<?php

/**
 * @package ActiveRecord
 */

namespace ActiveRecord;

require_once 'Column.php';

use PDO;
use PDOException;
use Closure;

/**
 * The base class for database connection adapters.
 *
 * @package ActiveRecord
 */
abstract class Connection
{

	/**
	 * The DateTime format to use when translating other DateTime-compatible objects.
	 *
	 * NOTE!: The DateTime "format" used must not include a time-zone (name, abbreviation, etc) or offset.
	 * Including one will cause PHP to ignore the passed in time-zone in the 3rd argument.
	 * See bug: https://bugs.php.net/bug.php?id=61022
	 *
	 * @var string
	 */
	const DATETIME_TRANSLATE_FORMAT = 'Y-m-d\TH:i:s';

	/**
	 * The PDO connection object.
	 * @var mixed
	 */
	public $connection;
	/**
	 * The last query run.
	 * @var string
	 */
	public $last_query;
	/**
	 * Switch for logging.
	 *
	 * @var bool
	 */
	private $logging = false;
	/**
	 * Contains a Logger object that must impelement a log() method.
	 *
	 * @var object
	 */
	private $logger;
	/**
	 * The name of the protocol that is used.
	 * @var string
	 */
	public $protocol;
	/**
	 * Database's date format
	 * @var string
	 */
	static $date_format = 'Y-m-d';
	/**
	 * Database's datetime format
	 * @var string
	 */
	static $datetime_format = 'Y-m-d H:i:s T';
	/**
	 * Default PDO options to set for each connection.
	 * @var array
	 */
	static $PDO_OPTIONS = array(
		PDO::ATTR_CASE => PDO::CASE_LOWER,
		PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
		PDO::ATTR_ORACLE_NULLS => PDO::NULL_NATURAL,
		PDO::ATTR_STRINGIFY_FETCHES => false);
	/**
	 * The quote character for stuff like column and field names.
	 * @var string
	 */
	static $QUOTE_CHARACTER = '`';
	/**
	 * Default port.
	 * @var int
	 */
	static $DEFAULT_PORT = 0;

	/**
	 * Retrieve a database connection.
	 *
	 * @param string $connection_string_or_connection_name A database connection string (ex. mysql://user:pass@host[:port]/dbname)
	 *   Everything after the protocol:// part is specific to the connection adapter.
	 *   OR
	 *   A connection name that is set in ActiveRecord\Config
	 *   If null it will use the default connection specified by ActiveRecord\Config->set_default_connection
	 * @return Connection
	 * @see parse_connection_url
	 */
	public static function instance($connection_string_or_connection_name=null)
	{
		$config = Config::instance();

		if (strpos($connection_string_or_connection_name, '://') === false)
		{
			$connection_string = $connection_string_or_connection_name ?
				$config->get_connection($connection_string_or_connection_name) :
				$config->get_default_connection_string();
		}
		else
			$connection_string = $connection_string_or_connection_name;

		if (!$connection_string)
			throw new DatabaseException("Empty connection string");

		$info = static::parse_connection_url($connection_string);
		$fqclass = static::load_adapter_class($info->protocol);

		try {
			$connection = new $fqclass($info);
			$connection->protocol = $info->protocol;
			$connection->logging = $config->get_logging();
			$connection->logger = $connection->logging ? $config->get_logger() : null;

			if (isset($info->charset))
				$connection->set_encoding($info->charset);
		} catch (PDOException $e) {
			throw new DatabaseException($e);
		}
		return $connection;
	}

	/**
	 * Loads the specified class for an adapter.
	 *
	 * @param string $adapter Name of the adapter.
	 * @return string The full name of the class including namespace.
	 */
	private static function load_adapter_class($adapter)
	{
		$class = ucwords($adapter) . 'Adapter';
		$fqclass = 'ActiveRecord\\' . $class;
		$source = __DIR__ . "/adapters/$class.php";

		if (!file_exists($source))
			throw new DatabaseException("$fqclass not found!");

		require_once($source);
		return $fqclass;
	}

	/**
	 * Use this for any adapters that can take connection info in the form below
	 * to set the adapters connection info.
	 *
	 * <code>
	 * protocol://username:password@host[:port]/dbname
	 * protocol://urlencoded%20username:urlencoded%20password@host[:port]/dbname?decode=true
	 * protocol://username:password@unix(/some/file/path)/dbname
	 * </code>
	 *
	 * Sqlite has a special syntax, as it does not need a database name or user authentication:
	 *
	 * <code>
	 * sqlite://file.db
	 * sqlite://../relative/path/to/file.db
	 * sqlite://unix(/absolute/path/to/file.db)
	 * sqlite://windows(c%2A/absolute/path/to/file.db)
	 * </code>
	 *
	 * @param string $connection_url A connection URL
	 * @return object the parsed URL as an object.
	 */
	public static function parse_connection_url($connection_url)
	{
		$url = @parse_url($connection_url);

		if (!isset($url['host']))
			throw new DatabaseException('Database host must be specified in the connection string. If you want to specify an absolute filename, use e.g. sqlite://unix(/path/to/file)');

		$info = new \stdClass();
		$info->protocol = $url['scheme'];
		$info->host = $url['host'];
		$info->db = isset($url['path']) ? substr($url['path'], 1) : null;
		$info->user = isset($url['user']) ? $url['user'] : null;
		$info->pass = isset($url['pass']) ? $url['pass'] : null;

		$allow_blank_db = ($info->protocol == 'sqlite');

		if ($info->host == 'unix(')
		{
			$socket_database = $info->host . '/' . $info->db;

			if ($allow_blank_db)
				$unix_regex = '/^unix\((.+)\)\/?().*$/';
			else
				$unix_regex = '/^unix\((.+)\)\/(.+)$/';

			if (preg_match_all($unix_regex, $socket_database, $matches) > 0)
			{
				$info->host = $matches[1][0];
				$info->db = $matches[2][0];
			}
		} elseif (substr($info->host, 0, 8) == 'windows(')
		{
			$info->host = urldecode(substr($info->host, 8) . '/' . substr($info->db, 0, -1));
			$info->db = null;
		}

		if ($allow_blank_db && $info->db)
			$info->host .= '/' . $info->db;

		if (isset($url['port']))
			$info->port = $url['port'];

		if (strpos($connection_url, 'decode=true') !== false)
		{
			if ($info->user)
				$info->user = urldecode($info->user);

			if ($info->pass)
				$info->pass = urldecode($info->pass);
		}

		if (isset($url['query']))
		{
			foreach (explode('/&/', $url['query']) as $pair) {
				list($name, $value) = explode('=', $pair);

				if ($name == 'charset')
					$info->charset = $value;
			}
		}

		return $info;
	}

	/**
	 * Class Connection is a singleton. Access it via instance().
	 *
	 * @param array $info Array containing URL parts
	 * @return Connection
	 */
	protected function __construct($info)
	{
		try {
			// unix sockets start with a /
			if ($info->host[0] != '/')
			{
				$host = "host=$info->host";

				if (isset($info->port))
					$host .= ";port=$info->port";
			}
			else
				$host = "unix_socket=$info->host";

			$this->connection = new PDO("$info->protocol:$host;dbname=$info->db", $info->user, $info->pass, static::$PDO_OPTIONS);
		} catch (PDOException $e) {
			throw new DatabaseException($e);
		}
	}

	/**
	 * Retrieves column meta data for the specified table.
	 *
	 * @param string $table Name of a table
	 * @return array An array of {@link Column} objects.
	 */
	public function columns($table)
	{
		$columns = array();
		$sth = $this->query_column_info($table);

		while (($row = $sth->fetch())) {
			$c = $this->create_column($row);
			$columns[$c->name] = $c;
		}
		return $columns;
	}

	/**
	 * Escapes quotes in a string.
	 *
	 * @param string $string The string to be quoted.
	 * @return string The string with any quotes in it properly escaped.
	 */
	public function escape($string)
	{
		return $this->connection->quote($string);
	}

	/**
	 * Retrieve the insert id of the last model saved.
	 *
	 * @param string $sequence Optional name of a sequence to use
	 * @return int
	 */
	public function insert_id($sequence=null)
	{
		return $this->connection->lastInsertId($sequence);
	}

	/**
	 * Execute a raw SQL query on the database.
	 *
	 * @param string $sql Raw SQL string to execute.
	 * @param array &$values Optional array of bind values
	 * @return mixed A result set object
	 */
	public function query($sql, &$values=array())
	{
		if ($this->logging)
		{
			$this->logger->log($sql);
			if ( $values ) $this->logger->log($values);
		}

		$this->last_query = $sql;

		try {
			if (!($sth = $this->connection->prepare($sql)))
				throw new DatabaseException($this);
		} catch (PDOException $e) {
			throw new DatabaseException($this);
		}

		$sth->setFetchMode(PDO::FETCH_ASSOC);

		try {
			if (!$sth->execute($values))
				throw new DatabaseException($this);
		} catch (PDOException $e) {
			throw new DatabaseException($e);
		}
		return $sth;
	}

	/**
	 * Execute a query that returns maximum of one row with one field and return it.
	 *
	 * @param string $sql Raw SQL string to execute.
	 * @param array &$values Optional array of values to bind to the query.
	 * @return string
	 */
	public function query_and_fetch_one($sql, &$values=array())
	{
		$sth = $this->query($sql, $values);
		$row = $sth->fetch(PDO::FETCH_NUM);
		return $row[0];
	}

	/**
	 * Execute a raw SQL query and fetch the results.
	 *
	 * @param string $sql Raw SQL string to execute.
	 * @param Closure $handler Closure that will be passed the fetched results.
	 */
	public function query_and_fetch($sql, Closure $handler)
	{
		$sth = $this->query($sql);

		while (($row = $sth->fetch(PDO::FETCH_ASSOC)))
			$handler($row);
	}

	/**
	 * Returns all tables for the current database.
	 *
	 * @return array Array containing table names.
	 */
	public function tables()
	{
		$tables = array();
		$sth = $this->query_for_tables();

		while (($row = $sth->fetch(PDO::FETCH_NUM)))
			$tables[] = $row[0];

		return $tables;
	}

	/**
	 * Starts a transaction.
	 */
	public function transaction()
	{
		if (!$this->connection->beginTransaction())
			throw new DatabaseException($this);
	}

	/**
	 * Commits the current transaction.
	 */
	public function commit()
	{
		if (!$this->connection->commit())
			throw new DatabaseException($this);
	}

	/**
	 * Rollback a transaction.
	 */
	public function rollback()
	{
		if (!$this->connection->rollback())
			throw new DatabaseException($this);
	}

	/**
	 * Tells you if this adapter supports sequences or not.
	 *
	 * @return boolean
	 */
	function supports_sequences()
	{
		return false;
	}

	/**
	 * Return a default sequence name for the specified table.
	 *
	 * @param string $table Name of a table
	 * @param string $column_name Name of column sequence is for
	 * @return string sequence name or null if not supported.
	 */
	public function get_sequence_name($table, $column_name)
	{
		return "{$table}_seq";
	}

	/**
	 * Return SQL for getting the next value in a sequence.
	 *
	 * @param string $sequence_name Name of the sequence
	 * @return string
	 */
	public function next_sequence_value($sequence_name)
	{
		return null;
	}

	/**
	 * Quote a name like table names and field names.
	 *
	 * @param string $string String to quote.
	 * @return string
	 */
	public function quote_name($string)
	{
		return $string[0] === static::$QUOTE_CHARACTER || $string[strlen($string) - 1] === static::$QUOTE_CHARACTER ?
			$string : static::$QUOTE_CHARACTER . $string . static::$QUOTE_CHARACTER;
	}

	/**
	 * Return a date time formatted into the database's date format.
	 *
	 * @param DateTime $datetime The DateTime object
	 * @return string
	 */
	public function date_to_string($datetime)
	{
		return $datetime->format(static::$date_format);
	}

	/**
	 * Return a date time formatted into the database's datetime format.
	 *
	 * @param DateTime $datetime The DateTime object
	 * @return string
	 */
	public function datetime_to_string($datetime)
	{
		return $datetime->format(static::$datetime_format);
	}

	/**
	 * Converts a string representation of a datetime into a DateTime object.
	 *
	 * @param string $string A datetime in the form accepted by date_create()
	 * @return object The date_class set in Config
	 */
	public function string_to_datetime($string)
	{
		$date = date_create($string);
		$errors = \DateTime::getLastErrors();

		if ($errors['warning_count'] > 0 || $errors['error_count'] > 0)
			return null;

		$date_class = Config::instance()->get_date_class();

		return $date_class::createFromFormat(
			static::DATETIME_TRANSLATE_FORMAT,
			$date->format(static::DATETIME_TRANSLATE_FORMAT),
			$date->getTimezone()
		);
	}

	/**
	 * Adds a limit clause to the SQL query.
	 *
	 * @param string $sql The SQL statement.
	 * @param int $offset Row offset to start at.
	 * @param int $limit Maximum number of rows to return.
	 * @return string The SQL query that will limit results to specified parameters
	 */
	abstract function limit($sql, $offset, $limit);

	/**
	 * Query for column meta info and return statement handle.
	 *
	 * @param string $table Name of a table
	 * @return PDOStatement
	 */
	abstract public function query_column_info($table);

	/**
	 * Query for all tables in the current database. The result must only
	 * contain one column which has the name of the table.
	 *
	 * @return PDOStatement
	 */
	abstract function query_for_tables();

	/**
	 * Executes query to specify the character set for this connection.
	 */
	abstract function set_encoding($charset);

	/*
	 * Returns an array mapping of native database types
	 */

	abstract public function native_database_types();

	/**
	 * Specifies whether or not adapter can use LIMIT/ORDER clauses with DELETE & UPDATE operations
	 *
	 * @internal
	 * @returns boolean (FALSE by default)
	 */
	public function accepts_limit_and_order_for_update_and_delete()
	{
		return false;
	}

}
