/*******************************************************************************
 * Copyright (c) 2000, 2018 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.swt.widgets;

import org.eclipse.swt.*;
import org.eclipse.swt.events.*;
import org.eclipse.swt.graphics.*;

/**
 * Instances of this class support the layout of selectable
 * expand bar items.
 * <p>
 * The item children that may be added to instances of this class
 * must be of type <code>ExpandItem</code>.
 * </p><p>
 * <dl>
 * <dt><b>Styles:</b></dt>
 * <dd>V_SCROLL</dd>
 * <dt><b>Events:</b></dt>
 * <dd>Expand, Collapse</dd>
 * </dl>
 * </p><p>
 * IMPORTANT: This class is <em>not</em> intended to be subclassed.
 * </p>
 *
 * @see ExpandItem
 * @see ExpandEvent
 * @see ExpandListener
 * @see ExpandAdapter
 * @see <a href="http://www.eclipse.org/swt/snippets/#expandbar">ExpandBar snippets</a>
 * @see <a href="http://www.eclipse.org/swt/examples.php">SWT Example: ControlExample</a>
 * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>
 *
 * @since 3.2
 * @noextend This class is not intended to be subclassed by clients.
 */
public class ExpandBar extends Composite {
	ExpandItem [] items;
	int itemCount;
	ExpandItem focusItem;
	int spacing;
	int yCurrentScroll;
	Font font;
	Color foreground;
	Listener listener;
	boolean inDispose;

/**
 * Constructs a new instance of this class given its parent
 * and a style value describing its behavior and appearance.
 * <p>
 * The style value is either one of the style constants defined in
 * class <code>SWT</code> which is applicable to instances of this
 * class, or must be built by <em>bitwise OR</em>'ing together
 * (that is, using the <code>int</code> "|" operator) two or more
 * of those <code>SWT</code> style constants. The class description
 * lists the style constants that are applicable to the class.
 * Style bits are also inherited from superclasses.
 * </p>
 *
 * @param parent a composite control which will be the parent of the new instance (cannot be null)
 * @param style the style of control to construct
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the parent is null</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li>
 *    <li>ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass</li>
 * </ul>
 *
 * @see SWT#V_SCROLL
 * @see Widget#checkSubclass
 * @see Widget#getStyle
 */
public ExpandBar (Composite parent, int style) {
	super (parent, checkStyle (style));
	items = new ExpandItem [4];

	listener = event -> {
		switch (event.type) {
			case SWT.Dispose:		onDispose (event);        	break;
			case SWT.MouseDown:		onMouseDown (event);   		break;
			case SWT.MouseUp:		onMouseUp (event);   		break;
			case SWT.Paint:			onPaint (event);     		break;
			case SWT.Resize:		onResize ();     			break;
			case SWT.KeyDown:		onKeyDown (event);    		break;
			case SWT.FocusIn:		onFocus ();     			break;
			case SWT.FocusOut:		onFocus ();     			break;
			case SWT.Traverse:		onTraverse (event);   		break;
		}
	};
	addListener (SWT.Dispose, listener);
	addListener (SWT.MouseDown, listener);
	addListener (SWT.MouseUp, listener);
	addListener (SWT.Paint, listener);
	addListener (SWT.Resize, listener);
	addListener (SWT.KeyDown, listener);
	addListener (SWT.FocusIn, listener);
	addListener (SWT.FocusOut, listener);
	addListener (SWT.Traverse, listener);

	ScrollBar verticalBar = getVerticalBar ();
	if (verticalBar != null) {
		verticalBar.addListener (SWT.Selection, event -> onScroll (event));
	}
}

/**
 * Adds the listener to the collection of listeners who will
 * be notified when an item in the receiver is expanded or collapsed
 * by sending it one of the messages defined in the <code>ExpandListener</code>
 * interface.
 *
 * @param listener the listener which should be notified
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see ExpandListener
 * @see #removeExpandListener
 */
public void addExpandListener (ExpandListener listener) {
	checkWidget ();
	if (listener == null) error (SWT.ERROR_NULL_ARGUMENT);
	TypedListener typedListener = new TypedListener (listener);
	addListener (SWT.Expand, typedListener);
	addListener (SWT.Collapse, typedListener);
}

static int checkStyle (int style) {
	return style & ~SWT.H_SCROLL;
}

@Override
protected void checkSubclass () {
	if (!isValidSubclass ()) error (SWT.ERROR_INVALID_SUBCLASS);
}

@Override
public Point computeSize (int wHint, int hHint, boolean changed) {
	checkWidget ();
	int height = 0, width = 0;
	if (wHint == SWT.DEFAULT || hHint == SWT.DEFAULT) {
		if (itemCount > 0) {
			height += spacing;
			GC gc = new GC (this);
			for (int i = 0; i < itemCount; i++) {
				ExpandItem item = items [i];
				height += item.getHeaderHeight ();
				if (item.expanded) height += item.height;
				height += spacing;
				width = Math.max (width, item.getPreferredWidth (gc));
			}
			gc.dispose ();
		}
	}
	if (width == 0) width = DEFAULT_WIDTH;
	if (height == 0) height = DEFAULT_HEIGHT;
	if (wHint != SWT.DEFAULT) width = wHint;
	if (hHint != SWT.DEFAULT) height = hHint;
	Rectangle trim = computeTrim (0, 0, width, height);
	return new Point (trim.width, trim.height);
}

void createItem (ExpandItem item, int style, int index) {
	if (!(0 <= index && index <= itemCount)) error (SWT.ERROR_INVALID_RANGE);
	if (itemCount == items.length) {
		ExpandItem [] newItems = new ExpandItem [itemCount + 4];
		System.arraycopy (items, 0, newItems, 0, items.length);
		items = newItems;
	}
	System.arraycopy (items, index, items, index + 1, itemCount - index);
	items [index] = item;
	itemCount++;
	if (focusItem == null) focusItem = item;
	item.width = Math.max (0, getClientArea ().width - spacing * 2);
	layoutItems (index, true);
}

void destroyItem (ExpandItem item) {
	if (inDispose) return;
	int index = 0;
	while (index < itemCount) {
		if (items [index] == item) break;
		index++;
	}
	if (index == itemCount) return;
	if (item == focusItem) {
		int focusIndex = index > 0 ? index - 1 : 1;
		if (focusIndex < itemCount) {
			focusItem = items [focusIndex];
			focusItem.redraw ();
		} else {
			focusItem = null;
		}
	}
	System.arraycopy (items, index + 1, items, index, --itemCount - index);
	items [itemCount] = null;
	item.redraw ();
	layoutItems (index, true);
}

int getBandHeight () {
	if (font == null) return ExpandItem.CHEVRON_SIZE;
	GC gc = new GC (this);
	FontMetrics metrics = gc.getFontMetrics ();
	gc.dispose ();
	return Math.max (ExpandItem.CHEVRON_SIZE, metrics.getHeight ());
}

@Override
public Color getForeground () {
	checkWidget ();
	if (foreground == null) {
		Display display = getDisplay ();
		return display.getSystemColor (SWT.COLOR_TITLE_FOREGROUND);
	}
	return foreground;
}

/**
 * Returns the item at the given, zero-relative index in the
 * receiver. Throws an exception if the index is out of range.
 *
 * @param index the index of the item to return
 * @return the item at the given index
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_INVALID_RANGE - if the index is not between 0 and the number of elements in the list minus 1 (inclusive)</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public ExpandItem getItem (int index) {
	checkWidget ();
	if (!(0 <= index && index < itemCount)) error (SWT.ERROR_INVALID_RANGE);
	return items [index];
}

/**
 * Returns the number of items contained in the receiver.
 *
 * @return the number of items
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public int getItemCount () {
	checkWidget ();
	return itemCount;
}

/**
 * Returns an array of <code>ExpandItem</code>s which are the items
 * in the receiver.
 * <p>
 * Note: This is not the actual structure used by the receiver
 * to maintain its list of items, so modifying the array will
 * not affect the receiver.
 * </p>
 *
 * @return the items in the receiver
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public ExpandItem [] getItems () {
	checkWidget ();
	ExpandItem [] result = new ExpandItem [itemCount];
	System.arraycopy (items, 0, result, 0, itemCount);
	return result;
}

/**
 * Returns the receiver's spacing.
 *
 * @return the spacing
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public int getSpacing () {
	checkWidget ();
	return spacing;
}

/**
 * Searches the receiver's list starting at the first item
 * (index 0) until an item is found that is equal to the
 * argument, and returns the index of that item. If no item
 * is found, returns -1.
 *
 * @param item the search item
 * @return the index of the item
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the item is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the item has been disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public int indexOf (ExpandItem item) {
	checkWidget ();
	if (item == null) error (SWT.ERROR_NULL_ARGUMENT);
	for (int i = 0; i < itemCount; i++) {
		if (items [i] == item) return i;
	}
	return -1;
}

void layoutItems (int index, boolean setScrollbar) {
	if (index < itemCount) {
		int y = spacing - yCurrentScroll;
		for (int i = 0; i < index; i++) {
			ExpandItem item = items [i];
			if (item.expanded) y += item.height;
			y += item.getHeaderHeight() + spacing;
		}
		for (int i = index; i < itemCount; i++) {
			ExpandItem item = items [i];
			item.setBounds (spacing, y, 0, 0, true, false);
			if (item.expanded) y += item.height;
			y += item.getHeaderHeight() + spacing;
		}
	}
	if (setScrollbar) setScrollbar ();
}

/**
 * Removes the listener from the collection of listeners who will
 * be notified when items in the receiver are expanded or collapsed.
 *
 * @param listener the listener which should no longer be notified
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see ExpandListener
 * @see #addExpandListener
 */
public void removeExpandListener (ExpandListener listener) {
	checkWidget ();
	if (listener == null) error (SWT.ERROR_NULL_ARGUMENT);
	if (eventTable == null) return;
	eventTable.unhook (SWT.Expand, listener);
	eventTable.unhook (SWT.Collapse, listener);
}

@Override
void reskinChildren (int flags) {
	if (items != null) {
		for (int i=0; i<items.length; i++) {
			ExpandItem item = items [i];
			if (item != null ) item.reskin (flags);
		}
	}
	super.reskinChildren (flags);
}

@Override
public void setFont(Font font) {
	super.setFont (font);
	this.font = font;
	layoutItems (0, true);
}

@Override
public void setForeground (Color color) {
	super.setForeground (color);
	foreground = color;
}

void setScrollbar () {
	if (itemCount == 0) return;
	ScrollBar verticalBar = getVerticalBar ();
	if (verticalBar == null) return;
	int height = getClientArea ().height;
	ExpandItem item = items [itemCount - 1];
	int maxHeight = item.y + getBandHeight () + spacing;
	if (item.expanded) maxHeight += item.height;

	//claim bottom free space
	if (yCurrentScroll > 0 && height > maxHeight) {
		yCurrentScroll = Math.max (0, yCurrentScroll + maxHeight - height);
		layoutItems (0, false);
	}
	maxHeight += yCurrentScroll;

	int selection = Math.min (yCurrentScroll, maxHeight);
	int increment = verticalBar.getIncrement ();
	int pageIncrement = verticalBar.getPageIncrement ();
	verticalBar.setValues(selection, 0, maxHeight, height, increment, pageIncrement);
	verticalBar.setVisible(maxHeight > height);
}

/**
 * Sets the receiver's spacing. Spacing specifies the number of points allocated around
 * each item.
 *
 * @param spacing the spacing around each item
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public void setSpacing (int spacing) {
	checkWidget ();
	if (spacing < 0) return;
	if (spacing == this.spacing) return;
	this.spacing = spacing;
	int width = Math.max (0, getClientArea ().width - spacing * 2);
	for (int i = 0; i < itemCount; i++) {
		ExpandItem item = items[i];
		if (item.width != width) item.setBounds (0, 0, width, item.height, false, true);
	}
	layoutItems (0, true);
	redraw ();
}

void showItem (ExpandItem item) {
	Control control = item.control;
	if (control != null && !control.isDisposed ()) {
		control.setVisible (item.expanded);
	}
	item.redraw ();
	int index = indexOf (item);
	layoutItems (index + 1, true);
}

void onDispose (Event event) {
	removeListener (SWT.Dispose, listener);
	notifyListeners (SWT.Dispose, event);
	event.type = SWT.None;
	/*
	 * Usually when an item is disposed, destroyItem will change the size of the items array,
	 * reset the bounds of all the tabs and manage the widget associated with the tab.
	 * Since the whole folder is being disposed, this is not necessary.  For speed
	 * the inDispose flag is used to skip over this part of the item dispose.
	 */
	inDispose = true;

	for (int i = 0; i < itemCount; i++) {
		items [i].dispose ();
	}
	items = null;
	font = null;
	foreground = null;
	focusItem = null;
}

void onFocus () {
	if (focusItem != null) focusItem.redraw ();
}

void onKeyDown (Event event) {
	if (focusItem == null) return;
	switch (event.keyCode) {
		case 13: /* Return */
		case 32: /* Space */
			Event ev = new Event ();
			ev.item = focusItem;
			sendEvent (focusItem.expanded ? SWT.Collapse :SWT.Expand, ev);
			focusItem.expanded = !focusItem.expanded;
			showItem (focusItem);
			break;
		case SWT.ARROW_UP: {
			int focusIndex = indexOf (focusItem);
			if (focusIndex > 0) {
				focusItem.redraw ();
				focusItem = items [focusIndex - 1];
				focusItem.redraw ();
			}
			break;
		}
		case SWT.ARROW_DOWN: {
			int focusIndex = indexOf (focusItem);
			if (focusIndex < itemCount - 1) {
				focusItem.redraw ();
				focusItem = items [focusIndex + 1];
				focusItem.redraw ();
			}
			break;
		}
	}
}

void onMouseDown (Event event) {
	if (event.button != 1) return;
	int x = event.x;
	int y = event.y;
	for (int i = 0; i < itemCount; i++) {
		ExpandItem item = items[i];
		boolean hover = item.x <= x && x < (item.x + item.width) && item.y <= y && y < (item.y + getBandHeight ());
		if (hover && item != focusItem) {
			focusItem.redraw ();
			focusItem = item;
			focusItem.redraw ();
			forceFocus ();
			break;
		}
	}
}

void onMouseUp (Event event) {
	if (event.button != 1) return;
	if (focusItem == null) return;
	int x = event.x;
	int y = event.y;
	boolean hover = focusItem.x <= x && x < (focusItem.x + focusItem.width) && focusItem.y <= y && y < (focusItem.y + getBandHeight ());
	if (hover) {
		Event ev = new Event ();
		ev.item = focusItem;
		notifyListeners (focusItem.expanded ? SWT.Collapse : SWT.Expand, ev);
		focusItem.expanded = !focusItem.expanded;
		showItem (focusItem);
	}
}

void onPaint (Event event) {
	boolean hasFocus = isFocusControl ();
	for (int i = 0; i < itemCount; i++) {
		ExpandItem item = items [i];
		item.drawItem (event.gc, hasFocus && item == focusItem);
	}
}

void onResize () {
	Rectangle rect = getClientArea ();
	int width = Math.max (0, rect.width - spacing * 2);
	for (int i = 0; i < itemCount; i++) {
		ExpandItem item = items[i];
		item.setBounds (0, 0, width, item.height, false, true);
	}
	setScrollbar ();
}

void onScroll (Event event) {
	ScrollBar verticalBar = getVerticalBar ();
	if (verticalBar != null) {
		yCurrentScroll = verticalBar.getSelection();
		layoutItems (0, false);
	}
}

void onTraverse (Event event) {
	switch (event.detail) {
		case SWT.TRAVERSE_TAB_NEXT:
		case SWT.TRAVERSE_TAB_PREVIOUS:
			event.doit = true;
			break;
	}
}

}
