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Provides common utility functions
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/*
 * Copyright (c) CQSE GmbH
 *
 * 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 org.conqat.lib.commons.color;

import java.awt.Color;
import java.util.function.Function;
import java.util.regex.Pattern;

import org.conqat.lib.commons.assertion.CCSMAssert;
import org.conqat.lib.commons.enums.EnumUtils;

/**
 * Methods for handling colors.
 */
public class ColorUtils {

	/** Pattern used for finding */
	public static Pattern HTML_COLOR_PATTERN = Pattern.compile("#[0-9a-f]{6}", Pattern.CASE_INSENSITIVE);

	/** Converts a color to a HTML color in the format #RRGGBB. */
	public static String toHtmlString(Color color) {
		return String.format("#%06X", color.getRGB() & 0xffffff);
	}

	/**
	 * Returns a color from a string. If the string could not be decoded, null is returned. This methods
	 * supports the html color format (i.e. #RRGGBB) and some predefined names (e.g. red, green, etc.).
	 */
	public static Color fromString(String s) {
		if (HTML_COLOR_PATTERN.matcher(s).matches()) {
			return Color.decode("0x" + s.substring(1));
		}

		EAWTColors color = EnumUtils.valueOfIgnoreCase(EAWTColors.class, s);
		if (color != null) {
			return color.getColor();
		}

		return null;
	}

	/** List of colors defined in AWT used as a lookup table. */
	private enum EAWTColors {

		/** Red */
		RED(Color.RED),

		/** Green */
		GREEN(Color.GREEN),

		/** Blue */
		BLUE(Color.BLUE),

		/** Yellow */
		YELLOW(Color.YELLOW),

		/** Orange */
		ORANGE(Color.ORANGE),

		/** White */
		WHITE(Color.WHITE),

		/** Black */
		BLACK(Color.BLACK),

		/** Gray */
		GRAY(Color.GRAY),

		/** Cyan */
		CYAN(Color.CYAN),

		/** Magenta */
		MAGENTA(Color.MAGENTA);

		/** The color actual color. */
		private final Color color;

		/** Constructor. */
		EAWTColors(Color color) {
			this.color = color;
		}

		/** Returns the color for a enum constant. */
		public Color getColor() {
			return color;
		}
	}

	/**
	 * Blend together two colors, using the specified factor to indicate the weight given to the first
	 * color.
	 */
	public static Color blend(double factor, Color color1, Color color2) {
		CCSMAssert.isTrue(factor >= 0 && factor <= 1, "Factor must be between 0 and 1 but is: " + factor);
		int r = getColorComponent(factor, color1, color2, Color::getRed);
		int g = getColorComponent(factor, color1, color2, Color::getGreen);
		int b = getColorComponent(factor, color1, color2, Color::getBlue);
		return new Color(r, g, b);
	}

	/** Get the color component. */
	protected static int getColorComponent(double factor, Color color1, Color color2,
			Function function) {
		return (int) Math.round(factor * function.apply(color1) + (1.0 - factor) * function.apply(color2));
	}
}