/* SPDX-License-Identifier: LGPL-2.0-or-later
 *
 * This was part of the KDE project - see KGuiAddons
 * Copyright (C) 2007 Matthew Woehlke <mw_triad@users.sourceforge.net>
 * Copyright (C) 2007 Olaf Schmidt <ojschmidt@kde.org>
 * Copyright (C) 2007 Thomas Zander <zander@kde.org>
 * Copyright (C) 2007 Zack Rusin <zack@kde.org>
 * Copyright (C) 2015 Petr Mrazek <peterix@gmail.com>
 * Copyright (C) 2026 Project Tick
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

#pragma once

#include "rainbow_config.h"

#include <QPainter>
class QColor;

/**
 * A set of methods used to work with colors.
 */
namespace Rainbow
{
	/**
	 * Calculate the luma of a color. Luma is weighted sum of gamma-adjusted
	 * R'G'B' components of a color. The result is similar to qGray. The range
	 * is from 0.0 (black) to 1.0 (white).
	 *
	 * Rainbow::darken(), Rainbow::lighten() and Rainbow::shade()
	 * operate on the luma of a color.
	 *
	 * @see http://en.wikipedia.org/wiki/Luma_(video)
	 */
	RAINBOW_EXPORT qreal luma(const QColor&);

	/**
	 * Calculate hue, chroma and luma of a color in one call.
	 * @since 5.0
	 */
	RAINBOW_EXPORT void getHcy(const QColor&, qreal* hue, qreal* chroma,
							   qreal* luma, qreal* alpha = 0);

	/**
	 * Calculate the contrast ratio between two colors, according to the
	 * W3C/WCAG2.0 algorithm, (Lmax + 0.05)/(Lmin + 0.05), where Lmax and Lmin
	 * are the luma values of the lighter color and the darker color,
	 * respectively.
	 *
	 * A contrast ration of 5:1 (result == 5.0) is the minimum for "normal"
	 * text to be considered readable (large text can go as low as 3:1). The
	 * ratio ranges from 1:1 (result == 1.0) to 21:1 (result == 21.0).
	 *
	 * @see Rainbow::luma
	 */
	RAINBOW_EXPORT qreal contrastRatio(const QColor&, const QColor&);

	/**
	 * Adjust the luma of a color by changing its distance from white.
	 *
	 * @li amount == 1.0 gives white
	 * @li amount == 0.5 results in a color whose luma is halfway between 1.0
	 * and that of the original color
	 * @li amount == 0.0 gives the original color
	 * @li amount == -1.0 gives a color that is 'twice as far from white' as
	 * the original color, that is luma(result) == 1.0 - 2*(1.0 - luma(color))
	 *
	 * @param amount factor by which to adjust the luma component of the color
	 * @param chromaInverseGain (optional) factor by which to adjust the chroma
	 * component of the color; 1.0 means no change, 0.0 maximizes chroma
	 * @see Rainbow::shade
	 */
	RAINBOW_EXPORT QColor lighten(const QColor&, qreal amount = 0.5,
								  qreal chromaInverseGain = 1.0);

	/**
	 * Adjust the luma of a color by changing its distance from black.
	 *
	 * @li amount == 1.0 gives black
	 * @li amount == 0.5 results in a color whose luma is halfway between 0.0
	 * and that of the original color
	 * @li amount == 0.0 gives the original color
	 * @li amount == -1.0 gives a color that is 'twice as far from black' as
	 * the original color, that is luma(result) == 2*luma(color)
	 *
	 * @param amount factor by which to adjust the luma component of the color
	 * @param chromaGain (optional) factor by which to adjust the chroma
	 * component of the color; 1.0 means no change, 0.0 minimizes chroma
	 * @see Rainbow::shade
	 */
	RAINBOW_EXPORT QColor darken(const QColor&, qreal amount = 0.5,
								 qreal chromaGain = 1.0);

	/**
	 * Adjust the luma and chroma components of a color. The amount is added
	 * to the corresponding component.
	 *
	 * @param lumaAmount amount by which to adjust the luma component of the
	 * color; 0.0 results in no change, -1.0 turns anything black, 1.0 turns
	 * anything white
	 * @param chromaAmount (optional) amount by which to adjust the chroma
	 * component of the color; 0.0 results in no change, -1.0 minimizes chroma,
	 * 1.0 maximizes chroma
	 * @see Rainbow::luma
	 */
	RAINBOW_EXPORT QColor shade(const QColor&, qreal lumaAmount,
								qreal chromaAmount = 0.0);

	/**
	 * Create a new color by tinting one color with another. This function is
	 * meant for creating additional colors withings the same class (background,
	 * foreground) from colors in a different class. Therefore when @p amount
	 * is low, the luma of @p base is mostly preserved, while the hue and
	 * chroma of @p color is mostly inherited.
	 *
	 * @param base color to be tinted
	 * @param color color with which to tint
	 * @param amount how strongly to tint the base; 0.0 gives @p base,
	 * 1.0 gives @p color
	 */
	RAINBOW_EXPORT QColor tint(const QColor& base, const QColor& color,
							   qreal amount = 0.3);

	/**
	 * Blend two colors into a new color by linear combination.
	 * @code
		QColor lighter = Rainbow::mix(myColor, Qt::white)
	 * @endcode
	 * @param c1 first color.
	 * @param c2 second color.
	 * @param bias weight to be used for the mix. @p bias <= 0 gives @p c1,
	 * @p bias >= 1 gives @p c2. @p bias == 0.5 gives a 50% blend of @p c1
	 * and @p c2.
	 */
	RAINBOW_EXPORT QColor mix(const QColor& c1, const QColor& c2,
							  qreal bias = 0.5);

	/**
	 * Blend two colors into a new color by painting the second color over the
	 * first using the specified composition mode.
	 * @code
		QColor white(Qt::white);
		white.setAlphaF(0.5);
		QColor lighter = Rainbow::overlayColors(myColor, white);
	   @endcode
	 * @param base the base color (alpha channel is ignored).
	 * @param paint the color to be overlayed onto the base color.
	 * @param comp the CompositionMode used to do the blending.
	 */
	RAINBOW_EXPORT QColor overlayColors(
		const QColor& base, const QColor& paint,
		QPainter::CompositionMode comp = QPainter::CompositionMode_SourceOver);
} // namespace Rainbow
