split parser and add tests

src/Demo/HeaderParser.php

@@ -0,0 +1,46 @@
+<?php declare(strict_types=1);
+
+namespace Demostf\API\Demo;
+
+class HeaderParser {
+	/**
+	 * @param string $head string containing the demo header binary data
+	 * @return Header
+	 * @throws \InvalidArgumentException
+	 */
+	public function parseString(string $head): Header {
+		$info = @unpack('A8type/Iversion/Iprotocol/A260server/A260nick/A260map/A260game/fduration/Vticks/Vframes/Vsigon',
+			$head);
+		if (!isset($info['type']) || $info['type'] !== 'HL2DEMO') {
+			throw new \InvalidArgumentException('Not an HL2 demo');
+		}
+		return new Header($info);
+	}
+
+	/**
+	 * Parse demo info from a stream
+	 *
+	 * @param resource $stream
+	 * @return Header
+	 * @throws \InvalidArgumentException
+	 */
+	public function parseStream($stream): Header {
+		$head = fread($stream, 2048);
+		return $this->parseString($head);
+	}
+
+	/**
+	 * Parse demo info from a local file
+	 *
+	 * @param string $path
+	 * @return Header
+	 * @throws \InvalidArgumentException
+	 */
+	public function parseHeader(string $path): Header {
+		if (!is_readable($path)) {
+			throw new \InvalidArgumentException('Unable to open demo: ' . $path);
+		}
+		$fh = fopen($path, 'rb');
+		return $this->parseStream($fh);
+	}
+}