/*
 * Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibWeb/Bindings/MainThreadVM.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/ElementFactory.h>
#include <LibWeb/DOM/Event.h>
#include <LibWeb/DOM/HTMLCollection.h>
#include <LibWeb/DOM/Range.h>
#include <LibWeb/DOMURL/DOMURL.h>
#include <LibWeb/HTML/BrowsingContext.h>
#include <LibWeb/HTML/BrowsingContextGroup.h>
#include <LibWeb/HTML/CrossOrigin/CrossOriginOpenerPolicy.h>
#include <LibWeb/HTML/DocumentState.h>
#include <LibWeb/HTML/HTMLAnchorElement.h>
#include <LibWeb/HTML/HTMLDocument.h>
#include <LibWeb/HTML/HTMLInputElement.h>
#include <LibWeb/HTML/NavigableContainer.h>
#include <LibWeb/HTML/SandboxingFlagSet.h>
#include <LibWeb/HTML/Scripting/WindowEnvironmentSettingsObject.h>
#include <LibWeb/HTML/TraversableNavigable.h>
#include <LibWeb/HTML/Window.h>
#include <LibWeb/HTML/WindowProxy.h>
#include <LibWeb/HighResolutionTime/TimeOrigin.h>
#include <LibWeb/Layout/BreakNode.h>
#include <LibWeb/Layout/Viewport.h>
#include <LibWeb/Namespace.h>
#include <LibWeb/Page/Page.h>
#include <LibWeb/Painting/Paintable.h>

namespace Web::HTML {

JS_DEFINE_ALLOCATOR(BrowsingContext);

// https://html.spec.whatwg.org/multipage/urls-and-fetching.html#matches-about:blank
bool url_matches_about_blank(URL const& url)
{
    // A URL matches about:blank if its scheme is "about", its path contains a single string "blank", its username and password are the empty string, and its host is null.
    return url.scheme() == "about"sv
        && url.serialize_path() == "blank"sv
        && url.raw_username().is_empty()
        && url.raw_password().is_empty()
        && url.host().has<Empty>();
}

// https://html.spec.whatwg.org/multipage/urls-and-fetching.html#matches-about:srcdoc
bool url_matches_about_srcdoc(URL const& url)
{
    // A URL matches about:srcdoc if its scheme is "about", its path contains a single string "srcdoc", its query is null, its username and password are the empty string, and its host is null.
    return url.scheme() == "about"sv
        && url.serialize_path() == "srcdoc"sv
        && !url.query().has_value()
        && url.raw_username().is_empty()
        && url.raw_password().is_empty()
        && url.host().has<Empty>();
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#determining-the-origin
HTML::Origin determine_the_origin(URL const& url, SandboxingFlagSet sandbox_flags, Optional<HTML::Origin> source_origin)
{
    // 1. If sandboxFlags has its sandboxed origin browsing context flag set, then return a new opaque origin.
    if (has_flag(sandbox_flags, SandboxingFlagSet::SandboxedOrigin)) {
        return HTML::Origin {};
    }

    // FIXME: 2. If url is null, then return a new opaque origin.
    // FIXME: There appears to be no way to get a null URL here, so it might be a spec bug.

    // 3. If url is about:srcdoc, then:
    if (url == "about:srcdoc"sv) {
        // 1. Assert: sourceOrigin is non-null.
        VERIFY(source_origin.has_value());

        // 2. Return sourceOrigin.
        return source_origin.release_value();
    }

    // 4. If url matches about:blank and sourceOrigin is non-null, then return sourceOrigin.
    if (url_matches_about_blank(url) && source_origin.has_value())
        return source_origin.release_value();

    // 5. Return url's origin.
    return DOMURL::url_origin(url);
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#creating-a-new-auxiliary-browsing-context
WebIDL::ExceptionOr<BrowsingContext::BrowsingContextAndDocument> BrowsingContext::create_a_new_auxiliary_browsing_context_and_document(JS::NonnullGCPtr<Page> page, JS::NonnullGCPtr<HTML::BrowsingContext> opener)
{
    // 1. Let openerTopLevelBrowsingContext be opener's top-level traversable's active browsing context.
    auto opener_top_level_browsing_context = opener->top_level_traversable()->active_browsing_context();

    // 2. Let group be openerTopLevelBrowsingContext's group.
    auto group = opener_top_level_browsing_context->group();

    // 3. Assert: group is non-null, as navigating invokes this directly.
    VERIFY(group);

    // 4. Set browsingContext and document be the result of creating a new browsing context and document with opener's active document, null, and group.
    auto [browsing_context, document] = TRY(create_a_new_browsing_context_and_document(page, opener->active_document(), nullptr, *group));

    // FIXME: 5. Set browsingContext's is auxiliary to true.

    // 6. Append browsingContext to group.
    group->append(browsing_context);

    // 7. Set browsingContext's opener browsing context to opener.
    browsing_context->set_opener_browsing_context(opener);

    // FIXME: 8. Set browsingContext's virtual browsing context group ID to openerTopLevelBrowsingContext's virtual browsing context group ID.

    // FIXME: 9. Set browsingContext's opener origin at creation to opener's active document's origin.

    // 10. Return browsingContext and document.
    return BrowsingContext::BrowsingContextAndDocument { browsing_context, document };
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#creating-a-new-browsing-context
WebIDL::ExceptionOr<BrowsingContext::BrowsingContextAndDocument> BrowsingContext::create_a_new_browsing_context_and_document(JS::NonnullGCPtr<Page> page, JS::GCPtr<DOM::Document> creator, JS::GCPtr<DOM::Element> embedder, JS::NonnullGCPtr<BrowsingContextGroup> group)
{
    auto& vm = group->vm();

    // 1. Let browsingContext be a new browsing context.
    JS::NonnullGCPtr<BrowsingContext> browsing_context = *vm.heap().allocate_without_realm<BrowsingContext>(page);

    // 2. Let unsafeContextCreationTime be the unsafe shared current time.
    [[maybe_unused]] auto unsafe_context_creation_time = HighResolutionTime::unsafe_shared_current_time();

    // 3. Let creatorOrigin be null.
    Optional<Origin> creator_origin = {};

    // FIXME: This algorithm needs re-aligned with the spec
    Optional<URL> creator_base_url = {};

    // 4. If creator is non-null, then:
    if (creator) {
        // 1. Set creatorOrigin to creator's origin.
        creator_origin = creator->origin();

        // FIXME: This algorithm needs re-aligned with the spec
        creator_base_url = creator->base_url();

        // FIXME: 2. Set browsingContext's creator base URL to an algorithm which returns creator's base URL.

        // FIXME: 3. Set browsingContext's virtual browsing context group ID to creator's browsing context's top-level browsing context's virtual browsing context group ID.
    }

    // FIXME: 5. Let sandboxFlags be the result of determining the creation sandboxing flags given browsingContext and embedder.
    SandboxingFlagSet sandbox_flags = {};

    // 6. Let origin be the result of determining the origin given about:blank, sandboxFlags, and creatorOrigin.
    auto origin = determine_the_origin(URL("about:blank"sv), sandbox_flags, creator_origin);

    // FIXME: 7. Let permissionsPolicy be the result of creating a permissions policy given browsingContext and origin. [PERMISSIONSPOLICY]

    // FIXME: 8. Let agent be the result of obtaining a similar-origin window agent given origin, group, and false.

    JS::GCPtr<Window> window;

    // 9. Let realm execution context be the result of creating a new JavaScript realm given agent and the following customizations:
    auto realm_execution_context = Bindings::create_a_new_javascript_realm(
        Bindings::main_thread_vm(),
        [&](JS::Realm& realm) -> JS::Object* {
            auto window_proxy = realm.heap().allocate<WindowProxy>(realm, realm);
            browsing_context->set_window_proxy(window_proxy);

            // - For the global object, create a new Window object.
            window = Window::create(realm);
            return window.ptr();
        },
        [&](JS::Realm&) -> JS::Object* {
            // - For the global this binding, use browsingContext's WindowProxy object.
            return browsing_context->window_proxy();
        });

    // 10. Let topLevelCreationURL be about:blank if embedder is null; otherwise embedder's relevant settings object's top-level creation URL.
    auto top_level_creation_url = !embedder ? URL("about:blank") : relevant_settings_object(*embedder).top_level_creation_url;

    // 11. Let topLevelOrigin be origin if embedder is null; otherwise embedder's relevant settings object's top-level origin.
    auto top_level_origin = !embedder ? origin : relevant_settings_object(*embedder).origin();

    // 12. Set up a window environment settings object with about:blank, realm execution context, null, topLevelCreationURL, and topLevelOrigin.
    WindowEnvironmentSettingsObject::setup(
        page,
        URL("about:blank"),
        move(realm_execution_context),
        {},
        top_level_creation_url,
        top_level_origin);

    // 13. Let loadTimingInfo be a new document load timing info with its navigation start time set to the result of calling
    //     coarsen time with unsafeContextCreationTime and the new environment settings object's cross-origin isolated capability.
    auto load_timing_info = DOM::DocumentLoadTimingInfo();
    load_timing_info.navigation_start_time = HighResolutionTime::coarsen_time(
        unsafe_context_creation_time,
        verify_cast<WindowEnvironmentSettingsObject>(Bindings::host_defined_environment_settings_object(window->realm())).cross_origin_isolated_capability() == CanUseCrossOriginIsolatedAPIs::Yes);

    // 14. Let document be a new Document, with:
    auto document = HTML::HTMLDocument::create(window->realm());

    // Non-standard
    window->set_associated_document(*document);

    // type: "html"
    document->set_document_type(DOM::Document::Type::HTML);

    // content type: "text/html"
    document->set_content_type("text/html"_string);

    // mode: "quirks"
    document->set_quirks_mode(DOM::QuirksMode::Yes);

    // origin: origin
    document->set_origin(origin);

    // browsing context: browsingContext
    document->set_browsing_context(browsing_context);

    // FIXME: permissions policy: permissionsPolicy

    // FIXME: active sandboxing flag set: sandboxFlags

    // load timing info: loadTimingInfo
    document->set_load_timing_info(load_timing_info);

    // is initial about:blank: true
    document->set_is_initial_about_blank(true);

    // about base URL: creatorBaseURL
    document->set_about_base_url(creator_base_url);

    // 15. If creator is non-null, then:
    if (creator) {
        // 1. Set document's referrer to the serialization of creator's URL.
        document->set_referrer(MUST(String::from_byte_string(creator->url().serialize())));

        // FIXME: 2. Set document's policy container to a clone of creator's policy container.

        // 3. If creator's origin is same origin with creator's relevant settings object's top-level origin,
        if (creator->origin().is_same_origin(creator->relevant_settings_object().top_level_origin)) {
            // then set document's cross-origin opener policy to creator's browsing context's top-level browsing context's active document's cross-origin opener policy.
            VERIFY(creator->browsing_context());
            VERIFY(creator->browsing_context()->top_level_browsing_context()->active_document());
            document->set_cross_origin_opener_policy(creator->browsing_context()->top_level_browsing_context()->active_document()->cross_origin_opener_policy());
        }
    }

    // 16. Assert: document's URL and document's relevant settings object's creation URL are about:blank.
    VERIFY(document->url() == "about:blank"sv);
    VERIFY(document->relevant_settings_object().creation_url == "about:blank"sv);

    // 17. Mark document as ready for post-load tasks.
    document->set_ready_for_post_load_tasks(true);

    // 18. Ensure that document has a single child html node, which itself has two empty child nodes: a head element, and a body element.
    auto html_node = TRY(DOM::create_element(document, HTML::TagNames::html, Namespace::HTML));
    auto head_element = TRY(DOM::create_element(document, HTML::TagNames::head, Namespace::HTML));
    TRY(html_node->append_child(head_element));
    auto body_element = TRY(DOM::create_element(document, HTML::TagNames::body, Namespace::HTML));
    TRY(html_node->append_child(body_element));
    TRY(document->append_child(html_node));

    // 19. Make active document.
    document->make_active();

    // 20. Completely finish loading document.
    document->completely_finish_loading();

    // 21. Return browsingContext and document.
    return BrowsingContext::BrowsingContextAndDocument { browsing_context, document };
}

BrowsingContext::BrowsingContext(JS::NonnullGCPtr<Page> page)
    : m_page(page)
    , m_event_handler({}, *this)
{
    m_cursor_blink_timer = Core::Timer::create_repeating(500, [this] {
        if (!is_focused_context())
            return;
        if (m_cursor_position && m_cursor_position->node()->paintable()) {
            m_cursor_blink_state = !m_cursor_blink_state;
            m_cursor_position->node()->paintable()->set_needs_display();
        }
    }).release_value_but_fixme_should_propagate_errors();
}

BrowsingContext::~BrowsingContext() = default;

void BrowsingContext::visit_edges(Cell::Visitor& visitor)
{
    Base::visit_edges(visitor);

    visitor.visit(m_page);
    visitor.visit(m_cursor_position);
    visitor.visit(m_window_proxy);
    visitor.visit(m_group);
    visitor.visit(m_parent);
    visitor.visit(m_first_child);
    visitor.visit(m_last_child);
    visitor.visit(m_next_sibling);
    visitor.visit(m_previous_sibling);
    visitor.visit(m_opener_browsing_context);

    m_event_handler.visit_edges(visitor);
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#bc-traversable
JS::NonnullGCPtr<HTML::TraversableNavigable> BrowsingContext::top_level_traversable() const
{
    // A browsing context's top-level traversable is its active document's node navigable's top-level traversable.
    auto traversable = active_document()->navigable()->top_level_traversable();
    VERIFY(traversable);
    VERIFY(traversable->is_top_level_traversable());
    return *traversable;
}

void BrowsingContext::did_edit(Badge<EditEventHandler>)
{
    reset_cursor_blink_cycle();

    if (m_cursor_position && is<DOM::Text>(*m_cursor_position->node())) {
        auto& text_node = static_cast<DOM::Text&>(*m_cursor_position->node());
        if (auto* text_node_owner = text_node.editable_text_node_owner())
            text_node_owner->did_edit_text_node({});
    }
}

void BrowsingContext::reset_cursor_blink_cycle()
{
    m_cursor_blink_state = true;
    m_cursor_blink_timer->restart();
    if (m_cursor_position && m_cursor_position->node()->paintable())
        m_cursor_position->node()->paintable()->set_needs_display();
}

// https://html.spec.whatwg.org/multipage/browsers.html#top-level-browsing-context
bool BrowsingContext::is_top_level() const
{
    // A browsing context that has no parent browsing context is the top-level browsing context for itself and all of the browsing contexts for which it is an ancestor browsing context.
    return !parent();
}

bool BrowsingContext::is_focused_context() const
{
    return &m_page->focused_context() == this;
}

JS::GCPtr<BrowsingContext> BrowsingContext::top_level_browsing_context() const
{
    auto const* start = this;

    // 1. If start's active document is not fully active, then return null.
    if (!start->active_document()->is_fully_active()) {
        return nullptr;
    }

    // 2. Let navigable be start's active document's node navigable.
    auto navigable = start->active_document()->navigable();

    // 3. While navigable's parent is not null, set navigable to navigable's parent.
    while (navigable->parent()) {
        navigable = navigable->parent();
    }

    // 4. Return navigable's active browsing context.
    return navigable->active_browsing_context();
}

void BrowsingContext::set_cursor_position(JS::NonnullGCPtr<DOM::Position> position)
{
    if (m_cursor_position && m_cursor_position->equals(position))
        return;

    if (m_cursor_position && m_cursor_position->node()->paintable())
        m_cursor_position->node()->paintable()->set_needs_display();

    m_cursor_position = position;

    if (m_cursor_position && m_cursor_position->node()->paintable())
        m_cursor_position->node()->paintable()->set_needs_display();

    reset_cursor_blink_cycle();
}

static String visible_text_in_range(DOM::Range const& range)
{
    // NOTE: This is an adaption of Range stringification, but we skip over DOM nodes that don't have a corresponding layout node.
    StringBuilder builder;

    if (range.start_container() == range.end_container() && is<DOM::Text>(*range.start_container())) {
        if (!range.start_container()->layout_node())
            return String {};
        return MUST(static_cast<DOM::Text const&>(*range.start_container()).data().substring_from_byte_offset(range.start_offset(), range.end_offset() - range.start_offset()));
    }

    if (is<DOM::Text>(*range.start_container()) && range.start_container()->layout_node())
        builder.append(static_cast<DOM::Text const&>(*range.start_container()).data().bytes_as_string_view().substring_view(range.start_offset()));

    for (DOM::Node const* node = range.start_container(); node != range.end_container()->next_sibling(); node = node->next_in_pre_order()) {
        if (is<DOM::Text>(*node) && range.contains_node(*node) && node->layout_node())
            builder.append(static_cast<DOM::Text const&>(*node).data());
    }

    if (is<DOM::Text>(*range.end_container()) && range.end_container()->layout_node())
        builder.append(static_cast<DOM::Text const&>(*range.end_container()).data().bytes_as_string_view().substring_view(0, range.end_offset()));

    return MUST(builder.to_string());
}

String BrowsingContext::selected_text() const
{
    auto const* document = active_document();
    if (!document)
        return String {};
    auto selection = const_cast<DOM::Document&>(*document).get_selection();
    auto range = selection->range();
    if (!range)
        return String {};
    return visible_text_in_range(*range);
}

void BrowsingContext::select_all()
{
    auto* document = active_document();
    if (!document)
        return;
    auto* body = document->body();
    if (!body)
        return;
    auto selection = document->get_selection();
    if (!selection)
        return;
    (void)selection->select_all_children(*document->body());
}

bool BrowsingContext::increment_cursor_position_offset()
{
    if (!m_cursor_position->increment_offset())
        return false;
    reset_cursor_blink_cycle();
    return true;
}

bool BrowsingContext::decrement_cursor_position_offset()
{
    if (!m_cursor_position->decrement_offset())
        return false;
    reset_cursor_blink_cycle();
    return true;
}

// https://html.spec.whatwg.org/multipage/interaction.html#currently-focused-area-of-a-top-level-browsing-context
JS::GCPtr<DOM::Node> BrowsingContext::currently_focused_area()
{
    // 1. If topLevelBC does not have system focus, then return null.
    if (!is_focused_context())
        return nullptr;

    // 2. Let candidate be topLevelBC's active document.
    auto* candidate = active_document();

    // 3. While candidate's focused area is a browsing context container with a non-null nested browsing context:
    //    set candidate to the active document of that browsing context container's nested browsing context.
    while (candidate->focused_element()
        && is<HTML::NavigableContainer>(candidate->focused_element())
        && static_cast<HTML::NavigableContainer&>(*candidate->focused_element()).nested_browsing_context()) {
        candidate = static_cast<HTML::NavigableContainer&>(*candidate->focused_element()).nested_browsing_context()->active_document();
    }

    // 4. If candidate's focused area is non-null, set candidate to candidate's focused area.
    if (candidate->focused_element()) {
        // NOTE: We return right away here instead of assigning to candidate,
        //       since that would require compromising type safety.
        return candidate->focused_element();
    }

    // 5. Return candidate.
    return candidate;
}

DOM::Document const* BrowsingContext::active_document() const
{
    auto* window = active_window();
    if (!window)
        return nullptr;
    return &window->associated_document();
}

DOM::Document* BrowsingContext::active_document()
{
    auto* window = active_window();
    if (!window)
        return nullptr;
    return &window->associated_document();
}

// https://html.spec.whatwg.org/multipage/browsers.html#active-window
HTML::Window* BrowsingContext::active_window()
{
    return m_window_proxy->window();
}

// https://html.spec.whatwg.org/multipage/browsers.html#active-window
HTML::Window const* BrowsingContext::active_window() const
{
    return m_window_proxy->window();
}

HTML::WindowProxy* BrowsingContext::window_proxy()
{
    return m_window_proxy.ptr();
}

HTML::WindowProxy const* BrowsingContext::window_proxy() const
{
    return m_window_proxy.ptr();
}

void BrowsingContext::set_window_proxy(JS::GCPtr<WindowProxy> window_proxy)
{
    m_window_proxy = move(window_proxy);
}

BrowsingContextGroup* BrowsingContext::group()
{
    return m_group;
}

void BrowsingContext::set_group(BrowsingContextGroup* group)
{
    m_group = group;
}

// https://html.spec.whatwg.org/multipage/browsers.html#bcg-remove
void BrowsingContext::remove()
{
    // 1. Assert: browsingContext's group is non-null, because a browsing context only gets discarded once.
    VERIFY(group());

    // 2. Let group be browsingContext's group.
    JS::NonnullGCPtr<BrowsingContextGroup> group = *this->group();

    // 3. Set browsingContext's group to null.
    set_group(nullptr);

    // 4. Remove browsingContext from group's browsing context set.
    group->browsing_context_set().remove(*this);

    // 5. If group's browsing context set is empty, then remove group from the user agent's browsing context group set.
    // NOTE: This is done by ~BrowsingContextGroup() when the refcount reaches 0.
}

// https://html.spec.whatwg.org/multipage/origin.html#one-permitted-sandboxed-navigator
BrowsingContext const* BrowsingContext::the_one_permitted_sandboxed_navigator() const
{
    // FIXME: Implement this.
    return nullptr;
}

JS::GCPtr<BrowsingContext> BrowsingContext::first_child() const
{
    return m_first_child;
}
JS::GCPtr<BrowsingContext> BrowsingContext::next_sibling() const
{
    return m_next_sibling;
}

bool BrowsingContext::is_ancestor_of(BrowsingContext const& other) const
{
    for (auto ancestor = other.parent(); ancestor; ancestor = ancestor->parent()) {
        if (ancestor == this)
            return true;
    }
    return false;
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#familiar-with
bool BrowsingContext::is_familiar_with(BrowsingContext const& other) const
{
    // A browsing context A is familiar with a second browsing context B if the following algorithm returns true:
    auto const& A = *this;
    auto const& B = other;

    // 1. If A's active document's origin is same origin with B's active document's origin, then return true.
    if (A.active_document()->origin().is_same_origin(B.active_document()->origin()))
        return true;

    // 2. If A's top-level browsing context is B, then return true.
    if (A.top_level_browsing_context() == &B)
        return true;

    // 3. If B is an auxiliary browsing context and A is familiar with B's opener browsing context, then return true.
    if (B.opener_browsing_context() != nullptr && A.is_familiar_with(*B.opener_browsing_context()))
        return true;

    // 4. If there exists an ancestor browsing context of B whose active document has the same origin as the active document of A, then return true.
    // NOTE: This includes the case where A is an ancestor browsing context of B.
    for (auto ancestor = B.parent(); ancestor; ancestor = ancestor->parent()) {
        if (ancestor->active_document()->origin().is_same_origin(A.active_document()->origin()))
            return true;
    }

    // 5. Return false.
    return false;
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#snapshotting-target-snapshot-params
SandboxingFlagSet determine_the_creation_sandboxing_flags(BrowsingContext const&, JS::GCPtr<DOM::Element>)
{
    // FIXME: Populate this once we have the proper flag sets on BrowsingContext
    return {};
}

bool BrowsingContext::has_navigable_been_destroyed() const
{
    auto navigable = active_document()->navigable();
    return navigable && navigable->has_been_destroyed();
}

}