package com.limegroup.gnutella.http;

import java.io.IOException;
import java.io.OutputStream;
import java.util.Locale;

/**
 * Type-safe enum for HTTP request methods, as specified in RFC 2616. The only
 * required methods for HTTP 1.1 compliance are GET and HEAD.
 */
public abstract class HTTPRequestMethod {

    /**
     * Constant for the name of the HTTP request method, in uppercase.
     */
    private final String METHOD_NAME;

    /**
     * Constructor creates a new <tt>HTTPRequestMethod</tt> with the specified
     * identifying string.
     * 
     * @param methodName the http request method as a string
     */
    private HTTPRequestMethod(String methodName) {
        // store the method name in upper case to make string
        // comparisons easier
        METHOD_NAME = methodName.toUpperCase(Locale.US);
    }

    public String getMethod() {
        return METHOD_NAME;
    }

    /**
     * Abstract method for writing the HTTP response based on the HTTP request
     * method.
     * 
     * @param response the <tt>HTTPMessage</tt> instance that handles writing
     *        the actual message
     * @param os the <tt>OutputStream</tt> to write to
     * @throws <tt>IOException</tt> if there was an IO error writing the
     *         response
     * @throws <tt>NullPointerException</tt> if either the <tt>response</tt> or
     *         the <tt>os</tt> arguments are <tt>null</tt>
     */
    public abstract void writeHttpResponse(HTTPMessage response, OutputStream os)
            throws IOException;

    /**
     * Constant for the "GET" request method.
     */
    public static final HTTPRequestMethod GET = new HTTPRequestMethod("GET") {
        @Override
        public void writeHttpResponse(HTTPMessage response, OutputStream os) throws IOException {
            if (response == null) {
                throw new NullPointerException("cannot write null response object");
            } else if (os == null) {
                throw new NullPointerException("cannot write to null output stream");
            }
            response.writeMessageHeaders(os);
            response.writeMessageBody(os);
            os.flush();
        }
    };

    /**
     * Constant for the "HEAD" request method.
     */
    public static final HTTPRequestMethod HEAD = new HTTPRequestMethod("HEAD") {
        @Override
        public void writeHttpResponse(HTTPMessage response, OutputStream os) throws IOException {
            if (response == null) {
                throw new NullPointerException("cannot write null response object");
            } else if (os == null) {
                throw new NullPointerException("cannot write to null output stream");
            }
            response.writeMessageHeaders(os);
            os.flush();
        }
    };

    // overrides Object.toString to report more information
    @Override
    public String toString() {
        return "HTTPRequestMethod: " + METHOD_NAME;
    }
}