<?php

namespace Program\Builder;

use Program\Block;
use Program\Program;
use Program\Word;
use RuntimeException;

class ProgramBuilder
{
	/**
	 * @param Word[] $words
	 * @return Program
	 */
	public function build(array $words): Program
	{
		$firstWord = array_shift($words);
		if (!preg_match('/^N9\d\d\d$/i', $firstWord)) {
			throw new RuntimeException('Expected program number (N9xxx), got ' . $firstWord);
		}

		$program = new Program($firstWord->value);

		$blockBuffer = null;
		while ($word = array_shift($words)) {
			if ($word->register === 'N') {
				if (!is_null($blockBuffer)) {
					$program->addBlock($blockBuffer);
				}
				$blockBuffer = new Block($word->value);
				continue;
			}
			$blockBuffer->addWord($word);
		}
		if (!is_null($blockBuffer)) {
			$program->addBlock($blockBuffer);
		}

		return $program;
	}
}