<?php
/**
 *
 * This file is part of phpFastCache.
 *
 * @license MIT License (MIT)
 *
 * For full copyright and license information, please see the docs/CREDITS.txt file.
 *
 * @author Khoa Bui (khoaofgod)  <khoaofgod@gmail.com> http://www.phpfastcache.com
 * @author Georges.L (Geolim4)  <contact@geolim4.com>
 *
 */

namespace phpFastCache\Drivers\Sqlite;

use PDO;
use PDOException;
use phpFastCache\Core\Pool\DriverBaseTrait;
use phpFastCache\Core\Pool\ExtendedCacheItemPoolInterface;
use phpFastCache\Core\Pool\IO\IOHelperTrait;
use phpFastCache\Exceptions\phpFastCacheDriverCheckException;
use phpFastCache\Exceptions\phpFastCacheInvalidArgumentException;
use phpFastCache\Exceptions\phpFastCacheIOException;
use Psr\Cache\CacheItemInterface;

/**
 * Class Driver
 * @package phpFastCache\Drivers
 * @todo Remove "exp" column in V7
 */
class Driver implements ExtendedCacheItemPoolInterface
{
    use DriverBaseTrait, IOHelperTrait;

    /**
     *
     */
    const FILE_DIR = 'sqlite';
    /**
     *
     */
    const INDEXING_FILE = 'indexing';

    /**
     * @var int
     */
    protected $maxSize = 10; // 10 mb

    /**
     * @var int
     */
    protected $currentDB = 1;

    /**
     * @var string
     */
    protected $SqliteDir = '';

    /**
     * @var \PDO
     */
    protected $indexing;

    /**
     * Driver constructor.
     * @param array $config
     * @throws phpFastCacheDriverCheckException
     * @throws phpFastCacheIOException
     */
    public function __construct(array $config = [])
    {
        $this->setup($config);

        if (!$this->driverCheck()) {
            throw new phpFastCacheDriverCheckException(sprintf(self::DRIVER_CHECK_FAILURE, $this->getDriverName()));
        } else {
            if (!file_exists($this->getSqliteDir()) && !@mkdir($this->getSqliteDir(), $this->getDefaultChmod(), true)) {
                throw new phpFastCacheIOException(sprintf('Sqlite cannot write in "%s", aborting...', $this->getPath()));
            } else {
                $this->driverConnect();
            }
        }
    }

    /**
     * @return string
     * @throws \phpFastCache\Exceptions\phpFastCacheCoreException
     */
    public function getSqliteDir()
    {
        return $this->SqliteDir ?: $this->getPath() . DIRECTORY_SEPARATOR . self::FILE_DIR;
    }

    /**
     * @return bool
     */
    public function driverCheck()
    {
        return extension_loaded('pdo_sqlite') && (is_writable($this->getSqliteDir()) || @mkdir($this->getSqliteDir(), $this->getDefaultChmod(), true));
    }

    /**
     * INIT NEW DB
     * @param \PDO $db
     */
    public function initDB(\PDO $db)
    {
        $db->exec('drop table if exists "caching"');
        $db->exec('CREATE TABLE "caching" ("id" INTEGER PRIMARY KEY AUTOINCREMENT, "keyword" VARCHAR UNIQUE, "object" BLOB, "exp" INTEGER)');
        $db->exec('CREATE UNIQUE INDEX "cleanup" ON "caching" ("keyword","exp")');
        $db->exec('CREATE INDEX "exp" ON "caching" ("exp")');
        $db->exec('CREATE UNIQUE INDEX "keyword" ON "caching" ("keyword")');
    }

    /**
     * INIT Indexing DB
     * @param \PDO $db
     */
    public function initIndexing(\PDO $db)
    {

        // delete everything before reset indexing
        $dir = opendir($this->SqliteDir);
        while ($file = readdir($dir)) {
            if ($file != '.' && $file != '..' && $file != 'indexing' && $file != 'dbfastcache') {
                unlink($this->SqliteDir . '/' . $file);
            }
        }

        $db->exec('drop table if exists "balancing"');
        $db->exec('CREATE TABLE "balancing" ("keyword" VARCHAR PRIMARY KEY NOT NULL UNIQUE, "db" INTEGER)');
        $db->exec('CREATE INDEX "db" ON "balancing" ("db")');
        $db->exec('CREATE UNIQUE INDEX "lookup" ON "balancing" ("keyword")');

    }

    /**
     * INIT Instant DB
     * Return Database of Keyword
     * @param $keyword
     * @return int
     */
    public function indexing($keyword)
    {
        if ($this->indexing == null) {
            $createTable = false;
            if (!file_exists($this->SqliteDir . '/indexing')) {
                $createTable = true;
            }

            $PDO = new PDO("sqlite:" . $this->SqliteDir . '/' . self::INDEXING_FILE);
            $PDO->setAttribute(PDO::ATTR_ERRMODE,
              PDO::ERRMODE_EXCEPTION);

            if ($createTable == true) {
                $this->initIndexing($PDO);
            }

            // Added by Observium developers
            // Improve write speed, see:
            // http://stackoverflow.com/questions/1711631/improve-insert-per-second-performance-of-sqlite
            $PDO->exec('PRAGMA synchronous=OFF');
            $PDO->exec('PRAGMA journal_mode=MEMORY');
            $PDO->exec('PRAGMA temp_store=MEMORY');
            //$PDO->exec('PRAGMA count_changes=false');

            $this->indexing = $PDO;
            unset($PDO);

            $stm = $this->indexing->prepare("SELECT MAX(`db`) as `db` FROM `balancing`");
            $stm->execute();
            $row = $stm->fetch(PDO::FETCH_ASSOC);
            if (!isset($row[ 'db' ])) {
                $db = 1;
            } elseif ($row[ 'db' ] <= 1) {
                $db = 1;
            } else {
                $db = $row[ 'db' ];
            }

            // check file size

            $size = file_exists($this->SqliteDir . '/db' . $db) ? filesize($this->SqliteDir . '/db' . $db) : 1;
            $size = round($size / 1024 / 1024, 1);


            if ($size > $this->maxSize) {
                $db++;
            }
            $this->currentDB = $db;

        }

        // look for keyword
        $stm = $this->indexing->prepare("SELECT * FROM `balancing` WHERE `keyword`=:keyword LIMIT 1");
        $stm->execute([
          ':keyword' => $keyword,
        ]);
        $row = $stm->fetch(PDO::FETCH_ASSOC);
        if (isset($row[ 'db' ]) && $row[ 'db' ] != '') {
            $db = $row[ 'db' ];
        } else {
            /*
             * Insert new to Indexing
             */
            $db = $this->currentDB;
            $stm = $this->indexing->prepare("INSERT INTO `balancing` (`keyword`,`db`) VALUES(:keyword, :db)");
            $stm->execute([
              ':keyword' => $keyword,
              ':db' => $db,
            ]);
        }

        return $db;
    }

    /**
     * @param $keyword
     * @param bool $reset
     * @return PDO
     */
    public function getDb($keyword, $reset = false)
    {
        /**
         * Default is fastcache
         */
        $instant = $this->indexing($keyword);

        /**
         * init instant
         */
        if (!isset($this->instance[ $instant ])) {
            // check DB Files ready or not
            $createTable = false;
            if (!file_exists($this->SqliteDir . '/db' . $instant) || $reset == true) {
                $createTable = true;
            }
            $PDO = new PDO('sqlite:' . $this->SqliteDir . '/db' . $instant);
            $PDO->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

            if ($createTable == true) {
                $this->initDB($PDO);
            }

            // Added by Observium developers
            // Improve write speed, see:
            // http://stackoverflow.com/questions/1711631/improve-insert-per-second-performance-of-sqlite
            $PDO->exec('PRAGMA synchronous=OFF');
            $PDO->exec('PRAGMA journal_mode=MEMORY');
            $PDO->exec('PRAGMA temp_store=MEMORY');
            //$PDO->exec('PRAGMA count_changes=false');

            $this->instance[ $instant ] = $PDO;
            unset($PDO);

        }

        return $this->instance[ $instant ];
    }

    /**
     * @param \Psr\Cache\CacheItemInterface $item
     * @return mixed
     * @throws phpFastCacheInvalidArgumentException
     */
    protected function driverWrite(CacheItemInterface $item)
    {
        /**
         * Check for Cross-Driver type confusion
         */
        if ($item instanceof Item) {
            $skipExisting = isset($this->config[ 'skipExisting' ]) ? $this->config[ 'skipExisting' ] : false;
            $toWrite = true;

            // check in cache first
            $in_cache = $this->driverRead($item);

            if ($skipExisting == true) {
                if ($in_cache == null) {
                    $toWrite = true;
                } else {
                    $toWrite = false;
                }
            }

            if ($toWrite == true) {
                $sql = "INSERT OR REPLACE INTO `caching` (`keyword`,`object`,`exp`) values(:keyword,:object,:exp)";
                try {
                    $stm = $this->getDb($item->getKey())
                      ->prepare($sql);
                    $stm->execute([
                      ':keyword' => $item->getKey(),
                      ':object' => $this->encode($this->driverPreWrap($item)),
                      ':exp' => $item->getExpirationDate()->getTimestamp(),
                    ]);

                    return true;
                } catch (\PDOException $e) {
                    try {
                        $stm = $this->getDb($item->getKey(), true)
                          ->prepare($sql);
                        $stm->execute([
                          ':keyword' => $item->getKey(),
                          ':object' => $this->encode($this->driverPreWrap($item)),
                          ':exp' => $item->getExpirationDate()->getTimestamp(),
                        ]);
                    } catch (PDOException $e) {
                        return false;
                    }
                }
            }

            return false;
        } else {
            throw new phpFastCacheInvalidArgumentException('Cross-Driver type confusion detected');
        }
    }

    /**
     * @param \Psr\Cache\CacheItemInterface $item
     * @return null|array
     */
    protected function driverRead(CacheItemInterface $item)
    {
        $sql = "SELECT * FROM `caching` WHERE `keyword`=:keyword LIMIT 1";
        try {
            $stm = $this->getDb($item->getKey())
              ->prepare($sql);
            $stm->execute([
              ':keyword' => $item->getKey(),
            ]);
            $row = $stm->fetch(PDO::FETCH_ASSOC);
        } catch (PDOException $e) {
            try {
                $stm = $this->getDb($item->getKey(), true)
                  ->prepare($sql);
                $stm->execute([
                  ':keyword' => $item->getKey(),
                ]);
                $row = $stm->fetch(PDO::FETCH_ASSOC);
            } catch (PDOException $e) {
                return null;
            }
        }

        if (isset($row[ 'object' ])) {
            return $this->decode($row[ 'object' ]);
        }

        return null;
    }

    /**
     * @param \Psr\Cache\CacheItemInterface $item
     * @return bool
     * @throws phpFastCacheInvalidArgumentException
     */
    protected function driverDelete(CacheItemInterface $item)
    {
        /**
         * Check for Cross-Driver type confusion
         */
        if ($item instanceof Item) {
            try {
                $stm = $this->getDb($item->getKey())
                  ->prepare("DELETE FROM `caching` WHERE (`exp` <= :U) OR (`keyword`=:keyword) ");

                return $stm->execute([
                  ':keyword' => $item->getKey(),
                  ':U' => time(),
                ]);
            } catch (PDOException $e) {
                return false;
            }
        } else {
            throw new phpFastCacheInvalidArgumentException('Cross-Driver type confusion detected');
        }
    }

    /**
     * @return bool
     */
    protected function driverClear()
    {
        $this->instance = [];
        $this->indexing = null;

        // delete everything before reset indexing
        $dir = opendir($this->getSqliteDir());
        while ($file = readdir($dir)) {
            if ($file != '.' && $file != '..') {
                unlink($this->getSqliteDir() . '/' . $file);
            }
        }

        return true;
    }

    /**
     * @return bool
     */
    protected function driverConnect()
    {
        if (!file_exists($this->getPath() . '/' . self::FILE_DIR)) {
            if (!mkdir($this->getPath() . '/' . self::FILE_DIR, $this->getDefaultChmod(), true)
            ) {
                $this->fallback = true;
            }
        }
        $this->SqliteDir = $this->getPath() . '/' . self::FILE_DIR;

        return true;
    }

    /**
     * @return array
     */
    public function __sleep()
    {
        return array_diff(array_keys(get_object_vars($this)), ['indexing', 'instance']);
    }
}