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/*
 * Copyright 2008 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package com.badlogic.gdx.backends.gwt.widgets;

import com.google.gwt.user.client.DOM;
import com.google.gwt.user.client.Element;
import com.google.gwt.user.client.ui.Widget;

/** A widget that displays progress on an arbitrary scale.
 * 
 * CSS Style Rules
 * 
 * .gwt-ProgressBar-shell { primary style }
 * .gwt-ProgressBar-shell .gwt-ProgressBar-bar { the actual progress bar }
 * .gwt-ProgressBar-shell .gwt-ProgressBar-text { text on the bar }
 * .gwt-ProgressBar-shell .gwt-ProgressBar-text-firstHalf { applied to text when progress is less than 50 percent }
 * .gwt-ProgressBar-shell .gwt-ProgressBar-text-secondHalf { applied to text when progress is greater than 50 percent }
 *  */
public class ProgressBar extends Widget implements ResizableWidget {

	private static final String DEFAULT_TEXT_CLASS_NAME = "gwt-ProgressBar-text";

	private String textClassName = DEFAULT_TEXT_CLASS_NAME;
	private String textFirstHalfClassName = DEFAULT_TEXT_CLASS_NAME + "-firstHalf";
	private String textSecondHalfClassName = DEFAULT_TEXT_CLASS_NAME + "-secondHalf";

	/** A formatter used to format the text displayed in the progress bar widget. */
	public abstract static class TextFormatter {
		/** Generate the text to display in the ProgressBar based on the current value.
		 * 
		 * Override this method to change the text displayed within the ProgressBar.
		 * 
		 * @param bar the progress bar
		 * @param curProgress the current progress
		 * @return the text to display in the progress bar */
		protected abstract String getText (ProgressBar bar, double curProgress);
	}

	/** The bar element that displays the progress. */
	private Element barElement;

	/** The current progress. */
	private double curProgress;

	/** The maximum progress. */
	private double maxProgress;

	/** The minimum progress. */
	private double minProgress;

	/** A boolean that determines if the text is visible. */
	private boolean textVisible = true;

	/** The element that displays text on the page. */
	private Element textElement;

	/** The current text formatter. */
	private TextFormatter textFormatter;

	/** Create a progress bar with default range of 0 to 100. */
	public ProgressBar () {
		this(0.0, 100.0, 0.0);
	}

	/** Create a progress bar with an initial progress and a default range of 0 to 100.
	 * 
	 * @param curProgress the current progress */
	public ProgressBar (double curProgress) {
		this(0.0, 100.0, curProgress);
	}

	/** Create a progress bar within the given range.
	 * 
	 * @param minProgress the minimum progress
	 * @param maxProgress the maximum progress */
	public ProgressBar (double minProgress, double maxProgress) {
		this(minProgress, maxProgress, 0.0);
	}

	/** Create a progress bar within the given range starting at the specified progress amount.
	 * 
	 * @param minProgress the minimum progress
	 * @param maxProgress the maximum progress
	 * @param curProgress the current progress */
	public ProgressBar (double minProgress, double maxProgress, double curProgress) {
		this(minProgress, maxProgress, curProgress, null);
	}

	/** Create a progress bar within the given range starting at the specified progress amount.
	 * 
	 * @param minProgress the minimum progress
	 * @param maxProgress the maximum progress
	 * @param curProgress the current progress
	 * @param textFormatter the text formatter */
	public ProgressBar (double minProgress, double maxProgress, double curProgress, TextFormatter textFormatter) {
		this.minProgress = minProgress;
		this.maxProgress = maxProgress;
		this.curProgress = curProgress;
		setTextFormatter(textFormatter);

		// Create the outer shell
		setElement(DOM.createDiv());
		DOM.setStyleAttribute(getElement(), "position", "relative");
		setStyleName("gwt-ProgressBar-shell");

		// Create the bar element
		barElement = DOM.createDiv();
		DOM.appendChild(getElement(), barElement);
		DOM.setStyleAttribute(barElement, "height", "100%");
		setBarStyleName("gwt-ProgressBar-bar");

		// Create the text element
		textElement = DOM.createDiv();
		DOM.appendChild(getElement(), textElement);
		DOM.setStyleAttribute(textElement, "position", "absolute");
		DOM.setStyleAttribute(textElement, "top", "0px");

		// Set the current progress
		setProgress(curProgress);
	}

	/** Get the maximum progress.
	 * 
	 * @return the maximum progress */
	public double getMaxProgress () {
		return maxProgress;
	}

	/** Get the minimum progress.
	 * 
	 * @return the minimum progress */
	public double getMinProgress () {
		return minProgress;
	}

	/** Get the current percent complete, relative to the minimum and maximum values. The percent will always be between 0.0 - 1.0.
	 * 
	 * @return the current percent complete */
	public double getPercent () {
		// If we have no range
		if (maxProgress <= minProgress) {
			return 0.0;
		}

		// Calculate the relative progress
		double percent = (curProgress - minProgress) / (maxProgress - minProgress);
		return Math.max(0.0, Math.min(1.0, percent));
	}

	/** Get the current progress.
	 * 
	 * @return the current progress */
	public double getProgress () {
		return curProgress;
	}

	/** Get the text formatter.
	 * 
	 * @return the text formatter */
	public TextFormatter getTextFormatter () {
		return textFormatter;
	}

	/** Check whether the text is visible or not.
	 * 
	 * @return true if the text is visible */
	public boolean isTextVisible () {
		return textVisible;
	}

	/** This method is called when the dimensions of the parent element change. Subclasses should override this method as needed.
	 * 
	 * Move the text to the center of the progress bar.
	 * 
	 * @param width the new client width of the element
	 * @param height the new client height of the element */
	public void onResize (int width, int height) {
		if (textVisible) {
			int textWidth = DOM.getElementPropertyInt(textElement, "offsetWidth");
			int left = (width / 2) - (textWidth / 2);
			DOM.setStyleAttribute(textElement, "left", left + "px");
		}
	}

	/** Redraw the progress bar when something changes the layout. */
	public void redraw () {
		if (isAttached()) {
			int width = DOM.getElementPropertyInt(getElement(), "clientWidth");
			int height = DOM.getElementPropertyInt(getElement(), "clientHeight");
			onResize(width, height);
		}
	}

	public void setBarStyleName (String barClassName) {
		DOM.setElementProperty(barElement, "className", barClassName);
	}

	/** Set the maximum progress. If the minimum progress is more than the current progress, the current progress is adjusted to be
	 * within the new range.
	 * 
	 * @param maxProgress the maximum progress */
	public void setMaxProgress (double maxProgress) {
		this.maxProgress = maxProgress;
		curProgress = Math.min(curProgress, maxProgress);
		resetProgress();
	}

	/** Set the minimum progress. If the minimum progress is more than the current progress, the current progress is adjusted to be
	 * within the new range.
	 * 
	 * @param minProgress the minimum progress */
	public void setMinProgress (double minProgress) {
		this.minProgress = minProgress;
		curProgress = Math.max(curProgress, minProgress);
		resetProgress();
	}

	/** Set the current progress.
	 * 
	 * @param curProgress the current progress */
	public void setProgress (double curProgress) {
		this.curProgress = Math.max(minProgress, Math.min(maxProgress, curProgress));

		// Calculate percent complete
		int percent = (int)(100 * getPercent());
		DOM.setStyleAttribute(barElement, "width", percent + "%");
		DOM.setElementProperty(textElement, "innerHTML", generateText(curProgress));
		updateTextStyle(percent);

		// Realign the text
		redraw();
	}

	public void setTextFirstHalfStyleName (String textFirstHalfClassName) {
		this.textFirstHalfClassName = textFirstHalfClassName;
		onTextStyleChange();
	}

	/** Set the text formatter.
	 * 
	 * @param textFormatter the text formatter */
	public void setTextFormatter (TextFormatter textFormatter) {
		this.textFormatter = textFormatter;
	}

	public void setTextSecondHalfStyleName (String textSecondHalfClassName) {
		this.textSecondHalfClassName = textSecondHalfClassName;
		onTextStyleChange();
	}

	public void setTextStyleName (String textClassName) {
		this.textClassName = textClassName;
		onTextStyleChange();
	}

	/** Sets whether the text is visible over the bar.
	 * 
	 * @param textVisible True to show text, false to hide it */
	public void setTextVisible (boolean textVisible) {
		this.textVisible = textVisible;
		if (this.textVisible) {
			DOM.setStyleAttribute(textElement, "display", "");
			redraw();
		} else {
			DOM.setStyleAttribute(textElement, "display", "none");
		}
	}

	/** Generate the text to display within the progress bar. Override this function to change the default progress percent to a
	 * more informative message, such as the number of kilobytes downloaded.
	 * 
	 * @param curProgress the current progress
	 * @return the text to display in the progress bar */
	protected String generateText (double curProgress) {
		if (textFormatter != null) {
			return textFormatter.getText(this, curProgress);
		} else {
			return (int)(100 * getPercent()) + "%";
		}
	}

	/** Get the bar element.
	 * 
	 * @return the bar element */
	protected Element getBarElement () {
		return barElement;
	}

	/** Get the text element.
	 * 
	 * @return the text element */
	protected Element getTextElement () {
		return textElement;
	}

	/** This method is called immediately after a widget becomes attached to the browser's document. */
	@Override
	protected void onLoad () {
		// Reset the position attribute of the parent element
		DOM.setStyleAttribute(getElement(), "position", "relative");
		ResizableWidgetCollection.get().add(this);
		redraw();
	}

	@Override
	protected void onUnload () {
		ResizableWidgetCollection.get().remove(this);
	}

	/** Reset the progress text based on the current min and max progress range. */
	protected void resetProgress () {
		setProgress(getProgress());
	}

	private void onTextStyleChange () {
		int percent = (int)(100 * getPercent());
		updateTextStyle(percent);
	}

	private void updateTextStyle (int percent) {
		// Set the style depending on the size of the bar
		if (percent < 50) {
			DOM.setElementProperty(textElement, "className", textClassName + " " + textFirstHalfClassName);
		} else {
			DOM.setElementProperty(textElement, "className", textClassName + " " + textSecondHalfClassName);
		}
	}
}