<?php

namespace app\common;

/**
 * Europe PMC REST API
 * @see https://europepmc.org/RestfulWebService
 */
class EuropePmcService
{
    private $base = 'https://www.ebi.ac.uk/europepmc/webservices/rest';
    private $timeout = 25;

    public function searchByDoi($doi)
    {
        $doi = trim((string)$doi);
        if ($doi === '') {
            return null;
        }
        $query = 'DOI:"' . str_replace('"', '', $doi) . '"';
        return $this->searchFirst($query);
    }

    public function searchByBibliographic($title, $author, $year = '')
    {
        $title = trim((string)$title);
        if ($title === '') {
            return null;
        }
        $parts = ['TITLE:"' . str_replace('"', '', $title) . '"'];
        $author = trim((string)$author);
        if ($author !== '') {
            $firstAuthor = preg_split('/[,;]/', $author);
            $firstAuthor = trim((string)($firstAuthor[0] ?? ''));
            if ($firstAuthor !== '') {
                $parts[] = 'AUTH:"' . str_replace('"', '', $firstAuthor) . '"';
            }
        }
        $year = trim((string)$year);
        if ($year !== '' && preg_match('/^(19|20)\d{2}$/', $year)) {
            $parts[] = 'PUB_YEAR:' . $year;
        }
        return $this->searchFirst(implode(' AND ', $parts));
    }

    public function fetchFullTextByPmcid($pmcid)
    {
        $pmcid = strtoupper(trim((string)$pmcid));
        if ($pmcid === '') {
            return '';
        }
        if (strpos($pmcid, 'PMC') !== 0) {
            $pmcid = 'PMC' . preg_replace('/\D/', '', $pmcid);
        }
        $url = $this->base . '/' . rawurlencode($pmcid) . '/fullTextXML';
        $xml = $this->httpGet($url);
        if ($xml === '') {
            return '';
        }
        return $this->xmlToPlainText($xml);
    }

    private function searchFirst($query)
    {
        $url = $this->base . '/search?' . http_build_query([
            'query'    => $query,
            'format'   => 'json',
            'pageSize' => 1,
        ]);
        $raw = $this->httpGet($url);
        if ($raw === '') {
            return null;
        }
        $json = json_decode($raw, true);
        $list = $json['resultList']['result'] ?? [];
        if (empty($list[0]) || !is_array($list[0])) {
            return null;
        }
        $row = $list[0];
        return [
            'title'         => trim((string)($row['title'] ?? '')),
            'abstract'      => trim((string)($row['abstractText'] ?? '')),
            'doi'           => trim((string)($row['doi'] ?? '')),
            'pmid'          => trim((string)($row['pmid'] ?? '')),
            'pmcid'         => trim((string)($row['pmcid'] ?? '')),
            'journal'       => trim((string)($row['journalTitle'] ?? '')),
            'year'          => trim((string)($row['pubYear'] ?? '')),
            'source'        => 'europe_pmc',
        ];
    }

    private function xmlToPlainText($xml)
    {
        $xml = trim((string)$xml);
        if ($xml === '') {
            return '';
        }
        libxml_use_internal_errors(true);
        $doc = new \DOMDocument();
        if (!$doc->loadXML($xml)) {
            return trim(strip_tags($xml));
        }
        return trim(preg_replace('/\s+/u', ' ', $doc->textContent));
    }

    private function httpGet($url)
    {
        $ch = curl_init();
        curl_setopt_array($ch, [
            CURLOPT_URL            => $url,
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_TIMEOUT        => $this->timeout,
            CURLOPT_SSL_VERIFYPEER => false,
            CURLOPT_HTTPHEADER     => ['User-Agent: TMRjournals-EuropePMC/1.0'],
        ]);
        $res = curl_exec($ch);
        curl_close($ch);
        return is_string($res) ? $res : '';
    }
}