<?php

namespace Machine\Memory;

use InvalidArgumentException;
use Program\Program;

class ProgramMemory
{
	/** @var Program[] */
	private array $memory = [];


	public function write(Program $program): void
	{
		$this->guardInvalidProgramNumber($program->N);
		$this->memory[$program->N] = $program;
	}


	public function read(int $N): ?Program
	{
		return @$this->memory[$N];
	}


	private function guardInvalidProgramNumber(int $N): void
	{
		if ($N > 9998 || $N < 9001) {
			throw new InvalidArgumentException('Program number must be in range 9001 - 9998');
		}
	}
}