/*
 * Copyright (C) 2010, Christian Halstrick <christian.halstrick@sap.com> 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
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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package org.eclipse.jgit.api;

import java.text.MessageFormat;
import java.util.concurrent.Callable;
import java.util.concurrent.atomic.AtomicBoolean;

import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.lib.Repository;

Common superclass of all commands in the package org.eclipse.jgit.api 
 This class ensures that all commands fulfill the Callable interface. It also has a property GitCommand<T>.repo holding a reference to the git Repository this command should work with. 
 Finally this class stores a state telling whether it is allowed to call call() on this instance. Instances of GitCommand can only be used for one single successful call to call(). Afterwards this instance may not be used anymore to set/modify any properties or to call call() again. This is achieved by setting the GitCommand<T>.callable property to false after the successful execution of call() and to check the state (by calling checkCallable()) before setting of properties and inside call(). 
Type parameters:
<T> –  the return type which is expected from call()/**
 * Common superclass of all commands in the package {@code org.eclipse.jgit.api}
 * <p>
 * This class ensures that all commands fulfill the
 * {@link java.util.concurrent.Callable} interface. It also has a property
 * {@link #repo} holding a reference to the git
 * {@link org.eclipse.jgit.lib.Repository} this command should work with.
 * <p>
 * Finally this class stores a state telling whether it is allowed to call
 * {@link #call()} on this instance. Instances of
 * {@link org.eclipse.jgit.api.GitCommand} can only be used for one single
 * successful call to {@link #call()}. Afterwards this instance may not be used
 * anymore to set/modify any properties or to call {@link #call()} again. This
 * is achieved by setting the {@link #callable} property to false after the
 * successful execution of {@link #call()} and to check the state (by calling
 * {@link #checkCallable()}) before setting of properties and inside
 * {@link #call()}.
 *
 * @param <T>
 *            the return type which is expected from {@link #call()}
 */
public abstract class GitCommand<T> implements Callable<T> {
	
The repository this command is working with /** The repository this command is working with */
	final protected Repository repo;

	
a state which tells whether it is allowed to call call() on this instance. /**
	 * a state which tells whether it is allowed to call {@link #call()} on this
	 * instance.
	 */
	private AtomicBoolean callable = new AtomicBoolean(true);

	
Creates a new command which interacts with a single repository
Params:
repo –  the Repository this command should interact with/**
	 * Creates a new command which interacts with a single repository
	 *
	 * @param repo
	 *            the {@link org.eclipse.jgit.lib.Repository} this command
	 *            should interact with
	 */
	protected GitCommand(Repository repo) {
		this.repo = repo;
	}

	
Get repository this command is working on
Returns:
the Repository this command is interacting with/**
	 * Get repository this command is working on
	 *
	 * @return the {@link org.eclipse.jgit.lib.Repository} this command is
	 *         interacting with
	 */
	public Repository getRepository() {
		return repo;
	}

	
Set's the state which tells whether it is allowed to call call() on this instance. checkCallable() will throw an exception when called and this property is set to false 
Params:
callable – 
           if true it is allowed to call call() on this instance./**
	 * Set's the state which tells whether it is allowed to call {@link #call()}
	 * on this instance. {@link #checkCallable()} will throw an exception when
	 * called and this property is set to {@code false}
	 *
	 * @param callable
	 *            if <code>true</code> it is allowed to call {@link #call()} on
	 *            this instance.
	 */
	protected void setCallable(boolean callable) {
		this.callable.set(callable);
	}

	
Checks that the property GitCommand<T>.callable is true. If not then an IllegalStateException is thrown 
Throws:
IllegalStateException –  when this method is called and the property GitCommand<T>.callable is false/**
	 * Checks that the property {@link #callable} is {@code true}. If not then
	 * an {@link java.lang.IllegalStateException} is thrown
	 *
	 * @throws java.lang.IllegalStateException
	 *             when this method is called and the property {@link #callable}
	 *             is {@code false}
	 */
	protected void checkCallable() {
		if (!callable.get())
			throw new IllegalStateException(MessageFormat.format(
					JGitText.get().commandWasCalledInTheWrongState
					, this.getClass().getName()));
	}

	
{@inheritDoc}

Execute the command
/**
	 * {@inheritDoc}
	 * <p>
	 * Execute the command
	 */
	@Override
	public abstract T call() throws GitAPIException;
}