#include <AK/String.h>
#include <LibGC/Heap.h>
#include <LibJS/Runtime/AbstractOperations.h>
#include <LibJS/Runtime/Error.h>
#include <LibJS/Runtime/FunctionObject.h>
#include <LibJS/Runtime/PropertyDescriptor.h>
#include <LibJS/Runtime/Realm.h>
#include <LibJS/Runtime/VM.h>
#include <LibJS/Runtime/Value.h>
#include <LibJS/Runtime/ValueInlines.h>
#include <LibWeb/Bindings/EventSource.h>
#include <LibWeb/Bindings/EventTarget.h>
#include <LibWeb/Bindings/ExceptionOrUtils.h>
#include <LibWeb/Bindings/Intrinsics.h>
#include <LibWeb/HTML/EventSource.h>
#include <LibWeb/HTML/Scripting/Environments.h>
#include <LibWeb/WebIDL/AbstractOperations.h>
#include <LibWeb/WebIDL/CallbackType.h>
#include <LibWeb/WebIDL/Tracing.h>
#include <LibWeb/WebIDL/Types.h>

namespace Web::Bindings {

void EventSourceConstructor::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<EventTargetPrototype>(realm, "EventTarget"_fly_string));
    object.define_direct_property(vm.names.length, JS::Value(1), JS::Attribute::Configurable);
    object.define_direct_property(vm.names.name, JS::PrimitiveString::create(vm, "EventSource"_utf16), JS::Attribute::Configurable);
    object.define_direct_property(vm.names.prototype, &ensure_web_prototype<EventSourcePrototype>(realm, "EventSource"_fly_string), 0);

    // 1. FIXME: If const is not exposed in realm, then continue.
    // 2. Let value be the result of converting const’s IDL value to a JavaScript value.
    // 3. Let desc be the PropertyDescriptor{[[Writable]]: false, [[Enumerable]]: true, [[Configurable]]: false, [[Value]]: value}.
    // 4. Let id be const’s identifier.
    // 5. Perform ! DefinePropertyOrThrow(target, id, desc).
    object.define_direct_property("CONNECTING"_utf16_fly_string, JS::Value(static_cast<WebIDL::UnsignedShort>(0)), JS::Attribute::Enumerable);
    // 1. FIXME: If const is not exposed in realm, then continue.
    // 2. Let value be the result of converting const’s IDL value to a JavaScript value.
    // 3. Let desc be the PropertyDescriptor{[[Writable]]: false, [[Enumerable]]: true, [[Configurable]]: false, [[Value]]: value}.
    // 4. Let id be const’s identifier.
    // 5. Perform ! DefinePropertyOrThrow(target, id, desc).
    object.define_direct_property("OPEN"_utf16_fly_string, JS::Value(static_cast<WebIDL::UnsignedShort>(1)), JS::Attribute::Enumerable);
    // 1. FIXME: If const is not exposed in realm, then continue.
    // 2. Let value be the result of converting const’s IDL value to a JavaScript value.
    // 3. Let desc be the PropertyDescriptor{[[Writable]]: false, [[Enumerable]]: true, [[Configurable]]: false, [[Value]]: value}.
    // 4. Let id be const’s identifier.
    // 5. Perform ! DefinePropertyOrThrow(target, id, desc).
    object.define_direct_property("CLOSED"_utf16_fly_string, JS::Value(static_cast<WebIDL::UnsignedShort>(2)), JS::Attribute::Enumerable);
}

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

    // To internally create a new object implementing the interface EventSource:

    // 3.2. Let prototype be ? Get(newTarget, "prototype").
    auto prototype = TRY(new_target.get(vm.names.prototype));

    // 3.3. If Type(prototype) is not Object, then:
    if (!prototype.is_object()) {
        // 1. Let targetRealm be ? GetFunctionRealm(newTarget).
        auto* target_realm = TRY(JS::get_function_realm(vm, new_target));

        // 2. Set prototype to the interface prototype object for interface in targetRealm.
        VERIFY(target_realm);
        prototype = &Bindings::ensure_web_prototype<EventSourcePrototype>(*target_realm, "EventSource"_fly_string);
    }

    if (vm.argument_count() < 1)
        return vm.throw_completion<JS::TypeError>(JS::ErrorType::BadArgCountOne, "EventSource");

    auto arg0 = vm.argument(0);
    auto url = TRY(throw_dom_exception_if_needed(vm, [&] { return [&]() -> JS::ThrowCompletionOr<String> {
        return TRY(WebIDL::to_usv_string(vm, arg0));
    }(); }));

    auto arg1 = vm.argument(1);
    EventSourceInit event_source_init_dict = EventSourceInit {};
    if (!arg1.is_undefined())
        event_source_init_dict = TRY(throw_dom_exception_if_needed(vm, [&] { return convert_to_idl_value_for_event_source_init(vm, arg1); }));

    auto impl = TRY(throw_dom_exception_if_needed(vm, [&] { return HTML::EventSource::construct_impl(realm, url, event_source_init_dict); }));

    // 7. Set instance.[[Prototype]] to prototype.
    VERIFY(prototype.is_object());
    impl->set_prototype(&prototype.as_object());

    // FIXME: Steps 8...11. of the "internally create a new object implementing the interface EventSource" algorithm
    // (https://webidl.spec.whatwg.org/#js-platform-objects) are currently not handled, or are handled within HTML::EventSource::construct_impl().

    return *impl;
}

void EventSourcePrototype::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<EventTargetPrototype>(realm, "EventTarget"_fly_string) });

    auto url_id = "url"_utf16_fly_string;
    auto native_url_getter = JS::NativeFunction::create(realm, url_getter, 0, url_id, &realm, "get"sv);
    GC::Ptr<JS::NativeFunction> native_url_setter;

    // 4. Let configurable be false if attr is unforgeable and true otherwise.
    auto url_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(url_id, native_url_getter, native_url_setter, url_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.
    auto with_credentials_id = "withCredentials"_utf16_fly_string;
    auto native_with_credentials_getter = JS::NativeFunction::create(realm, with_credentials_getter, 0, with_credentials_id, &realm, "get"sv);
    GC::Ptr<JS::NativeFunction> native_with_credentials_setter;

    // 4. Let configurable be false if attr is unforgeable and true otherwise.
    auto with_credentials_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(with_credentials_id, native_with_credentials_getter, native_with_credentials_setter, with_credentials_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.
    auto ready_state_id = "readyState"_utf16_fly_string;
    auto native_ready_state_getter = JS::NativeFunction::create(realm, ready_state_getter, 0, ready_state_id, &realm, "get"sv);
    GC::Ptr<JS::NativeFunction> native_ready_state_setter;

    // 4. Let configurable be false if attr is unforgeable and true otherwise.
    auto ready_state_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(ready_state_id, native_ready_state_getter, native_ready_state_setter, ready_state_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.
    auto onopen_id = "onopen"_utf16_fly_string;
    auto native_onopen_getter = JS::NativeFunction::create(realm, onopen_getter, 0, onopen_id, &realm, "get"sv);
    auto native_onopen_setter = JS::NativeFunction::create(realm, onopen_setter, 1, onopen_id, &realm, "set"sv);

    // 4. Let configurable be false if attr is unforgeable and true otherwise.
    auto onopen_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(onopen_id, native_onopen_getter, native_onopen_setter, onopen_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.
    auto onmessage_id = "onmessage"_utf16_fly_string;
    auto native_onmessage_getter = JS::NativeFunction::create(realm, onmessage_getter, 0, onmessage_id, &realm, "get"sv);
    auto native_onmessage_setter = JS::NativeFunction::create(realm, onmessage_setter, 1, onmessage_id, &realm, "set"sv);

    // 4. Let configurable be false if attr is unforgeable and true otherwise.
    auto onmessage_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(onmessage_id, native_onmessage_getter, native_onmessage_setter, onmessage_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.
    auto onerror_id = "onerror"_utf16_fly_string;
    auto native_onerror_getter = JS::NativeFunction::create(realm, onerror_getter, 0, onerror_id, &realm, "get"sv);
    auto native_onerror_setter = JS::NativeFunction::create(realm, onerror_setter, 1, onerror_id, &realm, "set"sv);

    // 4. Let configurable be false if attr is unforgeable and true otherwise.
    auto onerror_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(onerror_id, native_onerror_getter, native_onerror_setter, onerror_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, "close"_utf16_fly_string, close, 0, default_attributes);


    // 1. FIXME: If const is not exposed in realm, then continue.
    // 2. Let value be the result of converting const’s IDL value to a JavaScript value.
    // 3. Let desc be the PropertyDescriptor{[[Writable]]: false, [[Enumerable]]: true, [[Configurable]]: false, [[Value]]: value}.
    // 4. Let id be const’s identifier.
    // 5. Perform ! DefinePropertyOrThrow(target, id, desc).
    object.define_direct_property("CONNECTING"_utf16_fly_string, JS::Value(static_cast<WebIDL::UnsignedShort>(0)), JS::Attribute::Enumerable);
    // 1. FIXME: If const is not exposed in realm, then continue.
    // 2. Let value be the result of converting const’s IDL value to a JavaScript value.
    // 3. Let desc be the PropertyDescriptor{[[Writable]]: false, [[Enumerable]]: true, [[Configurable]]: false, [[Value]]: value}.
    // 4. Let id be const’s identifier.
    // 5. Perform ! DefinePropertyOrThrow(target, id, desc).
    object.define_direct_property("OPEN"_utf16_fly_string, JS::Value(static_cast<WebIDL::UnsignedShort>(1)), JS::Attribute::Enumerable);
    // 1. FIXME: If const is not exposed in realm, then continue.
    // 2. Let value be the result of converting const’s IDL value to a JavaScript value.
    // 3. Let desc be the PropertyDescriptor{[[Writable]]: false, [[Enumerable]]: true, [[Configurable]]: false, [[Value]]: value}.
    // 4. Let id be const’s identifier.
    // 5. Perform ! DefinePropertyOrThrow(target, id, desc).
    object.define_direct_property("CLOSED"_utf16_fly_string, JS::Value(static_cast<WebIDL::UnsignedShort>(2)), JS::Attribute::Enumerable);
    object.define_direct_property(vm.well_known_symbol_to_string_tag(), JS::PrimitiveString::create(vm, "EventSource"_utf16), JS::Attribute::Configurable);
}

void EventSourcePrototype::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::EventSource*> impl_from(JS::VM& vm, JS::Value js_value)
{

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

[[maybe_unused]] static JS::ThrowCompletionOr<HTML::EventSource*> 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(EventSourcePrototype::url_getter)
{
    WebIDL::log_trace(vm, "EventSourcePrototype::url_getter");
    [[maybe_unused]] auto& realm = *vm.current_realm();

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


    auto R = TRY(throw_dom_exception_if_needed(vm, [&] { return idl_object->url(); }));

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

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

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


    auto R = TRY(throw_dom_exception_if_needed(vm, [&] { return idl_object->with_credentials(); }));

    return JS::Value(R);
}

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

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


    auto R = TRY(throw_dom_exception_if_needed(vm, [&] { return idl_object->ready_state(); }));

    return JS::Value(static_cast<WebIDL::UnsignedShort>(R));
}

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

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


    auto R = TRY(throw_dom_exception_if_needed(vm, [&] { return idl_object->onopen(); }));

    return [&]() -> JS::Value {
        // 1. If the IDL nullable type T? value is null, then the JavaScript value is null.
        if (!R)
            return JS::js_null();

        // 2. Otherwise, the JavaScript value is the result of converting the IDL nullable type value to the inner IDL type T.
        return JS::Value(R->callback);
    }();
}

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

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


    auto R = TRY(throw_dom_exception_if_needed(vm, [&] { return idl_object->onmessage(); }));

    return [&]() -> JS::Value {
        // 1. If the IDL nullable type T? value is null, then the JavaScript value is null.
        if (!R)
            return JS::js_null();

        // 2. Otherwise, the JavaScript value is the result of converting the IDL nullable type value to the inner IDL type T.
        return JS::Value(R->callback);
    }();
}

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

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


    auto R = TRY(throw_dom_exception_if_needed(vm, [&] { return idl_object->onerror(); }));

    return [&]() -> JS::Value {
        // 1. If the IDL nullable type T? value is null, then the JavaScript value is null.
        if (!R)
            return JS::js_null();

        // 2. Otherwise, the JavaScript value is the result of converting the IDL nullable type value to the inner IDL type T.
        return JS::Value(R->callback);
    }();
}

JS_DEFINE_NATIVE_FUNCTION(EventSourcePrototype::onopen_setter)
{
    WebIDL::log_trace(vm, "EventSourcePrototype::onopen_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::EventSource* 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<GC::Ptr<WebIDL::CallbackType>> {
        GC::Ptr<WebIDL::CallbackType> value;
        if (V.is_object()) {

        if (!V.is_nullish()) {

            value = TRY([&]() -> JS::ThrowCompletionOr<GC::Ptr<WebIDL::CallbackType>> {

        return vm.heap().allocate<WebIDL::CallbackType>(V.as_object(),  HTML::incumbent_realm(), WebIDL::OperationReturnsPromise::No);
    }());
        }
        }
        return value;
    }(); }));

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

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

        return JS::js_undefined();
    };

    // 8. Return undefined.
    return TRY(original_steps());
}

JS_DEFINE_NATIVE_FUNCTION(EventSourcePrototype::onmessage_setter)
{
    WebIDL::log_trace(vm, "EventSourcePrototype::onmessage_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::EventSource* 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<GC::Ptr<WebIDL::CallbackType>> {
        GC::Ptr<WebIDL::CallbackType> value;
        if (V.is_object()) {

        if (!V.is_nullish()) {

            value = TRY([&]() -> JS::ThrowCompletionOr<GC::Ptr<WebIDL::CallbackType>> {

        return vm.heap().allocate<WebIDL::CallbackType>(V.as_object(),  HTML::incumbent_realm(), WebIDL::OperationReturnsPromise::No);
    }());
        }
        }
        return value;
    }(); }));

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

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

        return JS::js_undefined();
    };

    // 8. Return undefined.
    return TRY(original_steps());
}

JS_DEFINE_NATIVE_FUNCTION(EventSourcePrototype::onerror_setter)
{
    WebIDL::log_trace(vm, "EventSourcePrototype::onerror_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::EventSource* 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<GC::Ptr<WebIDL::CallbackType>> {
        GC::Ptr<WebIDL::CallbackType> value;
        if (V.is_object()) {

        if (!V.is_nullish()) {

            value = TRY([&]() -> JS::ThrowCompletionOr<GC::Ptr<WebIDL::CallbackType>> {

        return vm.heap().allocate<WebIDL::CallbackType>(V.as_object(),  HTML::incumbent_realm(), WebIDL::OperationReturnsPromise::No);
    }());
        }
        }
        return value;
    }(); }));

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

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

        return JS::js_undefined();
    };

    // 8. Return undefined.
    return TRY(original_steps());
}

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

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

// https://webidl.spec.whatwg.org/#es-dictionary
JS::ThrowCompletionOr<EventSourceInit> convert_to_idl_value_for_event_source_init(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, "EventSourceInit");

    // 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 EventSourceInit {
        .with_credentials = 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("withCredentials"_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