<?php

class ShoppingCart implements ArrayAccess, Iterator  {
	
	private $data = [];
		
	public function add(string $name, int $count = 1) {
		if (isset($this->data[$name])) {
			$this->data[$name] += $count;
		} else {
			$this->data[$name] = $count;
		}
	}
	
	public function remove(string $name) {
		if (!isset($this->data[$name])) {
			return;
		}
		unset($this->data[$name]);
	}
	
	public function __toString() {
		$lines = ['Content:'];
		foreach ($this->data as $name => $count) {
			$lines[] = "  $name : $count";
		}		
		$lines[] = '';
		return implode("\n", $lines);
	}
	
	// Exercise 2

	public function offsetExists($offset): bool {
		return isset($this->data[$offset]);
	}
	
	public function &offsetGet($offset) {
		return $this->data[$offset];
	}

	public function offsetSet($offset, $value): void {
		$this->data[$offset] = $value;
	}
	
	public function offsetUnset($offset): void {
		if (!isset($this->data[$offset])) {
			return;
		}
		unset($this->data[$offset]);
	}
	
	//

	public function current() {
		return current($this->data);
	}
	
	public function key() {
		return key($this->position);
	}
	
	public function next(){
		next($this->data);
	}
	
	public function rewind() {
		reset($this->data);		
	}
	
	public function valid() {
		return isset($this->data[$this->position]);
	}
	
}

// Exercise 3

interface Writer {
	public function write(ShoppingCart &$cart);
}

class JsonWriter implements Writer {
	public function write(ShoppingCart &$cart) {
		$content = [];
		foreach($cart as $key => $value) {
			$content[$key] = $value;
		}
		return json_encode($content);
	}
}

class StringWriter implements Writer {
	public function write(ShoppingCart &$cart) {
		return (string)$cart;
	}
}

function createWriter($name): Writer {
	$className = ucfirst($name)."Writer";
	return new $className();
}

// Exercise 1 

$cart = new ShoppingCart();
$cart->add('milk', 1);
$cart->add('bread', 1);
$cart->add('basil', 1);
$cart->add('milk', 1);
$cart->remove('basil');
print($cart);

// Exercise 2

print("Content:\n");
$cart['apple'] = 2;
++$cart['apple'];
foreach($cart as $name => $count) {
	print( "  $name : $count\n");
}

// Exercise 3

print("JSON\n");
print(createWriter("json")->write($cart));
print("\nSTRING\n");
print(createWriter("string")->write($cart));
print("\n");