/*******************************************************************************
 * Copyright (c) 2006, 2007 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 * Port to the D programming language:
 *     Frank Benoit <benoit@tionex.de>
 *******************************************************************************/
module dwtx.jface.internal.text.revisions.Colors;

import dwtx.jface.internal.text.revisions.HunkComputer; // packageimport
import dwtx.jface.internal.text.revisions.LineIndexOutOfBoundsException; // packageimport
import dwtx.jface.internal.text.revisions.Hunk; // packageimport
import dwtx.jface.internal.text.revisions.ChangeRegion; // packageimport
import dwtx.jface.internal.text.revisions.Range; // packageimport
import dwtx.jface.internal.text.revisions.RevisionPainter; // packageimport
import dwtx.jface.internal.text.revisions.RevisionSelectionProvider; // packageimport


import dwt.dwthelper.utils;


import dwt.DWT;
import dwt.graphics.RGB;
import dwtx.core.runtime.Assert;

/**
 * Utility for color operations.
 *
 * @since 3.3
 */
public final class Colors {
    /*
     * Implementation note: Color computation assumes sRGB, which is probably not true, and does not
     * always give good results. CIE based algorithms would be better, see
     * http://www.w3.org/TR/PNG-ColorAppendix.html and http://en.wikipedia.org/wiki/Lab_color_space
     */

    /**
     * Returns the human-perceived brightness of a color as float in [0.0, 1.0]. The used RGB
     * weights come from http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC9.
     *
     * @param rgb the color
     * @return the gray-scale value
     */
    public static float brightness(RGB rgb) {
        return Math.min(1f, (0.2126f * rgb.red + 0.7152f * rgb.green + 0.0722f * rgb.blue + 0.5f) / 255f);
    }

    /**
     * Normalizes a color in its perceived brightness. Yellows are darkened, while blues and reds
     * are lightened. Depending on the hue, the brightness range within the RGB gamut may be
     * different, outside values are clipped. Note that this is an approximation; the returned RGB
     * is not guaranteed to have the requested {@link #brightness(RGB) brightness}.
     *
     * @param color the color to normalize
     * @param brightness the requested brightness, in [0,&nbsp;1]
     * @return a normalized version of <code>color</code>
     * @see #brightness(RGB)
     */
    public static RGB adjustBrightness(RGB color, float brightness) {
        float[] hsi= toHSI(color);
        float psychoFactor= brightness - brightness(color);
        float weight= 0.5f; // found by trial and error
        hsi[2]= Math.max(0, Math.min(1.0f, hsi[2] + psychoFactor * weight));
        color= fromHSI(hsi);
        return color;
    }

    /**
     * Converts an {@link RGB} to an <a href="http://en.wikipedia.org/wiki/HSL_color_space">HSI</a>
     * triplet.
     *
     * @param color the color to convert
     * @return the HSI float array of length 3
     */
    private static float[] toHSI(RGB color) {
        float r = color.red / 255f;
        float g = color.green / 255f;
        float b = color.blue / 255f;
        float max = Math.max(Math.max(r, g), b);
        float min = Math.min(Math.min(r, g), b);
        float delta = max - min;
        float maxPlusMin= max + min;
        float intensity = maxPlusMin / 2;
        float saturation= intensity < 0.5 ? delta / maxPlusMin : delta / (2 - maxPlusMin);

        float hue = 0;
        if (delta !is 0) {
            if (r is max) {
                hue = (g  - b) / delta;
            } else {
                if (g is max) {
                    hue = 2 + (b - r) / delta;
                } else {
                    hue = 4 + (r - g) / delta;
                }
            }
            hue *= 60;
            if (hue < 0) hue += 360;
        }
        return [hue, saturation, intensity];
    }

    /**
     * Converts a <a href="http://en.wikipedia.org/wiki/HSL_color_space">HSI</a> triplet to an RGB.
     *
     * @param hsi the HSI values
     * @return the RGB corresponding to the HSI spec
     */
    private static RGB fromHSI(float[] hsi) {
        float r, g, b;
        float hue= hsi[0];
        float saturation= hsi[1];
        float intensity= hsi[2];
        if (saturation is 0) {
            r = g = b = intensity;
        } else {
            float temp2= intensity < 0.5f ? intensity * (1.0f + saturation) : (intensity + saturation) - (intensity * saturation);
            float temp1= 2f * intensity - temp2;
            if (hue is 360) hue = 0;
            hue /= 360;

            r= hue2RGB(temp1, temp2, hue + 1f/3f);
            g= hue2RGB(temp1, temp2, hue);
            b= hue2RGB(temp1, temp2, hue - 1f/3f);
        }

        int red = cast(int)(r * 255 + 0.5);
        int green = cast(int)(g * 255 + 0.5);
        int blue = cast(int)(b * 255 + 0.5);
        return new RGB(red, green, blue);
    }

    private static float hue2RGB(float t1, float t2, float hue) {
        if (hue < 0)
            hue += 1;
        else if (hue > 1)
            hue -= 1;
        if (6f * hue < 1)
            return t1 +(t2 - t1) * 6f * hue;
        if (2f * hue < 1)
            return t2;
        if (3f * hue < 2)
            return t1 + (t2 - t1) * (2f/3f - hue) * 6f;
        return t1;
    }

    /**
     * Returns an RGB that lies between the given foreground and background
     * colors using the given mixing factor. A <code>factor</code> of 1.0 will produce a
     * color equal to <code>fg</code>, while a <code>factor</code> of 0.0 will produce one
     * equal to <code>bg</code>.
     * @param bg the background color
     * @param fg the foreground color
     * @param factor the mixing factor, must be in [0,&nbsp;1]
     *
     * @return the interpolated color
     */
    public static RGB blend(RGB bg, RGB fg, float factor) {
        Assert.isLegal(bg !is null);
        Assert.isLegal(fg !is null);
        Assert.isLegal(factor >= 0f && factor <= 1f);

        float complement= 1f - factor;
        return new RGB(
                cast(int) (complement * bg.red + factor * fg.red),
                cast(int) (complement * bg.green + factor * fg.green),
                cast(int) (complement * bg.blue + factor * fg.blue)
        );
    }

    /**
     * Returns an array of colors in a smooth palette from <code>start</code> to <code>end</code>.
     * <p>
     * The returned array has size <code>steps</code>, and the color at index 0 is <code>start</code>, the color
     * at index <code>steps&nbsp;-&nbsp;1</code> is <code>end</code>.
     *
     * @param start the start color of the palette
     * @param end the end color of the palette
     * @param steps the requested size, must be &gt; 0
     * @return an array of <code>steps</code> colors in the palette from <code>start</code> to <code>end</code>
     */
    public static RGB[] palette(RGB start, RGB end, int steps) {
        Assert.isLegal(start !is null);
        Assert.isLegal(end !is null);
        Assert.isLegal(steps > 0);

        if (steps is 1)
            return [ start ];

        float step= 1.0f / (steps - 1);
        RGB[] gradient= new RGB[steps];
        for (int i= 0; i < steps; i++)
            gradient[i]= blend(start, end, step * i);

        return gradient;
    }

    /**
     * Returns an array of colors with hues evenly distributed on the hue wheel defined by the <a
     * href="http://en.wikipedia.org/wiki/HSV_color_space">HSB color space</a>. The returned array
     * has size <code>steps</code>. The distance <var>d</var> between two successive colors is
     * in [120&#176;,&nbsp;180&#176;].
     * <p>
     * The color at a given <code>index</code> has the hue returned by
     * {@linkplain #computeHue(int) computeHue(index)}; i.e. the computed hues are not equidistant,
     * but adaptively distributed on the color wheel.
     * </p>
     * <p>
     * The first six colors returned correspond to the following {@link DWT} color constants:
     * {@link DWT#COLOR_RED red}, {@link DWT#COLOR_GREEN green}, {@link DWT#COLOR_BLUE blue},
     * {@link DWT#COLOR_YELLOW yellow}, {@link DWT#COLOR_CYAN cyan},
     * {@link DWT#COLOR_MAGENTA magenta}.
     * </p>
     *
     * @param steps the requested size, must be &gt;= 2
     * @return an array of <code>steps</code> colors evenly distributed on the color wheel
     */
    public static RGB[] rainbow(int steps) {
        Assert.isLegal(steps >= 2);

        RGB[] rainbow= new RGB[steps];
        for (int i= 0; i < steps; i++)
            rainbow[i]= new RGB(computeHue(i), 1f, 1f);

        return rainbow;
    }

    /**
     * Returns an indexed hue in [0&#176;,&nbsp;360&#176;), distributing the hues evenly on the hue wheel
     * defined by the <a href="http://en.wikipedia.org/wiki/HSV_color_space">HSB (or HSV) color
     * space</a>. The distance <var>d</var> between two successive colors is in [120&#176;,&nbsp;180&#176;].
     * <p>
     * The first six colors returned correspond to the following {@link DWT} color constants:
     * {@link DWT#COLOR_RED red}, {@link DWT#COLOR_GREEN green}, {@link DWT#COLOR_BLUE blue},
     * {@link DWT#COLOR_YELLOW yellow}, {@link DWT#COLOR_CYAN cyan},
     * {@link DWT#COLOR_MAGENTA magenta}.
     * </p>
     *
     * @param index the index of the color, must be &gt;= 0
     * @return a color hue in [0&#176;,&nbsp;360&#176;)
     * @see RGB#RGB(float, float, float)
     */
    public static float computeHue(final int index) {
        Assert.isLegal(index >= 0);
        /*
         * Base 3 gives a nice partitioning for RGB colors with red, green, blue being the colors
         * 0,1,2, and yellow, cyan, magenta colors 3,4,5.
         */
        final int base= 3;
        final float range= 360f;

        // partition the baseRange by using the least significant bit to select one half of the
        // partitioning
        int baseIndex= index / base;
        float baseRange= range / base;
        float baseOffset= 0f;
        while (baseIndex > 0) {
            baseRange /= 2;
            int lsb= baseIndex % 2;
            baseOffset += lsb * baseRange;
            baseIndex >>= 1;
        }

        final int baseMod= index % base;
        final float hue= baseOffset + baseMod * range / base;
        Assert.isTrue(hue >= 0 && hue < 360);
        return hue;
    }

    private this() {
        // not instantiatable
    }

}