jgit/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/CommandRef.java

/*
 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.eclipse.jgit.pgm;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.text.MessageFormat;

/**
 * Description of a command (a {@link TextBuiltin} subclass.
 * <p>
 * These descriptions are lightweight compared to creating a command instance
 * and are therefore suitable for catalogs of "known" commands without linking
 * the command's implementation and creating a dummy instance of the command.
 */
public class CommandRef {
	private final Class<? extends TextBuiltin> impl;

	private final String name;

	private String usage;

	boolean common;

	CommandRef(final Class<? extends TextBuiltin> clazz) {
		this(clazz, guessName(clazz));
	}

	CommandRef(final Class<? extends TextBuiltin> clazz, final Command cmd) {
		this(clazz, cmd.name().length() > 0 ? cmd.name() : guessName(clazz));
		usage = cmd.usage();
		common = cmd.common();
	}

	private CommandRef(final Class<? extends TextBuiltin> clazz, final String cn) {
		impl = clazz;
		name = cn;
		usage = "";
	}

	private static String guessName(final Class<? extends TextBuiltin> clazz) {
		final StringBuilder s = new StringBuilder();
		if (clazz.getName().startsWith("org.eclipse.jgit.pgm.debug."))
			s.append("debug-");

		boolean lastWasDash = true;
		for (final char c : clazz.getSimpleName().toCharArray()) {
			if (Character.isUpperCase(c)) {
				if (!lastWasDash)
					s.append('-');
				lastWasDash = !lastWasDash;
				s.append(Character.toLowerCase(c));
			} else {
				s.append(c);
			}
		}
		return s.toString();
	}

	/**
	 * @return name the command is invoked as from the command line.
	 */
	public String getName() {
		return name;
	}

	/**
	 * @return one line description of the command's feature set.
	 */
	public String getUsage() {
		return usage;
	}

	/**
	 * @return true if this command is considered to be commonly used.
	 */
	public boolean isCommon() {
		return common;
	}

	/**
	 * @return name of the Java class which implements this command.
	 */
	public String getImplementationClassName() {
		return impl.getName();
	}

	/**
	 * @return loader for {@link #getImplementationClassName()}.
	 */
	public ClassLoader getImplementationClassLoader() {
		return impl.getClassLoader();
	}

	/**
	 * @return a new instance of the command implementation.
	 */
	public TextBuiltin create() {
		final Constructor<? extends TextBuiltin> c;
		try {
			c = impl.getDeclaredConstructor();
		} catch (SecurityException e) {
			throw new RuntimeException(MessageFormat.format(CLIText.get().cannotCreateCommand, getName(), e));
		} catch (NoSuchMethodException e) {
			throw new RuntimeException(MessageFormat.format(CLIText.get().cannotCreateCommand, getName(), e));
		}
		c.setAccessible(true);

		final TextBuiltin r;
		try {
			r = c.newInstance();
		} catch (InstantiationException e) {
			throw new RuntimeException(MessageFormat.format(CLIText.get().cannotCreateCommand, getName(), e));
		} catch (IllegalAccessException e) {
			throw new RuntimeException(MessageFormat.format(CLIText.get().cannotCreateCommand, getName(), e));
		} catch (IllegalArgumentException e) {
			throw new RuntimeException(MessageFormat.format(CLIText.get().cannotCreateCommand, getName(), e));
		} catch (InvocationTargetException e) {
			throw new RuntimeException(MessageFormat.format(CLIText.get().cannotCreateCommand, getName(), e));
		}
		r.setCommandName(getName());
		return r;
	}
}