<?php


class DB {

		private static $instance;
		private static $con;
		private static $customError;	
		private static $queryObject;	

		public static function init($host, $user, $pass, $db) {

			if(!isset(self::$instance)) {

				try {
					self::$instance = new PDO('mysql:host='.$host.';dbname='.$db, $user, $pass);
					//self::$instance->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
					self::$con = true;
				}
				catch (PDOException $e) {
					
					self::$customError = $e->getMessage();
					self::$con = false;
				}
			}
		}
		
		public static function isConnected() {
			
			return self::$con;	
		}
		
		public static function select($table, $columns = '*', $where = NULL, $limit = NULL, $column2return = NULL)
		{	
			$params = array();
			$sql = "SELECT ";
			
			if(is_array($columns))
			{
				for($i = 0; $i < count($columns); $i++)
				{
					$c = $columns[$i];
					$sql .= "`$c`";
					
					if($i != count($columns)-1)
					{
						$sql .= ", ";	
					}
				}
			}
			else
			{
				if($columns == '*')
				{
					$sql .= '*';	
				}
				else
				{
					$sql .= "`$columns`";	
				}
			}
			
			$sql .= " FROM `$table`";
			
			if($where != NULL)
			{
				//Check if there are WHERE parameters
				if(!is_array($where))
				{
					echo 'Error in DB::select function: \'where\' parameter must be Array';
					return false;
				}
				
				//If WHERE is two values, example: user_id, 1
				//Put them into array for for loop
				if(!is_array($where[0]) && count($where) == 2)
				{
					$where = array($where);	
				}	
				
				$sql .= " WHERE";
				
				for($i = 0; $i < count($where); $i++)
				{
					//This current website
					$w = $where[$i];
					
					//Only add if array
					if(is_array($w))
					{
						//column = value
						//Example: user_id = 19
						if(count($w) == 2)
						{
							$sql .= " `$w[0]` = ?";
							$params[] = $w[1];
						}
						//column operator value
						//array("user_age", ">", 18)
						//Example: user_age > 18
						else if(count($w) == 3)
						{
							$sql .= " `$w[0]` $w[1] = ?";
							$params[] = $w[2];	
						}
						
						//If not last item, append "AND" to query
						if($i != count($where)-1)
						{
							$sql = " AND";		
						}						
					}
				}
			}
			
			if($limit != NULL && is_int($limit))
			{
				$sql .= " LIMIT $limit";	
			}
			
			$results = self::query($sql, $params);
			
			if(count($results) == 1)
			{
				$results = $results[0];	
			}
			
			if($column2return != NULL)
			{
				if(is_array($column2return))
				{
					$arr = array();
					
					foreach($column2return as $col)
					{
						if(isset($results[$col]))
						{
							$arr[$col] = $results[$col];	
						}
					}
					
					return $arr;
				}
				else
				{
					return $results[$column2return];	
				}
			}
			else
			{
				return $results;
			}
		}

		public static function query($query, $params = array()) {
			
			try {
				$params = !is_array($params) ? array($params) : $params;
				$data = array();
				$is_select = strtoupper(substr($query,0,6)) == "SELECT" ? true : false;
				
				if(count($params) > 0) {
					
					$stmt = self::$instance->prepare($query);
					
					if(!$stmt)
					{
						return false;	
					}
					
					$stmt->execute($params);			
					self::$queryObject = $stmt;
					
					if($is_select)
						$data = $stmt->fetchAll(PDO::FETCH_ASSOC);
					else {
						$data = true;	
					}
					
					$stmt->closeCursor();
				}
				else {
	
					$res = self::$instance->query($query);
					self::$queryObject = $res;
	
					if(!$res)
					{					
						return false;	
					}
					else if($is_select)
					{
						foreach($res as $row)
							$data[] = $row;
					}
					else
					{
						$data = true;	
					}
				}
				
				self::$customError = "";
				
				return $data;
			}
			catch(Exception $e) {
				
				self::setError($e->getMessage());
				return false;	
			}
		}
		
		public static function getQueryObj()
		{
			return isset(self::$queryObject) ? self::$queryObject : false;	
		}
		
		public static function getError() {
			
			if(strlen(self::$customError) > 0)
			{
				return self::$customError;
			}
			else
			{
				$err = self::$instance->errorInfo();	
				return $err[count($err)-1];
			}
		}
		
		public static function setError($e) {
			
			self::$customError = $e;	
		}
	}