<?php

class Db
{
    private $pdo = null;
    private static $instance = null;
    private static $sql_host = 'localhost';
    private static $sql_base = 'demo';
    private static $sql_user = 'root';
    private static $sql_password = 'root';

    private function __construct()
    {
        $options = [
            \PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES 'utf8'",
            \PDO::ATTR_DEFAULT_FETCH_MODE => \PDO::FETCH_ASSOC
        ];

        $this->pdo = new \PDO('mysql:host=' . self::$sql_host . ';dbname=' . self::$sql_base, self::$sql_user, self::$sql_password, $options);
    }

    public static function get()
    {
        if (is_null(self::$instance))
        {
            self::$instance = new self;
        }

        return self::$instance;
    }

    public function __call($method, $arguments)
    {
        if (method_exists($this->pdo, $method) === true)
        {
            return call_user_func_array([$this->pdo, $method], $arguments);
        }
    }
}

abstract class Entity
{
	public $fields = [];

	public $pk = 'id';

	public $table = '';

	public function all()
	{
		$query = "SELECT * FROM {$this->table} ORDER BY id DESC";
		$statement = Db::get()->query($query);

		return $statement->rowCount() > 0 ? $statement->fetchAll(PDO::FETCH_ASSOC) : false;
	}

	public function get($id)
	{
		$query = "SELECT * FROM {$this->table} WHERE {$this->pk} = $id LIMIT 1";
		$statement = Db::get()->query($query);

		return $statement->rowCount() == 1 ? $statement->fetch() : false;
	}

	public function add($data)
	{
		$cols = implode(',', array_keys($data));
		$query = "INSERT INTO {$this->table}($cols) VALUES (";

		foreach ($data as $key => $value) {
			if (in_array($key, $this->fields)) {
				$query .= ":$key,";
			}
		}

		reset($data);

		$query = substr($query, 0, -1);
		$query .= ")";

		$statement = Db::get()->prepare($query);

		foreach ($data as $key => $value) {
			if (in_array($key, $this->fields)) {
				$statement->bindValue(':'.$key, $value);
			}
		}

		$result = $statement->execute();

		return $result;
	}

	public function update($id, $data = [])
	{
		$query = "UPDATE {$this->table} SET ";

		foreach ($data as $key => $value) {
			if (in_array($key, $this->fields)) {
				$query .= "$key = :$key,";
			}
		}

		reset($data);

		$query = substr($query, 0, -1);
		$query .= " WHERE {$this->pk} = $id LIMIT 1";

		$statement = Db::get()->prepare($query);

		foreach ($data as $key => $value) {
			if (in_array($key, $this->fields)) {
				$statement->bindValue(':'.$key, $value);
			}
		}

		$result = $statement->execute();

		return $result;
	}

	public function delete($id)
	{
		$query = "DELETE FROM {$this->table} WHERE {$this->pk} = $id LIMIT 1";
		$result = Db::get()->exec($query);

		return $result;
	}

	public static function __callStatic($method, $args)
	{
		return (new static)->$method(...$args);
	}
}

class Post extends Entity
{
	public $fields = [
		'title',
		'content',
		'status'
	];

	public $table = 'posts';
}

//Post::add(['title' => 'Jean', 'content' => 'Marie']);
var_dump(Post::get(1));
//var_dump(Post::update(1, ['title' => 'Bar']));