patchtester/administrator/components/com_patchtester/PatchTester/Model/PullModel.php

<?php
/**
 * Patch testing component for the Joomla! CMS
 *
 * @copyright  Copyright (C) 2011 - 2012 Ian MacLennan, Copyright (C) 2013 - 2018 Open Source Matters, Inc. All rights reserved.
 * @license    GNU General Public License version 2 or later
 */

namespace PatchTester\Model;

use Joomla\Archive\Zip;
use Joomla\CMS\Component\ComponentHelper;
use Joomla\CMS\Factory;
use Joomla\CMS\Filesystem\Path;
use Joomla\CMS\Http\Response;
use Joomla\CMS\Language\Text;
use Joomla\CMS\Version;
use Joomla\Filesystem\File;
use Joomla\Filesystem\Folder;
use PatchTester\GitHub\Exception\UnexpectedResponse;
use PatchTester\GitHub\GitHub;
use PatchTester\Helper;

/**
 * Methods supporting pull requests.
 *
 * @since  2.0
 */
class PullModel extends AbstractModel
{
	/**
	 * Array containing top level non-production folders
	 *
	 * @var    array
	 * @since  2.0
	 */
	protected $nonProductionFolders = array(
		'build',
		'docs',
		'installation',
		'tests',
		'.github',
	);

	/**
	 * Array containing non-production files
	 *
	 * @var    array
	 * @since  2.0
	 */
	protected $nonProductionFiles = array(
		'.drone.yml',
		'.gitignore',
		'.php_cs',
		'.travis.yml',
		'README.md',
		'build.xml',
		'composer.json',
		'composer.lock',
		'phpunit.xml.dist',
		'robots.txt.dist',
		'travisci-phpunit.xml',
		'LICENSE',
		'RoboFile.dist.ini',
		'RoboFile.php',
		'codeception.yml',
		'jorobo.dist.ini',
		'manifest.xml',
		'crowdin.yaml',
	);

	/**
	 * Parse the list of modified files from a pull request
	 *
	 * @param   object  $files  The modified files to parse
	 *
	 * @return  array
	 *
	 * @since   3.0.0
	 */
	protected function parseFileList($files)
	{
		$parsedFiles = array();

		/*
		 * Check if the patch tester is running in a development environment
		 * If we are not in development, we'll need to check the exclusion lists
		 */
		$isDev = file_exists(JPATH_INSTALLATION . '/index.php');

		foreach ($files as $file)
		{
			if (!$isDev)
			{
				$filePath = explode('/', $file->filename);

				if (in_array($filePath[0], $this->nonProductionFiles))
				{
					continue;
				}

				if (in_array($filePath[0], $this->nonProductionFolders))
				{
					continue;
				}
			}

			// Sometimes the repo filename is not the production file name
			$prodFileName        = $file->filename;
			$prodRenamedFileName = isset($file->previous_filename) ? $file->previous_filename : false;
			$filePath            = explode('/', $prodFileName);

			// Remove the `src` here to match the CMS paths if needed
			if ($filePath[0] === 'src')
			{
				$prodFileName = str_replace('src/', '', $prodFileName);
			}

			if ($prodRenamedFileName)
			{
				$filePath = explode('/', $prodRenamedFileName);

				// Remove the `src` here to match the CMS paths if needed
				if ($filePath[0] === 'src')
				{
					$prodRenamedFileName = str_replace('src/', '', $prodRenamedFileName);
				}
			}

			$parsedFiles[] = (object) array(
				'action'       => $file->status,
				'filename'     => $prodFileName,
				'repofilename' => $file->filename,
				'fileurl'      => $file->contents_url,
				'originalFile' => $prodRenamedFileName,
			);
		}

		return $parsedFiles;
	}

	/**
	 * Patches the code with the supplied pull request
	 * However uses different methods for different repositories.
	 *
	 * @param   integer  $id  ID of the pull request to apply
	 *
	 * @return  boolean
	 *
	 * @since   3.0
	 *
	 * @throws  \RuntimeException
	 */
	public function apply($id)
	{
		$params = ComponentHelper::getParams('com_patchtester');

		// Decide based on repository settings whether patch will be applied through Github or CIServer
		if (version_compare(JVERSION, "4", "ge") && (bool) $params->get('ci_switch', 1))
		{
			return $this->applyWithCIServer($id);
		}
		else
		{
			return $this->applyWithGitHub($id);
		}
	}

	/**
	 * Patches the code with the supplied pull request
	 *
	 * @param   integer  $id  ID of the pull request to apply
	 *
	 * @return  boolean
	 *
	 * @since   3.0
	 *
	 * @throws  \RuntimeException
	 */
	private function applyWithCIServer($id)
	{
		// Get the CIServer Registry
		$ciSettings = Helper::initializeCISettings();

		// Get the Github object
		$github = Helper::initializeGithub();

		// Retrieve pullData for sha later on.
		try
		{
			$pull = $this->retrieveGitHubData($github, $id);
			$sha  = $pull->head->sha;
		}
		catch (\RuntimeException $e)
		{
			// Catch the Exception and continue, because the hash is not that
			// necessary for applying patches
			$sha = "Error:429";
		}

		// Create tmp folder if it does not exist
		if (!file_exists($ciSettings->get('folder.temp')))
		{
			Folder::create($ciSettings->get('folder.temp'));
		}

		$tempPath                 = $ciSettings->get('folder.temp') . "/$id";
		$backupsPath              = $ciSettings->get('folder.backups') . "/$id";

		$delLogPath               = $tempPath . '/' . $ciSettings->get('zip.log.name');
		$zipPath                  = $tempPath . '/' . $ciSettings->get('zip.name');

		$serverZipPath            = sprintf($ciSettings->get('zip.url'), $id);

		// Patch has already been applied
		if (file_exists($backupsPath))
		{
			return false;
		}

		// Check if zip folder exists on server
		$serverHeaders = @get_headers($serverZipPath);

		if (!$serverHeaders || $serverHeaders[0] != 'HTTP/1.1 200 OK')
		{
			throw new \RuntimeException(Text::_('COM_PATCHTESTER_SERVER_RESPONDED_NOT_200'));
		}

		Folder::create($tempPath);
		file_put_contents($zipPath, fopen($serverZipPath, "r"));

		// Check if zip folder could have been downloaded
		if (!file_exists($zipPath))
		{
			Folder::delete($tempPath);
			throw new \RuntimeException(Text::_('COM_PATCHTESTER_ZIP_DOES_NOT_EXIST'));
		}

		$zip = new Zip;

		if (!$zip->extract($zipPath, $tempPath))
		{
			Folder::delete($tempPath);
			throw new \RuntimeException(Text::_('COM_PATCHTESTER_ZIP_EXTRACT_FAILED'));
		}

		// Remove zip to avoid get listing afterwards
		File::delete($zipPath);

		// Get files from deleted_logs
		$deletedFiles = (file_exists($delLogPath) ? file($delLogPath) : array());
		$deletedFiles = array_map('trim', $deletedFiles);

		if (file_exists($delLogPath))
		{
			// Remove deleted_logs to avoid get listing afterwards
			File::delete($delLogPath);
		}

		// Retrieve all files and merge them into one array
		$files = Folder::files($tempPath, null, true, true);
		$files = str_replace(Path::clean("$tempPath\\"), '', $files);
		$files = array_merge($files, $deletedFiles);

		Folder::create($backupsPath);

		// Moves existent files to backup and replace them or creates new one if they don't exist
		foreach ($files as $key => $file)
		{
			try
			{
				$filePath = explode("\\", Path::clean($file));
				array_pop($filePath);
				$filePath = implode("\\", $filePath);

				// Deleted_logs returns files as well as folder, if value is folder, unset and skip
				if (is_dir(JPATH_ROOT . "/$file"))
				{
					unset($files[$key]);
					continue;
				}

				if (file_exists(JPATH_ROOT . "/$file"))
				{
					// Create directories if they don't exist until file
					if (!file_exists("$backupsPath/$filePath"))
					{
						Folder::create("$backupsPath/$filePath");
					}

					File::move(JPATH_ROOT . "/$file", "$backupsPath/$file");
				}

				if (file_exists("$tempPath/$file"))
				{
					// Create directories if they don't exist until file
					if (!file_exists(JPATH_ROOT . "/$filePath") || !is_dir(JPATH_ROOT . "/$filePath"))
					{
						Folder::create(JPATH_ROOT . "/$filePath");
					}

					File::copy("$tempPath/$file", JPATH_ROOT . "/$file");
				}
			}
			catch (\RuntimeException $e)
			{
				Folder::delete($tempPath);

				Folder::move($backupsPath, $backupsPath . "_failed");
				throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_FAILED_APPLYING_PATCH', $file, $e->getMessage()));
			}
		}

		// Clear temp folder and store applied patch in database
		Folder::delete($tempPath);

		$lastInserted = $this->saveAppliedPatch($id, $files, $sha);

		// Write or create patch chain for correct order of patching
		$this->appendPatchChain($lastInserted, $id);

		// Change the media version
		$version = new Version;
		$version->refreshMediaVersion();

		return true;
	}

	/**
	 * Patches the code with the supplied pull request
	 *
	 * @param   integer  $id  ID of the pull request to apply
	 *
	 * @return  boolean
	 *
	 * @since   2.0
	 *
	 * @throws  \RuntimeException
	 */
	private function applyWithGitHub($id)
	{
		// Get the Github object
		$github = Helper::initializeGithub();

		$pull = $this->retrieveGitHubData($github, $id);

		if (is_null($pull->head->repo))
		{
			throw new \RuntimeException(Text::_('COM_PATCHTESTER_REPO_IS_GONE'));
		}

		try
		{
			$filesResponse = $github->getFilesForPullRequest($this->getState()->get('github_user'), $this->getState()->get('github_repo'), $id);
			$files         = json_decode($filesResponse->body);
		}
		catch (UnexpectedResponse $e)
		{
			throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_COULD_NOT_CONNECT_TO_GITHUB', $e->getMessage()), $e->getCode(), $e);
		}

		if (!count($files))
		{
			return false;
		}

		$parsedFiles = $this->parseFileList($files);

		if (!count($parsedFiles))
		{
			return false;
		}

		foreach ($parsedFiles as $file)
		{
			switch ($file->action)
			{
				case 'deleted':
					if (!file_exists(JPATH_ROOT . '/' . $file->filename))
					{
						throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_FILE_DELETED_DOES_NOT_EXIST_S', $file->filename));
					}

					break;

				case 'added':
				case 'modified':
				case 'renamed':
					// If the backup file already exists, we can't apply the patch
					if (file_exists(JPATH_COMPONENT . '/backups/' . md5($file->filename) . '.txt'))
					{
						throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_CONFLICT_S', $file->filename));
					}

					if ($file->action == 'modified' && !file_exists(JPATH_ROOT . '/' . $file->filename))
					{
						throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_FILE_MODIFIED_DOES_NOT_EXIST_S', $file->filename));
					}

					try
					{
						$contentsResponse = $github->getFileContents(
							$pull->head->user->login, $this->getState()->get('github_repo'), $file->repofilename, urlencode($pull->head->ref)
						);

						$contents = json_decode($contentsResponse->body);

						// In case encoding type ever changes
						switch ($contents->encoding)
						{
							case 'base64':
								$file->body = base64_decode($contents->content);

								break;

							default:
								throw new \RuntimeException(Text::_('COM_PATCHTESTER_ERROR_UNSUPPORTED_ENCODING'));
						}
					}
					catch (UnexpectedResponse $e)
					{
						throw new \RuntimeException(
							Text::sprintf('COM_PATCHTESTER_COULD_NOT_CONNECT_TO_GITHUB', $e->getMessage()),
							$e->getCode(),
							$e
						);
					}

					break;
			}
		}

		// At this point, we have ensured that we have all the new files and there are no conflicts
		foreach ($parsedFiles as $file)
		{
			// We only create a backup if the file already exists
			if ($file->action == 'deleted' || (file_exists(JPATH_ROOT . '/' . $file->filename) && $file->action == 'modified')
				|| (file_exists(JPATH_ROOT . '/' . $file->originalFile) && $file->action == 'renamed'))
			{
				$filename = $file->action == 'renamed' ? $file->originalFile : $file->filename;
				$src      = JPATH_ROOT . '/' . $filename;
				$dest     = JPATH_COMPONENT . '/backups/' . md5($filename) . '.txt';

				if (!File::copy(Path::clean($src), $dest))
				{
					throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_ERROR_CANNOT_COPY_FILE', $src, $dest));
				}
			}

			switch ($file->action)
			{
				case 'modified':
				case 'added':
					if (!File::write(Path::clean(JPATH_ROOT . '/' . $file->filename), $file->body))
					{
						throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_ERROR_CANNOT_WRITE_FILE', JPATH_ROOT . '/' . $file->filename));
					}

					break;

				case 'deleted':
					if (!File::delete(Path::clean(JPATH_ROOT . '/' . $file->filename)))
					{
						throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_ERROR_CANNOT_DELETE_FILE', JPATH_ROOT . '/' . $file->filename));
					}

					break;

				case 'renamed':
					if (!File::delete(Path::clean(JPATH_ROOT . '/' . $file->originalFile)))
					{
						throw new \RuntimeException(
							Text::sprintf('COM_PATCHTESTER_ERROR_CANNOT_DELETE_FILE', JPATH_ROOT . '/' . $file->originalFile)
						);
					}

					if (!File::write(Path::clean(JPATH_ROOT . '/' . $file->filename), $file->body))
					{
						throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_ERROR_CANNOT_WRITE_FILE', JPATH_ROOT . '/' . $file->filename));
					}

					break;
			}

			// We don't need the file's body any longer (and it causes issues with binary data when json_encode() is run), so remove it
			unset($file->body);
		}

		$this->saveAppliedPatch($pull->number, $parsedFiles, $pull->head->sha);

		// Change the media version
		$version = new Version;
		$version->refreshMediaVersion();

		return true;
	}

	/**
	 * Patches the code with the supplied pull request
	 *
	 * @param   GitHub   $github  github object
	 * @param   integer  $id      Id of the pull request
	 *
	 * @return  Response
	 *
	 * @since   2.0
	 *
	 * @throws  \RuntimeException
	 */
	private function retrieveGitHubData($github, $id)
	{
		try
		{
			$rateResponse = $github->getRateLimit();
			$rate         = json_decode($rateResponse->body);
		}
		catch (UnexpectedResponse $e)
		{
			throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_COULD_NOT_CONNECT_TO_GITHUB', $e->getMessage()), $e->getCode(), $e);
		}

		// If over the API limit, we can't build this list
		if ($rate->resources->core->remaining == 0)
		{
			throw new \RuntimeException(
				Text::sprintf('COM_PATCHTESTER_API_LIMIT_LIST', Factory::getDate($rate->resources->core->reset))
			);
		}

		try
		{
			$pullResponse = $github->getPullRequest($this->getState()->get('github_user'), $this->getState()->get('github_repo'), $id);
			$pull         = json_decode($pullResponse->body);
		}
		catch (UnexpectedResponse $e)
		{
			throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_COULD_NOT_CONNECT_TO_GITHUB', $e->getMessage()), $e->getCode(), $e);
		}

		return $pull;
	}

	/**
	 * Saves the applied patch into database
	 *
	 * @param   integer  $id        ID of the applied pull request
	 * @param   array    $fileList  List of files
	 * @param   string   $sha       sha-key from pull request
	 *
	 * @return  integer  $id    last inserted id
	 *
	 * @since   3.0
	 */
	private function saveAppliedPatch($id, $fileList, $sha = null)
	{
		$record = (object) array(
			'pull_id'         => $id,
			'data'            => json_encode($fileList),
			'patched_by'      => Factory::getUser()->id,
			'applied'         => 1,
			'applied_version' => JVERSION,
		);

		$db = $this->getDb();

		$db->insertObject('#__patchtester_tests', $record);
		$insertId = $db->insertid();

		if (!is_null($sha))
		{
			// Insert the retrieved commit SHA into the pulls table for this item
			$db->setQuery(
				$db->getQuery(true)
					->update('#__patchtester_pulls')
					->set('sha = ' . $db->quote($sha))
					->where($db->quoteName('pull_id') . ' = ' . (int) $id)
			)->execute();
		}

		return $insertId;
	}

	/**
	 * Reverts the specified pull request
	 * However uses different methods for different repositories.
	 *
	 * @param   integer  $id  ID of the pull request to revert
	 *
	 * @return  boolean
	 *
	 * @since   3.0
	 * @throws  \RuntimeException
	 */
	public function revert($id)
	{
		$params = ComponentHelper::getParams('com_patchtester');

		// Decide based on repository settings whether patch will be applied through Github or CIServer
		if (version_compare(JVERSION, "4", "ge") && ((bool) $params->get('ci_switch', 1) || $id === $this->getPatchChain($id)->insert_id))
		{
			return $this->revertWithCIServer($id);
		}
		else
		{
			return $this->revertWithGitHub($id);
		}
	}

	/**
	 * Reverts the specified pull request with CIServer options
	 *
	 * @param   integer  $id  ID of the pull request to revert
	 *
	 * @return  boolean
	 *
	 * @since   3.0
	 * @throws  \RuntimeException
	 */
	public function revertWithCIServer($id)
	{
		// Get the CIServer Registry
		$ciSettings = Helper::initializeCISettings();

		$testRecord = $this->getTestRecord($id);

		// Get PatchChain as array, remove any EOL set by php
		$patchChain = $this->getPatchChain(-1);

		// Allow only reverts in order of the patch chain
		if ($patchChain->insert_id != $id)
		{
			throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_NOT_IN_ORDER_OF_PATCHCHAIN', $patchChain->pull_id));
		}
		else
		{
			$this->removeLastChain($patchChain->insert_id);
		}

		// We don't want to restore files from an older version
		if ($testRecord->applied_version != JVERSION)
		{
			return $this->removeTest($testRecord);
		}

		$files = json_decode($testRecord->data);

		if (!$files)
		{
			throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_ERROR_READING_DATABASE_TABLE', __METHOD__, htmlentities($testRecord->data)));
		}

		$backupsPath = $ciSettings->get('folder.backups') . "/$testRecord->pull_id";

		foreach ($files as $file)
		{
			try
			{
				$filePath = explode("\\", $file);
				array_pop($filePath);
				$filePath = implode("\\", $filePath);

				// Delete file from root of it exists
				if (file_Exists(JPATH_ROOT . "/$file"))
				{
					File::delete(JPATH_ROOT . "/$file");

					// Move from backup, if it exists there
					if (file_exists("$backupsPath/$file"))
					{
						File::move("$backupsPath/$file", JPATH_ROOT . "/$file");
					}

					// If folder is empty, remove it as well
					if (count(glob(JPATH_ROOT . "/$filePath/*")) === 0)
					{
						Folder::delete(JPATH_ROOT . "/$filePath");
					}
				}
				// Move from backup, if file exists there - got deleted by patch
				elseif (file_exists("$backupsPath/$file"))
				{
					if (!file_exists(JPATH_ROOT . "/$filePath"))
					{
						Folder::create(JPATH_ROOT . "/$filePath");
					}

					File::move("$backupsPath/$file", JPATH_ROOT . "/$file");
				}
			}
			catch (\RuntimeException $e)
			{
				throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_FAILED_REVERT_PATCH', $file, $e->getMessage()));
			}
		}

		Folder::delete($backupsPath);

		// Change the media version
		$version = new Version;
		$version->refreshMediaVersion();

		return $this->removeTest($testRecord);
	}

	/**
	 * Reverts the specified pull request with Github Requests
	 *
	 * @param   integer  $id  ID of the pull request to revert
	 *
	 * @return  boolean
	 *
	 * @since   2.0
	 * @throws  \RuntimeException
	 */
	public function revertWithGitHub($id)
	{
		$testRecord = $this->getTestRecord($id);

		// We don't want to restore files from an older version
		if ($testRecord->applied_version != JVERSION)
		{
			return $this->removeTest($testRecord);
		}

		$files = json_decode($testRecord->data);

		if (!$files)
		{
			throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_ERROR_READING_DATABASE_TABLE', __METHOD__, htmlentities($testRecord->data)));
		}

		foreach ($files as $file)
		{
			switch ($file->action)
			{
				case 'deleted':
				case 'modified':
					$src  = JPATH_COMPONENT . '/backups/' . md5($file->filename) . '.txt';
					$dest = JPATH_ROOT . '/' . $file->filename;

					if (!File::copy($src, $dest))
					{
						throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_ERROR_CANNOT_COPY_FILE', $src, $dest));
					}

					if (file_exists($src))
					{
						if (!File::delete($src))
						{
							throw new \RuntimeException(
								Text::sprintf('COM_PATCHTESTER_ERROR_CANNOT_DELETE_FILE', $src)
							);
						}
					}

					break;

				case 'added':
					$src = JPATH_ROOT . '/' . $file->filename;

					if (file_exists($src))
					{
						if (!File::delete($src))
						{
							throw new \RuntimeException(
								Text::sprintf('COM_PATCHTESTER_ERROR_CANNOT_DELETE_FILE', $src)
							);
						}
					}

					break;

				case 'renamed':
					$originalSrc = JPATH_COMPONENT . '/backups/' . md5($file->originalFile) . '.txt';
					$newSrc      = JPATH_ROOT . '/' . $file->filename;
					$dest        = JPATH_ROOT . '/' . $file->originalFile;

					if (!File::copy($originalSrc, $dest))
					{
						throw new \RuntimeException(Text::sprintf('COM_PATCHTESTER_ERROR_CANNOT_COPY_FILE', $originalSrc, $dest));
					}

					if (file_exists($originalSrc))
					{
						if (!File::delete($originalSrc))
						{
							throw new \RuntimeException(
								Text::sprintf('COM_PATCHTESTER_ERROR_CANNOT_DELETE_FILE', $originalSrc)
							);
						}
					}

					if (file_exists($newSrc))
					{
						if (!File::delete($newSrc))
						{
							throw new \RuntimeException(
								Text::sprintf('COM_PATCHTESTER_ERROR_CANNOT_DELETE_FILE', $newSrc)
							);
						}
					}

					break;
			}
		}

		// Change the media version
		$version = new Version;
		$version->refreshMediaVersion();

		return $this->removeTest($testRecord);
	}

	/**
	 * Remove the database record for a test
	 *
	 * @param   stdClass  $testRecord  The record being deleted
	 *
	 * @return  boolean
	 *
	 * @since   3.0.0
	 */
	private function removeTest($testRecord)
	{
		$db = $this->getDb();

		// Remove the retrieved commit SHA from the pulls table for this item
		$db->setQuery(
			$db->getQuery(true)
				->update('#__patchtester_pulls')
				->set('sha = ' . $db->quote(''))
				->where($db->quoteName('id') . ' = ' . (int) $testRecord->id)
		)->execute();

		// And delete the record from the tests table
		$db->setQuery(
			$db->getQuery(true)
				->delete('#__patchtester_tests')
				->where('id = ' . (int) $testRecord->id)
		)->execute();

		return true;
	}

	/**
	 * Retrieves test data from database by specific id
	 *
	 * @param   integer  $id  ID of the record
	 *
	 * @return  stdClass  $testRecord  The record looking for
	 *
	 * @since   3.0.0
	 */
	private function getTestRecord($id)
	{
		$db = $this->getDb();

		return $db->setQuery(
			$db->getQuery(true)
				->select('*')
				->from('#__patchtester_tests')
				->where('id = ' . (int) $id)
		)->loadObject();
	}

	/**
	 * Retrieves a list of patches in chain
	 *
	 * @return  mixed
	 *
	 * @since   3.0
	 */
	private function getPatchChains()
	{
		$db = $this->getDb();

		$db->setQuery(
			$db->getQuery(true)
				->select('*')
				->from($db->quoteName('#__patchtester_chain'))
				->order('id DESC')
		);

		return $db->loadObjectList('pull_id');
	}

	/**
	 * Returns a chain by specific value, returns the last
	 * element on $id = -1 and the first on $id = null
	 *
	 * @param   integer  $id  specific id of a pull
	 *
	 * @return  stdClass  $chain  last chain of the table
	 *
	 * @since   3.0.0
	 */
	private function getPatchChain($id = null)
	{
		$db     = $this->getDb();

		$query  = $db->getQuery(true)
			->select('*')
			->from('#__patchtester_chain');

		if (!is_null($id) && $id !== -1)
		{
			$query = $query->where('insert_id =' . (int) $id);
		}

		if ($id === -1)
		{
			$query = $query->order('id DESC');
		}

		if (is_null($id))
		{
			$query = $query->order('id ASC');
		}

		return $db->setQuery($query, 0, 1)->loadObject();
	}

	/**
	 * Returns a two dimensional array with applied patches
	 * by the github or ci procedure
	 *
	 * @return  array   two-dimensional array with github patches
	 *                  and ci patches
	 *
	 * @since   3.0.0
	 */
	public function getPatchesDividedInProcs()
	{
		$db = $this->getDb();

		$appliedByGit = $db->setQuery(
			$db->getQuery(true)
				->select('tests.id, tests.pull_id')
				->from('#__patchtester_tests tests')
				->leftJoin('#__patchtester_chain chain', 'tests.id = chain.insert_id')
				->where('chain.insert_id IS NULL')
		)->loadObjectList('pull_id');

		$appliedByCI = $this->getPatchChains();

		return array('git' => $appliedByGit, 'ci' => $appliedByCI);
	}

	/**
	 * Adds a value to the patch chain in the database
	 *
	 * @param   integer  $insertId  ID of the patch in the database
	 * @param   integer  $pullId    ID of the pull request
	 *
	 * @return  integer  $insertId  last inserted element
	 *
	 * @since   3.0.0
	 */
	private function appendPatchChain($insertId, $pullId)
	{
		$record = (object) array(
			'insert_id'       => $insertId,
			'pull_id'         => $pullId,
		);

		$db = $this->getDb();

		$db->insertObject('#__patchtester_chain', $record);

		return $db->insertid();
	}

	/**
	 * Removes the last value of the chain
	 *
	 * @param   integer  $insertId  ID of the patch in the database
	 *
	 * @return  void
	 *
	 * @since   3.0.0
	 */
	private function removeLastChain($insertId)
	{
		$db = $this->getDb();

		$db->setQuery(
			$db->getQuery(true)
				->delete('#__patchtester_chain')
				->where('insert_id = ' . (int) $insertId)
		)->execute();
	}
}