/*

 * Copyright (c) 2024, Andrew Kaster <akaster@serenityos.org>

 * Copyright (c) 2024, Jamie Mansfield <jmansfield@cadixdev.org>

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#include <LibJS/Heap/Heap.h>

#include <LibJS/Runtime/Realm.h>

#include <LibJS/Runtime/Set.h>

#include <LibWeb/Bindings/ExceptionOrUtils.h>

#include <LibWeb/Bindings/FontFaceSetPrototype.h>

#include <LibWeb/Bindings/Intrinsics.h>

#include <LibWeb/CSS/FontFace.h>

#include <LibWeb/CSS/FontFaceSet.h>

#include <LibWeb/CSS/Parser/Parser.h>

#include <LibWeb/CSS/StyleValues/ShorthandStyleValue.h>

#include <LibWeb/CSS/StyleValues/StringStyleValue.h>

#include <LibWeb/CSS/StyleValues/StyleValueList.h>

#include <LibWeb/DOM/Document.h>

#include <LibWeb/HTML/EventNames.h>

#include <LibWeb/HTML/Scripting/TemporaryExecutionContext.h>

#include <LibWeb/Platform/EventLoopPlugin.h>

#include <LibWeb/WebIDL/Promise.h>

namespace Web::CSS {

JS_DEFINE_ALLOCATOR(FontFaceSet);

// https://drafts.csswg.org/css-font-loading/#dom-fontfaceset-fontfaceset

JS::NonnullGCPtr<FontFaceSet> FontFaceSet::construct_impl(JS::Realm& realm, Vector<JS::Handle<FontFace>> const& initial_faces)

{

    auto ready_promise = WebIDL::create_promise(realm);

    auto set_entries = JS::Set::create(realm);

    // The FontFaceSet constructor, when called, must iterate its initialFaces argument and add each value to its set entries.

    for (auto const& face : initial_faces)

        set_entries->set_add(face);

    if (set_entries->set_size() == 0)

        WebIDL::resolve_promise(realm, *ready_promise);

    return realm.heap().allocate<FontFaceSet>(realm, realm, ready_promise, set_entries);

}

JS::NonnullGCPtr<FontFaceSet> FontFaceSet::create(JS::Realm& realm)

{

    return construct_impl(realm, {});

}

FontFaceSet::FontFaceSet(JS::Realm& realm, JS::NonnullGCPtr<WebIDL::Promise> ready_promise, JS::NonnullGCPtr<JS::Set> set_entries)

    : DOM::EventTarget(realm)

    , m_set_entries(set_entries)

    , m_ready_promise(ready_promise)

{

    bool const is_ready = ready()->state() == JS::Promise::State::Fulfilled;

    m_status = is_ready ? Bindings::FontFaceSetLoadStatus::Loaded : Bindings::FontFaceSetLoadStatus::Loading;

}

void FontFaceSet::initialize(JS::Realm& realm)

{

    Base::initialize(realm);

    WEB_SET_PROTOTYPE_FOR_INTERFACE(FontFaceSet);

}

void FontFaceSet::visit_edges(Cell::Visitor& visitor)

{

    Base::visit_edges(visitor);

    visitor.visit(m_set_entries);

    visitor.visit(m_ready_promise);

    visitor.visit(m_loading_fonts);

    visitor.visit(m_loaded_fonts);

    visitor.visit(m_failed_fonts);

}

// https://drafts.csswg.org/css-font-loading/#dom-fontfaceset-add

WebIDL::ExceptionOr<JS::NonnullGCPtr<FontFaceSet>>

FontFaceSet::add(JS::Handle<FontFace> face)

{

    // 1. If font is already in the FontFaceSet’s set entries, skip to the last step of this algorithm immediately.

    if (m_set_entries->set_has(face))

        return JS::NonnullGCPtr<FontFaceSet>(*this);

    // 2. If font is CSS-connected, throw an InvalidModificationError exception and exit this algorithm immediately.

    if (face->is_css_connected()) {

        return WebIDL::InvalidModificationError::create(realm(), "Cannot add a CSS-connected FontFace to a FontFaceSet"_string);

    }

    // 3. Add the font argument to the FontFaceSet’s set entries.

    m_set_entries->set_add(face);

    // 4. If font’s status attribute is "loading"

    if (face->status() == Bindings::FontFaceLoadStatus::Loading) {

        // 1. If the FontFaceSet’s [[LoadingFonts]] list is empty, switch the FontFaceSet to loading.

        if (m_loading_fonts.is_empty()) {

            m_status = Bindings::FontFaceSetLoadStatus::Loading;

        }

        // 2. Append font to the FontFaceSet’s [[LoadingFonts]] list.

        m_loading_fonts.append(*face);

    }

    // 5. Return the FontFaceSet.

    return JS::NonnullGCPtr<FontFaceSet>(*this);

}

// https://drafts.csswg.org/css-font-loading/#dom-fontfaceset-delete

bool FontFaceSet::delete_(JS::Handle<FontFace> face)

{

    // 1. If font is CSS-connected, return false and exit this algorithm immediately.

    if (face->is_css_connected()) {

        return false;

    }

    // 2. Let deleted be the result of removing font from the FontFaceSet’s set entries.

    bool deleted = m_set_entries->set_remove(face);

    // 3. If font is present in the FontFaceSet’s [[LoadedFonts]], or [[FailedFonts]] lists, remove it.

    m_loaded_fonts.remove_all_matching([face](auto const& entry) { return entry == face; });

    m_failed_fonts.remove_all_matching([face](auto const& entry) { return entry == face; });

    // 4. If font is present in the FontFaceSet’s [[LoadingFonts]] list, remove it. If font was the last item in that list (and so the list is now empty), switch the FontFaceSet to loaded.

    m_loading_fonts.remove_all_matching([face](auto const& entry) { return entry == face; });

    if (m_loading_fonts.is_empty()) {

        m_status = Bindings::FontFaceSetLoadStatus::Loaded;

    }

    return deleted;

}

// https://drafts.csswg.org/css-font-loading/#dom-fontfaceset-clear

void FontFaceSet::clear()

{

    // FIXME: Do the actual spec steps

    m_set_entries->set_clear();

}

// https://drafts.csswg.org/css-font-loading/#dom-fontfaceset-onloading

void FontFaceSet::set_onloading(WebIDL::CallbackType* event_handler)

{

    set_event_handler_attribute(HTML::EventNames::loading, event_handler);

}

// https://drafts.csswg.org/css-font-loading/#dom-fontfaceset-onloading

WebIDL::CallbackType* FontFaceSet::onloading()

{

    return event_handler_attribute(HTML::EventNames::loading);

}

// https://drafts.csswg.org/css-font-loading/#dom-fontfaceset-onloadingdone

void FontFaceSet::set_onloadingdone(WebIDL::CallbackType* event_handler)

{

    set_event_handler_attribute(HTML::EventNames::loadingdone, event_handler);

}

// https://drafts.csswg.org/css-font-loading/#dom-fontfaceset-onloadingdone

WebIDL::CallbackType* FontFaceSet::onloadingdone()

{

    return event_handler_attribute(HTML::EventNames::loadingdone);

}

// https://drafts.csswg.org/css-font-loading/#dom-fontfaceset-onloadingerror

void FontFaceSet::set_onloadingerror(WebIDL::CallbackType* event_handler)

{

    set_event_handler_attribute(HTML::EventNames::loadingerror, event_handler);

}

// https://drafts.csswg.org/css-font-loading/#dom-fontfaceset-onloadingerror

WebIDL::CallbackType* FontFaceSet::onloadingerror()

{

    return event_handler_attribute(HTML::EventNames::loadingerror);

}

// https://drafts.csswg.org/css-font-loading/#find-the-matching-font-faces

static WebIDL::ExceptionOr<JS::NonnullGCPtr<JS::Set>> find_matching_font_faces(JS::Realm& realm, FontFaceSet& font_face_set, String const& font, String const&)

{

    // 1. Parse font using the CSS value syntax of the font property. If a syntax error occurs, return a syntax error.

    auto parser = CSS::Parser::Parser::create(CSS::Parser::ParsingContext(realm), font);

    auto property = parser.parse_as_css_value(PropertyID::Font);

    if (!property)

        return WebIDL::SyntaxError::create(realm, "Unable to parse font"_string);

    // If the parsed value is a CSS-wide keyword, return a syntax error.

    if (property->is_css_wide_keyword())

        return WebIDL::SyntaxError::create(realm, "Parsed font is a CSS-wide keyword"_string);

    // FIXME: Absolutize all relative lengths against the initial values of the corresponding properties. (For example, a

    //        relative font weight like bolder is evaluated against the initial value normal.)

    // FIXME: 2. If text was not explicitly provided, let it be a string containing a single space character (U+0020 SPACE).

    // 3. Let font family list be the list of font families parsed from font, and font style be the other font style

    //    attributes parsed from font.

    auto const& font_family_list = property->as_shorthand().longhand(PropertyID::FontFamily)->as_value_list();

    // 4. Let available font faces be the available font faces within source. If the allow system fonts flag is specified,

    //    add all system fonts to available font faces.

    auto available_font_faces = font_face_set.set_entries();

    // 5. Let matched font faces initially be an empty list.

    auto matched_font_faces = JS::Set::create(realm);

    // 6. For each family in font family list, use the font matching rules to select the font faces from available font

    //    faces that match the font style, and add them to matched font faces. The use of the unicodeRange attribute means

    //    that this may be more than just a single font face.

    for (auto const& font_family : font_family_list.values()) {

        // FIXME: The matching below is super basic. We currently just match font family names by their string value.

        if (!font_family->is_string())

            continue;

        auto const& font_family_name = font_family->as_string().string_value();

        for (auto font_face_value : *available_font_faces) {

            auto& font_face = verify_cast<FontFace>(font_face_value.key.as_object());

            if (font_face.family() != font_family_name)

                continue;

            matched_font_faces->set_add(font_face_value.key);

        }

    }

    // FIXME: 7. If matched font faces is empty, set the found faces flag to false. Otherwise, set it to true.

    // FIXME: 8. For each font face in matched font faces, if its defined unicode-range does not include the codepoint of at

    //           least one character in text, remove it from the list.

    // 9. Return matched font faces and the found faces flag.

    return matched_font_faces;

}

// https://drafts.csswg.org/css-font-loading/#dom-fontfaceset-load

JS::ThrowCompletionOr<JS::NonnullGCPtr<JS::Promise>> FontFaceSet::load(String const& font, String const& text)

{

    auto& realm = this->realm();

    // 1. Let font face set be the FontFaceSet object this method was called on. Let promise be a newly-created promise object.

    JS::NonnullGCPtr font_face_set = *this;

    auto promise = WebIDL::create_promise(realm);

    Platform::EventLoopPlugin::the().deferred_invoke([&realm, font_face_set, promise, font, text]() mutable {

        // 3. Find the matching font faces from font face set using the font and text arguments passed to the function,

        //    and let font face list be the return value (ignoring the found faces flag). If a syntax error was returned,

        //    reject promise with a SyntaxError exception and terminate these steps.

        auto result = find_matching_font_faces(realm, font_face_set, font, text);

        if (result.is_error()) {

            HTML::TemporaryExecutionContext execution_context { Bindings::host_defined_environment_settings_object(realm), HTML::TemporaryExecutionContext::CallbacksEnabled::Yes };

            WebIDL::reject_promise(realm, promise, Bindings::dom_exception_to_throw_completion(realm.vm(), result.release_error()).release_value().value());

            return;

        }

        auto matched_font_faces = result.release_value();

        // 4. Queue a task to run the following steps synchronously:

        HTML::queue_a_task(HTML::Task::Source::FontLoading, nullptr, nullptr, JS::create_heap_function(realm.heap(), [&realm, promise, matched_font_faces] {

            JS::MarkedVector<JS::NonnullGCPtr<WebIDL::Promise>> promises(realm.heap());

            // 1. For all of the font faces in the font face list, call their load() method.

            for (auto font_face_value : *matched_font_faces) {

                auto& font_face = verify_cast<FontFace>(font_face_value.key.as_object());

                font_face.load();

                promises.append(font_face.font_status_promise());

            }

            // 2. Resolve promise with the result of waiting for all of the [[FontStatusPromise]]s of each font face in

            //    the font face list, in order.

            HTML::TemporaryExecutionContext execution_context { Bindings::host_defined_environment_settings_object(realm), HTML::TemporaryExecutionContext::CallbacksEnabled::Yes };

            WebIDL::wait_for_all(

                realm, promises,

                [&realm, promise](auto const&) {

                    HTML::TemporaryExecutionContext execution_context { Bindings::host_defined_environment_settings_object(realm), HTML::TemporaryExecutionContext::CallbacksEnabled::Yes };

                    WebIDL::resolve_promise(realm, promise);

                },

                [&realm, promise](auto error) {

                    HTML::TemporaryExecutionContext execution_context { Bindings::host_defined_environment_settings_object(realm), HTML::TemporaryExecutionContext::CallbacksEnabled::Yes };

                    WebIDL::reject_promise(realm, promise, error);

                });

        }));

    });

    // 2. Return promise. Complete the rest of these steps asynchronously.

    return JS::NonnullGCPtr { verify_cast<JS::Promise>(*promise->promise()) };

}

// https://drafts.csswg.org/css-font-loading/#font-face-set-ready

JS::NonnullGCPtr<JS::Promise> FontFaceSet::ready() const

{

    return verify_cast<JS::Promise>(*m_ready_promise->promise());

}

}