/*
 * Copyright (c) 2018-2020, Andreas Kling <andreas@ladybird.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include <math.h>

#include <AK/Assertions.h>
#include <AK/Format.h>
#include <AK/Forward.h>
#include <AK/Math.h>
#include <AK/StdLibExtras.h>
#include <LibIPC/Forward.h>

namespace Gfx {

typedef u32 ARGB32;

enum class AlphaType {
    Premultiplied,
    Unpremultiplied,
};

inline bool is_valid_alpha_type(u32 alpha_type)
{
    switch (alpha_type) {
    case (u32)AlphaType::Premultiplied:
    case (u32)AlphaType::Unpremultiplied:
        return true;
    }
    return false;
}

struct HSV {
    double hue { 0 };
    double saturation { 0 };
    double value { 0 };
};

struct YUV {
    float y { 0 };
    float u { 0 };
    float v { 0 };
};

struct Oklab {
    float L { 0 };
    float a { 0 };
    float b { 0 };
};

class Color {
public:
    enum class NamedColor {
        Transparent,
        Black,
        White,
        Red,
        Green,
        Cyan,
        Blue,
        Yellow,
        Magenta,
        DarkGray,
        MidGray,
        LightGray,
        WarmGray,
        DarkCyan,
        DarkGreen,
        DarkBlue,
        DarkRed,
        MidCyan,
        MidGreen,
        MidRed,
        MidBlue,
        MidMagenta,
        LightBlue,
    };

    using enum NamedColor;

    constexpr Color() = default;
    constexpr Color(NamedColor);
    constexpr Color(u8 r, u8 g, u8 b)
        : m_value(0xff000000 | (r << 16) | (g << 8) | b)
    {
    }
    constexpr Color(u8 r, u8 g, u8 b, u8 a)
        : m_value((a << 24) | (r << 16) | (g << 8) | b)
    {
    }

    static constexpr Color from_rgb(unsigned rgb) { return Color(rgb | 0xff000000); }
    static constexpr Color from_argb(unsigned argb) { return Color(argb); }

    static constexpr Color from_yuv(YUV const& yuv) { return from_yuv(yuv.y, yuv.u, yuv.v); }
    static constexpr Color from_yuv(float y, float u, float v)
    {
        // https://www.itu.int/rec/R-REC-BT.1700-0-200502-I/en Table 4, Items 8 and 9 arithmetically inverted
        float r = y + v / 0.877f;
        float b = y + u / 0.493f;
        float g = (y - 0.299f * r - 0.114f * b) / 0.587f;
        r = clamp(r, 0.0f, 1.0f);
        g = clamp(g, 0.0f, 1.0f);
        b = clamp(b, 0.0f, 1.0f);

        return { static_cast<u8>(floorf(r * 255.0f)), static_cast<u8>(floorf(g * 255.0f)), static_cast<u8>(floorf(b * 255.0f)) };
    }

    // https://www.itu.int/rec/R-REC-BT.1700-0-200502-I/en Table 4
    constexpr YUV to_yuv() const
    {
        float r = red() / 255.0f;
        float g = green() / 255.0f;
        float b = blue() / 255.0f;
        // Item 8
        float y = 0.299f * r + 0.587f * g + 0.114f * b;
        // Item 9
        float u = 0.493f * (b - y);
        float v = 0.877f * (r - y);
        y = clamp(y, 0.0f, 1.0f);
        u = clamp(u, -1.0f, 1.0f);
        v = clamp(v, -1.0f, 1.0f);
        return { y, u, v };
    }

    static constexpr Color from_hsl(float h_degrees, float s, float l) { return from_hsla(h_degrees, s, l, 1.0); }
    static constexpr Color from_hsla(float h_degrees, float s, float l, float a)
    {
        // Algorithm from https://www.w3.org/TR/css-color-3/#hsl-color
        float h = clamp(h_degrees / 360.0f, 0.0f, 1.0f);
        s = clamp(s, 0.0f, 1.0f);
        l = clamp(l, 0.0f, 1.0f);
        a = clamp(a, 0.0f, 1.0f);

        // HOW TO RETURN hue.to.rgb(m1, m2, h):
        auto hue_to_rgb = [](float m1, float m2, float h) -> float {
            // IF h<0: PUT h+1 IN h
            if (h < 0.0f)
                h = h + 1.0f;
            // IF h>1: PUT h-1 IN h
            if (h > 1.0f)
                h = h - 1.0f;
            // IF h*6<1: RETURN m1+(m2-m1)*h*6
            if (h * 6.0f < 1.0f)
                return m1 + (m2 - m1) * h * 6.0f;
            // IF h*2<1: RETURN m2
            if (h * 2.0f < 1.0f)
                return m2;
            // IF h*3<2: RETURN m1+(m2-m1)*(2/3-h)*6
            if (h * 3.0f < 2.0f)
                return m1 + (m2 - m1) * (2.0f / 3.0f - h) * 6.0f;
            // RETURN m1
            return m1;
        };

        // SELECT:
        // l<=0.5: PUT l*(s+1) IN m2
        float m2;
        if (l <= 0.5f)
            m2 = l * (s + 1.0f);
        // ELSE: PUT l+s-l*s IN m2
        else
            m2 = l + s - l * s;
        // PUT l*2-m2 IN m1
        float m1 = l * 2.0f - m2;
        // PUT hue.to.rgb(m1, m2, h+1/3) IN r
        float r = hue_to_rgb(m1, m2, h + 1.0f / 3.0f);
        // PUT hue.to.rgb(m1, m2, h    ) IN g
        float g = hue_to_rgb(m1, m2, h);
        // PUT hue.to.rgb(m1, m2, h-1/3) IN b
        float b = hue_to_rgb(m1, m2, h - 1.0f / 3.0f);
        // RETURN (r, g, b)
        u8 r_u8 = clamp(lroundf(r * 255.0f), 0, 255);
        u8 g_u8 = clamp(lroundf(g * 255.0f), 0, 255);
        u8 b_u8 = clamp(lroundf(b * 255.0f), 0, 255);
        u8 a_u8 = clamp(lroundf(a * 255.0f), 0, 255);
        return Color(r_u8, g_u8, b_u8, a_u8);
    }

    static Color from_a98rgb(float r, float g, float b, float alpha = 1.0f);
    static Color from_display_p3(float r, float g, float b, float alpha = 1.0f);
    static Color from_lab(float L, float a, float b, float alpha = 1.0f);
    static Color from_linear_srgb(float r, float g, float b, float alpha = 1.0f);
    static Color from_pro_photo_rgb(float r, float g, float b, float alpha = 1.0f);
    static Color from_rec2020(float r, float g, float b, float alpha = 1.0f);
    static Color from_xyz50(float x, float y, float z, float alpha = 1.0f);
    static Color from_xyz65(float x, float y, float z, float alpha = 1.0f);

    // https://bottosson.github.io/posts/oklab/
    static constexpr Color from_oklab(float L, float a, float b, float alpha = 1.0f)
    {
        float l = L + 0.3963377774f * a + 0.2158037573f * b;
        float m = L - 0.1055613458f * a - 0.0638541728f * b;
        float s = L - 0.0894841775f * a - 1.2914855480f * b;

        l = l * l * l;
        m = m * m * m;
        s = s * s * s;

        float red = 4.0767416621f * l - 3.3077115913f * m + 0.2309699292f * s;
        float green = -1.2684380046f * l + 2.6097574011f * m - 0.3413193965f * s;
        float blue = -0.0041960863f * l - 0.7034186147f * m + 1.7076147010f * s;

        return from_linear_srgb(red, green, blue, alpha);
    }

    // https://bottosson.github.io/posts/oklab/
    constexpr Oklab to_oklab()
    {
        auto srgb_to_linear = [](float c) {
            return c >= 0.04045f ? pow((c + 0.055f) / 1.055f, 2.4f) : c / 12.92f;
        };

        float r = srgb_to_linear(red() / 255.f);
        float g = srgb_to_linear(green() / 255.f);
        float b = srgb_to_linear(blue() / 255.f);

        float l = cbrtf(0.4122214708f * r + 0.5363325363f * g + 0.0514459929f * b);
        float m = cbrtf(0.2119034982f * r + 0.6806995451f * g + 0.1073969566f * b);
        float s = cbrtf(0.0883024619f * r + 0.2817188376f * g + 0.6299787005f * b);

        return {
            0.2104542553f * l + 0.7936177850f * m - 0.0040720468f * s,
            1.9779984951f * l - 2.4285922050f * m + 0.4505937099f * s,
            0.0259040371f * l + 0.7827717662f * m - 0.8086757660f * s,
        };
    }

    constexpr u8 red() const { return (m_value >> 16) & 0xff; }
    constexpr u8 green() const { return (m_value >> 8) & 0xff; }
    constexpr u8 blue() const { return m_value & 0xff; }
    constexpr u8 alpha() const { return (m_value >> 24) & 0xff; }

    constexpr void set_alpha(u8 value, AlphaType alpha_type = AlphaType::Unpremultiplied)
    {
        switch (alpha_type) {
        case AlphaType::Premultiplied:
            m_value = value << 24
                | (red() * value / 255) << 16
                | (green() * value / 255) << 8
                | blue() * value / 255;
            break;
        case AlphaType::Unpremultiplied:
            m_value = (m_value & 0x00ffffff) | value << 24;
            break;
        default:
            VERIFY_NOT_REACHED();
        }
    }

    constexpr void set_red(u8 value)
    {
        m_value &= 0xff00ffff;
        m_value |= value << 16;
    }

    constexpr void set_green(u8 value)
    {
        m_value &= 0xffff00ff;
        m_value |= value << 8;
    }

    constexpr void set_blue(u8 value)
    {
        m_value &= 0xffffff00;
        m_value |= value;
    }

    constexpr Color with_alpha(u8 alpha, AlphaType alpha_type = AlphaType::Unpremultiplied) const
    {
        Color color_with_alpha = Color(m_value);
        color_with_alpha.set_alpha(alpha, alpha_type);
        return color_with_alpha;
    }

    constexpr Color to_unpremultiplied() const
    {
        if (alpha() == 0 || alpha() == 255)
            return *this;
        return Color(
            red() * 255 / alpha(),
            green() * 255 / alpha(),
            blue() * 255 / alpha(),
            alpha());
    }

    constexpr Color blend(Color source) const
    {
        if (alpha() == 0 || source.alpha() == 255)
            return source;

        if (source.alpha() == 0)
            return *this;

        int const d = 255 * (alpha() + source.alpha()) - alpha() * source.alpha();
        u8 r = (red() * alpha() * (255 - source.alpha()) + source.red() * 255 * source.alpha()) / d;
        u8 g = (green() * alpha() * (255 - source.alpha()) + source.green() * 255 * source.alpha()) / d;
        u8 b = (blue() * alpha() * (255 - source.alpha()) + source.blue() * 255 * source.alpha()) / d;
        u8 a = d / 255;
        return Color(r, g, b, a);
    }

    ALWAYS_INLINE Color mixed_with(Color other, float weight) const
    {
        if (alpha() == other.alpha() || with_alpha(0) == other.with_alpha(0))
            return interpolate(other, weight);
        // Fallback to slower, but more visually pleasing premultiplied alpha mix.
        // This is needed for linear-gradient()s in LibWeb.
        auto mixed_alpha = mix<float>(alpha(), other.alpha(), weight);
        auto premultiplied_mix_channel = [&](float channel, float other_channel, float weight) {
            return round_to<u8>(mix<float>(channel * alpha(), other_channel * other.alpha(), weight) / mixed_alpha);
        };
        return Gfx::Color {
            premultiplied_mix_channel(red(), other.red(), weight),
            premultiplied_mix_channel(green(), other.green(), weight),
            premultiplied_mix_channel(blue(), other.blue(), weight),
            round_to<u8>(mixed_alpha),
        };
    }

    ALWAYS_INLINE Color interpolate(Color other, float weight) const noexcept
    {
        return Gfx::Color {
            round_to<u8>(mix<float>(red(), other.red(), weight)),
            round_to<u8>(mix<float>(green(), other.green(), weight)),
            round_to<u8>(mix<float>(blue(), other.blue(), weight)),
            round_to<u8>(mix<float>(alpha(), other.alpha(), weight)),
        };
    }

    constexpr Color multiply(Color other) const
    {
        return Color(
            red() * other.red() / 255,
            green() * other.green() / 255,
            blue() * other.blue() / 255,
            alpha() * other.alpha() / 255);
    }

    constexpr float distance_squared_to(Color other) const
    {
        int delta_red = other.red() - red();
        int delta_green = other.green() - green();
        int delta_blue = other.blue() - blue();
        int delta_alpha = other.alpha() - alpha();
        auto rgb_distance = (delta_red * delta_red + delta_green * delta_green + delta_blue * delta_blue) / (3.0f * 255 * 255);
        return delta_alpha * delta_alpha / (2.0f * 255 * 255) + rgb_distance * alpha() * other.alpha() / (255 * 255);
    }

    constexpr u8 luminosity() const
    {
        return round_to<u8>(red() * 0.2126f + green() * 0.7152f + blue() * 0.0722f);
    }

    constexpr float contrast_ratio(Color other)
    {
        auto l1 = luminosity();
        auto l2 = other.luminosity();
        auto darkest = min(l1, l2) / 255.;
        auto brightest = max(l1, l2) / 255.;
        return (brightest + 0.05) / (darkest + 0.05);
    }

    constexpr Color to_grayscale() const
    {
        auto gray = luminosity();
        return Color(gray, gray, gray, alpha());
    }

    constexpr Color sepia(float amount = 1.0f) const
    {
        auto blend_factor = 1.0f - amount;

        auto r1 = 0.393f + 0.607f * blend_factor;
        auto r2 = 0.769f - 0.769f * blend_factor;
        auto r3 = 0.189f - 0.189f * blend_factor;

        auto g1 = 0.349f - 0.349f * blend_factor;
        auto g2 = 0.686f + 0.314f * blend_factor;
        auto g3 = 0.168f - 0.168f * blend_factor;

        auto b1 = 0.272f - 0.272f * blend_factor;
        auto b2 = 0.534f - 0.534f * blend_factor;
        auto b3 = 0.131f + 0.869f * blend_factor;

        auto r = red();
        auto g = green();
        auto b = blue();

        return Color(
            clamp(lroundf(r * r1 + g * r2 + b * r3), 0, 255),
            clamp(lroundf(r * g1 + g * g2 + b * g3), 0, 255),
            clamp(lroundf(r * b1 + g * b2 + b * b3), 0, 255),
            alpha());
    }

    constexpr Color with_opacity(float opacity) const
    {
        VERIFY(opacity >= 0 && opacity <= 1);
        return with_alpha(static_cast<u8>(round(alpha() * opacity)));
    }

    constexpr Color darkened(float amount = 0.5f) const
    {
        return Color(red() * amount, green() * amount, blue() * amount, alpha());
    }

    constexpr Color lightened(float amount = 1.2f) const
    {
        return Color(min(255, (int)((float)red() * amount)), min(255, (int)((float)green() * amount)), min(255, (int)((float)blue() * amount)), alpha());
    }

    Vector<Color> shades(u32 steps, float max = 1.f) const;
    Vector<Color> tints(u32 steps, float max = 1.f) const;

    constexpr Color saturated_to(float saturation) const
    {
        auto hsv = to_hsv();
        auto alpha = this->alpha();
        auto color = Color::from_hsv(hsv.hue, static_cast<double>(saturation), hsv.value);
        color.set_alpha(alpha);
        return color;
    }

    constexpr Color inverted() const
    {
        return Color(~red(), ~green(), ~blue(), alpha());
    }

    constexpr Color xored(Color other) const
    {
        return Color(((other.m_value ^ m_value) & 0x00ffffff) | (m_value & 0xff000000));
    }

    constexpr ARGB32 value() const { return m_value; }

    constexpr bool operator==(Color other) const
    {
        return m_value == other.m_value;
    }

    enum class HTMLCompatibleSerialization {
        No,
        Yes,
    };

    [[nodiscard]] String to_string(HTMLCompatibleSerialization = HTMLCompatibleSerialization::No) const;
    String to_string_without_alpha() const;

    ByteString to_byte_string() const;
    ByteString to_byte_string_without_alpha() const;
    static Optional<Color> from_string(StringView);
    static Optional<Color> from_named_css_color_string(StringView);

    constexpr HSV to_hsv() const
    {
        HSV hsv;
        double r = static_cast<double>(red()) / 255.0;
        double g = static_cast<double>(green()) / 255.0;
        double b = static_cast<double>(blue()) / 255.0;
        double max = AK::max(AK::max(r, g), b);
        double min = AK::min(AK::min(r, g), b);
        double chroma = max - min;

        if (!chroma)
            hsv.hue = 0.0;
        else if (max == r)
            hsv.hue = (60.0 * ((g - b) / chroma)) + 360.0;
        else if (max == g)
            hsv.hue = (60.0 * ((b - r) / chroma)) + 120.0;
        else
            hsv.hue = (60.0 * ((r - g) / chroma)) + 240.0;

        if (hsv.hue >= 360.0)
            hsv.hue -= 360.0;

        if (!max)
            hsv.saturation = 0;
        else
            hsv.saturation = chroma / max;

        hsv.value = max;

        VERIFY(hsv.hue >= 0.0 && hsv.hue < 360.0);
        VERIFY(hsv.saturation >= 0.0 && hsv.saturation <= 1.0);
        VERIFY(hsv.value >= 0.0 && hsv.value <= 1.0);

        return hsv;
    }

    static constexpr Color from_hsv(double hue, double saturation, double value)
    {
        return from_hsv({ hue, saturation, value });
    }

    static constexpr Color from_hsv(HSV const& hsv)
    {
        VERIFY(hsv.hue >= 0.0 && hsv.hue < 360.0);
        VERIFY(hsv.saturation >= 0.0 && hsv.saturation <= 1.0);
        VERIFY(hsv.value >= 0.0 && hsv.value <= 1.0);

        double hue = hsv.hue;
        double saturation = hsv.saturation;
        double value = hsv.value;

        int high = static_cast<int>(hue / 60.0) % 6;
        double f = (hue / 60.0) - high;
        double c1 = value * (1.0 - saturation);
        double c2 = value * (1.0 - saturation * f);
        double c3 = value * (1.0 - saturation * (1.0 - f));

        double r = 0;
        double g = 0;
        double b = 0;

        switch (high) {
        case 0:
            r = value;
            g = c3;
            b = c1;
            break;
        case 1:
            r = c2;
            g = value;
            b = c1;
            break;
        case 2:
            r = c1;
            g = value;
            b = c3;
            break;
        case 3:
            r = c1;
            g = c2;
            b = value;
            break;
        case 4:
            r = c3;
            g = c1;
            b = value;
            break;
        case 5:
            r = value;
            g = c1;
            b = c2;
            break;
        }

        auto out_r = static_cast<u8>(round(r * 255));
        auto out_g = static_cast<u8>(round(g * 255));
        auto out_b = static_cast<u8>(round(b * 255));
        return Color(out_r, out_g, out_b);
    }

    constexpr Color suggested_foreground_color() const
    {
        return luminosity() < 128 ? Color::White : Color::Black;
    }

private:
    constexpr explicit Color(ARGB32 argb)
        : m_value(argb)
    {
    }

    ARGB32 m_value { 0 };
};

constexpr Color::Color(NamedColor named)
{
    if (named == Transparent) {
        m_value = 0;
        return;
    }

    struct {
        u8 r;
        u8 g;
        u8 b;
    } rgb;

    switch (named) {
    case Black:
        rgb = { 0, 0, 0 };
        break;
    case White:
        rgb = { 255, 255, 255 };
        break;
    case Red:
        rgb = { 255, 0, 0 };
        break;
    case Green:
        rgb = { 0, 255, 0 };
        break;
    case Cyan:
        rgb = { 0, 255, 255 };
        break;
    case DarkCyan:
        rgb = { 0, 127, 127 };
        break;
    case MidCyan:
        rgb = { 0, 192, 192 };
        break;
    case Blue:
        rgb = { 0, 0, 255 };
        break;
    case Yellow:
        rgb = { 255, 255, 0 };
        break;
    case Magenta:
        rgb = { 255, 0, 255 };
        break;
    case DarkGray:
        rgb = { 64, 64, 64 };
        break;
    case MidGray:
        rgb = { 127, 127, 127 };
        break;
    case LightGray:
        rgb = { 192, 192, 192 };
        break;
    case MidGreen:
        rgb = { 0, 192, 0 };
        break;
    case MidBlue:
        rgb = { 0, 0, 192 };
        break;
    case MidRed:
        rgb = { 192, 0, 0 };
        break;
    case MidMagenta:
        rgb = { 192, 0, 192 };
        break;
    case DarkGreen:
        rgb = { 0, 128, 0 };
        break;
    case DarkBlue:
        rgb = { 0, 0, 128 };
        break;
    case DarkRed:
        rgb = { 128, 0, 0 };
        break;
    case WarmGray:
        rgb = { 212, 208, 200 };
        break;
    case LightBlue:
        rgb = { 173, 216, 230 };
        break;
    default:
        VERIFY_NOT_REACHED();
        break;
    }

    m_value = 0xff000000 | (rgb.r << 16) | (rgb.g << 8) | rgb.b;
}

}

using Gfx::Color;

namespace AK {

template<>
class Traits<Color> : public DefaultTraits<Color> {
public:
    static unsigned hash(Color const& color)
    {
        return int_hash(color.value());
    }
};

template<>
struct Formatter<Gfx::Color> : public Formatter<StringView> {
    ErrorOr<void> format(FormatBuilder&, Gfx::Color);
};

template<>
struct Formatter<Gfx::YUV> : public Formatter<FormatString> {
    ErrorOr<void> format(FormatBuilder&, Gfx::YUV);
};

template<>
struct Formatter<Gfx::HSV> : public Formatter<FormatString> {
    ErrorOr<void> format(FormatBuilder&, Gfx::HSV);
};

template<>
struct Formatter<Gfx::Oklab> : public Formatter<FormatString> {
    ErrorOr<void> format(FormatBuilder&, Gfx::Oklab);
};

}

namespace IPC {

template<>
ErrorOr<void> encode(Encoder&, Gfx::Color const&);

template<>
ErrorOr<Gfx::Color> decode(Decoder&);

}