/*
 * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/AnyOf.h>
#include <AK/StringBuilder.h>
#include <LibWeb/CSS/Parser/Parser.h>
#include <LibWeb/CSS/PropertyID.h>
#include <LibWeb/CSS/ResolvedCSSStyleDeclaration.h>
#include <LibWeb/CSS/StyleInvalidator.h>
#include <LibWeb/DOM/DOMException.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/Element.h>
#include <LibWeb/DOM/ExceptionOr.h>
#include <LibWeb/DOM/HTMLCollection.h>
#include <LibWeb/DOM/ShadowRoot.h>
#include <LibWeb/DOM/Text.h>
#include <LibWeb/DOMParsing/InnerHTML.h>
#include <LibWeb/HTML/EventLoop/EventLoop.h>
#include <LibWeb/HTML/Parser/HTMLDocumentParser.h>
#include <LibWeb/Layout/BlockBox.h>
#include <LibWeb/Layout/InlineNode.h>
#include <LibWeb/Layout/ListItemBox.h>
#include <LibWeb/Layout/TableBox.h>
#include <LibWeb/Layout/TableCellBox.h>
#include <LibWeb/Layout/TableRowBox.h>
#include <LibWeb/Layout/TableRowGroupBox.h>
#include <LibWeb/Layout/TreeBuilder.h>
#include <LibWeb/Namespace.h>

namespace Web::DOM {

Element::Element(Document& document, QualifiedName qualified_name)
    : ParentNode(document, NodeType::ELEMENT_NODE)
    , m_qualified_name(move(qualified_name))
{
    make_html_uppercased_qualified_name();
}

Element::~Element()
{
}

Attribute* Element::find_attribute(const FlyString& name)
{
    for (auto& attribute : m_attributes) {
        if (attribute.name() == name)
            return &attribute;
    }
    return nullptr;
}

const Attribute* Element::find_attribute(const FlyString& name) const
{
    for (auto& attribute : m_attributes) {
        if (attribute.name() == name)
            return &attribute;
    }
    return nullptr;
}

String Element::attribute(const FlyString& name) const
{
    if (auto* attribute = find_attribute(name))
        return attribute->value();
    return {};
}

ExceptionOr<void> Element::set_attribute(const FlyString& name, const String& value)
{
    // FIXME: Proper name validation
    if (name.is_empty())
        return InvalidCharacterError::create("Attribute name must not be empty");

    CSS::StyleInvalidator style_invalidator(document());

    if (auto* attribute = find_attribute(name))
        attribute->set_value(value);
    else
        m_attributes.empend(name, value);

    parse_attribute(name, value);
    return {};
}

void Element::remove_attribute(const FlyString& name)
{
    CSS::StyleInvalidator style_invalidator(document());

    m_attributes.remove_first_matching([&](auto& attribute) { return attribute.name() == name; });
}

bool Element::has_class(const FlyString& class_name, CaseSensitivity case_sensitivity) const
{
    return any_of(m_classes, [&](auto& it) {
        return case_sensitivity == CaseSensitivity::CaseSensitive
            ? it == class_name
            : it.to_lowercase() == class_name.to_lowercase();
    });
}

RefPtr<Layout::Node> Element::create_layout_node()
{
    auto style = document().style_resolver().resolve_style(*this);
    const_cast<Element&>(*this).m_specified_css_values = style;
    auto display = style->display();

    if (display == CSS::Display::None)
        return nullptr;

    if (local_name() == "noscript" && document().is_scripting_enabled())
        return nullptr;

    switch (display) {
    case CSS::Display::None:
        VERIFY_NOT_REACHED();
        break;
    case CSS::Display::Block:
        return adopt_ref(*new Layout::BlockBox(document(), this, move(style)));
    case CSS::Display::Inline:
        if (style->float_().value_or(CSS::Float::None) != CSS::Float::None)
            return adopt_ref(*new Layout::BlockBox(document(), this, move(style)));
        return adopt_ref(*new Layout::InlineNode(document(), *this, move(style)));
    case CSS::Display::ListItem:
        return adopt_ref(*new Layout::ListItemBox(document(), *this, move(style)));
    case CSS::Display::Table:
        return adopt_ref(*new Layout::TableBox(document(), this, move(style)));
    case CSS::Display::TableRow:
        return adopt_ref(*new Layout::TableRowBox(document(), this, move(style)));
    case CSS::Display::TableCell:
        return adopt_ref(*new Layout::TableCellBox(document(), this, move(style)));
    case CSS::Display::TableRowGroup:
    case CSS::Display::TableHeaderGroup:
    case CSS::Display::TableFooterGroup:
        return adopt_ref(*new Layout::TableRowGroupBox(document(), *this, move(style)));
    case CSS::Display::InlineBlock: {
        auto inline_block = adopt_ref(*new Layout::BlockBox(document(), this, move(style)));
        inline_block->set_inline(true);
        return inline_block;
    }
    case CSS::Display::Flex:
        return adopt_ref(*new Layout::BlockBox(document(), this, move(style)));
    case CSS::Display::TableColumn:
    case CSS::Display::TableColumnGroup:
    case CSS::Display::TableCaption:
        // FIXME: This is just an incorrect placeholder until we improve table layout support.
        return adopt_ref(*new Layout::BlockBox(document(), this, move(style)));
    }
    VERIFY_NOT_REACHED();
}

void Element::parse_attribute(const FlyString& name, const String& value)
{
    if (name == HTML::AttributeNames::class_) {
        auto new_classes = value.split_view(' ');
        m_classes.clear();
        m_classes.ensure_capacity(new_classes.size());
        for (auto& new_class : new_classes) {
            m_classes.unchecked_append(new_class);
        }
    } else if (name == HTML::AttributeNames::style) {
        auto parsed_style = parse_css_declaration(CSS::ParsingContext(document()), value);
        if (!parsed_style.is_null()) {
            m_inline_style = CSS::ElementInlineCSSStyleDeclaration::create_and_take_properties_from(*this, parsed_style.release_nonnull());
            set_needs_style_update(true);
        }
    }
}

enum class StyleDifference {
    None,
    NeedsRepaint,
    NeedsRelayout,
};

static StyleDifference compute_style_difference(CSS::StyleProperties const& old_style, CSS::StyleProperties const& new_style, Layout::NodeWithStyle const& node)
{
    if (old_style == new_style)
        return StyleDifference::None;

    bool needs_repaint = false;
    bool needs_relayout = false;

    if (new_style.display() != old_style.display())
        needs_relayout = true;

    if (new_style.color_or_fallback(CSS::PropertyID::Color, node, Color::Black) != old_style.color_or_fallback(CSS::PropertyID::Color, node, Color::Black))
        needs_repaint = true;
    else if (new_style.color_or_fallback(CSS::PropertyID::BackgroundColor, node, Color::Black) != old_style.color_or_fallback(CSS::PropertyID::BackgroundColor, node, Color::Black))
        needs_repaint = true;

    if (needs_relayout)
        return StyleDifference::NeedsRelayout;
    if (needs_repaint)
        return StyleDifference::NeedsRepaint;
    return StyleDifference::None;
}

void Element::recompute_style()
{
    set_needs_style_update(false);
    VERIFY(parent());
    auto old_specified_css_values = m_specified_css_values;
    auto new_specified_css_values = document().style_resolver().resolve_style(*this);
    m_specified_css_values = new_specified_css_values;
    if (!layout_node()) {
        if (new_specified_css_values->display() == CSS::Display::None)
            return;
        // We need a new layout tree here!
        Layout::TreeBuilder tree_builder;
        tree_builder.build(*this);
        return;
    }

    auto diff = StyleDifference::NeedsRelayout;
    if (old_specified_css_values && layout_node())
        diff = compute_style_difference(*old_specified_css_values, *new_specified_css_values, *layout_node());
    if (diff == StyleDifference::None)
        return;
    layout_node()->apply_style(*new_specified_css_values);
    if (diff == StyleDifference::NeedsRelayout) {
        document().schedule_forced_layout();
        return;
    }
    if (diff == StyleDifference::NeedsRepaint) {
        layout_node()->set_needs_display();
    }
}

NonnullRefPtr<CSS::StyleProperties> Element::computed_style()
{
    auto element_computed_style = CSS::ResolvedCSSStyleDeclaration::create(*this);
    auto properties = CSS::StyleProperties::create();

    for (auto i = to_underlying(CSS::first_property_id); i <= to_underlying(CSS::last_property_id); ++i) {
        auto property_id = (CSS::PropertyID)i;
        auto maybe_value = element_computed_style->property(property_id);
        if (!maybe_value.has_value())
            continue;
        properties->set_property(property_id, maybe_value.release_value().value);
    }

    return properties;
}

ExceptionOr<void> Element::set_inner_html(String const& markup)
{
    auto result = DOMParsing::InnerHTML::inner_html_setter(*this, markup);
    if (result.is_exception())
        return result.exception();

    set_needs_style_update(true);
    document().invalidate_layout();
    return {};
}

// https://w3c.github.io/DOM-Parsing/#dom-innerhtml-innerhtml
String Element::inner_html() const
{
    return serialize_fragment(/* FIXME: Providing true for the require well-formed flag (which may throw) */);
}

bool Element::is_focused() const
{
    return document().focused_element() == this;
}

bool Element::is_active() const
{
    return document().active_element() == this;
}

NonnullRefPtr<HTMLCollection> Element::get_elements_by_class_name(FlyString const& class_name)
{
    return HTMLCollection::create(*this, [class_name, quirks_mode = document().in_quirks_mode()](Element const& element) {
        return element.has_class(class_name, quirks_mode ? CaseSensitivity::CaseInsensitive : CaseSensitivity::CaseSensitive);
    });
}

void Element::set_shadow_root(RefPtr<ShadowRoot> shadow_root)
{
    if (m_shadow_root == shadow_root)
        return;
    m_shadow_root = move(shadow_root);
    invalidate_style();
}

NonnullRefPtr<CSS::CSSStyleDeclaration> Element::style_for_bindings()
{
    if (!m_inline_style)
        m_inline_style = CSS::ElementInlineCSSStyleDeclaration::create(*this);
    return *m_inline_style;
}

// https://dom.spec.whatwg.org/#element-html-uppercased-qualified-name
void Element::make_html_uppercased_qualified_name()
{
    // This is allowed by the spec: "User agents could optimize qualified name and HTML-uppercased qualified name by storing them in internal slots."
    if (namespace_() == Namespace::HTML /* FIXME: and its node document is an HTML document */)
        m_html_uppercased_qualified_name = qualified_name().to_uppercase();
    else
        m_html_uppercased_qualified_name = qualified_name();
}

// https://html.spec.whatwg.org/multipage/webappapis.html#queue-an-element-task
void Element::queue_an_element_task(HTML::Task::Source source, Function<void()> steps)
{
    auto task = HTML::Task::create(source, &document(), [strong_this = NonnullRefPtr(*this), steps = move(steps)] {
        steps();
    });
    HTML::main_thread_event_loop().task_queue().add(move(task));
}

// https://html.spec.whatwg.org/multipage/syntax.html#void-elements
bool Element::is_void_element() const
{
    return local_name().is_one_of(HTML::TagNames::area, HTML::TagNames::base, HTML::TagNames::br, HTML::TagNames::col, HTML::TagNames::embed, HTML::TagNames::hr, HTML::TagNames::img, HTML::TagNames::input, HTML::TagNames::link, HTML::TagNames::meta, HTML::TagNames::param, HTML::TagNames::source, HTML::TagNames::track, HTML::TagNames::wbr);
}

// https://html.spec.whatwg.org/multipage/parsing.html#serializes-as-void
bool Element::serializes_as_void() const
{
    return is_void_element() || local_name().is_one_of(HTML::TagNames::basefont, HTML::TagNames::bgsound, HTML::TagNames::frame, HTML::TagNames::keygen);
}

}