$item);
            if ($item !== '' && strcasecmp($item, 'Other') !== 0) {
                return $item;
            }
        }

        return '';
    }

    private function escapeSolr($text)
    {
        return trim(preg_replace('/["\\\\+\-!(){}\[\]^~*?:\/]+/u', ' ', (string)$text));
    }

    // ------------------------------------------------------------------
    // HTTP / 缓存
    // ------------------------------------------------------------------

    private function getJson($url)
    {
        $timeout = $this->timeout;
        if ($this->deadline > 0) {
            $left = (int)ceil($this->deadline - microtime(true));
            if ($left <= 0) {
                return [];
            }
            $timeout = min($timeout, $left);
        }

        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_TIMEOUT, $timeout);
        curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, min(5, $timeout));
        curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
        curl_setopt($ch, CURLOPT_HTTPHEADER, [
            'Accept: application/json',
            'User-Agent: TMRjournals-BookLookup/1.0 (' . $this->envGet('crossref_mailto', 'support@tmrjournals.com') . ')',
        ]);
        $res = curl_exec($ch);
        $code = intval(curl_getinfo($ch, CURLINFO_HTTP_CODE));
        curl_close($ch);

        if ($code !== 200 || !is_string($res) || $res === '') {
            return [];
        }
        $decoded = json_decode($res, true);

        return is_array($decoded) ? $decoded : [];
    }

    private function envGet($key, $default = '')
    {
        if (!class_exists('\think\Env')) {
            return $default;
        }

        return \think\Env::get($key, $default);
    }

    private function cacheDir()
    {
        return rtrim(ROOT_PATH, '/') . '/runtime/book_cache';
    }

    private function cacheGet($key, $ttlSeconds)
    {
        $file = $this->cacheDir() . '/' . $key . '.json';
        if (!is_file($file)) {
            return null;
        }
        $mtime = filemtime($file);
        if (!$mtime || (time() - $mtime) > $ttlSeconds) {
            return null;
        }

        return json_decode((string)@file_get_contents($file), true);
    }

    private function cacheSet($key, $value)
    {
        $dir = $this->cacheDir();
        if (!is_dir($dir)) {
            @mkdir($dir, 0777, true);
        }
        @file_put_contents($dir . '/' . $key . '.json', json_encode($value, JSON_UNESCAPED_UNICODE));
    }
}