//******************************************************************************
//
// File:    HttpResponse.java
// Package: edu.rit.http
// Unit:    Class edu.rit.http.HttpResponse
//
// This Java source file is copyright (C) 2006 by Alan Kaminsky. All rights
// reserved. For further information, contact the author, Alan Kaminsky, at
// ark@cs.rit.edu.
//
// This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
// software; you can redistribute it and/or modify it under the terms of the GNU
// General Public License as published by the Free Software Foundation; either
// version 3 of the License, or (at your option) any later version.
//
// PJ is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
//
// Linking this library statically or dynamically with other modules is making a
// combined work based on this library. Thus, the terms and conditions of the
// GNU General Public License cover the whole combination.
//
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent modules, and
// to copy and distribute the resulting executable under terms of your choice,
// provided that you also meet, for each linked independent module, the terms
// and conditions of the license of that module. An independent module is a
// module which is not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the library, but
// you are not obligated to do so. If you do not wish to do so, delete this
// exception statement from your version.
//
// A copy of the GNU General Public License is provided in the file gpl.txt. You
// may also obtain a copy of the GNU General Public License on the World Wide
// Web at http://www.gnu.org/licenses/gpl.html.
//
//******************************************************************************

package edu.rit.http;

import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;

import java.net.Socket;

import java.nio.charset.Charset;

import java.util.HashMap;
import java.util.Map;

// For unit test main program
// import java.net.InetSocketAddress;
// import java.net.ServerSocket;

/**
 * Class HttpResponse encapsulates an HTTP response returned to a web browser.
 * <P>
 * Only HTTP/1.0 responses are supported. This means that only one HTTP response
 * message can be sent over the connection to the web browser; the connection is
 * closed after sending the HTTP response message.
 * <P>
 * To send an HTTP response message:
 * <OL TYPE=1>
 * <LI>
 * Create an instance of class HttpResponse, giving the socket object
 * representing the open connection to the web browser.
 * <BR>&nbsp;
 * <LI>
 * Call methods to set the status code and headers as necessary.
 * <BR>&nbsp;
 * <LI>
 * Call the <TT>getPrintWriter()</TT> method, and write the entity body to the
 * print writer that is returned.
 * <BR>&nbsp;
 * <LI>
 * Call the <TT>close()</TT> method.
 * </OL>
 *
 * @author  Alan Kaminsky
 * @version 29-Jul-2010
 */
public class HttpResponse
	{

// Exported enumerations.

	/**
	 * Enumeration HttpResponse.Status enumerates the status codes for an HTTP
	 * response message.
	 *
	 * @author  Alan Kaminsky
	 * @version 10-Oct-2006
	 */
	public static enum Status
		{
		/**
		 * The request has succeeded.
		 */
		STATUS_200_OK ("200 OK"),
		/**
		 * The request has been fulfilled and resulted in a new resource being
		 * created.
		 */
		STATUS_201_CREATED ("201 Created"),
		/**
		 * The request has been accepted for processing, but the processing has
		 * not been completed.
		 */
		STATUS_202_ACCEPTED ("202 Accepted"),
		/**
		 * The server has fulfilled the request but there is no new information
		 * to send back.
		 */
		STATUS_204_NO_CONTENT ("204 No content"),
		/**
		 * The requested resource has been assigned a new permanent URL and any
		 * future references to this resource should be done using that URL.
		 */
		STATUS_301_MOVED_PERMANENTLY ("301 Moved Permanently"),
		/**
		 * The requested resource resides temporarily under a different URL.
		 */
		STATUS_302_MOVED_TEMPORARILY ("302 Moved Temporarily"),
		/**
		 * If the client has performed a conditional GET request and access is
		 * allowed, but the document has not been modified since the date and
		 * time specified in the If-Modified-Since field, the server must
		 * respond with this status code and not send an Entity-Body to the
		 * client.
		 */
		STATUS_304_NOT_MODIFIED ("304 Not Modified"),
		/**
		 * The request could not be understood by the server due to malformed
		 * syntax.
		 */
		STATUS_400_BAD_REQUEST ("400 Bad Request"),
		/**
		 * The request requires user authentication.
		 */
		STATUS_401_UNAUTHORIZED ("401 Unauthorized"),
		/**
		 * The server understood the request, but is refusing to fulfill it.
		 */
		STATUS_403_FORBIDDEN ("403 Forbidden"),
		/**
		 * The server has not found anything matching the Request-URI.
		 */
		STATUS_404_NOT_FOUND ("404 Not Found"),
		/**
		 * The server encountered an unexpected condition which prevented it
		 * from fulfilling the request.
		 */
		STATUS_500_INTERNAL_SERVER_ERROR ("500 Internal Server Error"),
		/**
		 * The server does not support the functionality required to fulfill the
		 * request.
		 */
		STATUS_501_NOT_IMPLEMENTED ("501 Not Implemented"),
		/**
		 * The server, while acting as a gateway or proxy, received an invalid
		 * response from the upstream server it accessed in attempting to
		 * fulfill the request.
		 */
		STATUS_502_BAD_GATEWAY ("502 Bad Gateway"),
		/**
		 * The server is currently unable to handle the request due to a
		 * temporary overloading or maintenance of the server.
		 */
		STATUS_503_SERVICE_UNAVAILABLE ("503 Service Unavailable");

		private final String stringForm;

		/**
		 * Construct a new Status value.
		 *
		 * @param  stringForm  String form.
		 */
		Status
			(String stringForm)
			{
			this.stringForm = stringForm;
			}

		/**
		 * Returns a string version of this Status value.
		 *
		 * @return  String version.
		 */
		public String toString()
			{
			return stringForm;
			}
		}

// Hidden data members.

	private Socket mySocket;

	private Status myStatusCode = Status.STATUS_200_OK;
	private String myContentType = "text/html";
	private Charset myCharset = Charset.defaultCharset();

	private Map<String,String> myHeaderMap = new HashMap<String,String>();

	private PrintWriter myPrintWriter;

// Exported constructors.

	/**
	 * Construct a new HTTP response. The response is written to the output
	 * stream of the given socket.
	 *
	 * @param  theSocket  Socket.
	 *
	 * @exception  NullPointerException
	 *     (unchecked exception) Thrown if <TT>theSocket</TT> is null.
	 */
	public HttpResponse
		(Socket theSocket)
		{
		if (theSocket == null)
			{
			throw new NullPointerException
				("HttpResponse(): theSocket is null");
			}
		mySocket = theSocket;
		recordContentType();
		}

// Exported operations.

	/**
	 * Set this HTTP response's status code. If not set, the default status code
	 * is STATUS_200_OK.
	 *
	 * @param  theStatusCode  Status code.
	 *
	 * @exception  NullPointerException
	 *     (unchecked exception) Thrown if <TT>theStatusCode</TT> is null.
	 * @exception  IllegalStateException
	 *     (unchecked exception) Thrown if the HTTP response headers have
	 *     already been written to the socket output stream.
	 */
	public void setStatusCode
		(Status theStatusCode)
		{
		if (theStatusCode == null)
			{
			throw new NullPointerException
				("HttpResponse.setStatusCode(): theStatusCode is null");
			}
		if (myPrintWriter != null)
			{
			throw new IllegalStateException
				("HttpResponse.setStatusCode(): Headers already written");
			}
		myStatusCode = theStatusCode;
		}

	/**
	 * Set this HTTP response's content type. If not set, the default content
	 * type is <TT>"text/html"</TT>.
	 *
	 * @param  theContentType  Content type.
	 *
	 * @exception  NullPointerException
	 *     (unchecked exception) Thrown if <TT>theContentType</TT> is null.
	 * @exception  IllegalArgumentException
	 *     (unchecked exception) Thrown if <TT>theContentType</TT> is zero
	 *     length.
	 * @exception  IllegalStateException
	 *     (unchecked exception) Thrown if the HTTP response headers have
	 *     already been written to the socket output stream.
	 */
	public void setContentType
		(String theContentType)
		{
		if (theContentType == null)
			{
			throw new NullPointerException
				("HttpResponse.setContentType(): theContentType is null");
			}
		if (theContentType.length() == 0)
			{
			throw new IllegalArgumentException
				("HttpResponse.setContentType(): theContentType is zero length");
			}
		if (myPrintWriter != null)
			{
			throw new IllegalStateException
				("HttpResponse.setContentType(): Headers already written");
			}
		myContentType = theContentType;
		recordContentType();
		}

	/**
	 * Set this HTTP response's character set. If not set, the default character
	 * set is the platform default character set.
	 *
	 * @param  theCharset  Character set.
	 *
	 * @exception  NullPointerException
	 *     (unchecked exception) Thrown if <TT>theCharset</TT> is null.
	 * @exception  IllegalStateException
	 *     (unchecked exception) Thrown if the HTTP response headers have
	 *     already been written to the socket output stream.
	 */
	public void setCharset
		(Charset theCharset)
		{
		if (theCharset == null)
			{
			throw new NullPointerException
				("HttpResponse.setCharset(): theCharset is null");
			}
		if (myPrintWriter != null)
			{
			throw new IllegalStateException
				("HttpResponse.setCharset(): Headers already written");
			}
		myCharset = theCharset;
		recordContentType();
		}

	/**
	 * Set this HTTP response's content length. If not set, the default is to
	 * omit the Content-Length header; closing this HTTP response marks the end
	 * of the entity body.
	 *
	 * @param  theContentLength  Content length.
	 *
	 * @exception  IllegalArgumentException
	 *     (unchecked exception) Thrown if <TT>theContentLength</TT> is less
	 *     than 0.
	 * @exception  IllegalStateException
	 *     (unchecked exception) Thrown if the HTTP response headers have
	 *     already been written to the socket output stream.
	 */
	public void setContentLength
		(int theContentLength)
		{
		if (theContentLength < 0)
			{
			throw new IllegalArgumentException
				("HttpResponse.setContentLength(): theContentLength < 0");
			}
		if (myPrintWriter != null)
			{
			throw new IllegalStateException
				("HttpResponse.setContentLength(): Headers already written");
			}
		myHeaderMap.put ("Content-Length", ""+theContentLength);
		}

	/**
	 * Set the given header in this HTTP response.
	 *
	 * @param  theHeaderName   Header name.
	 * @param  theHeaderValue  Header value.
	 *
	 * @exception  NullPointerException
	 *     (unchecked exception) Thrown if <TT>theHeaderName</TT> or
	 *     <TT>theHeaderValue</TT> is null.
	 * @exception  IllegalArgumentException
	 *     (unchecked exception) Thrown if <TT>theHeaderName</TT> or
	 *     <TT>theHeaderValue</TT> is zero length.
	 * @exception  IllegalStateException
	 *     (unchecked exception) Thrown if the HTTP response headers have
	 *     already been written to the socket output stream.
	 */
	public void setHeader
		(String theHeaderName,
		 String theHeaderValue)
		{
		if (theHeaderName == null)
			{
			throw new NullPointerException
				("HttpResponse.setHeader(): theHeaderName is null");
			}
		if (theHeaderName.length() == 0)
			{
			throw new IllegalArgumentException
				("HttpResponse.setHeader(): theHeaderName is zero length");
			}
		if (theHeaderValue == null)
			{
			throw new NullPointerException
				("HttpResponse.setHeader(): theHeaderValue is null");
			}
		if (theHeaderValue.length() == 0)
			{
			throw new IllegalArgumentException
				("HttpResponse.setHeader(): theHeaderValue is zero length");
			}
		if (myPrintWriter != null)
			{
			throw new IllegalStateException
				("HttpResponse.setHeader(): Headers already written");
			}
		myHeaderMap.put (theHeaderName, theHeaderValue);
		}

	/**
	 * Obtain the print writer for writing the entity body to this HTTP
	 * response. As a side effect, the HTTP response headers are written to the
	 * socket output stream.
	 *
	 * @return  Print writer.
	 *
	 * @exception  IOException
	 *     Thrown if an I/O error occurred.
	 */
	public PrintWriter getPrintWriter()
		throws IOException
		{
		return writeHeaders();
		}

	/**
	 * Close this HTTP response. If necessary, the HTTP response headers are
	 * written to the socket output stream.
	 *
	 * @exception  IOException
	 *     Thrown if an I/O error occurred.
	 */
	public void close()
		throws IOException
		{
		writeHeaders();
		myPrintWriter.close();
		mySocket.close();
		}

// Hidden operations.

	/**
	 * Record the Content-Type header.
	 */
	private void recordContentType()
		{
		myHeaderMap.put
			("Content-Type",
			 myContentType + "; charset=" + myCharset);
		}

	/**
	 * Write the headers to the socket output stream if not already written, and
	 * return the print writer for writing to the socket output stream.
	 *
	 * @return  Print writer.
	 *
	 * @exception  IOException
	 *     Thrown if an I/O error occurred.
	 */
	private PrintWriter writeHeaders()
		throws IOException
		{
		if (myPrintWriter == null)
			{
			myPrintWriter =
				new PrintWriter
					(new OutputStreamWriter
						(mySocket.getOutputStream(),
						 myCharset));
			myPrintWriter.write ("HTTP/1.0 " + myStatusCode + "\r\n");
			for (Map.Entry<String,String> entry : myHeaderMap.entrySet())
				{
				myPrintWriter.write
					(entry.getKey() + ": " + entry.getValue() + "\r\n");
				}
			myPrintWriter.write ("\r\n");
			}
		return myPrintWriter;
		}

// Unit test main program.

//	/**
//	 * Unit test main program. The program listens for connections to
//	 * localhost:8080. The program reads each HTTP request from a web browser
//	 * and merely echoes the request data back to the browser.
//	 * <P>
//	 * Usage: java edu.rit.http.HttpResponse
//	 */
//	public static void main
//		(String[] args)
//		throws Exception
//		{
//		ServerSocket serversocket = new ServerSocket();
//		serversocket.bind (new InetSocketAddress ("localhost", 8080));
//		for (;;)
//			{
//			Socket socket = serversocket.accept();
//			HttpRequest request = new HttpRequest (socket);
//			HttpResponse response = new HttpResponse (socket);
//			if (request.isValid())
//				{
//				PrintWriter out = response.getPrintWriter();
//				out.println ("<HTML>");
//				out.println ("<HEAD>");
//				out.println ("</HEAD>");
//				out.println ("<BODY>");
//				out.println ("<UL>");
//				out.println ("<LI>");
//				out.print   ("Method = <TT>\"");
//				out.print   (request.getMethod());
//				out.println ("\"</TT>");
//				out.println ("<LI>");
//				out.print   ("URI = <TT>\"");
//				out.print   (request.getUri());
//				out.println ("\"</TT>");
//				out.println ("<LI>");
//				out.print   ("Version = <TT>\"");
//				out.print   (request.getHttpVersion());
//				out.println ("\"</TT>");
//				for (Map.Entry<String,String> entry : request.getHeaders())
//					{
//					out.println ("<LI>");
//					out.print   ("Header name = <TT>\"");
//					out.print   (entry.getKey());
//					out.print   ("\"</TT>, value = <TT>\"");
//					out.print   (entry.getValue());
//					out.println ("\"</TT>");
//					}
//				out.println ("</UL>");
//				out.println ("</BODY>");
//				out.println ("</HTML>");
//				}
//			else
//				{
//				response.setStatusCode (Status.STATUS_400_BAD_REQUEST);
//				PrintWriter out = response.getPrintWriter();
//				out.println ("<HTML>");
//				out.println ("<HEAD>");
//				out.println ("</HEAD>");
//				out.println ("<BODY>");
//				out.println ("<P>");
//				out.println ("400 Bad Request");
//				out.println ("<P>");
//				out.println ("You idiot.");
//				out.println ("</BODY>");
//				out.println ("</HTML>");
//				}
//			response.close();
//			}
//		}

	}