/*******************************************************************************
 * Copyright (c) 2000, 2004 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.webdav.client;

import java.net.MalformedURLException;
import java.net.URL;
import java.util.Vector;
import org.eclipse.webdav.internal.kernel.utils.Assert;

/**
 * A utility for manipulating <code>URL</code>s.
 * <p>
 * <b>Note:</b> This class/interface is part of an interim API that is still under 
 * development and expected to change significantly before reaching stability. 
 * It is being made available at this early stage to solicit feedback from pioneering 
 * adopters on the understanding that any code that uses this API will almost 
 * certainly be broken (repeatedly) as the API evolves.
 * </p>
 */
public class URLTool {
	/**
	 * Returns the given URL with a trailing slash appended to it. If the URL
	 * already has a trailing slash the URL is returned unchanged.
	 * <table>
	 * <caption>Example</caption>
	 * <tr>
	 *   <th>Given URL</th>
	 *   <th>Returned URL</th>
	 * <tr>
	 *   <td>"http://hostname/folder"</td>
	 *   <td>"http://hostname/folder/"</td>
	 * <tr>
	 *   <td>"http://hostname/folder/</td>
	 *   <td>"http://hostname/folder/"</td>
	 * </table>
	 *
	 * @param url a URL
	 * @return    the given URL with a trailing slash
	 * @throws    MalformedURLException if the given URL is malformed
	 */
	public static URL appendTrailingSlash(String url) throws MalformedURLException {
		return appendTrailingSlash(new URL(url));
	}

	/**
	 * Returns the given <code>URL</code> with a trailing slash appended to
	 * it. If the <code>URL</code> already has a trailing slash the
	 * <code>URL</code> is returned unchanged.
	 * <table>
	 * <caption>Example</caption>
	 * <tr>
	 *   <th>Given URL</th>
	 *   <th>Returned URL</th>
	 * <tr>
	 *   <td>"http://hostname/folder"</td>
	 *   <td>"http://hostname/folder/"</td>
	 * <tr>
	 *   <td>"http://hostname/folder/</td>
	 *   <td>"http://hostname/folder/"</td>
	 * </table>
	 *
	 * @param url a URL
	 * @return    the given URL with a trailing slash
	 */
	public static URL appendTrailingSlash(URL url) {
		String file = url.getFile();
		if (file.endsWith("/")) { //$NON-NLS-1$
			return url;
		}
		try {
			return new URL(url.getProtocol(), url.getHost(), url.getPort(), file + "/"); //$NON-NLS-1$
		} catch (MalformedURLException e) {
			Assert.isTrue(false, Policy.bind("assert.internalError")); //$NON-NLS-1$
		}
		return null;
	}

	/**
	 * Returns the child URL formed by joining the given member with the
	 * given parent URL.
	 *
	 * @return a child URL of the given parent
	 * @throws MalformedURLException if the given parent is malformed
	 */
	public static URL getChild(String parent, String member) throws MalformedURLException {
		return getChild(new URL(parent), member);
	}

	/**
	 * Returns the child URL formed by joining the given member with the
	 * given parent URL.
	 *
	 * @return a child URL of the given parent
	 */
	public static URL getChild(URL parent, String member) {
		String file = parent.getFile();
		if (!file.endsWith("/")) //$NON-NLS-1$
			file = file + "/"; //$NON-NLS-1$
		try {
			return new URL(parent.getProtocol(), parent.getHost(), parent.getPort(), file + member);
		} catch (MalformedURLException e) {
			Assert.isTrue(false, Policy.bind("assert.internalError")); //$NON-NLS-1$
		}
		return null;
	}

	/**
	 * Returns all elements in the given URLs path.
	 * <table>
	 * <caption>Example</caption>
	 * <tr>
	 *   <th>Given URL</th>
	 *   <th>Element</th>
	 * <tr>
	 *   <td>"http://hostname/"</td>
	 *   <td>[]</td>
	 * <tr>
	 *   <td>"http://hostname/folder/</td>
	 *   <td>[folder]</td>
	 * <tr>
	 *   <td>"http://hostname/folder/file</td>
	 *   <td>[folder, file]</td>
	 * </table>
	 * @param url a URL
	 * @return    all elements in the given URLs path
	 * @throws    MalformedURLException if the given URL is malformed
	 */
	public static Vector getElements(String url) throws MalformedURLException {
		return getElements(new URL(url));
	}

	/**
	 * Returns all elements in the given URLs path.
	 * <table>
	 * <caption>Example</caption>
	 * <tr>
	 *   <th>Given URL</th>
	 *   <th>Element</th>
	 * <tr>
	 *   <td>"http://hostname/"</td>
	 *   <td>[]</td>
	 * <tr>
	 *   <td>"http://hostname/folder/</td>
	 *   <td>[folder]</td>
	 * <tr>
	 *   <td>"http://hostname/folder/file</td>
	 *   <td>[folder, file]</td>
	 * </table>
	 * @param url a URL
	 * @return    all elements in the given URLs path
	 */
	public static Vector getElements(URL url) {
		Vector result = new Vector(5);
		String lastElement = null;
		while ((lastElement = getLastElement(url)) != null) {
			result.insertElementAt(lastElement, 0);
			url = getParent(url);
		}
		return result;
	}

	/**
	 * Returns the last element in the given URLs path, or <code>null</code>
	 * if the URL is the root.
	 * <table>
	 * <caption>Example</caption>
	 * <tr>
	 *   <th>Given URL</th>
	 *   <th>Last Element</th>
	 * <tr>
	 *   <td>"http://hostname/"</td>
	 *   <td>null</td>
	 * <tr>
	 *   <td>"http://hostname/folder/</td>
	 *   <td>folder</td>
	 * <tr>
	 *   <td>"http://hostname/folder/file</td>
	 *   <td>file</td>
	 * </table>
	 * @param url a URL
	 * @return    the last element in the given URLs path, or
	 *            <code>null</code> if the URL is the root
	 * @throws    MalformedURLException if the given URL is malformed
	 */
	public static String getLastElement(String url) throws MalformedURLException {
		return getLastElement(new URL(url));
	}

	/**
	 * Returns the last element in the given URLs path, or <code>null</code>
	 * if the URL is the root.
	 * <table>
	 * <caption>Example</caption>
	 * <tr>
	 *   <th>Given URL</th>
	 *   <th>Last Element</th>
	 * <tr>
	 *   <td>"http://hostname/"</td>
	 *   <td>null</td>
	 * <tr>
	 *   <td>"http://hostname/folder/</td>
	 *   <td>folder</td>
	 * <tr>
	 *   <td>"http://hostname/folder/file</td>
	 *   <td>file</td>
	 * </table>
	 * @param url a URL
	 * @return    the last element in the given URLs path, or
	 *            <code>null</code> if the URL is the root
	 */
	public static String getLastElement(URL url) {
		String file = url.getFile();
		int len = file.length();

		if (len == 0 || len == 1 && file.charAt(0) == '/') {
			return null;
		}

		int lastSlashIndex = -1;
		for (int i = len - 2; lastSlashIndex == -1 && i >= 0; --i) {
			if (file.charAt(i) == '/') {
				lastSlashIndex = i;
			}
		}

		boolean isDirectory = file.charAt(len - 1) == '/';
		if (lastSlashIndex == -1) {
			if (isDirectory)
				return file.substring(0, len - 1);
			return file;
		}
		if (isDirectory)
			return file.substring(lastSlashIndex + 1, len - 1);
		return file.substring(lastSlashIndex + 1, len);
	}

	/**
	 * Returns the parent URL of the given URL, or <code>null</code> if the
	 * given URL is the root.
	 * <table>
	 * <caption>Example</caption>
	 * <tr>
	 *   <th>Given URL</th>
	 *   <th>Parent URL</th>
	 * <tr>
	 *   <td>"http://hostname/"</td>
	 *   <td>null</td>
	 * <tr>
	 *   <td>"http://hostname/folder/file</td>
	 *   <td>"http://hostname/folder/</td>
	 * </table>
	 *
	 * @param url a URL
	 * @return    the parent of the given URL
	 * @throws    MalformedURLException if the given URL is malformed
	 */
	public static URL getParent(String url) throws MalformedURLException {
		return getParent(new URL(url));
	}

	/**
	 * Returns the parent URL of the given URL, or <code>null</code> if the
	 * given URL is the root.
	 * <table>
	 * <caption>Example</caption>
	 * <tr>
	 *   <th>Given URL</th>
	 *   <th>Parent URL</th>
	 * <tr>
	 *   <td>"http://hostname/"</td>
	 *   <td>null</td>
	 * <tr>
	 *   <td>"http://hostname/folder/file</td>
	 *   <td>"http://hostname/folder/</td>
	 * </table>
	 *
	 * @param url a URL
	 * @return    the parent of the given URL
	 */
	public static URL getParent(URL url) {
		String file = url.getFile();
		int len = file.length();

		if (len == 0 || len == 1 && file.charAt(0) == '/')
			return null;

		int lastSlashIndex = -1;
		for (int i = len - 2; lastSlashIndex == -1 && i >= 0; --i) {
			if (file.charAt(i) == '/')
				lastSlashIndex = i;
		}

		if (lastSlashIndex == -1)
			file = ""; //$NON-NLS-1$
		else
			file = file.substring(0, lastSlashIndex + 1);

		try {
			url = new URL(url.getProtocol(), url.getHost(), url.getPort(), file);
		} catch (MalformedURLException e) {
			Assert.isTrue(false, e.getMessage());
		}

		return url;
	}

	/**
	 * Returns the root URL of the given URL.
	 * <table>
	 * <caption>Example</caption>
	 * <tr>
	 *   <th>Given URL</th>
	 *   <th>Root URL</th>
	 * <tr>
	 *   <td>"http://hostname/"</td>
	 *   <td>"http://hostname/"</td>
	 * <tr>
	 *   <td>"http://hostname/folder/file</td>
	 *   <td>"http://hostname/"</td>
	 * </table>
	 *
	 * @param urlString a URL
	 * @return          the root url of the given URL
	 * @throws          MalformedURLException if the given URL is malformed
	 */
	public static URL getRoot(String urlString) throws MalformedURLException {
		return getRoot(new URL(urlString));
	}

	/**
	 * Returns the root URL of the given URL.
	 * <table>
	 * <caption>Example</caption>
	 * <tr>
	 *   <th>Given URL</th>
	 *   <th>Root URL</th>
	 * <tr>
	 *   <td>"http://hostname/"</td>
	 *   <td>"http://hostname/"</td>
	 * <tr>
	 *   <td>"http://hostname/folder/file</td>
	 *   <td>"http://hostname/"</td>
	 * </table>
	 *
	 * @param url a URL
	 * @return    the root URL of the given URL
	 */
	public static URL getRoot(URL url) {
		try {
			return new URL(url.getProtocol(), url.getHost(), url.getPort(), "/"); //$NON-NLS-1$
		} catch (MalformedURLException e) {
			Assert.isTrue(false, Policy.bind("assert.internalError")); //$NON-NLS-1$
		}
		return null;
	}

	/**
	 * Returns the given URL with its trailing slash removed. If the URL has
	 * no trailing slash, the URL is returned unchanged.
	 * <table>
	 * <caption>Example</caption>
	 * <tr>
	 *   <th>Given URL</th>
	 *   <th>Returned URL</th>
	 * <tr>
	 *   <td>"http://hostname/folder"</td>
	 *   <td>"http://hostname/folder"</td>
	 * <tr>
	 *   <td>"http://hostname/folder/</td>
	 *   <td>"http://hostname/folder"</td>
	 * </table>
	 *
	 * @param url a URL
	 * @return    the given URL with its last slash removed
	 * @throws    MalformedURLException if the given URL is malformed
	 */
	public static URL removeTrailingSlash(String url) throws MalformedURLException {
		return removeTrailingSlash(new URL(url));
	}

	/**
	 * Returns the given URL with its trailing slash removed. If the URL has
	 * no trailing slash, the URL is returned unchanged.
	 * <table>
	 * <caption>Example</caption>
	 * <tr>
	 *   <th>Given URL</th>
	 *   <th>Returned URL</th>
	 * <tr>
	 *   <td>"http://hostname/folder"</td>
	 *   <td>"http://hostname/folder"</td>
	 * <tr>
	 *   <td>"http://hostname/folder/</td>
	 *   <td>"http://hostname/folder"</td>
	 * </table>
	 *
	 * @param url a URL
	 * @return    the given URL with its last slash removed
	 */
	public static URL removeTrailingSlash(URL url) {
		String file = url.getFile();

		if (file.endsWith("/")) { //$NON-NLS-1$
			file = file.substring(0, file.length() - 1);
			try {
				return new URL(url.getProtocol(), url.getHost(), url.getPort(), file);
			} catch (MalformedURLException e) {
				Assert.isTrue(false, e.getMessage());
			}
		} else {
			return url;
		}

		return null;
	}

	/**
	 * Returns a boolean indicating whether the given URLs overlap.
	 * <table>
	 * <caption>Example</caption>
	 * <tr>
	 *   <th>First URL</th>
	 *   <th>Second URL</th>
	 *   <th>Do they overlap</th>
	 * <tr>
	 *   <td>"http://hostname/folder/"</td>
	 *   <td>"http://hostname/folder/"</td>
	 *   <td>true</td>
	 * <tr>
	 *   <td>"http://hostname/folder/"</td>
	 *   <td>"http://hostname/folder/file"</td>
	 *   <td>true</td>
	 * <tr>
	 *   <td>"http://hostname/folder/file"</td>
	 *   <td>"http://hostname/folder/"</td>
	 *   <td>true</td>
	 * <tr>
	 *   <td>"http://hostname/folder1/"</td>
	 *   <td>"http://hostname/folder2/"</td>
	 *   <td>false</td>
	 * </table>
	 * @param  url1 firt URL
	 * @param  url2 second URL
	 * @return a boolean indicating whether the given URLs overlap
	 */
	public static boolean urlsOverlap(String url1, String url2) throws MalformedURLException {
		return urlsOverlap(new URL(url1), new URL(url2));
	}

	/**
	 * Returns a boolean indicating whether the given URLs overlap.
	 * <table>
	 * <caption>Example</caption>
	 * <tr>
	 *   <th>First URL</th>
	 *   <th>Second URL</th>
	 *   <th>Do they overlap</th>
	 * <tr>
	 *   <td>"http://hostname/folder/"</td>
	 *   <td>"http://hostname/folder/"</td>
	 *   <td>true</td>
	 * <tr>
	 *   <td>"http://hostname/folder/"</td>
	 *   <td>"http://hostname/folder/file"</td>
	 *   <td>true</td>
	 * <tr>
	 *   <td>"http://hostname/folder/file"</td>
	 *   <td>"http://hostname/folder/"</td>
	 *   <td>true</td>
	 * <tr>
	 *   <td>"http://hostname/folder1/"</td>
	 *   <td>"http://hostname/folder2/"</td>
	 *   <td>false</td>
	 * <tr>
	 *   <td>"http://hostname1/folder/"</td>
	 *   <td>"http://hostname2/folder/"</td>
	 *   <td>false</td>
	 * </table>
	 * @param  url1 firt URL
	 * @param  url2 second URL
	 * @return a boolean indicating whether the given URLs overlap
	 */
	public static boolean urlsOverlap(URL url1, URL url2) {
		if (!getRoot(url1).equals(getRoot(url2))) {
			return false;
		}
		Vector elements1 = URLTool.getElements(url1);
		Vector elements2 = URLTool.getElements(url2);
		for (int i = 0; i < elements1.size() && i < elements2.size(); ++i) {
			String element1 = (String) elements1.elementAt(i);
			String element2 = (String) elements2.elementAt(i);
			if (!element1.equals(element2)) {
				return false;
			}
		}
		return true;
	}
}
