<?php
header('Content-type: text/plain; charset=utf-8');
/**
 * User: Marvin Borner
 * Date: 16/09/2018
 * Time: 21:34
 */

class Database
{
    public static function getFromQueue($sort): string
    {
        print "\t\e[96mStarting at " . ($sort === 'DESC' ? 'bottom' : 'top') . " of queue\n";
        $conn = self::initDbConnection();
        $checkStmt = $conn->query('SELECT url FROM queue ORDER BY id ' . $sort . ' LIMIT 1');

        return $checkStmt->fetchAll(PDO::FETCH_ASSOC)[0]['url'] ?? '';
    }

    public static function insertIntoQueue($urls)
    {
        foreach ($urls as $url) {
            if (self::alreadyCrawled($url)) {
                print "\t\e[91mUrl already queued " . $url . "\n";
            } else {
                print "\t\e[92mQueueing url " . $url . "\n";
                $conn = self::initDbConnection();
                $hash = md5($url);
                $stmt = $conn->prepare('INSERT IGNORE INTO queue (url, hash) VALUES (:url, :hash)');
                $stmt->execute([':url' => $url, 'hash' => $hash]);
            }
        }
    }

    public static function removeFromQueue($url)
    {
        $hash = md5($url);
        $conn = self::initDbConnection();
        $checkStmt = $conn->prepare('DELETE FROM queue WHERE hash = :hash');
        $checkStmt->execute([':hash' => $hash]);
    }

    public static function alreadyCrawled($url): bool
    {
        print "\t\e[96mChecking if url has already been crawled " . $url . "\n";
        $hash = md5($url);
        $conn = self::initDbConnection();
        $checkStmt = $conn->prepare('(SELECT null FROM url_data WHERE hash = :hash) UNION (SELECT null FROM error_url WHERE hash = :hash)');
        $checkStmt->execute([':hash' => $hash]);
        $alreadyCrawled = $checkStmt->rowCount() !== 0;
        if ($alreadyCrawled) {
            print "\t\e[91mUrl already crawled " . $url . "\n";
        }
        return $alreadyCrawled; // return true if already crawled
    }

    public static function urlHasError($url)
    {
        $hash = md5($url);
        $conn = self::initDbConnection();
        $checkStmt = $conn->prepare('INSERT IGNORE INTO error_url (url, hash) VALUES (:url, :hash)');
        $checkStmt->execute([':url' => $url, 'hash' => $hash]);
    }

    public static function saveUrlData($url, $data)
    {
        $conn = self::initDbConnection();
        $stmt = $conn->prepare('INSERT IGNORE INTO url_data (url, title, description, lang, hash) VALUES (:url, :title, :description, :lang, :hash)');
        $stmt->execute([':url' => $url, ':title' => $data['title'] ?? '', ':description' => $data['description'] ?? '', ':lang' => $data['lang'] ?? 'en', ':hash' => md5($url)]);
    }

    public static function getUrlData($query)
    {
        $conn = self::initDbConnection();
        $checkStmt = $conn->prepare('SELECT url, title, description, lang FROM url_data WHERE title LIKE :query OR description LIKE :query');
        $checkStmt->execute([':query' => '%' . $query . '%']);
        return $checkStmt->fetchAll(PDO::FETCH_ASSOC);
    }

    private static function initDbConnection(): PDO
    {
        global $servername, $dbname, $username, $password;
        $conn = new PDO("mysql:host=$servername;dbname=$dbname;charset=utf8", $username, $password);
        $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        return $conn;
    }
}