<?php
/************************************************************************
 * This file is part of EspoCRM.
 *
 * EspoCRM - Open Source CRM application.
 * Copyright (C) 2014-2023 Yurii Kuznietsov, Taras Machyshyn, Oleksii Avramenko
 * Website: https://www.espocrm.com
 *
 * EspoCRM is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * EspoCRM is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with EspoCRM. If not, see http://www.gnu.org/licenses/.
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU General Public License version 3.
 *
 * In accordance with Section 7(b) of the GNU General Public License version 3,
 * these Appropriate Legal Notices must retain the display of the "EspoCRM" word.
 ************************************************************************/

namespace Espo\ORM;

use Espo\ORM\QueryComposer\QueryComposer;

use PDO;
use PDOException;
use RuntimeException;
use Throwable;
use Closure;

class TransactionManager
{
    private int $level = 0;

    public function __construct(private PDO $pdo, private QueryComposer $queryComposer)
    {}

    /**
     * Whether a transaction is started.
     */
    public function isStarted(): bool
    {
        return $this->level > 0;
    }

    /**
     * Get a current nesting level.
     */
    public function getLevel(): int
    {
        return $this->level;
    }

    /**
     * Run a function in a transaction. Commits if success, rolls back if an exception occurs.
     *
     * @return mixed A function result.
     */
    public function run(Closure $function)
    {
        $this->start();

        try {
            $result = $function();

            $this->commit();
        }
        catch (Throwable $e) {
            $this->rollback();

            /**
             * @var PDOException $e
             */
            throw $e;
        }

        return $result;
    }

    /**
     * Start a transaction.
     */
    public function start(): void
    {
        if ($this->level > 0) {
            $this->createSavepoint();

            $this->level++;

            return;
        }

        $this->pdo->beginTransaction();

        $this->level++;
    }

    /**
     * Commit a transaction.
     */
    public function commit(): void
    {
        if ($this->level === 0) {
            throw new RuntimeException("Can't commit not started transaction.");
        }

        $this->level--;

        if ($this->level > 0) {
            $this->releaseSavepoint();

            return;
        }

        $this->pdo->commit();
    }

    /**
     * Rollback a transaction.
     */
    public function rollback(): void
    {
        if ($this->level === 0) {
            throw new RuntimeException("Can't rollback not started transaction.");
        }

        $this->level--;

        if ($this->level > 0) {
            $this->rollbackToSavepoint();

            return;
        }

        $this->pdo->rollBack();
    }

    private function getCurrentSavepoint(): string
    {
        return 'POINT_' . (string) $this->level;
    }

    private function createSavepoint(): void
    {
        $sql = $this->queryComposer->composeCreateSavepoint($this->getCurrentSavepoint());

        $this->pdo->exec($sql);
    }

    private function releaseSavepoint(): void
    {
        $sql = $this->queryComposer->composeReleaseSavepoint($this->getCurrentSavepoint());

        $this->pdo->exec($sql);
    }

    private function rollbackToSavepoint(): void
    {
        $sql = $this->queryComposer->composeRollbackToSavepoint($this->getCurrentSavepoint());

        $this->pdo->exec($sql);
    }
}