/*
 * Copyright (c) 2020, the SerenityOS developers.
 * Copyright (c) 2021-2022, Andreas Kling <kling@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibWeb/HTML/HTMLFormElement.h>
#include <LibWeb/HTML/HTMLOptGroupElement.h>
#include <LibWeb/HTML/HTMLOptionElement.h>
#include <LibWeb/HTML/HTMLSelectElement.h>
#include <LibWeb/HTML/Window.h>

namespace Web::HTML {

HTMLSelectElement::HTMLSelectElement(DOM::Document& document, DOM::QualifiedName qualified_name)
    : HTMLElement(document, move(qualified_name))
{
    set_prototype(&window().cached_web_prototype("HTMLSelectElement"));
}

HTMLSelectElement::~HTMLSelectElement() = default;

void HTMLSelectElement::visit_edges(Cell::Visitor& visitor)
{
    Base::visit_edges(visitor);
    visitor.visit(m_options.ptr());
}

// https://html.spec.whatwg.org/multipage/form-elements.html#dom-select-options
JS::GCPtr<HTMLOptionsCollection> const& HTMLSelectElement::options()
{
    if (!m_options) {
        m_options = HTMLOptionsCollection::create(*this, [](DOM::Element const& element) {
            // https://html.spec.whatwg.org/multipage/form-elements.html#concept-select-option-list
            // The list of options for a select element consists of all the option element children of
            // the select element, and all the option element children of all the optgroup element children
            // of the select element, in tree order.
            return is<HTMLOptionElement>(element);
        });
    }
    return m_options;
}

// https://html.spec.whatwg.org/multipage/form-elements.html#dom-select-add
WebIDL::ExceptionOr<void> HTMLSelectElement::add(HTMLOptionOrOptGroupElement element, Optional<HTMLElementOrElementIndex> before)
{
    // Similarly, the add(element, before) method must act like its namesake method on that same options collection.
    return const_cast<HTMLOptionsCollection&>(*options()).add(move(element), move(before));
}

// https://html.spec.whatwg.org/multipage/form-elements.html#concept-select-option-list
Vector<JS::Handle<HTMLOptionElement>> HTMLSelectElement::list_of_options() const
{
    // The list of options for a select element consists of all the option element children of the select element,
    // and all the option element children of all the optgroup element children of the select element, in tree order.
    Vector<JS::Handle<HTMLOptionElement>> list;

    for_each_child_of_type<HTMLOptionElement>([&](HTMLOptionElement const& option_element) {
        list.append(JS::make_handle(const_cast<HTMLOptionElement&>(option_element)));
    });

    for_each_child_of_type<HTMLOptGroupElement>([&](HTMLOptGroupElement const& optgroup_element) {
        optgroup_element.for_each_child_of_type<HTMLOptionElement>([&](HTMLOptionElement const& option_element) {
            list.append(JS::make_handle(const_cast<HTMLOptionElement&>(option_element)));
        });
    });

    return list;
}

// https://html.spec.whatwg.org/multipage/form-elements.html#dom-select-selectedindex
int HTMLSelectElement::selected_index() const
{
    // The selectedIndex IDL attribute, on getting, must return the index of the first option element in the list of options
    // in tree order that has its selectedness set to true, if any. If there isn't one, then it must return −1.

    int index = 0;
    for (auto const& option_element : list_of_options()) {
        if (option_element->selected())
            return index;
        ++index;
    }
    return -1;
}

void HTMLSelectElement::set_selected_index(int index)
{
    // On setting, the selectedIndex attribute must set the selectedness of all the option elements in the list of options to false,
    // and then the option element in the list of options whose index is the given new value,
    // if any, must have its selectedness set to true and its dirtiness set to true.
    auto options = list_of_options();
    for (auto& option : options)
        option->m_selected = false;

    if (index < 0 || index >= static_cast<int>(options.size()))
        return;

    auto& selected_option = options[index];
    selected_option->m_selected = true;
    selected_option->m_dirty = true;
}

}