/*
    * Copyright (C) 2015 Obeo. and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  package org.eclipse.jgit.hooks;
  
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.util.concurrent.Callable;
  
  import org.eclipse.jgit.api.errors.AbortedByHookException;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.util.FS;
  import org.eclipse.jgit.util.ProcessResult;
  import org.eclipse.jgit.util.SystemReader;
  import org.eclipse.jgit.util.io.TeeOutputStream;
  
  /**
   * Git can fire off custom scripts when certain important actions occur. These
   * custom scripts are called "hooks". There are two groups of hooks: client-side
   * (that run on local operations such as committing and merging), and
   * server-side (that run on network operations such as receiving pushed
   * commits). This is the abstract super-class of the different hook
   * implementations in JGit.
   *
   * @param <T>
   *            the return type which is expected from {@link #call()}
   * @see <a href="http://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks">Git
   *      Hooks on the git-scm official site</a>
   * @since 5.11
   */
  public abstract class GitHook<T> implements Callable<T> {
  
  	private final Repository repo;
  
  	/**
  	 * The output stream to be used by the hook.
  	 */
  	private final OutputStream outputStream;
  
  	/**
  	 * The error stream to be used by the hook.
  	 */
  	private final OutputStream errorStream;
  
  	/**
  	 * Constructor for GitHook.
  	 * <p>
  	 * This constructor will use stderr for the error stream.
  	 * </p>
  	 *
  	 * @param repo
  	 *            a {@link org.eclipse.jgit.lib.Repository} object.
  	 * @param outputStream
  	 *            The output stream the hook must use. {@code null} is allowed,
  	 *            in which case the hook will use {@code System.out}.
  	 */
  	protected GitHook(Repository repo, OutputStream outputStream) {
  		this(repo, outputStream, null);
  	}
  
  	/**
  	 * Constructor for GitHook
  	 *
  	 * @param repo
  	 *            a {@link org.eclipse.jgit.lib.Repository} object.
  	 * @param outputStream
  	 *            The output stream the hook must use. {@code null} is allowed,
  	 *            in which case the hook will use {@code System.out}.
  	 * @param errorStream
  	 *            The error stream the hook must use. {@code null} is allowed,
  	 *            in which case the hook will use {@code System.err}.
  	 */
  	protected GitHook(Repository repo, OutputStream outputStream,
  			OutputStream errorStream) {
  		this.repo = repo;
  		this.outputStream = outputStream;
  		this.errorStream = errorStream;
  	}
  
  	/**
  	 * {@inheritDoc}
  	 * <p>
  	 * Run the hook.
  	 */
  	@Override
  	public abstract T call() throws IOException, AbortedByHookException;
  
  	/**
  	 * Get name of the hook
  	 *
  	 * @return The name of the hook, which must not be {@code null}.
  	 */
 	public abstract String getHookName();
 
 	/**
 	 * Get the repository
 	 *
 	 * @return The repository.
 	 */
 	protected Repository getRepository() {
 		return repo;
 	}
 
 	/**
 	 * Override this method when needed to provide relevant parameters to the
 	 * underlying hook script. The default implementation returns an empty
 	 * array.
 	 *
 	 * @return The parameters the hook receives.
 	 */
 	protected String[] getParameters() {
 		return new String[0];
 	}
 
 	/**
 	 * Override to provide relevant arguments via stdin to the underlying hook
 	 * script. The default implementation returns {@code null}.
 	 *
 	 * @return The parameters the hook receives.
 	 */
 	protected String getStdinArgs() {
 		return null;
 	}
 
 	/**
 	 * Get output stream
 	 *
 	 * @return The output stream the hook must use. Never {@code null},
 	 *         {@code System.out} is returned by default.
 	 */
 	protected OutputStream getOutputStream() {
 		return outputStream == null ? System.out : outputStream;
 	}
 
 	/**
 	 * Get error stream
 	 *
 	 * @return The error stream the hook must use. Never {@code null},
 	 *         {@code System.err} is returned by default.
 	 */
 	protected OutputStream getErrorStream() {
 		return errorStream == null ? System.err : errorStream;
 	}
 
 	/**
 	 * Runs the hook, without performing any validity checks.
 	 *
 	 * @throws org.eclipse.jgit.api.errors.AbortedByHookException
 	 *             If the underlying hook script exited with non-zero.
 	 * @throws IOException
 	 *             if an IO error occurred
 	 */
 	protected void doRun() throws AbortedByHookException, IOException {
 		final ByteArrayOutputStream errorByteArray = new ByteArrayOutputStream();
 		final TeeOutputStream stderrStream = new TeeOutputStream(errorByteArray,
 				getErrorStream());
 		Repository repository = getRepository();
 		FS fs = repository.getFS();
 		if (fs == null) {
 			fs = FS.DETECTED;
 		}
 		ProcessResult result = fs.runHookIfPresent(repository, getHookName(),
 				getParameters(), getOutputStream(), stderrStream,
 				getStdinArgs());
 		if (result.isExecutedWithError()) {
 			handleError(new String(errorByteArray.toByteArray(),
 					SystemReader.getInstance().getDefaultCharset().name()),
 					result);
 		}
 	}
 
 	/**
 	 * Process that the hook exited with an error. This default implementation
 	 * throws an {@link AbortedByHookException }. Hooks which need a different
 	 * behavior can overwrite this method.
 	 *
 	 * @param message
 	 *            error message
 	 * @param result
 	 *            The process result of the hook
 	 * @throws AbortedByHookException
 	 *             When the hook should be aborted
 	 * @since 5.11
 	 */
 	protected void handleError(String message,
 			final ProcessResult result)
 			throws AbortedByHookException {
 		throw new AbortedByHookException(message, getHookName(),
 				result.getExitCode());
 	}
 
 	/**
 	 * Check whether a 'native' (i.e. script) hook is installed in the
 	 * repository.
 	 *
 	 * @return whether a native hook script is installed in the repository.
 	 * @since 4.11
 	 */
 	public boolean isNativeHookPresent() {
 		FS fs = getRepository().getFS();
 		if (fs == null) {
 			fs = FS.DETECTED;
 		}
 		return fs.findHook(getRepository(), getHookName()) != null;
 	}
 
 }