/*
 * Copyright (c) 2023, Andreas Kling <kling@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibGfx/Bitmap.h>
#include <LibWeb/Bindings/MainThreadVM.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/Fetch/Infrastructure/HTTP/Responses.h>
#include <LibWeb/HTML/BrowsingContext.h>
#include <LibWeb/HTML/DocumentState.h>
#include <LibWeb/HTML/NavigationParams.h>
#include <LibWeb/HTML/Parser/HTMLParser.h>
#include <LibWeb/HTML/TraversableNavigable.h>
#include <LibWeb/Layout/Viewport.h>
#include <LibWeb/Page/Page.h>
#include <LibWeb/Painting/CommandExecutorCPU.h>
#include <LibWeb/Painting/PaintContext.h>
#include <LibWeb/Painting/ViewportPaintable.h>
#include <LibWeb/SVG/SVGDecodedImageData.h>
#include <LibWeb/SVG/SVGSVGElement.h>

namespace Web::SVG {

JS_DEFINE_ALLOCATOR(SVGDecodedImageData);
JS_DEFINE_ALLOCATOR(SVGDecodedImageData::SVGPageClient);

ErrorOr<JS::NonnullGCPtr<SVGDecodedImageData>> SVGDecodedImageData::create(JS::Realm& realm, JS::NonnullGCPtr<Page> host_page, URL::URL const& url, ByteBuffer data)
{
    auto page_client = SVGPageClient::create(Bindings::main_thread_vm(), host_page);
    auto page = Page::create(Bindings::main_thread_vm(), *page_client);
    page_client->m_svg_page = page.ptr();
    page->set_top_level_traversable(MUST(Web::HTML::TraversableNavigable::create_a_new_top_level_traversable(*page, nullptr, {})));
    JS::NonnullGCPtr<HTML::Navigable> navigable = page->top_level_traversable();
    auto response = Fetch::Infrastructure::Response::create(navigable->vm());
    response->url_list().append(url);
    auto navigation_params = navigable->heap().allocate_without_realm<HTML::NavigationParams>();
    navigation_params->navigable = navigable;
    navigation_params->response = response;
    navigation_params->origin = HTML::Origin {};
    navigation_params->policy_container = HTML::PolicyContainer {};
    navigation_params->final_sandboxing_flag_set = HTML::SandboxingFlagSet {};
    navigation_params->cross_origin_opener_policy = HTML::CrossOriginOpenerPolicy {};

    // FIXME: Use Navigable::navigate() instead of manually replacing the navigable's document.
    auto document = DOM::Document::create_and_initialize(DOM::Document::Type::HTML, "text/html"_string, navigation_params).release_value_but_fixme_should_propagate_errors();
    navigable->set_ongoing_navigation({});
    navigable->active_document()->destroy();
    navigable->active_session_history_entry()->document_state()->set_document(document);

    auto parser = HTML::HTMLParser::create_with_uncertain_encoding(document, data);
    parser->run(document->url());

    // Perform some DOM surgery to make the SVG root element be the first child of the Document.
    // FIXME: This is a huge hack until we figure out how to actually parse separate SVG files.
    auto* svg_root = document->body()->first_child_of_type<SVG::SVGSVGElement>();
    if (!svg_root)
        return Error::from_string_literal("SVGDecodedImageData: Invalid SVG input");

    svg_root->remove();
    document->remove_all_children();

    MUST(document->append_child(*svg_root));

    return realm.heap().allocate<SVGDecodedImageData>(realm, page, page_client, document, *svg_root);
}

SVGDecodedImageData::SVGDecodedImageData(JS::NonnullGCPtr<Page> page, JS::NonnullGCPtr<SVGPageClient> page_client, JS::NonnullGCPtr<DOM::Document> document, JS::NonnullGCPtr<SVG::SVGSVGElement> root_element)
    : m_page(page)
    , m_page_client(page_client)
    , m_document(document)
    , m_root_element(root_element)
{
}

SVGDecodedImageData::~SVGDecodedImageData() = default;

void SVGDecodedImageData::visit_edges(Cell::Visitor& visitor)
{
    Base::visit_edges(visitor);
    visitor.visit(m_page);
    visitor.visit(m_document);
    visitor.visit(m_page_client);
    visitor.visit(m_root_element);
}

RefPtr<Gfx::Bitmap> SVGDecodedImageData::render(Gfx::IntSize size) const
{
    auto bitmap = Gfx::Bitmap::create(Gfx::BitmapFormat::BGRA8888, size).release_value_but_fixme_should_propagate_errors();
    VERIFY(m_document->navigable());
    m_document->navigable()->set_viewport_rect({ 0, 0, size.width(), size.height() });
    m_document->update_layout();

    Painting::CommandList painting_commands;
    Painting::RecordingPainter recording_painter(painting_commands);
    Painting::CommandExecutorCPU executor { *bitmap };

    m_document->navigable()->paint(recording_painter, {});
    painting_commands.execute(executor);

    return bitmap;
}

RefPtr<Gfx::ImmutableBitmap> SVGDecodedImageData::bitmap(size_t, Gfx::IntSize size) const
{
    if (size.is_empty())
        return nullptr;

    if (auto it = m_cached_rendered_bitmaps.find(size); it != m_cached_rendered_bitmaps.end())
        return it->value;

    // Prevent the cache from growing too big.
    // FIXME: Evict least used entries.
    if (m_cached_rendered_bitmaps.size() > 10)
        m_cached_rendered_bitmaps.remove(m_cached_rendered_bitmaps.begin());

    auto immutable_bitmap = Gfx::ImmutableBitmap::create(*render(size));
    m_cached_rendered_bitmaps.set(size, immutable_bitmap);
    return immutable_bitmap;
}

Optional<CSSPixels> SVGDecodedImageData::intrinsic_width() const
{
    // https://www.w3.org/TR/SVG2/coords.html#SizingSVGInCSS
    m_document->update_style();
    auto const* root_element_style = m_root_element->computed_css_values();
    VERIFY(root_element_style);
    auto const& width_value = root_element_style->size_value(CSS::PropertyID::Width);
    if (width_value.is_length() && width_value.length().is_absolute())
        return width_value.length().absolute_length_to_px();
    return {};
}

Optional<CSSPixels> SVGDecodedImageData::intrinsic_height() const
{
    // https://www.w3.org/TR/SVG2/coords.html#SizingSVGInCSS
    m_document->update_style();
    auto const* root_element_style = m_root_element->computed_css_values();
    VERIFY(root_element_style);
    auto const& height_value = root_element_style->size_value(CSS::PropertyID::Height);
    if (height_value.is_length() && height_value.length().is_absolute())
        return height_value.length().absolute_length_to_px();
    return {};
}

Optional<CSSPixelFraction> SVGDecodedImageData::intrinsic_aspect_ratio() const
{
    // https://www.w3.org/TR/SVG2/coords.html#SizingSVGInCSS
    auto width = intrinsic_width();
    auto height = intrinsic_height();
    if (height.has_value() && *height == 0)
        return {};

    if (width.has_value() && height.has_value())
        return *width / *height;

    if (auto const& viewbox = m_root_element->view_box(); viewbox.has_value())
        return CSSPixels::nearest_value_for(viewbox->width) / CSSPixels::nearest_value_for(viewbox->height);

    return {};
}

void SVGDecodedImageData::SVGPageClient::visit_edges(Visitor& visitor)
{
    Base::visit_edges(visitor);
    visitor.visit(m_host_page);
    visitor.visit(m_svg_page);
}

}