<?php


/**
 * Description of doi
 *
 * @author may
 */
class doi {
    //put your code here
    public static $requests = 0;
    
    private $doi="x";
    
    public function __construct() {
                
    }

    // retrieves DOI data from thw doi server
    public static function fetchData($doi) {
        $data = -1;
        
        if (strlen ($doi) < 1) {
            return $data;
        }
        
        // check if it's already in the DB!
        if ($db_id = doi::isPublication($doi)) {
            return $db_id;
        }

        // limit number of requests (testing, importing huge databases, etc.        
        else if (doi::$requests < DOI_REQ_LIMIT) {
            $ch = curl_init();

            $headers = array('Accept: application/x-bibtex');

            curl_setopt($ch, CURLOPT_URL,  'http://dx.doi.org/' .$doi);
            curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
            curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);                 
            curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
            curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
            curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);    
            curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "GET");                 
            curl_setopt($ch, CURLOPT_TIMEOUT, 10);

            if ($res = curl_exec($ch)) {
                if(!curl_error($ch)) {
                    $data = doi::_bibtex2arr($res);
                }
            }

            doi::$requests++;

            curl_close($ch);
            return $data;
        }
        else {
            return $data ." (OVER DOI_REQ_LIMIT!!!)";
        }
        
    }
    
    // check if we already have this DOI
    public static function isPublication($doi) {
        global $PDO;
        
        $d_arr = explode ("doi.org/", $doi);
        if (count ($d_arr)> 1) {
            $doi = $d_arr[1];
        }
        
        try {
            $stmt = $PDO->prepare("SELECT id FROM publication where doi=:doi");
            $stmt->execute(array($doi));
            
            // this instead of rowCount to make in compatible with non-mysql DB
            if ($r = $stmt->fetch(PDO::FETCH_NUM)) {
                return $r[0];
            }
            else {
                return false;
            }
        }
        catch (exception $ex) {
            common::except ('Err: ' .$ex .' in ' .__DIR__ .'/' .__FILE__ .':' .__LINE__);
            return false;
        }  
        return false;
    }
    
    // converts from DOI to array (that canbe inserted into the DB)
    private static function _bibtex2arr($data) {
        
        $record = array();
        
        /*
            @article{R_der_2015,
            doi = {10.1111/imre.12113},
            url = {https://doi.org/10.1111%2Fimre.12113},
            year = 2015,
            month = {dec},
            publisher = {{SAGE} Publications},
            volume = {49},
            number = {4},
            pages = {1042--1070},
            author = {Antje Röder},
            title = {Immigrants' Attitudes toward Homosexuality: Socialization) Religion, and Acculturation in European Host Societies},
            journal = {International Migration Review}    
         * 
         * let's make it universal for all kinds of sources:
          - 1 data field (incl. name) per line (explode \n; trim \r; )    
          - ' = ' is separator; explode, again and name and value. Make sure only to explode ONE TIME
        */
        
        $line_arr = explode ("\n", $data);
        
        foreach ($line_arr as $line) {
            $fields = explode ("=", trim($line), 2);
            
            if (count ($fields) == 2) {
                $record[trim($fields[0])] = trim($fields[1], " \n\r\t\{\}\,");
            }
        }
        return $record;
    }
}