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<?php

/**
 * MvcCore
 *
 * This source file is subject to the BSD 3 License
 * For the full copyright and license information, please view
 * the LICENSE.md file that are distributed with this source code.
 *
 * @copyright   Copyright (c) 2016 Tom Flidr (https://github.com/mvccore)
 * @license  https://mvccore.github.io/docs/mvccore/5.0.0/LICENCE.md
 */

namespace MvcCore\Ext\Models\Db;

class Reader implements \MvcCore\Ext\Models\Db\IReader {

    /**
     * Statement wrapper object.
     * @var \MvcCore\Ext\Models\Db\Statement
     */
    protected $statement;

    /**
     * `\PDOstatement::execute()` result value.
     * @var bool|NULL
     */
    protected $providerExecResult = NULL;
    
    /** 
     * All fetched rows or single row. Not used for stream reader.
     * @var mixed
     */
    protected $rawData = NULL;
    
    /**
     * Internal reflection property to set `$this->reader->opened` protected property.
     * @var \ReflectionProperty
     */
    protected $stmntOpenedProp = NULL;



    /**
     * Internal constructor to create reader wrapper instance.
     * @param Statement $statement 
     */
    public function __construct (\MvcCore\Ext\Models\Db\Statement $statement) {
        $this->statement = $statement;
        $this->stmntOpenedProp = new \ReflectionProperty($statement, 'opened');
        $this->stmntOpenedProp->setAccessible(TRUE);
    }

    /**
     * @inheritDocs
     * @return bool
     */
    public function GetExecResult () {
        if ($this->providerExecResult === NULL) 
            $this->providerInvokeExecute();
        return $this->providerExecResult;
    }

    /**
     * @inheritDocs
     * @return array
     */
    public function GetRawData () {
        return $this->rawData;
    }

    /**
     * @inheritDocs
     * @return \MvcCore\Ext\Models\Db\Statement
     */
    public function GetStatement () {
        return $this->statement;
    }



    /**
     * Execute provider statement if necessary and 
     * fetch single or multiple rows into result variable,
     * close cursor and return the result.
     * @param bool $singleRow 
     * @param int $fetchMode 
     * @return array|NULL
     */
    protected function & fetchRawData ($singleRow, $fetchMode = \PDO::FETCH_ASSOC) {
        if ($this->providerExecResult === NULL && $this->statement->IsOpened() !== FALSE)
            $this->providerInvokeExecute();
        $statement = $this->statement->GetProviderStatement();
        if ($singleRow) {
            $this->rawData = $statement->fetch($fetchMode);
        } else {
            $this->rawData = $statement->fetchAll($fetchMode);
        }
        $autoCloseStatement = in_array(
            \MvcCore\Ext\Models\Db\IStatement::AUTO_CLOSE, 
            $this->statement->GetDriverOptions()
        );
        if ($autoCloseStatement) 
            $this->statement->Close();
        return $this->rawData;
    }

    /**
     * Execute prepared statement. If connection is lost, reconnect and 
     * if query is select, try to prepare it again and execute it again.
     * @throws \Exception 
     * @throws \PDOException 
     * @return \MvcCore\Ext\Models\Db\Reader
     */
    protected function providerInvokeExecute () {
        /*
        $testConn = $this->statement->GetConnection();
        $testConnType = new \ReflectionClass($testConn);
        $testProp = $testConnType->getProperty('retryAttempts');
        $testProp->setAccessible(TRUE);
        $testRetryAttempts = $testProp->getValue($testConn);
        */
        if ($this->providerExecResult !== NULL) return $this;

        $params = $this->statement->GetParams();
        $providerStatement = $this->statement->GetProviderStatement();
        /**
         * @var $exception \Throwable|NULL
         * @var $dbErrorMsg string
         */
        $exception = NULL;
        $dbErrorMsg = NULL;
        try {
            set_error_handler(function ($phpErrLevel, $errMessage) use (& $dbErrorMsg) {
                // $phpErrLevel is always with value `2` as warning
                $dbErrorMsg = $errMessage;
            });
            
            $this->providerExecResult = $providerStatement->execute($params);
            $this->stmntOpenedProp->setValue($this->statement, TRUE);
            
            restore_error_handler();
            if (!$this->providerExecResult) {
                $errInfo = $providerStatement->errorInfo();
                throw new \Exception($errInfo[2] ?: $dbErrorMsg, intval($errInfo[0]));
            }

            /*
            if ($testRetryAttempts === 0)
                throw new \PDOException(" server has gone away ");
            */
        } catch (\Exception $e) { // backward compatibility
            $exception = \MvcCore\Ext\Models\Db\Exception::Create($e)
                ->setQuery($providerStatement->queryString)
                ->setParams($params);
            $this->providerExecResult = FALSE;
        } catch (\Throwable $e) {
            $exception = \MvcCore\Ext\Models\Db\Exception::Create($e)
                ->setQuery($providerStatement->queryString)
                ->setParams($params);
            $this->providerExecResult = FALSE;
        }
        
        if ($this->providerExecResult === FALSE) {
            
            $connection = $this->statement->GetConnection();
            $testConnType = new \ReflectionClass($connection);
            $retryConnectMethod = $testConnType->getMethod('reConnectIfNecessaryOrThrownError');
            $retryConnectMethod->setAccessible(TRUE);
            
            $providerConn = $retryConnectMethod->invokeArgs(
                $connection, [$exception]
            );

            $firstWord = $this->getSqlCommandFirstWord($providerStatement->queryString);
            if ($firstWord === 'select') {
                $providerStatement = $providerConn->prepare($providerStatement->queryString . ';');
                $statementType = new \ReflectionClass($this->statement);
                $provStatementProp = $statementType->getProperty('providerStatement');
                $provStatementProp->setAccessible(TRUE);
                $provStatementProp->setValue($this->statement, $providerStatement);
                return $this->providerInvokeExecute();
            }
        }
        return $this;
    }

    /**
     * Clean up property `rawData` after reading is finished.
     * This function is not used in stream reader.
     * @return void
     */
    protected function cleanUpData () {
        $this->rawData = NULL;
    }

    /**
     * Get SQL command first word in lower case.
     * @param string $sql 
     * @return string|NULL
     */
    protected function getSqlCommandFirstWord ($sql) {
        $sqlTrimmed = trim($sql, "; \t\n\r\0\x0B");
        preg_match("#\s#", $sqlTrimmed, $matches, PREG_OFFSET_CAPTURE);
        if ($matches && $matches[0]) {
            $firstWhiteSpacePos = $matches[0][1];
            $firstWord = mb_strtolower(mb_substr($sqlTrimmed, 0, $firstWhiteSpacePos));
            return $firstWord;
        }
        return $sql;
    }
}