<?php

namespace app\api\controller;

use think\Cache;
use think\Db;
use GuzzleHttp\Client;

class ExpertFinder extends Base
{
    private $httpClient;
    private $ncbiBaseUrl = 'https://eutils.ncbi.nlm.nih.gov/entrez/eutils/';

    public function __construct(\think\Request $request = null)
    {
        parent::__construct($request);
        $this->httpClient = new Client([
            'timeout'         => 180,
            'connect_timeout' => 15,
            'verify'          => false,
        ]);
    }

    /**
     * Main search endpoint
     * Params:
     *   keyword      - search term (e.g. "biomedical engineering")
     *   page         - page number, default 1
     *   per_page     - articles per page, default 100, max 100
     *   min_year     - earliest publication year, default current-3
     *   source       - "pubmed" (fast, email from affiliation) or "pmc" (slower, structured email)
     */
    public function search()
    {
        $keyword = trim($this->request->param('keyword', ''));
        $page    = max(1, intval($this->request->param('page', 1)));
        $perPage = max(10, min(intval($this->request->param('per_page', 100)), 100));
        $minYear = intval($this->request->param('min_year', date('Y') - 3));
        $source  = $this->request->param('source', 'pubmed');

        if (empty($keyword)) {
            return jsonError('keyword is required');
        }

        $cacheKey = 'expert_finder_' . md5($keyword . $page . $perPage . $minYear . $source);
        $cached   = Cache::get($cacheKey);
        if ($cached) {
            return jsonSuccess($cached);
        }

        try {
            if ($source === 'pmc') {
                $result = $this->searchViaPMC($keyword, $perPage, $minYear, $page);
            } else {
                $result = $this->searchViaPubMed($keyword, $perPage, $minYear, $page);
            }
        } catch (\Exception $e) {
            return jsonError('Search failed: ' . $e->getMessage());
        }

        $saveResult = $this->saveExperts($result['experts'], $keyword, $source);
        $result['saved_new']   = $saveResult['inserted'];
        $result['saved_exist'] = $saveResult['existing'];

        Cache::set($cacheKey, $result, 3600);

        return jsonSuccess($result);
    }

    /**
     * Get experts from local database
     * Params:
     *   field       - filter by field keyword (searches t_expert_field)
     *   major_id    - filter by major_id (searches t_expert_field)
     *   state       - filter by state (0-5), -1 for all
     *   keyword     - search name/email/affiliation
     *   no_recent   - if 1, exclude experts promoted within last N days (default 30)
     *   recent_days - days threshold for no_recent filter, default 30
     *   page        - page number, default 1
     *   per_page    - items per page, default 20
     *   min_experts - auto-fetch threshold, default 50
     */
    public function getList()
    {
        $field      = trim($this->request->param('field', ''));
        $majorId    = intval($this->request->param('major_id', 0));
        $state      = $this->request->param('state', '-1');
        $keyword    = trim($this->request->param('keyword', ''));
        $noRecent   = intval($this->request->param('no_recent', 0));
        $recentDays = max(1, intval($this->request->param('recent_days', 30)));
        $page       = max(1, intval($this->request->param('page', 1)));
        $perPage    = max(1, min(intval($this->request->param('per_page', 20)), 100));
        $minExperts = max(0, intval($this->request->param('min_experts', 50)));

        $query = Db::name('expert')->alias('e');
        $needJoin = ($field !== '' || $majorId > 0);

        if ($needJoin) {
            $query->join('t_expert_field ef', 'ef.expert_id = e.expert_id AND ef.state = 0', 'inner');
            if ($field !== '') {
                $query->where('ef.field', 'like', '%' . $field . '%');
            }
            if ($majorId > 0) {
                $query->where('ef.major_id', $majorId);
            }
            $query->group('e.expert_id');
        }

        if ($state !== '-1' && $state !== '') {
            $query->where('e.state', intval($state));
        }
        if ($keyword !== '') {
            $query->where('e.name|e.email|e.affiliation', 'like', '%' . $keyword . '%');
        }
        if ($noRecent) {
            $cutoff = time() - ($recentDays * 86400);
            $query->where(function ($q) use ($cutoff) {
                $q->where('e.ltime', 0)->whereOr('e.ltime', '<', $cutoff);
            });
        }

        $countQuery = clone $query;
        $total = $countQuery->count('distinct e.expert_id');

        $list = $query
            ->field('e.*')
            ->order('e.ctime desc')
            ->page($page, $perPage)
            ->select();

        foreach ($list as &$item) {
            $item['fields'] = Db::name('expert_field')
                ->where('expert_id', $item['expert_id'])
                ->where('state', 0)
                ->column('field');
        }

        $fetching = false;
        if ($field !== '' && $total < $minExperts && $minExperts > 0) {
            $this->triggerBackgroundFetch($field);
            $fetching = true;
        }

        return jsonSuccess([
            'list'        => $list,
            'total'       => $total,
            'page'        => $page,
            'per_page'    => $perPage,
            'total_pages' => $total > 0 ? ceil($total / $perPage) : 0,
            'fetching'    => $fetching,
        ]);
    }

    /**
     * Get all fields associated with an expert
     */
    public function getExpertFields()
    {
        $expertId = intval($this->request->param('expert_id', 0));
        if (!$expertId) {
            return jsonError('expert_id is required');
        }

        $fields = Db::name('expert_field')
            ->where('expert_id', $expertId)
            ->where('state', 0)
            ->select();

        return jsonSuccess($fields);
    }

    /**
     * Update expert state
     * Params:
     *   expert_id  - single id or comma-separated ids
     *   state      - new state (0-5)
     */
    public function updateState()
    {
        $expertId = $this->request->param('expert_id', '');
        $state    = intval($this->request->param('state', 0));

        if (empty($expertId)) {
            return jsonError('expert_id is required');
        }
        if ($state < 0 || $state > 5) {
            return jsonError('state must be 0-5');
        }

        $ids = array_map('intval', explode(',', $expertId));
        $count = Db::name('expert')->where('expert_id', 'in', $ids)->update(['state' => $state]);

        return jsonSuccess(['updated' => $count]);
    }

    /**
     * Delete expert (soft: set state=5 blacklist, or hard delete)
     * Params:
     *   expert_id  - single id or comma-separated ids
     *   hard       - 1 for hard delete, default 0 (blacklist)
     */
    public function deleteExpert()
    {
        $expertId = $this->request->param('expert_id', '');
        $hard     = intval($this->request->param('hard', 0));

        if (empty($expertId)) {
            return jsonError('expert_id is required');
        }

        $ids = array_map('intval', explode(',', $expertId));

        if ($hard) {
            $count = Db::name('expert')->where('expert_id', 'in', $ids)->delete();
        } else {
            $count = Db::name('expert')->where('expert_id', 'in', $ids)->update(['state' => 5]);
        }

        return jsonSuccess(['affected' => $count]);
    }

    /**
     * Export search results to Excel
     * Same params as search(), exports current page results
     */
    public function export()
    {
        $keyword = trim($this->request->param('keyword', ''));
        $page    = max(1, intval($this->request->param('page', 1)));
        $perPage = max(10, min(intval($this->request->param('per_page', 100)), 100));
        $minYear = intval($this->request->param('min_year', date('Y') - 3));
        $source  = $this->request->param('source', 'pubmed');

        if (empty($keyword)) {
            return jsonError('keyword is required');
        }

        $cacheKey = 'expert_finder_' . md5($keyword . $page . $perPage . $minYear . $source);
        $cached   = Cache::get($cacheKey);

        if (!$cached) {
            try {
                if ($source === 'pmc') {
                    $cached = $this->searchViaPMC($keyword, $perPage, $minYear, $page);
                } else {
                    $cached = $this->searchViaPubMed($keyword, $perPage, $minYear, $page);
                }
                Cache::set($cacheKey, $cached, 3600);
            } catch (\Exception $e) {
                return jsonError('Search failed: ' . $e->getMessage());
            }
        }

        if (empty($cached['experts'])) {
            return jsonError('No experts found to export');
        }

        return $this->generateExcel($cached['experts'], $keyword, $page);
    }

    /**
     * Clear search cache
     */
    public function clearCache()
    {
        $keyword    = trim($this->request->param('keyword', ''));
        $maxResults = intval($this->request->param('max_results', 200));
        $minYear    = intval($this->request->param('min_year', date('Y') - 3));
        $source     = $this->request->param('source', 'pubmed');

        $cacheKey = 'expert_finder_' . md5($keyword . $maxResults . $minYear . $source);
        Cache::rm($cacheKey);

        return jsonSuccess(['msg' => 'Cache cleared']);
    }

    // ==================== Cron / Auto Fetch ====================

    /**
     * Cron job: daily fetch experts for given keywords
     * Params:
     *   keywords  - comma-separated keywords (e.g. "biomedical engineering,tissue engineering")
     *   source    - pubmed or pmc, default pubmed
     *   per_page  - articles per page, default 100
     *   min_year  - default current-3
     *
     * Uses cache to remember which page was last fetched per keyword,
     * so each cron run fetches the next page automatically.
     */
    public function cronFetch()
    {
        $keywordsStr = trim($this->request->param('keywords', ''));
        $source      = $this->request->param('source', 'pubmed');
        $perPage     = max(10, min(intval($this->request->param('per_page', 100)), 100));
        $minYear     = intval($this->request->param('min_year', date('Y') - 3));

        if (empty($keywordsStr)) {
            return jsonError('keywords is required');
        }

        set_time_limit(0);
        $keywords = array_map('trim', explode(',', $keywordsStr));
        $report   = [];

        foreach ($keywords as $kw) {
            if (empty($kw)) {
                continue;
            }

            $fetchLog = $this->getFetchLog($kw, $source);
            $page     = $fetchLog['last_page'] + 1;

            try {
                if ($source === 'pmc') {
                    $result = $this->searchViaPMC($kw, $perPage, $minYear, $page);
                } else {
                    $result = $this->searchViaPubMed($kw, $perPage, $minYear, $page);
                }

                $saveResult = $this->saveExperts($result['experts'], $kw, $source);

                $nextPage   = $result['has_more'] ? $page : 0;
                $totalPages = isset($result['total_pages']) ? $result['total_pages'] : 0;
                $this->updateFetchLog($kw, $source, $nextPage, $totalPages);

                $report[] = [
                    'keyword'        => $kw,
                    'page'           => $page,
                    'experts_found'  => $result['total'],
                    'saved_new'      => $saveResult['inserted'],
                    'saved_exist'    => $saveResult['existing'],
                    'field_enriched' => $saveResult['field_enriched'],
                    'has_more'       => $result['has_more'],
                ];
            } catch (\Exception $e) {
                $report[] = [
                    'keyword' => $kw,
                    'page'    => $page,
                    'error'   => $e->getMessage(),
                ];
            }

            sleep(2);
        }

        return jsonSuccess(['report' => $report]);
    }

    /**
     * Trigger a background fetch for a specific field via queue
     */
    private function triggerBackgroundFetch($field)
    {
        $lockKey = 'fetch_lock_' . md5($field);
        if (Cache::get($lockKey)) {
            return;
        }
        Cache::set($lockKey, 1, 300);

        \think\Queue::push('app\api\job\FetchExperts', [
            'field'    => $field,
            'source'   => 'pubmed',
            'per_page' => 100,
            'min_year' => date('Y') - 3,
        ], 'FetchExperts');
    }

    /**
     * Internal method: run a fetch for a single keyword (used by both cron and queue job)
     */
    public function doFetchForField($field, $source = 'pubmed', $perPage = 100, $minYear = null)
    {
        if ($minYear === null) {
            $minYear = date('Y') - 3;
        }

        $fetchLog = $this->getFetchLog($field, $source);
        $page     = $fetchLog['last_page'] + 1;

        if ($source === 'pmc') {
            $result = $this->searchViaPMC($field, $perPage, $minYear, $page);
        } else {
            $result = $this->searchViaPubMed($field, $perPage, $minYear, $page);
        }

        $saveResult = $this->saveExperts($result['experts'], $field, $source);

        $nextPage   = $result['has_more'] ? $page : 0;
        $totalPages = isset($result['total_pages']) ? $result['total_pages'] : 0;
        $this->updateFetchLog($field, $source, $nextPage, $totalPages);

        return [
            'keyword'        => $field,
            'page'           => $page,
            'experts_found'  => $result['total'],
            'saved_new'      => $saveResult['inserted'],
            'saved_exist'    => $saveResult['existing'],
            'field_enriched' => $saveResult['field_enriched'],
            'has_more'       => $result['has_more'],
        ];
    }

    // ==================== PubMed Search ====================

    private function searchViaPubMed($keyword, $perPage, $minYear, $page = 1)
    {
        set_time_limit(600);

        $searchResult = $this->esearch('pubmed', $keyword, $perPage, $minYear, $page);
        $ids          = $searchResult['ids'];
        $totalArticles = $searchResult['total'];

        if (empty($ids)) {
            return $this->buildPagedResult([], 0, 0, $totalArticles, $page, $perPage, 'pubmed');
        }

        $allAuthors = [];
        $batches = array_chunk($ids, 50);
        foreach ($batches as $batch) {
            $xml = $this->efetchWithRetry('pubmed', $batch);
            if ($xml) {
                $authors = $this->parsePubMedXml($xml);
                $allAuthors = array_merge($allAuthors, $authors);
            }
            usleep(400000);
        }

        $experts = $this->aggregateExperts($allAuthors);

        return $this->buildPagedResult($experts, count($experts), count($ids), $totalArticles, $page, $perPage, 'pubmed');
    }

    // ==================== PMC Search ====================

    private function searchViaPMC($keyword, $perPage, $minYear, $page = 1)
    {
        set_time_limit(600);

        $searchResult = $this->esearch('pmc', $keyword, $perPage, $minYear, $page);
        $ids          = $searchResult['ids'];
        $totalArticles = $searchResult['total'];

        if (empty($ids)) {
            return $this->buildPagedResult([], 0, 0, $totalArticles, $page, $perPage, 'pmc');
        }

        $allAuthors = [];
        $batches = array_chunk($ids, 5);
        foreach ($batches as $batch) {
            $xml = $this->efetchWithRetry('pmc', $batch);
            if ($xml) {
                $authors = $this->parsePMCXml($xml);
                $allAuthors = array_merge($allAuthors, $authors);
            }
            usleep(500000);
        }

        $experts = $this->aggregateExperts($allAuthors);

        return $this->buildPagedResult($experts, count($experts), count($ids), $totalArticles, $page, $perPage, 'pmc');
    }

    // ==================== NCBI API Calls ====================

    private function esearch($db, $keyword, $perPage, $minYear, $page = 1)
    {
        $term     = $keyword . ' AND ' . $minYear . ':' . date('Y') . '[pdat]';
        $retstart = ($page - 1) * $perPage;

        $response = $this->httpClient->get($this->ncbiBaseUrl . 'esearch.fcgi', [
            'query' => [
                'db'       => $db,
                'term'     => $term,
                'retstart' => $retstart,
                'retmax'   => $perPage,
                'retmode'  => 'json',
                'sort'     => 'relevance',
            ],
        ]);

        $data   = json_decode($response->getBody()->getContents(), true);
        $ids    = $data['esearchresult']['idlist'] ?? [];
        $total  = intval($data['esearchresult']['count'] ?? 0);

        return ['ids' => $ids, 'total' => $total];
    }

    private function efetch($db, $ids)
    {
        $response = $this->httpClient->post($this->ncbiBaseUrl . 'efetch.fcgi', [
            'form_params' => [
                'db'      => $db,
                'id'      => implode(',', $ids),
                'retmode' => 'xml',
            ],
        ]);

        return $response->getBody()->getContents();
    }

    private function efetchWithRetry($db, $ids, $maxRetries = 3)
    {
        for ($attempt = 1; $attempt <= $maxRetries; $attempt++) {
            try {
                return $this->efetch($db, $ids);
            } catch (\Exception $e) {
                if ($attempt === $maxRetries) {
                    if (count($ids) > 1) {
                        $half = ceil(count($ids) / 2);
                        $firstHalf  = array_slice($ids, 0, $half);
                        $secondHalf = array_slice($ids, $half);
                        $xml1 = $this->efetchWithRetry($db, $firstHalf, 2);
                        $xml2 = $this->efetchWithRetry($db, $secondHalf, 2);
                        return $this->mergeXml($xml1, $xml2);
                    }
                    return null;
                }
                sleep($attempt * 2);
            }
        }
        return null;
    }

    private function mergeXml($xml1, $xml2)
    {
        if (empty($xml1)) return $xml2;
        if (empty($xml2)) return $xml1;
        return $xml1 . "\n" . $xml2;
    }

    // ==================== PubMed XML Parsing ====================

    private function parsePubMedXml($xmlString)
    {
        $results = [];

        libxml_use_internal_errors(true);
        $xml = simplexml_load_string($xmlString);
        if ($xml === false) {
            return $results;
        }

        foreach ($xml->PubmedArticle as $article) {
            $citation   = $article->MedlineCitation;
            $articleData = $citation->Article;

            $title = $this->xmlNodeToString($articleData->ArticleTitle);
            $pmid  = (string) $citation->PMID;

            $journal = '';
            if (isset($articleData->Journal->Title)) {
                $journal = (string) $articleData->Journal->Title;
            }

            if (!isset($articleData->AuthorList->Author)) {
                continue;
            }

            foreach ($articleData->AuthorList->Author as $author) {
                $lastName   = (string) ($author->LastName ?? '');
                $foreName   = (string) ($author->ForeName ?? '');
                $fullName   = trim($foreName . ' ' . $lastName);

                if (empty($fullName)) {
                    continue;
                }

                $email       = '';
                $affiliation = '';

                if (isset($author->AffiliationInfo)) {
                    foreach ($author->AffiliationInfo as $affInfo) {
                        $affText = (string) $affInfo->Affiliation;
                        if (empty($affiliation)) {
                            $affiliation = $affText;
                        }
                        if (empty($email)) {
                            $email = $this->extractEmailFromText($affText);
                        }
                    }
                }

                if (empty($email)) {
                    continue;
                }

                $results[] = [
                    'name'          => $fullName,
                    'email'         => strtolower($email),
                    'affiliation'   => $this->cleanAffiliation($affiliation),
                    'article_title' => $title,
                    'article_id'    => $pmid,
                    'journal'       => $journal,
                ];
            }
        }

        return $results;
    }

    // ==================== PMC XML Parsing ====================

    private function parsePMCXml($xmlString)
    {
        $results = [];

        libxml_use_internal_errors(true);
        $xml = simplexml_load_string($xmlString);
        if ($xml === false) {
            return $results;
        }

        $articles = $xml->article ?? $xml->children();

        foreach ($articles as $article) {
            if ($article->getName() !== 'article') {
                continue;
            }

            $front = $article->front;
            if (!$front) {
                continue;
            }

            $articleMeta = $front->{'article-meta'};
            if (!$articleMeta) {
                continue;
            }

            $title = $this->xmlNodeToString($articleMeta->{'title-group'}->{'article-title'} ?? null);
            $pmcId = '';
            if (isset($articleMeta->{'article-id'})) {
                foreach ($articleMeta->{'article-id'} as $idNode) {
                    if ((string) $idNode['pub-id-type'] === 'pmc') {
                        $pmcId = (string) $idNode;
                    }
                }
            }

            $journal = '';
            if (isset($front->{'journal-meta'}->{'journal-title'})) {
                $journal = (string) $front->{'journal-meta'}->{'journal-title'};
            } elseif (isset($front->{'journal-meta'}->{'journal-title-group'}->{'journal-title'})) {
                $journal = (string) $front->{'journal-meta'}->{'journal-title-group'}->{'journal-title'};
            }

            $correspEmails = [];
            if (isset($articleMeta->{'author-notes'})) {
                $this->extractEmailsFromNode($articleMeta->{'author-notes'}, $correspEmails);
            }

            $affiliationMap = [];
            if (isset($articleMeta->{'contrib-group'})) {
                foreach ($articleMeta->{'contrib-group'}->children() as $child) {
                    if ($child->getName() === 'aff') {
                        $affId   = (string) ($child['id'] ?? '');
                        $affText = $this->xmlNodeToString($child);
                        if ($affId) {
                            $affiliationMap[$affId] = $affText;
                        }
                    }
                }
            }
            if (isset($front->{'article-meta'}->{'aff'})) {
                foreach ($front->{'article-meta'}->{'aff'} as $aff) {
                    $affId   = (string) ($aff['id'] ?? '');
                    $affText = $this->xmlNodeToString($aff);
                    if ($affId) {
                        $affiliationMap[$affId] = $affText;
                    }
                }
            }

            if (!isset($articleMeta->{'contrib-group'})) {
                continue;
            }

            foreach ($articleMeta->{'contrib-group'}->contrib as $contrib) {
                $contribType = (string) ($contrib['contrib-type'] ?? '');
                if ($contribType !== 'author') {
                    continue;
                }

                $nameNode  = $contrib->name;
                if (!$nameNode) {
                    continue;
                }
                $surname    = (string) ($nameNode->surname ?? '');
                $givenNames = (string) ($nameNode->{'given-names'} ?? '');
                $fullName   = trim($givenNames . ' ' . $surname);

                if (empty($fullName)) {
                    continue;
                }

                $email = '';
                if (isset($contrib->email)) {
                    $email = strtolower(trim((string) $contrib->email));
                }

                $affiliation = '';
                if (isset($contrib->xref)) {
                    foreach ($contrib->xref as $xref) {
                        if ((string) $xref['ref-type'] === 'aff') {
                            $rid = (string) $xref['rid'];
                            if (isset($affiliationMap[$rid])) {
                                $affiliation = $affiliationMap[$rid];
                                break;
                            }
                        }
                    }
                }
                if (empty($affiliation) && isset($contrib->aff)) {
                    $affiliation = $this->xmlNodeToString($contrib->aff);
                }

                $isCorresponding = false;
                if (isset($contrib->xref)) {
                    foreach ($contrib->xref as $xref) {
                        if ((string) $xref['ref-type'] === 'corresp') {
                            $isCorresponding = true;
                        }
                    }
                }
                if ((string) ($contrib['corresp'] ?? '') === 'yes') {
                    $isCorresponding = true;
                }

                if (empty($email) && $isCorresponding && !empty($correspEmails)) {
                    $email = $correspEmails[0];
                }

                if (empty($email)) {
                    $extracted = $this->extractEmailFromText($affiliation);
                    if ($extracted) {
                        $email = $extracted;
                    }
                }

                if (empty($email)) {
                    continue;
                }

                $results[] = [
                    'name'          => $fullName,
                    'email'         => strtolower($email),
                    'affiliation'   => $this->cleanAffiliation($affiliation),
                    'article_title' => $title,
                    'article_id'    => $pmcId,
                    'journal'       => $journal,
                ];
            }
        }

        return $results;
    }

    // ==================== Pagination ====================

    private function buildPagedResult($experts, $expertCount, $articlesScanned, $totalArticles, $page, $perPage, $source)
    {
        $totalPages = $totalArticles > 0 ? ceil($totalArticles / $perPage) : 0;

        return [
            'experts'          => $experts,
            'total'            => $expertCount,
            'articles_scanned' => $articlesScanned,
            'total_articles'   => $totalArticles,
            'page'             => $page,
            'per_page'         => $perPage,
            'total_pages'      => $totalPages,
            'has_more'         => $page < $totalPages,
            'source'           => $source,
        ];
    }

    // ==================== Aggregation ====================

    private function aggregateExperts($authorRecords)
    {
        $map = [];

        foreach ($authorRecords as $record) {
            $key = strtolower(trim($record['email']));
            if (empty($key)) {
                continue;
            }

            if (!isset($map[$key])) {
                $map[$key] = [
                    'name'        => $record['name'],
                    'email'       => $record['email'],
                    'affiliation' => $record['affiliation'],
                    'paper_count' => 0,
                    'papers'      => [],
                ];
            }

            $map[$key]['paper_count']++;

            if (count($map[$key]['papers']) < 10) {
                $map[$key]['papers'][] = [
                    'title'      => $record['article_title'],
                    'article_id' => $record['article_id'],
                    'journal'    => $record['journal'],
                ];
            }

            if (empty($map[$key]['affiliation']) && !empty($record['affiliation'])) {
                $map[$key]['affiliation'] = $record['affiliation'];
            }
        }

        $experts = array_values($map);

        usort($experts, function ($a, $b) {
            return $b['paper_count'] - $a['paper_count'];
        });

        return $experts;
    }

    // ==================== Excel Export ====================

    private function generateExcel($experts, $keyword, $page = 1)
    {
        vendor("PHPExcel.PHPExcel");

        $objPHPExcel = new \PHPExcel();
        $sheet = $objPHPExcel->getActiveSheet();
        $sheet->setTitle('Experts');

        $headers = ['A' => '#', 'B' => 'Name', 'C' => 'Email', 'D' => 'Affiliation', 'E' => 'Paper Count', 'F' => 'Representative Papers'];
        foreach ($headers as $col => $header) {
            $sheet->setCellValue($col . '1', $header);
        }

        $headerStyle = [
            'font'      => ['bold' => true, 'color' => ['rgb' => 'FFFFFF']],
            'fill'      => ['type' => \PHPExcel_Style_Fill::FILL_SOLID, 'startcolor' => ['rgb' => '4472C4']],
            'alignment' => ['horizontal' => \PHPExcel_Style_Alignment::HORIZONTAL_CENTER],
        ];
        $sheet->getStyle('A1:F1')->applyFromArray($headerStyle);

        foreach ($experts as $i => $expert) {
            $row = $i + 2;
            $paperTitles = array_map(function ($p) {
                return $p['title'];
            }, $expert['papers']);

            $sheet->setCellValue('A' . $row, $i + 1);
            $sheet->setCellValue('B' . $row, $expert['name']);
            $sheet->setCellValue('C' . $row, $expert['email']);
            $sheet->setCellValue('D' . $row, $expert['affiliation']);
            $sheet->setCellValue('E' . $row, $expert['paper_count']);
            $sheet->setCellValue('F' . $row, implode("\n", $paperTitles));
        }

        $sheet->getColumnDimension('A')->setWidth(6);
        $sheet->getColumnDimension('B')->setWidth(25);
        $sheet->getColumnDimension('C')->setWidth(35);
        $sheet->getColumnDimension('D')->setWidth(50);
        $sheet->getColumnDimension('E')->setWidth(12);
        $sheet->getColumnDimension('F')->setWidth(60);

        $filename = 'experts_' . preg_replace('/[^a-zA-Z0-9]/', '_', $keyword) . '_p' . $page . '_' . date('Ymd_His') . '.xlsx';
        $filepath = ROOT_PATH . 'public' . DS . 'exports' . DS . $filename;

        $dir = ROOT_PATH . 'public' . DS . 'exports';
        if (!is_dir($dir)) {
            mkdir($dir, 0777, true);
        }

        $writer = \PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
        $writer->save($filepath);

        return jsonSuccess([
            'file_url'  => '/exports/' . $filename,
            'file_name' => $filename,
            'count'     => count($experts),
        ]);
    }

    // ==================== Database Storage ====================

    private function saveExperts($experts, $field, $source)
    {
        $inserted    = 0;
        $existing    = 0;
        $fieldEnrich = 0;

        foreach ($experts as $expert) {
            $email = strtolower(trim($expert['email']));
            if (empty($email)) {
                continue;
            }

            $exists = Db::name('expert')->where('email', $email)->find();

            if ($exists) {
                $existing++;
                $fieldEnrich += $this->enrichExpertField($exists['expert_id'], $field);
                continue;
            }

            $insert = [
                'name'        => mb_substr($expert['name'], 0, 255),
                'email'       => mb_substr($email, 0, 128),
                'affiliation' => mb_substr($expert['affiliation'], 0, 128),
                'source'      => mb_substr($source, 0, 128),
                'ctime'       => time(),
                'ltime'       => 0,
                'state'       => 0,
            ];

            try {
                $expertId = Db::name('expert')->insertGetId($insert);
                $this->enrichExpertField($expertId, $field);
                $inserted++;
            } catch (\Exception $e) {
                $existing++;
            }
        }

        return ['inserted' => $inserted, 'existing' => $existing, 'field_enriched' => $fieldEnrich];
    }

    // ==================== Fetch Log (t_expert_fetch) ====================

    private function getFetchLog($field, $source)
    {
        $log = Db::name('expert_fetch')
            ->where('field', $field)
            ->where('source', $source)
            ->find();

        if (!$log) {
            return ['last_page' => 0, 'total_pages' => 0, 'last_time' => 0];
        }

        return $log;
    }

    private function updateFetchLog($field, $source, $lastPage, $totalPages)
    {
        $exists = Db::name('expert_fetch')
            ->where('field', $field)
            ->where('source', $source)
            ->find();

        if ($exists) {
            Db::name('expert_fetch')
                ->where('expert_fetch_id', $exists['expert_fetch_id'])
                ->update([
                    'last_page'   => $lastPage,
                    'total_pages' => $totalPages,
                    'last_time'   => time(),
                ]);
        } else {
            Db::name('expert_fetch')->insert([
                'field'       => mb_substr($field, 0, 128),
                'source'      => mb_substr($source, 0, 128),
                'last_page'   => $lastPage,
                'total_pages' => $totalPages,
                'last_time'   => time(),
            ]);
        }
    }

    private function enrichExpertField($expertId, $field)
    {
        $field = trim($field);
        if (empty($field)) {
            return 0;
        }

        $exists = Db::name('expert_field')
            ->where('expert_id', $expertId)
            ->where('field', $field)
            ->where('state', 0)
            ->find();

        if ($exists) {
            return 0;
        }

        Db::name('expert_field')->insert([
            'expert_id' => $expertId,
            'major_id'  => 0,
            'field'     => mb_substr($field, 0, 128),
            'state'     => 0,
        ]);

        return 1;
    }

    // ==================== Helper Methods ====================

    private function extractEmailFromText($text)
    {
        if (empty($text)) {
            return '';
        }

        if (preg_match('/[Ee]lectronic address:\s*([^\s;,]+@[^\s;,]+)/', $text, $m)) {
            return strtolower(trim($m[1], '.'));
        }

        if (preg_match('/[Ee]-?mail:\s*([^\s;,]+@[^\s;,]+)/', $text, $m)) {
            return strtolower(trim($m[1], '.'));
        }

        if (preg_match('/\b([a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,})\b/', $text, $m)) {
            return strtolower(trim($m[1], '.'));
        }

        return '';
    }

    private function extractEmailsFromNode($node, &$emails)
    {
        if ($node === null) {
            return;
        }

        foreach ($node->children() as $child) {
            if ($child->getName() === 'email') {
                $email = strtolower(trim((string) $child));
                if (!empty($email) && !in_array($email, $emails)) {
                    $emails[] = $email;
                }
            }
            $this->extractEmailsFromNode($child, $emails);
        }

        $text = (string) $node;
        if (preg_match_all('/\b([a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,})\b/', $text, $matches)) {
            foreach ($matches[1] as $email) {
                $email = strtolower(trim($email, '.'));
                if (!in_array($email, $emails)) {
                    $emails[] = $email;
                }
            }
        }
    }

    private function cleanAffiliation($text)
    {
        $text = preg_replace('/\s*[Ee]lectronic address:\s*[^\s;,]+@[^\s;,]+/', '', $text);
        $text = preg_replace('/\s*[Ee]-?mail:\s*[^\s;,]+@[^\s;,]+/', '', $text);
        $text = preg_replace('/\s*\b[a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,}\b/', '', $text);
        $text = trim($text, " \t\n\r\0\x0B.,;");
        return $text;
    }

    private function xmlNodeToString($node)
    {
        if ($node === null) {
            return '';
        }

        $xml = $node->asXML();
        $text = strip_tags($xml);
        $text = html_entity_decode($text, ENT_QUOTES | ENT_XML1, 'UTF-8');
        return trim(preg_replace('/\s+/', ' ', $text));
    }
}