/*******************************************************************************
 * 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 Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.runtime;

/**
 * A progress monitor that uses the a given amount of work ticks
 * form a parent monitor. It can be used as follows:
 * <pre>
 *     try {
 *         pm.beginTask("Main Task", 100);
 *         doSomeWork(pm, 30);
 *         SubProgressMonitor subMonitor= new SubProgressMonitor(pm, 40);
 *         try {
 *             subMonitor.beginTask("", 300);
 *             doSomeWork(subMonitor, 300);
 *         } finally {
 *             subMonitor.done();
 *         }
 *         doSomeWork(pm, 30);
 *     } finally {
 *         pm.done();
 *     }
 * </pre>
 * <p>
 * This class may be instantiated or subclassed by clients.
 * </p>
 */
public class SubProgressMonitor extends ProgressMonitorWrapper {

	/**
	 * Style constant indicating that calls to <code>subTask</code>
	 * should not have any effect.
	 *
	 * @see #SubProgressMonitor(IProgressMonitor,int,int)
	 */
	public static final int SUPPRESS_SUBTASK_LABEL = 1 << 1;
	/**
	 * Style constant indicating that the main task label 
	 * should be prepended to the subtask label.
	 *
	 * @see #SubProgressMonitor(IProgressMonitor,int,int)
	 */
	public static final int PREPEND_MAIN_LABEL_TO_SUBTASK = 1 << 2;

	private int parentTicks = 0;
	private double sentToParent = 0.0;
	private double scale = 0.0;
	private int nestedBeginTasks = 0;
	private boolean usedUp = false;
	private int style;
	private String mainTaskLabel;

	/**
	 * Creates a new sub-progress monitor for the given monitor. The sub 
	 * progress monitor uses the given number of work ticks from its 
	 * parent monitor.
	 *
	 * @param monitor the parent progress monitor
	 * @param ticks the number of work ticks allocated from the
	 *    parent monitor
	 */
	public SubProgressMonitor(IProgressMonitor monitor, int ticks) {
		this(monitor, ticks, 0);
	}

	/**
	 * Creates a new sub-progress monitor for the given monitor. The sub 
	 * progress monitor uses the given number of work ticks from its 
	 * parent monitor.
	 *
	 * @param monitor the parent progress monitor
	 * @param ticks the number of work ticks allocated from the
	 *    parent monitor
	 * @param style one of
	 *    <ul>
	 *    <li> <code>SUPPRESS_SUBTASK_LABEL</code> </li>
	 *    <li> <code>PREPEND_MAIN_LABEL_TO_SUBTASK</code> </li>
	 *    </ul>
	 * @see #SUPPRESS_SUBTASK_LABEL
	 * @see #PREPEND_MAIN_LABEL_TO_SUBTASK
	 */
	public SubProgressMonitor(IProgressMonitor monitor, int ticks, int style) {
		super(monitor);
		this.parentTicks = ticks;
		this.style = style;
	}

	/* (Intentionally not javadoc'd)
	 * Implements the method <code>IProgressMonitor.beginTask</code>.
	 *
	 * Starts a new main task. Since this progress monitor is a sub
	 * progress monitor, the given name will NOT be used to update
	 * the progress bar's main task label. That means the given 
	 * string will be ignored. If style <code>PREPEND_MAIN_LABEL_TO_SUBTASK
	 * <code> is specified, then the given string will be prepended to
	 * every string passed to <code>subTask(String)</code>.
	 */
	public void beginTask(String name, int totalWork) {
		nestedBeginTasks++;
		// Ignore nested begin task calls.
		if (nestedBeginTasks > 1) {
			return;
		}
		// be safe:  if the argument would cause math errors (zero or 
		// negative), just use 0 as the scale.  This disables progress for
		// this submonitor. 
		scale = totalWork <= 0 ? 0 : (double) parentTicks / (double) totalWork;
		if ((style & PREPEND_MAIN_LABEL_TO_SUBTASK) != 0) {
			mainTaskLabel = name;
		}
	}

	/* (Intentionally not javadoc'd)
	 * Implements the method <code>IProgressMonitor.done</code>.
	 */
	public void done() {
		// Ignore if more done calls than beginTask calls or if we are still
		// in some nested beginTasks
		if (nestedBeginTasks == 0 || --nestedBeginTasks > 0)
			return;
		// Send any remaining ticks and clear out the subtask text
		double remaining = parentTicks - sentToParent;
		if (remaining > 0)
			super.internalWorked(remaining);
		subTask(""); //$NON-NLS-1$
		sentToParent = 0;
	}

	/* (Intentionally not javadoc'd)
	 * Implements the internal method <code>IProgressMonitor.internalWorked</code>.
	 */
	public void internalWorked(double work) {
		if (usedUp || nestedBeginTasks != 1) {
			return;
		}

		double realWork = scale * work;
		// System.out.println("Sub monitor: " + realWork);
		super.internalWorked(realWork);
		sentToParent += realWork;
		if (sentToParent >= parentTicks) {
			usedUp = true;
		}
	}

	/* (Intentionally not javadoc'd)
	 * Implements the method <code>IProgressMonitor.subTask</code>.
	 */
	public void subTask(String name) {
		if ((style & SUPPRESS_SUBTASK_LABEL) != 0) {
			return;
		}

		String label = name;
		if ((style & PREPEND_MAIN_LABEL_TO_SUBTASK) != 0 && mainTaskLabel != null && mainTaskLabel.length() > 0) {
			label = mainTaskLabel + ' ' + label;
		}
		super.subTask(label);
	}

	/* (Intentionally not javadoc'd)
	 * Implements the method <code>IProgressMonitor.worked</code>.
	 */
	public void worked(int work) {
		internalWorked(work);
	}
}