#include <AK/Utf16String.h>
#include <LibGC/Heap.h>
#include <LibJS/Runtime/AbstractOperations.h>
#include <LibJS/Runtime/Array.h>
#include <LibJS/Runtime/Error.h>
#include <LibJS/Runtime/FunctionObject.h>
#include <LibJS/Runtime/Iterator.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/Intrinsics.h>
#include <LibWeb/Bindings/MutationObserver.h>
#include <LibWeb/DOM/MutationObserver.h>
#include <LibWeb/DOM/MutationRecord.h>
#include <LibWeb/DOM/Node.h>
#include <LibWeb/HTML/Scripting/Environments.h>
#include <LibWeb/WebIDL/AbstractOperations.h>
#include <LibWeb/WebIDL/CallbackType.h>
#include <LibWeb/WebIDL/Tracing.h>

namespace Web::Bindings {

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

    
    object.define_direct_property(vm.names.length, JS::Value(1), JS::Attribute::Configurable);
    object.define_direct_property(vm.names.name, JS::PrimitiveString::create(vm, "MutationObserver"_utf16), JS::Attribute::Configurable);
    object.define_direct_property(vm.names.prototype, &ensure_web_prototype<MutationObserverPrototype>(realm, "MutationObserver"_fly_string), 0);
}

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

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

    // 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<MutationObserverPrototype>(*target_realm, "MutationObserver"_fly_string);
    }

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

    auto arg0 = vm.argument(0);
    auto callback = TRY(throw_dom_exception_if_needed(vm, [&] { return [&]() -> JS::ThrowCompletionOr<GC::Ref<WebIDL::CallbackType>> {

        if (!arg0.is_function())
            return vm.throw_completion<JS::TypeError>(JS::ErrorType::NotAFunction, arg0);

        return vm.heap().allocate<WebIDL::CallbackType>(arg0.as_object(),  HTML::incumbent_realm(), WebIDL::OperationReturnsPromise::No);
    }(); }));

    auto impl = TRY(throw_dom_exception_if_needed(vm, [&] { return DOM::MutationObserver::construct_impl(realm, callback); }));

    // 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 MutationObserver" algorithm
    // (https://webidl.spec.whatwg.org/#js-platform-objects) are currently not handled, or are handled within DOM::MutationObserver::construct_impl().

    return *impl;
}

void MutationObserverPrototype::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(realm.intrinsics().object_prototype());
    object.define_native_function(realm, "observe"_utf16_fly_string, observe, 1, default_attributes);

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

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

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

void MutationObserverPrototype::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<DOM::MutationObserver*> impl_from(JS::VM& vm, JS::Value js_value)
{

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

[[maybe_unused]] static JS::ThrowCompletionOr<DOM::MutationObserver*> 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(MutationObserverPrototype::observe)
{
    WebIDL::log_trace(vm, "MutationObserverPrototype::observe");
    [[maybe_unused]] auto& realm = *vm.current_realm();
    [[maybe_unused]] DOM::MutationObserver* idl_object = TRY(impl_from(vm));

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

    auto arg0 = vm.argument(0);
    auto target = TRY(throw_dom_exception_if_needed(vm, [&] { return [&]() -> JS::ThrowCompletionOr<GC::Ref<DOM::Node>> {
        if (auto impl = arg0.as_if<DOM::Node>())
            return *impl;
        return vm.throw_completion<JS::TypeError>(JS::ErrorType::NotAnObjectOfType, "Node");
    }(); }));

    auto arg1 = vm.argument(1);
    MutationObserverInit options = MutationObserverInit {};
    if (!arg1.is_undefined())
        options = TRY(throw_dom_exception_if_needed(vm, [&] { return convert_to_idl_value_for_mutation_observer_init(vm, arg1); }));

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

JS_DEFINE_NATIVE_FUNCTION(MutationObserverPrototype::disconnect)
{
    WebIDL::log_trace(vm, "MutationObserverPrototype::disconnect");
    [[maybe_unused]] auto& realm = *vm.current_realm();
    [[maybe_unused]] DOM::MutationObserver* idl_object = TRY(impl_from(vm));

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

JS_DEFINE_NATIVE_FUNCTION(MutationObserverPrototype::take_records)
{
    WebIDL::log_trace(vm, "MutationObserverPrototype::take_records");
    [[maybe_unused]] auto& realm = *vm.current_realm();
    [[maybe_unused]] DOM::MutationObserver* idl_object = TRY(impl_from(vm));

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

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

    // 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 MutationObserverInit {
        .attribute_filter = TRY([&]() -> JS::ThrowCompletionOr<Optional<Vector<Utf16FlyString>>> {
            // 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("attributeFilter"_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::ThrowCompletionOr<Vector<Utf16FlyString>> {
        if (!js_member_value.is_object())
            return vm.throw_completion<JS::TypeError>(JS::ErrorType::NotAnObject, js_member_value);

        auto method = TRY(js_member_value.get_method(vm, vm.well_known_symbol_iterator()));
        if (!method)
            return vm.throw_completion<JS::TypeError>(JS::ErrorType::NotIterable, js_member_value);

        return TRY([&]() -> JS::ThrowCompletionOr<Vector<Utf16FlyString>> {
        // To create an IDL value of type sequence<T> given an iterable iterable and an iterator getter method, perform the following steps:
        // 1. Let iteratorRecord be ? GetIteratorFromMethod(iterable, method).
        auto iterator = TRY(JS::get_iterator_from_method(vm, js_member_value, *method));

        Vector<Utf16FlyString> sequence;

        // 2. Initialize i to be 0.
        // 3. Repeat
        for (;;) {
            // 1. Let next be ? IteratorStepValue(iteratorRecord).
            auto next = TRY(JS::iterator_step_value(vm, iterator));

            // 2. If next is done, then return an IDL sequence value of type sequence<T> of length i, where the value of the element at index j is Sj.
            if (!next.has_value())
                break;

            // 3. Initialize Si to the result of converting next to an IDL value of type T.
            auto next_value = next.release_value();
            auto sequence_item = TRY(throw_dom_exception_if_needed(vm, [&] { return [&]() -> JS::ThrowCompletionOr<Utf16String> {
        return TRY(WebIDL::to_utf16_string(vm, next_value));
    }(); }));

            // 4. Set i to i + 1.
            sequence.append(sequence_item);
        }

        return sequence;
    }());
    }(); }));

                // 2. Set idlDict[key] to idlMemberValue.
                return idl_member_value;
            }
            // 7. Otherwise, jsMemberValue is undefined and the member is optional.
            return OptionalNone {};
        }()),
        .attribute_old_value = TRY([&]() -> JS::ThrowCompletionOr<Optional<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("attributeOldValue"_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;
            }
            // 7. Otherwise, jsMemberValue is undefined and the member is optional.
            return OptionalNone {};
        }()),
        .attributes = TRY([&]() -> JS::ThrowCompletionOr<Optional<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("attributes"_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;
            }
            // 7. Otherwise, jsMemberValue is undefined and the member is optional.
            return OptionalNone {};
        }()),
        .character_data = TRY([&]() -> JS::ThrowCompletionOr<Optional<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("characterData"_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;
            }
            // 7. Otherwise, jsMemberValue is undefined and the member is optional.
            return OptionalNone {};
        }()),
        .character_data_old_value = TRY([&]() -> JS::ThrowCompletionOr<Optional<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("characterDataOldValue"_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;
            }
            // 7. Otherwise, jsMemberValue is undefined and the member is optional.
            return OptionalNone {};
        }()),
        .child_list = 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("childList"_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;
        }()),
        .subtree = 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("subtree"_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