/*
 * @(#)URLStreamHandler.java	1.43 01/04/21
 *
 * Copyright 1995-2001 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the proprietary information of Sun Microsystems, Inc.  
 * Use is subject to license terms.
 * 
 */

package java.net;

import java.io.IOException;
import java.io.InputStream;
import java.io.File;
import java.io.OutputStream;
import java.util.Hashtable;

/**
 * The abstract class <code>URLStreamHandler</code> is the common
 * superclass for all stream protocol handlers. A stream protocol
 * handler knows how to make a connection for a particular protocol
 * type, such as <code>http</code>, <code>ftp</code>, or
 * <code>gopher</code>.
 * <p>
 * In most cases, an instance of a <code>URLStreamHandler</code>
 * subclass is not created directly by an application. Rather, the
 * first time a protocol name is encountered when constructing a
 * <code>URL</code>, the appropriate stream protocol handler is
 * automatically loaded.
 *
 * @author  James Gosling
 * @version 1.43, 04/21/01
 * @see     java.net.URL#URL(java.lang.String, java.lang.String, int, java.lang.String)
 * @since   JDK1.0
 */
public abstract class URLStreamHandler {
    /**
     * Opens a connection to the object referenced by the
     * <code>URL</code> argument.
     * This method should be overridden by a subclass.
     *
     * <p>If for the handler's protocol (such as HTTP or JAR), there
     * exists a public, specialized URLConnection subclass belonging
     * to one of the following packages or one of their subpackages:
     * java.lang, java.io, java.util, java.net, the connection
     * returned will be of that subclass. For example, for HTTP an
     * HttpURLConnection will be returned, and for JAR a
     * JarURLConnection will be returned.
     *
     * @param      u   the URL that this connects to.
     * @return     a <code>URLConnection</code> object for the <code>URL</code>.
     * @exception  IOException  if an I/O error occurs while opening the
     *               connection.
     */
    abstract protected URLConnection openConnection(URL u) throws IOException;

    /**
     * Parses the string representation of a <code>URL</code> into a
     * <code>URL</code> object.
     * <p>
     * If there is any inherited context, then it has already been
     * copied into the <code>URL</code> argument.
     * <p>
     * The <code>parseURL</code> method of <code>URLStreamHandler</code>
     * parses the string representation as if it were an
     * <code>http</code> specification. Most URL protocol families have a
     * similar parsing. A stream protocol handler for a protocol that has
     * a different syntax must override this routine.
     *
     * @param   u       the <code>URL</code> to receive the result of parsing
     *                  the spec.
     * @param   spec    the <code>String</code> representing the URL that
     *                  must be parsed.
     * @param   start   the character index at which to begin parsing. This is
     *                  just past the '<code>:</code>' (if there is one) that
     *                  specifies the determination of the protocol name.
     * @param   limit   the character position to stop parsing at. This is the
     *                  end of the string or the position of the
     *                  "<code>#</code>" character, if present. All information
     *                  after the sharp sign indicates an anchor.
     */
    protected void parseURL(URL u, String spec, int start, int limit) {
        // These fields may receive context content if this was relative URL
        String protocol = u.getProtocol();
        String authority = u.getAuthority(); 
        String userInfo = u.getUserInfo();
        String host = u.getHost();
        int port = u.getPort();
        String file = u.getFile();

        // This field has already been parsed
        String ref = u.getRef();

        // These fields will not inherit context content
        String query = null;

	boolean isRelPath = false;
	boolean queryOnly = false;

// FIX: should not assume query if opaque
        // Strip off the query part
	if (start < limit) {
            int queryStart = spec.indexOf('?');
            queryOnly = queryStart == start;
            if (queryStart != -1) {
                query = spec.substring(queryStart+1, limit);
                if (limit > queryStart)
                    limit = queryStart;
                spec = spec.substring(0, queryStart);
            }
	}

	int i = 0;
        // Parse the authority part if any
	if ((start <= limit - 2) && (spec.charAt(start) == '/') &&
	    (spec.charAt(start + 1) == '/')) {
	    start += 2;
	    i = spec.indexOf('/', start);
            if (i < 0) {
	        i = spec.indexOf('?', start);
		if (i < 0)
                    i = limit;
	    }

            host = authority = spec.substring(start, i);
            int ind = authority.indexOf('@');
            if (ind != -1) {
                userInfo = authority.substring(0, ind);
                host = authority.substring(ind+1);
	    }
            ind = host.indexOf(':');
	    port = -1;
	    if (ind >= 0) {
		// port can be null according to RFC2396
		if (host.length() > (ind + 1)) {
		    port = Integer.parseInt(host.substring(ind + 1));
		}
		host = host.substring(0, ind);
	    }

	    start = i;
	    // If the authority is defined then the path is defined by the
            // spec only; See RFC 2396 Section 5.2.4.
            if (authority != null && authority.length() > 0)
                file = "";
	} 
        if (host == null) {
	    host = "";
	}

        // Parse the file path if any
	if (start < limit) {
	    if (spec.charAt(start) == '/') {
		file = spec.substring(start, limit);
	    } else if (file != null && file.length() > 0) {
		isRelPath = true;
		int ind = file.lastIndexOf('/');
		String seperator = "";
		if (ind == -1 && authority != null)
		    seperator = "/";
		file = file.substring(0, ind + 1) + seperator +
		         spec.substring(start, limit);
					
	    } else {
		String seperator = (authority != null) ? "/" : "";
		file = seperator + spec.substring(start, limit);
	    }
	} else if (queryOnly && file != null) {
            int ind = file.lastIndexOf('/');
            if (ind < 0)
                ind = 0;
            file = file.substring(0, ind) + "/";
        }
	if (file == null)
	    file = "";

	if (isRelPath) {
            // Remove embedded /./
            while ((i = file.indexOf("/./")) >= 0) {
	        file = file.substring(0, i) + file.substring(i + 2);
	    }
            // Remove embedded /../
	    while ((i = file.indexOf("/../")) >= 0) {
	        if ((limit = file.lastIndexOf('/', i - 1)) >= 0) {
		    file = file.substring(0, limit) + file.substring(i + 3);
	        } else {
		    file = file.substring(i + 3);
	        }
	    }
            // Remove trailing ..
            while (file.endsWith("/..")) {
                i = file.indexOf("/..");
	        if ((limit = file.lastIndexOf('/', i - 1)) >= 0) {
		    file = file.substring(0, limit+1);
	        } else {
		    file = file.substring(0, i);
	        }
	    }
            // Remove trailing .
            if (file.endsWith("/."))
                file = file.substring(0, file.length() -1);
	}

	setURL(u, protocol, host, port, authority, userInfo, file, query, ref);
    }

    /**
     * Returns the default port for a URL parsed by this handler. This method
     * is meant to be overidden by handlers with default port numbers.
     * @return the default port for a <code>URL</code> parsed by this handler.
     */
    protected int getDefaultPort() {
        return -1;
    }

    /**
     * Provides the default equals calculation. May be overidden by handlers
     * for other protocols that have different requirements for equals().
     * This method requires that none of its arguments is null. This is 
     * guaranteed by the fact that it is only called by java.net.URL class.
     * @return <tt>true</tt> if the two urls are 
     * considered equal, ie. they refer to the same 
     * fragment in the same file.
     */
    protected boolean equals(URL u1, URL u2) {
        String ref1 = u1.getRef();
        String ref2 = u2.getRef();
        return sameFile(u1, u2) && 
            (ref1 == ref2 ||
            (ref1 != null && ref1.equals(ref2)));
    }

    /**
     * Provides the default hash calculation. May be overidden by handlers for
     * other protocols that have different requirements for hashCode
     * calculation.
     * @return an <tt>int</tt> suitable for hash table indexing
     */
    protected int hashCode(URL u) {
        int h = 0;

        // Generate the protocol part.
        String protocol = u.getProtocol();
        if (protocol != null)
	    h += protocol.hashCode();

        // Generate the host part.
	InetAddress addr = getHostAddress(u);
	if (addr != null) {
	    h += addr.hashCode();
	} else {
            String host = u.getHost();
            if (host != null)
	        h += host.toLowerCase().hashCode();
        }

        // Generate the file part.
        String file = u.getFile();
	if (file != null)
	    h += file.hashCode();

        // Generate the port part.
	if (u.getPort() == -1)
            h += getDefaultPort();
	else
            h += u.getPort();

        // Generate the ref part.
        String ref = u.getRef();
	if (ref != null)
            h += ref.hashCode();

	return h;
    }

    /**
     * Compare two urls to see whether they refer to the same file,
     * i.e., having the same protocol, host, port, and path.
     * This method requires that none of its arguments is null. This is 
     * guaranteed by the fact that it is only called indirectly
     * by java.net.URL class.
     * @return true if u1 and u2 refer to the same file
     */
    protected boolean sameFile(URL u1, URL u2) {
        // Compare the protocols.
        if (!((u1.getProtocol() == u2.getProtocol()) ||
              (u1.getProtocol() != null &&
               u1.getProtocol().equalsIgnoreCase(u2.getProtocol()))))
            return false;

	// Compare the hosts.
	if (!hostsEqual(u1, u2))
            return false;

	// Compare the files.
	if (!(u1.getFile() == u2.getFile() ||
              (u1.getFile() != null && u1.getFile().equals(u2.getFile()))))
	    return false;

	// Compare the ports.
        int port1, port2;
        port1 = (u1.getPort() != -1) ? u1.getPort() : u1.handler.getDefaultPort();
        port2 = (u2.getPort() != -1) ? u2.getPort() : u2.handler.getDefaultPort();
	if (port1 != port2)
	    return false;

        return true;
    }

    /**
     * Get the IP address of our host. An empty host field or a DNS failure
     * will result in a null return.
     *
     * @return an <code>InetAddress</code> representing the host
     * IP address.
     */
    protected synchronized InetAddress getHostAddress(URL u) {
	if (u.hostAddress != null)
            return u.hostAddress;
    
        String host = u.getHost();
        if (host == null || host.equals("")) {
            return null;
        } else {
            try {
                u.hostAddress = InetAddress.getByName(host);
            } catch (UnknownHostException ex) {
                return null;
            } catch (SecurityException se) {
                return null;
            }
        }
	return u.hostAddress;
    }

    /**
     * Compares the host components of two URLs.
     * @param u1 the URL of the first host to compare 
     * @param u2 the URL of the second host to compare 
     * @return	<tt>true</tt> if and only if they 
     * are equal, <tt>false</tt> otherwise.
     * @exception UnknownHostException If an unknown host is found.
     */
    protected boolean hostsEqual(URL u1, URL u2) {
	InetAddress a1 = getHostAddress(u1);
        InetAddress a2 = getHostAddress(u2);
	// if we have internet address for both, compare them
	if (a1 != null && a2 != null) {
	    return a1.equals(a2);
        // else, if both have host names, compare them
	} else if (u1.getHost() != null && u2.getHost() != null) 
            return u1.getHost().equalsIgnoreCase(u2.getHost());
	 else
            return u1.getHost() == null && u2.getHost() == null;
    }

    /**
     * Converts a <code>URL</code> of a specific protocol to a
     * <code>String</code>.
     *
     * @param   u   the URL.
     * @return  a string representation of the <code>URL</code> argument.
     */
    protected String toExternalForm(URL u) {
	StringBuffer result = new StringBuffer(u.getProtocol());
        result.append(":");
        if (u.getAuthority() != null && u.getAuthority().length() > 0) {
            result.append("//");
            result.append(u.getAuthority());
        }
        if (u.getFile() != null) {
            result.append(u.getFile());
        }
	if (u.getRef() != null) {
	    result.append("#");
            result.append(u.getRef());
	}
	return result.toString();
    }

    /**
     * Sets the fields of the <code>URL</code> argument to the indicated values.
     * Only classes derived from URLStreamHandler are supposed to be able
     * to call the set method on a URL.
     *
     * @param   u         the URL to modify.
     * @param   protocol  the protocol name.
     * @param   host      the remote host value for the URL.
     * @param   port      the port on the remote machine.
     * @param   authority the authority part for the URL.
     * @param   path      the path component of the URL. 
     * @param   query     the query part for the URL.
     * @param   ref       the reference.
     * @see     java.net.URL#set(java.lang.String, java.lang.String, int, java.lang.String, java.lang.String)
     */
       protected void setURL(URL u, String protocol, String host, int port,
		             String authority, String userInfo, String path,
                             String query, String ref) {
	if (this != u.handler) {
	    throw new SecurityException("handler for url different from " +
					"this handler");
	}
	// ensure that no one can reset the protocol on a given URL.
        u.set(u.getProtocol(), host, port, authority, userInfo, path, query, ref);
    }

    /**
     * Sets the fields of the <code>URL</code> argument to the indicated values.
     * Only classes derived from URLStreamHandler are supposed to be able
     * to call the set method on a URL.
     *
     * @param   u         the URL to modify.
     * @param   protocol  the protocol name. This value is ignored since 1.2.
     * @param   host      the remote host value for the URL.
     * @param   port      the port on the remote machine.
     * @param   file      the file.
     * @param   ref       the reference.
     * @deprecated Use setURL(URL, String, String, int, String, String, String,
     *             String);
     */
    protected void setURL(URL u, String protocol, String host, int port,
                          String file, String ref) {
        /*
         * Only old URL handlers call this, so assume that the host
         * field might contain "user:passwd@host". Fix as necessary.
         */
        String authority = null;
        String userInfo = null;
        if (host != null && host.length() != 0) {
	    authority = (port == -1) ? host : host + ":" + port;
            int at = host.lastIndexOf('@');
            if (at != -1) {
                userInfo = host.substring(0, at);
                host = host.substring(at+1);
            }
        }
        
        /*
         * Assume file might contain query part. Fix as necessary.
         */
        String path = null;
        String query = null;
        if (file != null) {
            int q = file.lastIndexOf('?');
            if (q != -1) {
                query = file.substring(q+1);
                path = file.substring(0, q);
            } else
                path = file;
        }
        setURL(u, protocol, host, port, authority, userInfo, path, query, ref); 
    }
}