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package com.sun.grizzly.util.http;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import java.util.Date;

/**
 * Utility class used to generate HTML pages.
 *
 * @author Jean-Francois Arcand
 */
public class HtmlHelper{    
    
    private final static String CSS =
        "H1 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:22px;} " +
        "H2 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:16px;} " +
        "H3 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:14px;} " +
        "BODY {font-family:Tahoma,Arial,sans-serif;color:black;background-color:white;} " +
        "B {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;} " +
        "P {font-family:Tahoma,Arial,sans-serif;background:white;color:black;font-size:12px;}" +
        "A {color : black;}" +
        "HR {color : #525D76;}";

    /**
     * <code>CharBuffer</code> used to store the HTML response, containing
     * the headers and the body of the response.
     */
    private static CharBuffer reponseBuffer = CharBuffer.allocate(4096);
    

    /**
     * Encoder used to encode the HTML response
     */
    private static CharsetEncoder encoder =
                                          Charset.forName("UTF-8").newEncoder();

    /**
     * HTTP end line.
     */
    private static String NEWLINE = "\r\n";


    /**
     * HTTP OK header
     */
    public final static String OK = "HTTP/1.1 200 OK" + NEWLINE;
    

    /**
     * HTTP Bas Request
     */
    public final static String BAD_REQUEST 
        = "HTTP/1.1 400 Bad Request" + NEWLINE;
 
    
    /**
     * Return a defauk error page.
     *
     * @return A {@link ByteBuffer} containings the HTTP response.
     */
    public synchronized static ByteBuffer 
            getErrorPage(String message, String code, String serverName) throws IOException {
        String body = prepareBody(message,serverName);
        reponseBuffer.clear();
        reponseBuffer.put(body);
        reponseBuffer.flip();
        return encoder.encode(reponseBuffer);
    }

    
    /**
     * Utility to add headers to the HTTP response.
     */
    private static void appendHeaderValue(String name, String value) {
        reponseBuffer.put(name);
        reponseBuffer.put(": ");
        reponseBuffer.put(value);
        reponseBuffer.put(NEWLINE);
    }


    /**
     * Prepare the HTTP body containing the error messages.
     */
    private static String prepareBody(String message, String serverName){
        StringBuilder sb = new StringBuilder();

        sb.append("<html><head><title>");
        sb.append(serverName);
        sb.append("</title>");
        sb.append("<style><!--");
        sb.append(CSS);
        sb.append("--></style> ");
        sb.append("</head><body>");
        sb.append("<h1>");
        sb.append(message);
        sb.append("</h1>");
        sb.append("<HR size=\"1\" noshade>");
        sb.append("<h3>").append(serverName).append("</h3>");
        sb.append("</body></html>");
        return sb.toString();
    }

}