<?php
/**
 * @copyright Copyright (C) 2010-2022, the Friendica project
 *
 * @license GNU AGPL version 3 or any later version
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 */

namespace Friendica\Database;

use Exception;
use Friendica\Core\Hook;
use Friendica\DI;

class View
{
	/**
	 * view definition loaded from static/dbview.config.php
	 *
	 * @var array
	 */
	private static $definition = [];

	/**
	 * Loads the database structure definition from the static/dbview.config.php file.
	 * On first pass, defines DB_UPDATE_VERSION constant.
	 *
	 * @see static/dbview.config.php
	 * @param string  $basePath              The base path of this application
	 * @param boolean $with_addons_structure Whether to tack on addons additional tables
	 * @return array
	 * @throws Exception
	 */
	public static function definition(string $basePath = '', bool $with_addons_structure = true): array
	{
		if (!self::$definition) {
			if (empty($basePath)) {
				$basePath = DI::app()->getBasePath();
			}

			$filename = $basePath . '/static/dbview.config.php';

			if (!is_readable($filename)) {
				throw new Exception('Missing database view config file static/dbview.config.php');
			}

			$definition = require $filename;

			if (!$definition) {
				throw new Exception('Corrupted database view config file static/dbview.config.php');
			}

			self::$definition = $definition;
		} else {
			$definition = self::$definition;
		}

		if ($with_addons_structure) {
			Hook::callAll('dbview_definition', $definition);
		}

		return $definition;
	}

	/**
	 * Creates a view
	 *
	 * @param bool $verbose Whether to show SQL statements
	 * @param bool $action Whether to execute SQL statements
	 * @return void
	 */
	public static function create(bool $verbose, bool $action)
	{
		// Delete previously used views that aren't used anymore
		foreach(['post-view', 'post-thread-view'] as $view) {
			if (self::isView($view)) {
				$sql = sprintf("DROP VIEW IF EXISTS `%s`", DBA::escape($view));
				if (!empty($sql) && $verbose) {
					echo $sql . ";\n";
				}
		
				if (!empty($sql) && $action) {
					DBA::e($sql);
				}
			}
		}

		$definition = self::definition();

		foreach ($definition as $name => $structure) {
			self::createView($name, $structure, $verbose, $action);
		}
	}

	/**
	 * Prints view structure
	 *
	 * @param string $basePath Base path
	 * @return void
	 */
	public static function printStructure(string $basePath)
	{
		$database = self::definition($basePath, false);

		foreach ($database as $name => $structure) {
			echo "--\n";
			echo "-- VIEW $name\n";
			echo "--\n";
			self::createView($name, $structure, true, false);

			echo "\n";
		}
	}

	/**
	 * Creates view
	 *
	 * @param string $name Name of view
	 * @param array $structure Structure of view
	 * @param bool $verbose Whether to show SQL statements
	 * @param bool $action Whether to execute SQL statements
	 * @return bool Whether execution went fine
	 */
	private static function createView(string $name, array $structure, bool $verbose, bool $action): bool
	{
		$r = true;

		$sql_rows = [];
		foreach ($structure['fields'] as $fieldname => $origin) {
			if (is_string($origin)) {
				$sql_rows[] = $origin . " AS `" . DBA::escape($fieldname) . "`";
			} elseif (is_array($origin) && (sizeof($origin) == 2)) {
				$sql_rows[] = "`" . DBA::escape($origin[0]) . "`.`" . DBA::escape($origin[1]) . "` AS `" . DBA::escape($fieldname) . "`";
			}
		}

		if (self::isView($name)) {
			$sql = sprintf("DROP VIEW IF EXISTS `%s`", DBA::escape($name));
		} elseif (self::isTable($name)) {
			$sql = sprintf("DROP TABLE IF EXISTS `%s`", DBA::escape($name));
		}

		if (!empty($sql) && $verbose) {
			echo $sql . ";\n";
		}

		if (!empty($sql) && $action) {
			DBA::e($sql);
		}

		$sql = sprintf("CREATE VIEW `%s` AS SELECT \n\t", DBA::escape($name)) .
			implode(",\n\t", $sql_rows) . "\n\t" . $structure['query'];
	
		if ($verbose) {
			echo $sql . ";\n";
		}

		if ($action) {
			$r = DBA::e($sql);
		}

		return $r;
	}

	/**
	 * Check if the given table/view is a view
	 *
	 * @param string $view
	 * @return boolean "true" if it's a view
	 */
	private static function isView(string $view): bool
	{
		$status = DBA::selectFirst('INFORMATION_SCHEMA.TABLES', ['TABLE_TYPE'],
			['TABLE_SCHEMA' => DBA::databaseName(), 'TABLE_NAME' => $view]);

		if (empty($status['TABLE_TYPE'])) {
			return false;
		}

		return $status['TABLE_TYPE'] == 'VIEW';
	}

	/**
	 * Check if the given table/view is a table
	 *
	 * @param string $table
	 * @return boolean "true" if it's a table
	 */
	private static function isTable(string $table): bool
	{
		$status = DBA::selectFirst('INFORMATION_SCHEMA.TABLES', ['TABLE_TYPE'],
			['TABLE_SCHEMA' => DBA::databaseName(), 'TABLE_NAME' => $table]);

		if (empty($status['TABLE_TYPE'])) {
			return false;
		}

		return $status['TABLE_TYPE'] == 'BASE TABLE';
	}
}