/*
 *  Copyright (C) 2012 Roderick Baier
 *  
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *  
 *  	http://www.apache.org/licenses/LICENSE-2.0
 *  
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License. 
 */

package ibt.ortc.plugins.websocket;

import java.net.URI;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;

public class WebSocketHandshake
{
	private URI url = null;
	private String protocol = null;
	private String nonce = null;
	private Map<String, String> extraHeaders = null;
	
	
	public WebSocketHandshake(URI url, String protocol, Map<String, String> extraHeaders)
	{
		this.url = url;
		this.protocol = protocol;
		this.extraHeaders = extraHeaders;
		this.nonce = this.createNonce();
	}

	public byte[] getHandshake()
	{
		String path = url.getPath();
		String host = url.getHost();

		if (url.getPort() != -1) {
			host += ":" + url.getPort();
		}

		LinkedHashMap<String, String> header = new LinkedHashMap<String, String>();
		header.put("Host", host);
		header.put("Upgrade", "websocket");
		header.put("Connection", "Upgrade");
		header.put("Sec-WebSocket-Version", String.valueOf(WebSocket.getVersion()));
		header.put("Sec-WebSocket-Key", this.nonce);

		if (this.protocol != null) {
			header.put("Sec-WebSocket-Protocol", this.protocol);
		}

		if (this.extraHeaders != null) {
			for (String fieldName : this.extraHeaders.keySet()) {
				// Only checks for Field names with the exact same text,
				// but according to RFC 2616 (HTTP) field names are case-insensitive.
				if (!header.containsKey(fieldName)) {
					header.put(fieldName, this.extraHeaders.get(fieldName));
				}
			}
		}

		String handshake = "GET " + path + " HTTP/1.1\r\n";
		handshake += this.generateHeader(header);
		handshake += "\r\n";

		byte[] handshakeBytes = new byte[handshake.getBytes().length];
		System.arraycopy(handshake.getBytes(), 0, handshakeBytes, 0, handshake.getBytes().length);

		return handshakeBytes;
	}

	private String generateHeader(LinkedHashMap<String, String> headers)
	{
		String header = new String();
		for (String fieldName : headers.keySet()) {
			header += fieldName + ": " + headers.get(fieldName) + "\r\n";
		}
		return header;
	}

	private String createNonce()
	{
		byte[] nonce = new byte[16];
		for (int i = 0; i < 16; i++) {
			nonce[i] = (byte) rand(0, 255);
		}
		return Base64.encodeBytes(nonce);
	}

	public void verifyServerStatusLine(String statusLine)
			throws WebSocketException
	{
		int statusCode = Integer.valueOf(statusLine.substring(9, 12));

		if (statusCode == 407) {
			throw new WebSocketException("connection failed: proxy authentication not supported");
		} else if (statusCode == 404) {
			throw new WebSocketException("connection failed: 404 not found");
		} else if (statusCode != 101) {
			throw new WebSocketException("connection failed: unknown status code " + statusCode);
		}
	}

	public void verifyServerHandshakeHeaders(HashMap<String, String> headers)
			throws WebSocketException
	{
		if (!headers.get("Upgrade").toLowerCase().equals("websocket")) {
			throw new WebSocketException("connection failed: missing header field in server handshake: Upgrade");
		} else if (!headers.get("Connection").equals("Upgrade")) {
			throw new WebSocketException("connection failed: missing header field in server handshake: Connection");
		}
	}

	private int rand(int min, int max)
	{
		int rand = (int) (Math.random() * max + min);
		return rand;
	}
}
