#include <AK/Optional.h>
#include <AK/TypeCasts.h>
#include <AK/Utf16FlyString.h>
#include <AK/Utf16String.h>
#include <AK/Variant.h>
#include <LibGC/ConservativeVector.h>
#include <LibGC/Ptr.h>
#include <LibJS/Runtime/AbstractOperations.h>
#include <LibJS/Runtime/Array.h>
#include <LibJS/Runtime/Error.h>
#include <LibJS/Runtime/Realm.h>
#include <LibJS/Runtime/VM.h>
#include <LibJS/Runtime/Value.h>
#include <LibJS/Runtime/ValueInlines.h>
#include <LibWeb/Bindings/ExceptionOrUtils.h>
#include <LibWeb/Bindings/HTMLElement.h>
#include <LibWeb/Bindings/HTMLSlotElement.h>
#include <LibWeb/Bindings/Intrinsics.h>
#include <LibWeb/Bindings/MainThreadVM.h>
#include <LibWeb/Bindings/PlatformObject.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/Element.h>
#include <LibWeb/DOM/ElementFactory.h>
#include <LibWeb/DOM/Node.h>
#include <LibWeb/DOM/Text.h>
#include <LibWeb/HTML/CustomElements/CustomElementDefinition.h>
#include <LibWeb/HTML/CustomElements/CustomElementRegistry.h>
#include <LibWeb/HTML/HTMLSlotElement.h>
#include <LibWeb/HTML/Scripting/SimilarOriginWindowAgent.h>
#include <LibWeb/HTML/Window.h>
#include <LibWeb/WebIDL/AbstractOperations.h>
#include <LibWeb/WebIDL/Tracing.h>

namespace Web::Bindings {

void HTMLSlotElementConstructor::initialize(JS::Realm& realm, JS::NativeFunction& object)
{
    auto& vm = realm.vm();
    [[maybe_unused]] u8 default_attributes = JS::Attribute::Enumerable;

    object.set_prototype(&ensure_web_constructor<HTMLElementPrototype>(realm, "HTMLElement"_fly_string));
    object.define_direct_property(vm.names.length, JS::Value(0), JS::Attribute::Configurable);
    object.define_direct_property(vm.names.name, JS::PrimitiveString::create(vm, "HTMLSlotElement"_utf16), JS::Attribute::Configurable);
    object.define_direct_property(vm.names.prototype, &ensure_web_prototype<HTMLSlotElementPrototype>(realm, "HTMLSlotElement"_fly_string), 0);
}

JS::ThrowCompletionOr<GC::Ref<JS::Object>> HTMLSlotElementConstructor::construct([[maybe_unused]] InterfaceConstructor& constructor, [[maybe_unused]] JS::FunctionObject& new_target)
{
    WebIDL::log_trace(constructor.vm(), "HTMLSlotElementConstructor::construct");
    auto& vm = constructor.vm();
    auto& realm = *vm.current_realm();
    auto& window = as<HTML::Window>(HTML::current_global_object());

    // 1. If NewTarget is equal to the active function object, then throw a TypeError.
    if (&new_target == vm.active_function_object())
        return vm.throw_completion<JS::TypeError>("Cannot directly construct an HTML element, it must be inherited"_utf16);

    // 2. Let registry be null.
    GC::Ptr<HTML::CustomElementRegistry> registry;

    // 3. If the surrounding agent's active custom element constructor map[NewTarget] exists:
    auto& surrounding_agent = HTML::relevant_similar_origin_window_agent(window);
    if (auto registry_for_constructor = surrounding_agent.active_custom_element_constructor_map.get(GC::Ref { new_target }); registry_for_constructor.has_value() && !registry_for_constructor->is_null()) {
        // 1. Set registry to the surrounding agent's active custom element constructor map[NewTarget].
        registry = registry_for_constructor.value();

        // 2. Remove the surrounding agent's active custom element constructor map[NewTarget].
        surrounding_agent.active_custom_element_constructor_map.remove(GC::Ref { new_target });
    }
    // 4. Otherwise, set registry to current global object's associated Document's custom element registry.
    else {
        registry = window.associated_document().custom_element_registry();
    }

    // 5. Let definition be the item in registry's custom element definition set with constructor equal to NewTarget.
    //    If there is no such item, then throw a TypeError.
    auto definition = registry->get_definition_from_new_target(new_target);
    if (!definition)
        return vm.throw_completion<JS::TypeError>("There is no custom element definition assigned to the given constructor"_utf16);

    // 6. Let isValue be null.
    Optional<Utf16FlyString> is_value;

    // 7. If definition's local name is equal to definition's name (i.e., definition is for an autonomous custom element):
    if (definition->local_name() == definition->name()) {
        // 1. If the active function object is not HTMLElement, then throw a TypeError.
        return vm.throw_completion<JS::TypeError>("Autonomous custom elements can only inherit from HTMLElement"_utf16);
    }
    // 8. Otherwise (i.e., if definition is for a customized built-in element):
    else {
        // 1. Let valid local names be the list of local names for elements defined in this specification or in other applicable specifications that use the active function object as their element interface.
        static auto const& valid_local_names = *new auto(MUST(DOM::valid_local_names_for_given_html_element_interface("HTMLSlotElement"sv)));

        // 2. If valid local names does not contain definition's local name, then throw a TypeError.
        if (!valid_local_names.contains_slow(definition->local_name()))
            return vm.throw_completion<JS::TypeError>(Utf16String::formatted("Local name '{}' of customized built-in element is not a valid local name for HTMLSlotElement", definition->local_name()));

        // 3. Set isValue to definition's name.
        is_value = definition->name();
    }

    // 9. If definition's construction stack is empty:
    if (definition->construction_stack().is_empty()) {
        // 1. Let element be the result of internally creating a new object implementing the interface to which the active function object corresponds, given the current Realm Record and NewTarget.
        // 2. Set element's node document to the current global object's associated Document.
        // 3. Set element's namespace to the HTML namespace.
        // 4. Set element's namespace prefix to null.
        // 5. Set element's local name to definition's local name.
        auto element = realm.create<HTML::HTMLSlotElement>(window.associated_document(), DOM::QualifiedName { definition->local_name(), {}, Namespace::HTML });

        // https://webidl.spec.whatwg.org/#internally-create-a-new-object-implementing-the-interface
        TRY(WebIDL::set_prototype_from_new_target<HTMLSlotElementPrototype>(vm, new_target, "HTMLSlotElement"_fly_string, *element));

        // 6. Set element's custom element registry to registry.
        element->set_custom_element_registry(registry);

        // 7. Set element's custom element state to "custom".
        // 8. Set element's custom element definition to definition.
        // 9. Set element's is value to isValue.
        element->setup_custom_element_from_constructor(*definition, is_value);

        // 10. Return element.
        return *element;
    }

    // 10. Let prototype be ? Get(NewTarget, "prototype").
    auto prototype = TRY(new_target.get(vm.names.prototype));

    // 11. If Type(prototype) is not Object, then:
    if (!prototype.is_object()) {
        // 1. Let realm be ? GetFunctionRealm(NewTarget).
        auto* function_realm = TRY(JS::get_function_realm(vm, new_target));

        // 2. Set prototype to the interface prototype object of realm whose interface is the same as the interface of the active function object.
        VERIFY(function_realm);
        prototype = &Bindings::ensure_web_prototype<HTMLSlotElementPrototype>(*function_realm, "HTMLSlotElement"_fly_string);
    }

    VERIFY(prototype.is_object());

    // 12. Let element be the last entry in definition's construction stack.
    auto& element = definition->construction_stack().last();

    // 13. If element is an already constructed marker, then throw a TypeError.
    if (element.has<HTML::AlreadyConstructedCustomElementMarker>())
        return vm.throw_completion<JS::TypeError>("Custom element has already been constructed"_utf16);

    // 14. Perform ? element.[[SetPrototypeOf]](prototype).
    auto actual_element = element.get<GC::Ref<DOM::Element>>();
    TRY(actual_element->internal_set_prototype_of(&prototype.as_object()));

    // 15. Replace the last entry in definition's construction stack with an already constructed marker.
    definition->construction_stack().last() = HTML::AlreadyConstructedCustomElementMarker {};

    // 16. Return element.
    return *actual_element;
}

void HTMLSlotElementPrototype::initialize(JS::Realm& realm, JS::Object& object)
{
    [[maybe_unused]] auto& vm = realm.vm();
    [[maybe_unused]] u8 default_attributes = JS::Attribute::Enumerable | JS::Attribute::Configurable | JS::Attribute::Writable;

    object.set_prototype(GC::Ref { ensure_web_prototype<HTMLElementPrototype>(realm, "HTMLElement"_fly_string) });

    auto name_id = "name"_utf16_fly_string;
    auto native_name_getter = JS::NativeFunction::create(realm, name_getter, 0, name_id, &realm, "get"sv);
    auto native_name_setter = JS::NativeFunction::create(realm, name_setter, 1, name_id, &realm, "set"sv);

    // 4. Let configurable be false if attr is unforgeable and true otherwise.
    auto name_attributes = default_attributes;

    // 5. Let desc be the PropertyDescriptor{[[Get]]: getter, [[Set]]: setter, [[Enumerable]]: true, [[Configurable]]: configurable}.

    // 7. Perform ! DefinePropertyOrThrow(target, id, desc).
    object.define_direct_accessor(name_id, native_name_getter, native_name_setter, name_attributes);

    // 8. FIXME: If attr’s type is an observable array type with type argument T, then set target’s backing observable array exotic object for attr to the result of creating an observable array exotic object in realm, given T, attr’s set an indexed value algorithm, and attr’s delete an indexed value algorithm.
    object.define_native_function(realm, "assignedNodes"_utf16_fly_string, assigned_nodes, 0, default_attributes);

    object.define_native_function(realm, "assignedElements"_utf16_fly_string, assigned_elements, 0, default_attributes);

    object.define_native_function(realm, "assign"_utf16_fly_string, assign, 0, default_attributes);

    object.define_direct_property(vm.well_known_symbol_to_string_tag(), JS::PrimitiveString::create(vm, "HTMLSlotElement"_utf16), JS::Attribute::Configurable);
}

void HTMLSlotElementPrototype::define_unforgeable_attributes(JS::Realm& realm, [[maybe_unused]] JS::Object& object)
{
    [[maybe_unused]] auto& vm = realm.vm();
    [[maybe_unused]] u8 default_attributes = JS::Attribute::Enumerable;
}

[[maybe_unused]] static JS::ThrowCompletionOr<HTML::HTMLSlotElement*> impl_from(JS::VM& vm, JS::Value js_value)
{

    if (auto impl = js_value.as_if<HTML::HTMLSlotElement>())
        return impl.ptr();
    return vm.throw_completion<JS::TypeError>(JS::ErrorType::NotAnObjectOfType, "HTMLSlotElement");
}

[[maybe_unused]] static JS::ThrowCompletionOr<HTML::HTMLSlotElement*> impl_from(JS::VM& vm)
{
    auto this_value = vm.this_value();
    if (this_value.is_nullish())
        this_value = &vm.current_realm()->global_object();
    return impl_from(vm, this_value);
}

JS_DEFINE_NATIVE_FUNCTION(HTMLSlotElementPrototype::name_getter)
{
    WebIDL::log_trace(vm, "HTMLSlotElementPrototype::name_getter");
    [[maybe_unused]] auto& realm = *vm.current_realm();

    auto* idl_object = TRY(impl_from(vm));


    // If a reflected IDL attribute has the type DOMString:
    // 1. Let element be the result of running this's get the element.
    // 2. Let contentAttributeValue be the result of running this's get the content attribute.
    // 5. If contentAttributeValue is null, then return the empty string.
    // 6. Return contentAttributeValue.
    auto R = idl_object->get_attribute_value("name"_utf16_fly_string);

    return WebIDL::primitive_string_from_string(vm, R);
}

JS_DEFINE_NATIVE_FUNCTION(HTMLSlotElementPrototype::name_setter)
{
    WebIDL::log_trace(vm, "HTMLSlotElementPrototype::name_setter");
    [[maybe_unused]] auto& realm = *vm.current_realm();

    // 1. Let V be undefined.
    auto V = JS::js_undefined();

    // 2. If any arguments were passed, then set V to the value of the first argument passed.
    if (vm.argument_count() > 0)
        V = vm.argument(0);

    // 3. Let id be attribute’s identifier.

    // 4. Let idlObject be null.
    [[maybe_unused]] HTML::HTMLSlotElement* idl_object = nullptr;

    // 5. If attribute is a regular attribute:

    // 1. Let jsValue be the this value, if it is not null or undefined, or realm’s global object otherwise. (This will subsequently cause a TypeError in a few steps, if the global object does not implement target and [LegacyLenientThis] is not specified.)
    auto js_value = vm.this_value();
    if (js_value.is_nullish())
        js_value = &realm.global_object();

    // 2. FIXME: If jsValue is a platform object, then perform a security check, passing jsValue, attribute’s identifier, and "setter".

    // 3. Let validThis be true if jsValue implements target, or false otherwise.
    auto maybe_idl_object = impl_from(vm, js_value);

    // 4. If validThis is false and attribute was not specified with the [LegacyLenientThis] extended attribute, then throw a TypeError.
    idl_object = TRY(maybe_idl_object);

    auto original_steps = [&]() -> JS::ThrowCompletionOr<JS::Value> {
        // 6. Let idlValue be determined as follows:
        // -> Otherwise, idlValue is the result of converting V to an IDL value of attribute’s type.
        auto idl_value = TRY(throw_dom_exception_if_needed(vm, [&] { return [&]() -> JS::ThrowCompletionOr<Utf16String> {
        return TRY(WebIDL::to_utf16_string(vm, V));
    }(); }));

        // 7. Run the setter steps of attribute with idlObject as this and idlValue as the value.
        auto setter_result = [&]() -> JS::ThrowCompletionOr<void> {
            idl_object->set_attribute_value("name"_utf16_fly_string, attribute_value_to_utf16(idl_value));
    return {};
        }();

        if (setter_result.is_error())
            return setter_result.release_error();

        return JS::js_undefined();
    };

    // 8. Return undefined.
    return TRY([&]() -> decltype(original_steps()) {
        // For [CEReactions]: https://html.spec.whatwg.org/multipage/custom-elements.html#cereactions

        // 1. Push a new element queue onto this object's relevant agent's custom element reactions stack.
        auto& reactions_stack = HTML::relevant_similar_origin_window_agent(*idl_object).custom_element_reactions_stack;
        reactions_stack.element_queue_stack.append({});

        // 2. Run the originally-specified steps for this construct, catching any exceptions. If the steps return a value, let value be the returned value. If they throw an exception, let exception be the thrown exception.
        auto value_or_exception = original_steps();

        // 3. Let queue be the result of popping from this object's relevant agent's custom element reactions stack.
        // 4. Invoke custom element reactions in queue.
        auto queue = reactions_stack.element_queue_stack.take_last();
        Bindings::invoke_custom_element_reactions(queue);

        // 5. If an exception exception was thrown by the original steps, rethrow exception.
        if (value_or_exception.is_error())
            return value_or_exception.release_error();

        // 6. If a value value was returned from the original steps, return value.
        return value_or_exception.release_value();
    }());
}

JS_DEFINE_NATIVE_FUNCTION(HTMLSlotElementPrototype::assigned_nodes)
{
    WebIDL::log_trace(vm, "HTMLSlotElementPrototype::assigned_nodes");
    [[maybe_unused]] auto& realm = *vm.current_realm();
    [[maybe_unused]] HTML::HTMLSlotElement* idl_object = TRY(impl_from(vm));

    auto arg0 = vm.argument(0);
    AssignedNodesOptions options = AssignedNodesOptions {};
    if (!arg0.is_undefined())
        options = TRY(throw_dom_exception_if_needed(vm, [&] { return convert_to_idl_value_for_assigned_nodes_options(vm, arg0); }));

    [[maybe_unused]] auto R = TRY(throw_dom_exception_if_needed(vm, [&] { return idl_object->assigned_nodes(options); }));
    return [&]() -> JS::Value {
        // An IDL sequence<T> value S is converted to a JavaScript value as follows:
        // 1. Let n be the length of S.
        auto sequence_length = R.size();

        // 2. Let A be a new Array object created as if by the expression [].
        auto sequence_array = MUST(JS::Array::create(realm, sequence_length));

        // 3. Initialize i to be 0.
        // 4. While i < n:
        for (size_t sequence_index = 0; sequence_index < sequence_length; ++sequence_index) {
            // 1. Let V be the value in S at index i.
            auto& sequence_element = R.at(sequence_index);

            // 2. Let E be the result of converting V to a JavaScript value.
            JS::Value js_sequence_element = JS::Value(sequence_element);

            // 3. Let P be the result of calling ! ToString(i).
            // 4. Perform ! CreateDataPropertyOrThrow(A, P, E).
            MUST(sequence_array->create_data_property(JS::PropertyKey { sequence_index }, js_sequence_element));

            // 5. Set i to i + 1.
        }

        // 5. Return A.
        return sequence_array;
    }();
}

JS_DEFINE_NATIVE_FUNCTION(HTMLSlotElementPrototype::assigned_elements)
{
    WebIDL::log_trace(vm, "HTMLSlotElementPrototype::assigned_elements");
    [[maybe_unused]] auto& realm = *vm.current_realm();
    [[maybe_unused]] HTML::HTMLSlotElement* idl_object = TRY(impl_from(vm));

    auto arg0 = vm.argument(0);
    AssignedNodesOptions options = AssignedNodesOptions {};
    if (!arg0.is_undefined())
        options = TRY(throw_dom_exception_if_needed(vm, [&] { return convert_to_idl_value_for_assigned_nodes_options(vm, arg0); }));

    [[maybe_unused]] auto R = TRY(throw_dom_exception_if_needed(vm, [&] { return idl_object->assigned_elements(options); }));
    return [&]() -> JS::Value {
        // An IDL sequence<T> value S is converted to a JavaScript value as follows:
        // 1. Let n be the length of S.
        auto sequence_length = R.size();

        // 2. Let A be a new Array object created as if by the expression [].
        auto sequence_array = MUST(JS::Array::create(realm, sequence_length));

        // 3. Initialize i to be 0.
        // 4. While i < n:
        for (size_t sequence_index = 0; sequence_index < sequence_length; ++sequence_index) {
            // 1. Let V be the value in S at index i.
            auto& sequence_element = R.at(sequence_index);

            // 2. Let E be the result of converting V to a JavaScript value.
            JS::Value js_sequence_element = JS::Value(sequence_element);

            // 3. Let P be the result of calling ! ToString(i).
            // 4. Perform ! CreateDataPropertyOrThrow(A, P, E).
            MUST(sequence_array->create_data_property(JS::PropertyKey { sequence_index }, js_sequence_element));

            // 5. Set i to i + 1.
        }

        // 5. Return A.
        return sequence_array;
    }();
}

JS_DEFINE_NATIVE_FUNCTION(HTMLSlotElementPrototype::assign)
{
    WebIDL::log_trace(vm, "HTMLSlotElementPrototype::assign");
    [[maybe_unused]] auto& realm = *vm.current_realm();
    [[maybe_unused]] HTML::HTMLSlotElement* idl_object = TRY(impl_from(vm));

    GC::ConservativeVector<Variant<GC::Ref<DOM::Element>, GC::Ref<DOM::Text>>> nodes;
    if (vm.argument_count() > 0) {
        nodes.ensure_capacity(vm.argument_count() - 0);
        for (size_t i = 0; i < vm.argument_count(); ++i) {
            auto argument = TRY(throw_dom_exception_if_needed(vm, [&] { return [&]() -> JS::ThrowCompletionOr<Variant<GC::Ref<DOM::Element>, GC::Ref<DOM::Text>>> {

        if (vm.argument(i).is_object()) {
            [[maybe_unused]] auto& object = vm.argument(i).as_object();

            if (is<PlatformObject>(object)) {

                if (auto* result = as_if<DOM::Element>(object))
                    return Variant<GC::Ref<DOM::Element>, GC::Ref<DOM::Text>> { GC::Ref { *result } };

                if (auto* result = as_if<DOM::Text>(object))
                    return Variant<GC::Ref<DOM::Element>, GC::Ref<DOM::Text>> { GC::Ref { *result } };
            }
        }

        return vm.throw_completion<JS::TypeError>("No union types matched"_utf16);
    }(); }));
            nodes.unchecked_append(move(argument));
        }
    }

    [[maybe_unused]] auto R = TRY(throw_dom_exception_if_needed(vm, [&] { return idl_object->assign(nodes); }));
    return JS::js_undefined();
}

// https://webidl.spec.whatwg.org/#es-dictionary
JS::ThrowCompletionOr<AssignedNodesOptions> convert_to_idl_value_for_assigned_nodes_options(JS::VM& vm, JS::Value js_dict)
{
    // 1. If jsDict is not an Object and jsDict is neither undefined nor null, then throw a TypeError.
    if (!js_dict.is_object() && !js_dict.is_nullish())
        return vm.throw_completion<JS::TypeError>(JS::ErrorType::NotAnObjectOfType, "AssignedNodesOptions");

    // 2. Let idlDict be an empty ordered map, representing a dictionary of type D.
    // 3. Let dictionaries be a list consisting of D and all of D’s inherited dictionaries, in order from least to most derived.
    // 4. For each dictionary dictionary in dictionaries, in order:
    // NB: We defer construction until the return initializer because some members may not be default-constructible. Inherited dictionaries are represented by the generated C++ struct inheritance.

    // 5. Return idlDict.
    return AssignedNodesOptions {
        .flatten = TRY([&]() -> JS::ThrowCompletionOr<bool> {
            // 1. Let key be the identifier of member.
            // 2. If jsDict is either undefined or null, then:
            //     1. Let jsMemberValue be undefined.
            // 3. Otherwise,
            //     1. Let jsMemberValue be ? Get(jsDict, key).
            auto js_member_value = JS::js_undefined();
            if (js_dict.is_object())
                js_member_value = TRY(js_dict.as_object().get("flatten"_utf16_fly_string));

            // 4. If jsMemberValue is not undefined, then:
            if (!js_member_value.is_undefined()) {
                // 1. Let idlMemberValue be the result of converting jsMemberValue to an IDL value whose type is the type member is declared to be of.
                auto idl_member_value = TRY(throw_dom_exception_if_needed(vm, [&] { return js_member_value.to_boolean(); }));

                // 2. Set idlDict[key] to idlMemberValue.
                return idl_member_value;
            }
            // 5. Otherwise, if jsMemberValue is undefined but member has a default value, then:
            // 1. Let idlMemberValue be the result of converting member's default value to an IDL value whose type is the type member is declared to be of.
            auto idl_member_value = false;

            // 2. Set idlDict[key] to idlMemberValue.
            return idl_member_value;
        }()),
    };
}

} // namespace Web::Bindings