/*
 * Copyright (c) 2024-2025, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include <LibJS/Runtime/DataView.h>
#include <LibJS/Runtime/TypedArray.h>
#include <LibWeb/Forward.h>
#include <LibWeb/WebIDL/Buffers.h>
#include <LibWeb/WebIDL/Types.h>

namespace Web::WebGL {

static constexpr int UNPACK_FLIP_Y_WEBGL = 0x9240;

// NOTE: This is the Variant created by the IDL wrapper generator, and needs to be updated accordingly.
using TexImageSource = Variant<GC::Root<HTML::ImageBitmap>, GC::Root<HTML::ImageData>, GC::Root<HTML::HTMLImageElement>, GC::Root<HTML::HTMLCanvasElement>, GC::Root<HTML::OffscreenCanvas>, GC::Root<HTML::HTMLVideoElement>>;

// FIXME: This object should inherit from Bindings::PlatformObject and implement the WebGLRenderingContextBase IDL interface.
//        We should make WebGL code generator to produce implementation for this interface.
class WebGLRenderingContextBase {
public:
    using Float32List = Variant<GC::Root<JS::Float32Array>, Vector<float>>;
    using Int32List = Variant<GC::Root<JS::Int32Array>, Vector<WebIDL::Long>>;
    using Uint32List = Variant<GC::Root<JS::Uint32Array>, Vector<WebIDL::UnsignedLong>>;

    virtual GC::Cell const* gc_cell() const = 0;
    virtual void visit_edges(JS::Cell::Visitor&) = 0;
    virtual OpenGLContext& context() = 0;
    virtual bool ext_texture_filter_anisotropic_extension_enabled() const = 0;

    template<typename T>
    static ErrorOr<Span<T>> get_offset_span(Span<T> src_span, WebIDL::UnsignedLongLong src_offset, WebIDL::UnsignedLong src_length_override = 0)
    {
        Checked<WebIDL::UnsignedLongLong> length = src_offset;
        length += src_length_override;
        if (length.has_overflow() || length.value_unchecked() > src_span.size()) [[unlikely]]
            return Error::from_errno(EINVAL);

        if (src_length_override == 0)
            return src_span.slice(src_offset, src_span.size() - src_offset);

        return src_span.slice(src_offset, src_length_override);
    }

    template<typename T>
    static ErrorOr<Span<T>> get_offset_span(GC::Ref<WebIDL::BufferableObjectBase> src_data, WebIDL::UnsignedLongLong src_offset, WebIDL::UnsignedLong src_length_override = 0)
    {
        auto buffer_size = src_data->byte_length();
        if (buffer_size % sizeof(T) != 0) [[unlikely]]
            return Error::from_errno(EINVAL);

        auto raw_object = src_data->raw_object();

        if (auto* array_buffer = as_if<JS::ArrayBuffer>(*raw_object)) {
            return TRY(get_offset_span(array_buffer->buffer().span(), src_offset, src_length_override)).reinterpret<T>();
        }

        if (auto* data_view = as_if<JS::DataView>(*raw_object)) {
            return TRY(get_offset_span(data_view->viewed_array_buffer()->buffer().span(), src_offset, src_length_override)).reinterpret<T>();
        }

        // NOTE: This has to be done because src_offset is the number of elements to offset by, not the number of bytes.
#define __JS_ENUMERATE(ClassName, snake_name, PrototypeName, ConstructorName, Type)                         \
    if (auto* typed_array = as_if<JS::ClassName>(*raw_object)) {                                            \
        return TRY(get_offset_span(typed_array->data(), src_offset, src_length_override)).reinterpret<T>(); \
    }
        JS_ENUMERATE_TYPED_ARRAYS
#undef __JS_ENUMERATE

        VERIFY_NOT_REACHED();
    }

    static ErrorOr<Span<float>> span_from_float32_list(Float32List& float32_list, WebIDL::UnsignedLongLong src_offset, WebIDL::UnsignedLong src_length_override = 0)
    {
        if (float32_list.has<Vector<float>>()) {
            auto& vector = float32_list.get<Vector<float>>();
            return get_offset_span(vector.span(), src_offset, src_length_override);
        }
        auto& buffer = float32_list.get<GC::Root<JS::Float32Array>>();
        return get_offset_span(buffer->data(), src_offset, src_length_override);
    }

    static ErrorOr<Span<int>> span_from_int32_list(Int32List& int32_list, WebIDL::UnsignedLongLong src_offset, WebIDL::UnsignedLong src_length_override = 0)
    {
        if (int32_list.has<Vector<int>>()) {
            auto& vector = int32_list.get<Vector<int>>();
            return get_offset_span(vector.span(), src_offset, src_length_override);
        }
        auto& buffer = int32_list.get<GC::Root<JS::Int32Array>>();
        return get_offset_span(buffer->data(), src_offset, src_length_override);
    }

    static ErrorOr<Span<u32>> span_from_uint32_list(Uint32List& uint32_list, WebIDL::UnsignedLongLong src_offset, WebIDL::UnsignedLong src_length_override = 0)
    {
        if (uint32_list.has<Vector<u32>>()) {
            auto& vector = uint32_list.get<Vector<u32>>();
            return get_offset_span(vector.span(), src_offset, src_length_override);
        }
        auto& buffer = uint32_list.get<GC::Root<JS::Uint32Array>>();
        return get_offset_span(buffer->data(), src_offset, src_length_override);
    }

    struct ConvertedTexture {
        ByteBuffer buffer;
        int width { 0 };
        int height { 0 };
    };
    Optional<ConvertedTexture> read_and_pixel_convert_texture_image_source(TexImageSource const& source, WebIDL::UnsignedLong format, WebIDL::UnsignedLong type, Optional<int> destination_width = OptionalNone {}, Optional<int> destination_height = OptionalNone {});

protected:
    // UNPACK_FLIP_Y_WEBGL of type boolean
    //      If set, then during any subsequent calls to texImage2D or texSubImage2D, the source data is flipped along
    //      the vertical axis, so that conceptually the last row is the first one transferred. The initial value is false.
    //      Any non-zero value is interpreted as true.
    bool m_unpack_flip_y { false };
};

}