<?php
/*****************************************************************************
 * Database.php
 * Contains key class Database.
 *
 * Adapted from SMF 2.0's DBA (C) 2011 Simple Machines
 * Used under BSD 3-clause license.
 *
 * Kabuki CMS (C) 2013-2015, Aaron van Geffen
 *****************************************************************************/

/**
 * The database model used to communicate with the MySQL server.
 */
class Database
{
	private $connection;
	private $query_count = 0;
	private $logged_queries = [];
	private array $db_callback;

	/**
	 * Initialises a new database connection.
	 * @param server: server to connect to.
	 * @param user: username to use for authentication.
	 * @param password: password to use for authentication.
	 * @param name: database to select.
	 */
	public function __construct($server, $user, $password, $name)
	{
		$this->connection = @mysqli_connect($server, $user, $password, $name);

		// Give up if we have a connection error.
		if (mysqli_connect_error())
		{
			header('HTTP/1.1 503 Service Temporarily Unavailable');
			echo '<h2>Database Connection Problems</h2><p>Our software could not connect to the database. We apologise for any inconvenience and ask you to check back later.</p>';
			exit;
		}

		$this->query('SET NAMES {string:utf8mb4}', ['utf8mb4' => 'utf8mb4']);
	}

	public function getQueryCount()
	{
		return $this->query_count;
	}

	public function getLoggedQueries()
	{
		return $this->logged_queries;
	}

	/**
	 * Fetches a row from a given recordset, using field names as keys.
	 */
	public function fetch_assoc($resource)
	{
		return mysqli_fetch_assoc($resource);
	}

	/**
	 * Fetches a row from a given recordset, using numeric keys.
	 */
	public function fetch_row($resource)
	{
		return mysqli_fetch_row($resource);
	}

	/**
	 * Destroys a given recordset.
	 */
	public function free_result($resource)
	{
		return mysqli_free_result($resource);
	}

	public function data_seek($result, $row_num)
	{
		return mysqli_data_seek($result, $row_num);
	}

	/**
	 * Returns the amount of rows in a given recordset.
	 */
	public function num_rows($resource)
	{
		return mysqli_num_rows($resource);
	}

	/**
	 * Returns the amount of fields in a given recordset.
	 */
	public function num_fields($resource)
	{
		return mysqli_num_fields($resource);
	}

	/**
	 * Escapes a string.
	 */
	public function escape_string($string)
	{
		return mysqli_real_escape_string($this->connection, $string);
	}

	/**
	 * Unescapes a string.
	 */
	public function unescape_string($string)
	{
		return stripslashes($string);
	}

	/**
	 * Returns the last MySQL error.
	 */
	public function error()
	{
		return mysqli_error($this->connection);
	}

	public function server_info()
	{
		return mysqli_get_server_info($this->connection);
	}

	/**
	 * Selects a database on a given connection.
	 */
	public function select_db($database)
	{
		return mysqli_select_db($database, $this->connection);
	}

	/**
	 * Returns the amount of rows affected by the previous query.
	 */
	public function affected_rows()
	{
		return mysqli_affected_rows($this->connection);
	}

	/**
	 * Returns the id of the row created by a previous query.
	 */
	public function insert_id()
	{
		return mysqli_insert_id($this->connection);
	}

	/**
	 * Do a MySQL transaction.
	 */
	public function transaction($operation = 'commit')
	{
		switch ($operation)
		{
				case 'begin':
				case 'rollback':
				case 'commit':
					return @mysqli_query($this->connection, strtoupper($operation));
			default:
				return false;
		}
	}

	/**
	 * Function used as a callback for the preg_match function that parses variables into database queries.
	 */
	private function replacement_callback($matches)
	{
		list ($values, $connection) = $this->db_callback;

		if (!isset($matches[2]))
			trigger_error('Invalid value inserted or no type specified.', E_USER_ERROR);

		if (!isset($values[$matches[2]]))
			trigger_error('The database value you\'re trying to insert does not exist: ' . htmlspecialchars($matches[2]), E_USER_ERROR);

		$replacement = $values[$matches[2]];

		switch ($matches[1])
		{
			case 'int':
				if ((!is_numeric($replacement) || (string) $replacement !== (string) (int) $replacement) && $replacement !== 'NULL')
					trigger_error('Wrong value type sent to the database for field: ' . $matches[2] . '. Integer expected.', E_USER_ERROR);
				return $replacement !== 'NULL' ? (string) (int) $replacement : 'NULL';
			break;

			case 'string':
			case 'text':
				return $replacement !== 'NULL' ? sprintf('\'%1$s\'', mysqli_real_escape_string($connection, $replacement)) : 'NULL';
			break;

			case 'array_int':
				if (is_array($replacement))
				{
					if (empty($replacement))
						trigger_error('Database error, given array of integer values is empty.', E_USER_ERROR);

					foreach ($replacement as $key => $value)
					{
						if (!is_numeric($value) || (string) $value !== (string) (int) $value)
							trigger_error('Wrong value type sent to the database for field: ' . $matches[2] . '. Array of integers expected.', E_USER_ERROR);

						$replacement[$key] = (string) (int) $value;
					}

					return implode(', ', $replacement);
				}
				else
					trigger_error('Wrong value type sent to the database for field: ' . $matches[2] . '. Array of integers expected.', E_USER_ERROR);

			break;

			case 'array_string':
				if (is_array($replacement))
				{
					if (empty($replacement))
						trigger_error('Database error, given array of string values is empty.', E_USER_ERROR);

					foreach ($replacement as $key => $value)
						$replacement[$key] = sprintf('\'%1$s\'', mysqli_real_escape_string($connection, $value));

					return implode(', ', $replacement);
				}
				else
					trigger_error('Wrong value type sent to the database for field: ' . $matches[2] . '. Array of strings expected.', E_USER_ERROR);
			break;

			case 'date':
				if (preg_match('~^(\d{4})-([0-1]?\d)-([0-3]?\d)$~', $replacement, $date_matches) === 1)
					return sprintf('\'%04d-%02d-%02d\'', $date_matches[1], $date_matches[2], $date_matches[3]);
				elseif ($replacement === 'NULL')
					return 'NULL';
				else
					trigger_error('Wrong value type sent to the database for field: ' . $matches[2] . '. Date expected.', E_USER_ERROR);
			break;

			case 'datetime':
				if (is_a($replacement, 'DateTime'))
					return $replacement->format('\'Y-m-d H:i:s\'');
				elseif (preg_match('~^(\d{4})-([0-1]?\d)-([0-3]?\d) (\d{2}):(\d{2}):(\d{2})$~', $replacement, $date_matches) === 1)
					return sprintf('\'%04d-%02d-%02d %02d:%02d:%02d\'', $date_matches[1], $date_matches[2], $date_matches[3], $date_matches[4], $date_matches[5], $date_matches[6]);
				elseif ($replacement === 'NULL')
					return 'NULL';
				else
					trigger_error('Wrong value type sent to the database for field: ' . $matches[2] . '. DateTime expected.', E_USER_ERROR);
			break;

			case 'float':
				if (!is_numeric($replacement) && $replacement !== 'NULL')
					trigger_error('Wrong value type sent to the database for field: ' . $matches[2] . '. Floating point number expected.', E_USER_ERROR);
				return $replacement !== 'NULL' ? (string) (float) $replacement : 'NULL';
			break;

			case 'identifier':
				// Backticks inside identifiers are supported as of MySQL 4.1. We don't need them here.
				return '`' . strtr($replacement, ['`' => '', '.' => '']) . '`';
			break;

			case 'raw':
				return $replacement;
			break;

			case 'bool':
			case 'boolean':
				// In mysql this is a synonym for tinyint(1)
				return (bool)$replacement ? 1 : 0;
			break;

			default:
				trigger_error('Undefined type <b>' . $matches[1] . '</b> used in the database query', E_USER_ERROR);
			break;
		}
	}

	/**
	 * Escapes and quotes a string using values passed, and executes the query.
	 */
	public function query($db_string, $db_values = [])
	{
		// One more query....
		$this->query_count ++;

		// Overriding security? This is evil!
		$security_override = $db_values === 'security_override' || !empty($db_values['security_override']);

		// Please, just use new style queries.
		if (strpos($db_string, '\'') !== false && !$security_override)
			trigger_error('Hack attempt!', 'Illegal character (\') used in query.', E_USER_ERROR);

		if (!$security_override && !empty($db_values))
		{
			// Set some values for use in the callback function.
			$this->db_callback = [$db_values, $this->connection];

			// Insert the values passed to this function.
			$db_string = preg_replace_callback('~{([a-z_]+)(?::([a-zA-Z0-9_-]+))?}~', [&$this, 'replacement_callback'], $db_string);

			// Save some memory.
			$this->db_callback = [];
		}

		if (defined("DB_LOG_QUERIES") && DB_LOG_QUERIES)
			$this->logged_queries[] = $db_string;

		try
		{
			$return = @mysqli_query($this->connection, $db_string, empty($this->unbuffered) ? MYSQLI_STORE_RESULT : MYSQLI_USE_RESULT);
		}
		catch (Exception $e)
		{
			$clean_sql = implode("\n", array_map('trim', explode("\n", $db_string)));
			trigger_error($this->error() . '<br>' . $clean_sql, E_USER_ERROR);
		}

		return $return;
	}

	/**
	 * Escapes and quotes a string just like db_query, but does not execute the query.
	 * Useful for debugging purposes.
	 */
	public function quote($db_string, $db_values = [])
	{
		// Please, just use new style queries.
		if (strpos($db_string, '\'') !== false)
			trigger_error('Hack attempt!', 'Illegal character (\') used in query.', E_USER_ERROR);

		// Save some values for use in the callback function.
		$this->db_callback = [$db_values, $this->connection];

		// Insert the values passed to this function.
		$db_string = preg_replace_callback('~{([a-z_]+)(?::([a-zA-Z0-9_-]+))?}~', [&$this, 'replacement_callback'], $db_string);

		// Save some memory.
		$this->db_callback = [];

		return $db_string;
	}

	/**
	 * Executes a query, returning an array of all the rows it returns.
	 */
	public function queryRow($db_string, $db_values = [])
	{
		$res = $this->query($db_string, $db_values);

		if (!$res || $this->num_rows($res) == 0)
			return [];

		$row = $this->fetch_row($res);
		$this->free_result($res);

		return $row;
	}

	/**
	 * Executes a query, returning an array of all the rows it returns.
	 */
	public function queryRows($db_string, $db_values = [])
	{
		$res = $this->query($db_string, $db_values);

		if (!$res || $this->num_rows($res) == 0)
			return [];

		$rows = [];
		while ($row = $this->fetch_row($res))
			$rows[] = $row;

		$this->free_result($res);

		return $rows;
	}

	/**
	 * Executes a query, returning an array of all the rows it returns.
	 */
	public function queryPair($db_string, $db_values = [])
	{
		$res = $this->query($db_string, $db_values);

		if (!$res || $this->num_rows($res) == 0)
			return [];

		$rows = [];
		while ($row = $this->fetch_row($res))
			$rows[$row[0]] = $row[1];

		$this->free_result($res);

		return $rows;
	}

	/**
	 * Executes a query, returning an array of all the rows it returns.
	 */
	public function queryPairs($db_string, $db_values = [])
	{
		$res = $this->query($db_string, $db_values);

		if (!$res || $this->num_rows($res) == 0)
			return [];

		$rows = [];
		while ($row = $this->fetch_assoc($res))
		{
			$key_value = reset($row);
			$rows[$key_value] = $row;
		}

		$this->free_result($res);

		return $rows;
	}

	/**
	 * Executes a query, returning an associative array of all the rows it returns.
	 */
	public function queryAssoc($db_string, $db_values = [])
	{
		$res = $this->query($db_string, $db_values);

		if (!$res || $this->num_rows($res) == 0)
			return [];

		$row = $this->fetch_assoc($res);
		$this->free_result($res);

		return $row;
	}

	/**
	 * Executes a query, returning an associative array of all the rows it returns.
	 */
	public function queryAssocs($db_string, $db_values = [], $connection = null)
	{
		$res = $this->query($db_string, $db_values);

		if (!$res || $this->num_rows($res) == 0)
			return [];

		$rows = [];
		while ($row = $this->fetch_assoc($res))
			$rows[] = $row;

		$this->free_result($res);

		return $rows;
	}

	/**
	 * Executes a query, returning the first value of the first row.
	 */
	public function queryValue($db_string, $db_values = [])
	{
		$res = $this->query($db_string, $db_values);

		// If this happens, you're doing it wrong.
		if (!$res || $this->num_rows($res) == 0)
			return null;

		list($value) = $this->fetch_row($res);
		$this->free_result($res);

		return $value;
	}

	/**
	 * Executes a query, returning an array of the first value of each row.
	 */
	public function queryValues($db_string, $db_values = [])
	{
		$res = $this->query($db_string, $db_values);

		if (!$res || $this->num_rows($res) == 0)
			return [];

		$rows = [];
		while ($row = $this->fetch_row($res))
			$rows[] = $row[0];

		$this->free_result($res);

		return $rows;
	}

	/**
	 * This function can be used to insert data into the database in a secure way.
	 */
	public function insert($method, $table, $columns, $data)
	{
		// With nothing to insert, simply return.
		if (empty($data))
			return;

		// Inserting data as a single row can be done as a single array.
		if (!is_array($data[array_rand($data)]))
			$data = [$data];

		// Create the mold for a single row insert.
		$insertData = '(';
		foreach ($columns as $columnName => $type)
		{
			// Are we restricting the length?
			if (strpos($type, 'string-') !== false)
				$insertData .= sprintf('SUBSTRING({string:%1$s}, 1, ' . substr($type, 7) . '), ', $columnName);
			else
				$insertData .= sprintf('{%1$s:%2$s}, ', $type, $columnName);
		}
		$insertData = substr($insertData, 0, -2) . ')';

		// Create an array consisting of only the columns.
		$indexed_columns = array_keys($columns);

		// Here's where the variables are injected to the query.
		$insertRows = [];
		foreach ($data as $dataRow)
			$insertRows[] = $this->quote($insertData, array_combine($indexed_columns, $dataRow));

		// Determine the method of insertion.
		$queryTitle = $method === 'replace' ? 'REPLACE' : ($method === 'ignore' ? 'INSERT IGNORE' : 'INSERT');

		// Do the insert.
		return $this->query('
			' . $queryTitle . ' INTO ' . $table . ' (`' . implode('`, `', $indexed_columns) . '`)
			VALUES
				' . implode(',
				', $insertRows),
			['security_override' => true]);
	}
}