/*

 * Copyright (c) 2022, the SerenityOS developers.

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#pragma once

#include <AK/Array.h>

#include <AK/Error.h>

#include <AK/SIMD.h>

#include <AK/SIMDMath.h>

namespace Gfx::PNG {

// https://www.w3.org/TR/PNG/#5PNG-file-signature

static constexpr Array<u8, 8> header = { 0x89, 'P', 'N', 'G', 13, 10, 26, 10 };

// https://www.w3.org/TR/PNG/#6Colour-values

enum class ColorType : u8 {

    Greyscale = 0,

    Truecolor = 2, // RGB

    IndexedColor = 3,

    GreyscaleWithAlpha = 4,

    TruecolorWithAlpha = 6,

};

// https://www.w3.org/TR/PNG/#9Filter-types

enum class FilterType : u8 {

    None,

    Sub,

    Up,

    Average,

    Paeth,

};

inline ErrorOr<FilterType> filter_type(u8 byte)

{

    if (byte <= 4)

        return static_cast<FilterType>(byte);

    return Error::from_string_literal("PNGImageDecoderPlugin: Invalid PNG filter");

}

// https://www.w3.org/TR/PNG/#9Filter-type-4-Paeth

ALWAYS_INLINE u8 paeth_predictor(u8 a, u8 b, u8 c)

{

    int p = a + b - c;

    int pa = AK::abs(p - a);

    int pb = AK::abs(p - b);

    int pc = AK::abs(p - c);

    if (pa <= pb && pa <= pc)

        return a;

    if (pb <= pc)

        return b;

    return c;

}

ALWAYS_INLINE AK::SIMD::u8x4 paeth_predictor(AK::SIMD::u8x4 a, AK::SIMD::u8x4 b, AK::SIMD::u8x4 c)

{

    using namespace AK::SIMD;

    auto a16 = simd_cast<i16x4>(a);

    auto b16 = simd_cast<i16x4>(b);

    auto c16 = simd_cast<i16x4>(c);

    auto p16 = a16 + b16 - c16;

    auto pa16 = abs(p16 - a16);

    auto pb16 = abs(p16 - b16);

    auto pc16 = abs(p16 - c16);

    auto mask_a = simd_cast<u8x4>((pa16 <= pb16) & (pa16 <= pc16));

    auto mask_b = ~mask_a & simd_cast<u8x4>(pb16 <= pc16);

    auto mask_c = ~(mask_a | mask_b);

    return (a & mask_a) | (b & mask_b) | (c & mask_c);

}

};