<?php

class Author
{
    private $name;
    private $email;
    private $gender;

    private $genders  = ['m','f'];

    public function __construct($name, $email, $gender)
    {
        $this->name = $name;
        $this->setEmail($email);
        $this->setGender($gender);
    }

    public function __toString()
    {
        return sprintf('Author[name=%1$s,email=%2$s,gender=%3$s]', $this->name, $this->email, $this->gender);
    }

    /**
     * @return mixed
     */
    public function getName()
    {
        return $this->name;
    }

    /**
     * @return mixed
     */
    public function getEmail()
    {
        return $this->email;
    }

    /**
     * @param mixed $email
     */
    public function setEmail($email)
    {
        if (!$this->isValidEmail($email)){
            throw new InvalidArgumentException('Email is not valid');
        }
        $this->email = $email;
    }

    /**
     * @return mixed
     */
    public function getGender()
    {
        return $this->gender;
    }

    /**
     * @param mixed $gender
     */
    private function setGender($gender)
    {
        if(!$this->isValidGender($gender)){
            throw new InvalidArgumentException('Gender is not valid');
        }
        $this->gender = $gender;
    }

    private function isValidEmail($email) {
        return filter_var($email, FILTER_VALIDATE_EMAIL)
            && preg_match('/@.+\./', $email);
    }

    private function isValidGender($gender)
    {
        return in_array($gender,$this->genders, true);
    }
}

class Book
{
    private $name;
    private $author;
    private $qty;
    private $price;

    public function __construct($name, Author $author, $price, $qty = 0)
    {
        $this->name = $name;
        $this->author = $author;
        $this->setPrice($price);
        $this->setQty($qty);
    }

    public function __toString()
    {
        return
            sprintf('Book[name=%1$s,Author[name=%2$s,email=%3$s,gender=%4$s],price=%5$0.2f,qty=%6$d]',
            $this->name, $this->author->getName(),$this->author->getEmail(),$this->author->getGender(), $this->price, $this->qty);
    }

    /**
     * @return mixed
     */
    public function getName()
    {
        return $this->name;
    }

    /**
     * @return mixed
     */
    public function getAuthor()
    {
        return $this->author;
    }

    /**
     * @return mixed
     */
    public function getQty()
    {
        return $this->qty;
    }

    /**
     * @param mixed $qty
     */
    public function setQty($qty)
    {
        $this->qty = (int) $qty;
    }

    /**
     * @return mixed
     */
    public function getPrice()
    {
        return $this->price;
    }

    /**
     * @param mixed $price
     */
    public function setPrice($price)
    {
        if($price <= 0){
            throw new InvalidArgumentException('Price must be greater then zero');
        }

        $this->price = (float) $price;
    }
}