<?php
	require_once('sql.class.php');
	abstract class ORM implements ArrayAccess, JsonSerializable {
		// Model definition
		protected static $primary_key = 'id';
		protected static $foreign_key_suffix = '_id';
		protected static $has_one = [];
		protected static $has_many = [];
		protected static $belongs_to = [];
		// Data tracking
		private $_data = [];
		private $_changed = [];
		private $_related = [];
		private static $aliases = [];
		private static $instances = [];
		private static $sql;
		protected static $name = null;
		// Magic functions
		private function __construct($idOrData){
			if(!isset(self::$aliases[$this->name])){
				foreach(static::$belongs_to as $alias => $details){
					self::$aliases[$this->name]['belongs_to'][$alias] = array_merge(
						[
							'model'=>$alias,
							'foreign_key'=>$alias.static::$foreign_key_suffix
						],
						$details
					);
				}
				foreach(static::$has_one as $alias => $details){
					self::$aliases[$this->name]['has_one'][$alias] = array_merge(
						[
							'model'=>$alias,
							'foreign_key'=>$alias.static::$foreign_key_suffix
						],
						$details
					);
				}
				foreach(static::$has_many as $alias => $details){
					self::$aliases[$this->name]['has_many'][$alias] = array_merge(
						[
							'model'=>$alias,
							'foreign_key'=>$alias.static::$foreign_key_suffix,
							'through'=> null
						],
						$details
					);
				}
			}
			// Clear relationship definitions to save memory
			static::$belongs_to = static::$has_one = static::$has_many =null;
			if(is_array($idOrData)){
				if(isset($idOrData[static::$primary_key]) && self::cached($idOrData[static::$primary_key])){
					throw new Exception('Instance already cached');
				}
				foreach($idOrData as $key => $val){
					$this->_data[$key] = $val;
				}
			}else{
				if(self::cached($idOrData)){
					throw new Exception('Instance already cached');
				}
				$this->_data[static::$primary_key] = (int)$idOrData;
			}
			self::$instances[] = $this;
		}
		private function __destruct(){
			$this->__sleep();
			$this->_changed = [];
			$this->_data = [];
			$this->_related = [];
			$key = array_search(self::$instances, $this);
			if($key !== false){
				array_splice(self::$instances, $key, 1);
			}
		}
		public function __get(string $name){
			switch($name){
				case 'name':
					return static::name();
				break;
				case 'id':
					return $this->get(static::$primary_key);
				break;
				default:
					throw new Exception('Unknown property '.$name);
			}
		}
		public function __set(string $name, $val){
			switch($name){
				case 'id':case 'name':
					throw new Exception('Property '.$name.' is read only');
				break;
				default:
					throw new Exception('Unknown property '.$name);
			}
		}
		public function __sleep(){
			$this->save();
		}
		public function __wakeup(){
			$this->reload(true);
		}
		public function __toString(){
			return $this->name.'('.$this->id.')';
		}
		public function __invoke(){
			return $this->_data;
		}
		public function __clone(){
			unset($this->$_data[static::$primary_key]);
		}
		// JsonSerializable
		public function jsonSerialize(){
			return $this->_data;
		}
		// ArrayAccess
		public function offsetSet($key, $val){
			$this->set($key, $val);
		}
		public function offsetExists($key){
			return $this->has($key);
		}
		public function offsetUnset($key){
			return $this->unset($key);
		}
		public function offsetGet($key){
			return $this->get($key);
		}
		// Main API
		public static function name(){
			if(is_null(static::$name)){
				$name = get_called_class();
				static::$name = substr($name, strrpos($name, '\\') + 1);
			}
			return static::$name;
		}
		public static function bind(SQL $sql){
			self::$sql = $sql;
			// @todo handle updating live instances
		}
		public static function query(...$args){
			return self::$sql->query(...$args);
		}
		public static function instance(int $id){
			$instance = self::cached_instance($id);
			if(!is_null($instance)){
				return $instance;
			}elseif(self::exists($id)){
				return new static($id);
			}
			return null;
		}
		public static function exists(int $id){
			return (int)self::query(
				"select count(1) as count ".
				"from ".static::name().' '.
				"where ".static::$primary_key." = ?",
				'i',
				$id
			)->assoc_result["count"] > 0;
		}
		public static function cached_instance(int $id){
			$name = static::name();
			if(isset(self::$instances[$name])){
				$instances = array_filter(self::$instances[$name], function(&$instance){
					return $instance->id === $id;
				});
				return isset($instances[0]) ? $instances[0] : null;
			}
			return null;
		}
		public static function cached(int $id){
			return !is_null(self::cached_instance($id));
		}
		public static function delete(int $id){
			$query = self::query(
				"delete from ".static::name().' '.
				"where ".static::$primary_key." = ?",
				'i',
				$id
			);
			return $query->execute() && $query->affected_rows > 0;
		}
		public static function each_cached(callable $fn){
			$name = static::name();
			if(self::$instances[$name]){
				array_walk(self::$instances[$name], $fn);
			}
		}
		public static function each_where(callable $fn, array $filter = null, int $start = null, int $amount = null){
			$limit = ' ';
			if(!is_null($start) && !is_null($amount)){
				$limit .= "limit {$start}, {$amount}";
			}
			$where = ' ';
			$types = null;
			$bindings = null;
			if(!is_null($filter)){
				$types = '';
				$bindings = array();
				foreach($filter as $key => $val){
					if(is_string($val)){
						$types .= 's';
					}elseif(is_double($val)){
						$types .= 'd';
					}elseif(is_int($val)){
						$types .= 'i';
					}else{
						throw new Exception("Unknown data type");
					}
					$where .= 'and {$key} = ? ';
					$bindings[] = $val;
				}
				$where = self::str_replace_first(' and ', ' ', $where);
			}
			self::query(
				"select ".static::$primary_key.' id '.
				"from ".static::name().
				$where.
				$limit,
				$types,
				$bindings
			)->each_assoc(function($row) use($fn){
				$fn(self::instance((int)$row['id']));
			});
		}
		public static function each(callable $fn, int $start = null, int $amount = null){
			self::each_where($fn, null, $start, $amount);
		}
		public static function fetch(array $filter = null, int $start = null, int $amount = null){
			$results = [];
			self::each_where(function($item) use($results){
				$results[] = $item;
			}, $filter, $start, $amount);
			return $results;
		}
		public static function str_replace_first($search, $replace, $source) {
			$explode = explode($search, $source);
			$shift = array_shift($explode);
			$implode = implode($search, $explode);
			return $shift.$replace.$implode;
		}
		// Instance Api
		public function values($values){
			foreach($values as $key => $val){
				$this->set($key, $val);
			}
			return $this;
		}
		public function load(bool $force = false){
			if(!$force && $this->dirty()){
				throw new Exception('Cannot load, there are pending changes');
			}else{
				if(!is_null($this->id)){
					$data = self::query(
						"select * " .
						"from {$this->name} ".
						"where ".static::$primary_key." = ?",
						'i',
						$this->id
					)->assoc_result;
					if($data === false){
						throw new Exception("{$this->name} with ".static::$primary_key." of {$this->id} does not exist");
					}
					$this->_data = $data;
				}
			}
			return $this;
		}
		public function save(){
			if($this->dirty()){
				$data = [];
				$set = "set ";
				$types = '';
				foreach($this->_changed as $key){
					if(isset($this->_data[$key]) || is_null($this->_data[$key])){
						$data[$key] = $this->_data[$key];
					}else{
						$set .= "{$key} = null";
					}
				}
				foreach($data as $key => $val){
					if(is_string($val)){
						$types .= 's';
					}elseif(is_double($val)){
						$types .= 'd';
					}elseif(is_int($val)){
						$types .= 'i';
					}else{
						throw new Exception('Unknown data type');
					}
					$set .= "{$key} = ? ";
				}
				if(!is_null($this->id) && !in_array(static::$primary_key, $this->_changed)){
					$data = array_merge(array_values($data), [$this->id]);
					self::query(
						"update {$this->name} {$set} where ".static::$primary_key." = ?",
						$types.'i',
						$data
					)->execute();
				}else{
					self::query(
						"insert {$this->name} {$set}"
					)->execute();
					$this->_data[static::$primary_key] = self::$sql->insert_id;
				}
			}
			// Always fetch again from the database in case saving
			// forces something to change at the database level
			return $this->reload(true);
		}
		public function reload(bool $force = false){
			if($force){
				$this->_changed = [];
			}
			return $this->load($force);
		}
		public function clear(){
			return $this->reload(true);
		}
		public function get($key){
			return $this->_data[$key];
		}
		public function set($key, $val){
			if($key === static::$primary_key && !is_null($this->id)){
				throw new Exception('You are not allowed to change the primary key');
			}
			$this->_data[$key] = $val;
			$this->_changed = array_merge($this->_changed, [$key]);
			return $this;
		}
		public function unset($key){
			unset($this->_data[$key]);
			return $this;
		}
		public function has($key){
			return isset($this->_data[$key]);
		}
		public function dirty(string $key = null){
			if(is_null($key)){
				return count($this->_changed) > 0;
			}else{
				return in_array($key, $this->_changed);
			}
		}
		public function related(string $name){
			if(isset($this->_related[$name])){
				return $this->_related[$name];
			}else{
				$class = "Model\\{$name}";
				if(self::$aliases['belongs_to'][$name]){
					$this->_related[$name] = $class::fetch([static::$foreign_key => $this->id]);
				}elseif(self::$aliases['has_one'][$name]){
					$this->_related[$name] = $class::fetch([$this->name.static::$foreign_key_suffix => $this->id]);
				}elseif(self::$aliases['has_many'][$name]){
					//$this->_related[$name] = $class::fetch([$this->name.static::$foreign_key_suffix => $this->id]);
					throw new Exception("has_many relationships are not implemented yet");
				}
			}
			if(isset($this->_related[$name])){
				return $this->_related[$name];
			}else{
				throw new Exception("Relationship {$name} does not exist");
			}
		}
	}
?>