/*
 * Copyright (c) 2020-2025, Andreas Kling <andreas@ladybird.org>
 * Copyright (c) 2020-2022, Linus Groh <linusg@serenityos.org>
 * Copyright (c) 2023, Andreas Kling <andreas@ladybird.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include <LibJS/Export.h>
#include <LibJS/Runtime/ClassFieldDefinition.h>
#include <LibJS/Runtime/ExecutionContext.h>
#include <LibJS/Runtime/FunctionObject.h>
#include <LibJS/Runtime/SharedFunctionInstanceData.h>
#include <LibJS/Runtime/VM.h>

namespace JS {

template<typename T>
void async_block_start(VM&, T const& async_body, PromiseCapability const&, ExecutionContext&);

template<typename T>
void async_function_start(VM&, PromiseCapability const&, T const& async_function_body);

// 10.2 ECMAScript Function Objects, https://tc39.es/ecma262/#sec-ecmascript-function-objects
class JS_API ECMAScriptFunctionObject final : public FunctionObject {
    JS_OBJECT(ECMAScriptFunctionObject, FunctionObject);
    GC_DECLARE_ALLOCATOR(ECMAScriptFunctionObject);

public:
    [[nodiscard]] static GC::Ref<ECMAScriptFunctionObject> create_from_function_data(
        GC::Ref<Realm>,
        GC::Ref<SharedFunctionInstanceData>,
        GC::Ptr<Environment>,
        GC::Ptr<PrivateEnvironment>,
        Object& prototype);

    [[nodiscard]] static GC::Ref<ECMAScriptFunctionObject> create_from_function_data(
        GC::Ref<Realm>,
        GC::Ref<SharedFunctionInstanceData>,
        GC::Ptr<Environment>,
        GC::Ptr<PrivateEnvironment>);

    virtual void initialize(Realm&) override;
    virtual ~ECMAScriptFunctionObject() override = default;

    virtual void get_stack_frame_info(size_t& registers_and_locals_count, ReadonlySpan<Value>& constants, size_t& argument_count) override;
    virtual ThrowCompletionOr<Value> internal_call(ExecutionContext&, Value this_argument) override;
    virtual ThrowCompletionOr<GC::Ref<Object>> internal_construct(ExecutionContext&, FunctionObject& new_target) override;

    void make_method(Object& home_object);

    [[nodiscard]] bool is_module_wrapper() const { return shared_data().m_is_module_wrapper; }
    void set_is_module_wrapper(bool b) { const_cast<SharedFunctionInstanceData&>(shared_data()).m_is_module_wrapper = b; }

    [[nodiscard]] u32 formal_parameter_count() const { return shared_data().m_formal_parameter_count; }
    [[nodiscard]] ReadonlySpan<Utf16FlyString> parameter_names_for_mapped_arguments() const { return shared_data().m_parameter_names_for_mapped_arguments; }

    virtual Utf16String name_for_call_stack() const override;

    Utf16FlyString const& name() const
    {
        if (m_name.has_value())
            return *m_name;
        return shared_data().m_name;
    }
    void set_name(Utf16FlyString const& name);
    void set_inferred_name(Variant<PropertyKey, PrivateName> const& name, Optional<StringView> const& prefix = {});

    void set_is_class_constructor() { const_cast<SharedFunctionInstanceData&>(shared_data()).set_is_class_constructor(); }

    auto& bytecode_executable() const { return shared_data().m_executable; }
    [[nodiscard]] bool can_inline_call() const { return shared_data().can_inline_call(); }
    [[nodiscard]] Bytecode::Executable& inline_call_executable() const
    {
        VERIFY(can_inline_call());
        return *shared_data().m_executable;
    }

    Environment* environment() { return m_environment; }
    virtual Realm* realm() const override { return &shape().realm(); }

    [[nodiscard]] ConstructorKind constructor_kind() const { return shared_data().m_constructor_kind; }
    void set_constructor_kind(ConstructorKind constructor_kind) { const_cast<SharedFunctionInstanceData&>(shared_data()).m_constructor_kind = constructor_kind; }

    [[nodiscard]] ThisMode this_mode() const { return shared_data().m_this_mode; }
    [[nodiscard]] bool is_arrow_function() const { return shared_data().m_is_arrow_function; }
    [[nodiscard]] bool is_class_constructor() const { return shared_data().m_is_class_constructor; }
    [[nodiscard]] bool uses_this() const { return shared_data().m_uses_this; }
    [[nodiscard]] bool this_value_needs_environment_resolution() const
    {
        return shared_data().m_this_value_needs_environment_resolution;
    }
    [[nodiscard]] i32 function_length() const { return shared_data().m_function_length; }

    Object* home_object() const { return m_home_object; }
    void set_home_object(Object* home_object) { m_home_object = home_object; }

    [[nodiscard]] Utf16String source_text() const { return shared_data().source_text(); }
    void set_source_text(Utf16View source_text) { const_cast<SharedFunctionInstanceData&>(shared_data()).set_source_text(source_text); }
    void set_source_text_range(SourceCode const& source_code, size_t source_text_offset, size_t source_text_length)
    {
        const_cast<SharedFunctionInstanceData&>(shared_data()).set_source_text_range(source_code, source_text_offset, source_text_length);
    }

    Vector<ClassFieldDefinition> const& fields() const { return ensure_class_data().fields; }
    void add_field(ClassFieldDefinition field) { ensure_class_data().fields.append(move(field)); }

    Vector<PrivateElement> const& private_methods() const { return ensure_class_data().private_methods; }
    void add_private_method(PrivateElement method) { ensure_class_data().private_methods.append(move(method)); }

    [[nodiscard]] bool has_class_data() const { return m_class_data; }

    // This is for IsSimpleParameterList (static semantics)
    bool has_simple_parameter_list() const { return shared_data().m_has_simple_parameter_list; }

    // Equivalent to absence of [[Construct]]
    virtual bool has_constructor() const override { return kind() == FunctionKind::Normal && !shared_data().m_is_arrow_function && !m_is_method; }

    virtual Vector<LocalVariable> const& local_variables_names() const override { return shared_data().m_local_variables_names; }

    FunctionKind kind() const { return shared_data().m_kind; }

    // This is used by LibWeb to disassociate event handler attribute callback functions from the nearest script on the call stack.
    // https://html.spec.whatwg.org/multipage/webappapis.html#getting-the-current-value-of-the-event-handler Step 3.11
    void set_script_or_module(ScriptOrModule script_or_module) { m_script_or_module = move(script_or_module); }

    Variant<PropertyKey, PrivateName, Empty> const& class_field_initializer_name() const { return shared_data().m_class_field_initializer_name; }

    bool allocates_function_environment() const { return shared_data().m_function_environment_needed; }

    friend class Bytecode::Generator;
    friend class VM;

private:
    ECMAScriptFunctionObject(
        GC::Ref<SharedFunctionInstanceData>,
        Environment* parent_environment,
        PrivateEnvironment* private_environment,
        Object& prototype);

    virtual ThrowCompletionOr<Optional<PropertyDescriptor>> internal_get_own_property(PropertyKey const&) const override;
    virtual ThrowCompletionOr<GC::RootVector<Value>> internal_own_property_keys() const override;

    virtual bool is_strict_mode() const override { return shared_data().m_strict; }

    ThrowCompletionOr<Value> ordinary_call_evaluate_body(VM&, ExecutionContext&);

    [[nodiscard]] bool function_environment_needed() const { return shared_data().m_function_environment_needed; }
    SharedFunctionInstanceData& shared_data() { return m_shared_data; }
    SharedFunctionInstanceData const& shared_data() const { return m_shared_data; }

    virtual void visit_edges(Visitor&) override;

    void prepare_for_ordinary_call(VM&, ExecutionContext& callee_context, Object* new_target);
    void ordinary_call_bind_this(VM&, ExecutionContext&, Value this_argument);
    bool supports_legacy_caller_or_arguments() const;
    Value legacy_caller() const;
    Value legacy_arguments() const;

    GC::Ref<SharedFunctionInstanceData> m_shared_data;

    Optional<Utf16FlyString> m_name;
    GC::Ptr<PrimitiveString> m_name_string;

    // Internal Slots of ECMAScript Function Objects, https://tc39.es/ecma262/#table-internal-slots-of-ecmascript-function-objects
    GC::Ptr<Environment> m_environment;                // [[Environment]]
    GC::Ptr<PrivateEnvironment> m_private_environment; // [[PrivateEnvironment]]
    ScriptOrModule m_script_or_module;                 // [[ScriptOrModule]]
    GC::Ptr<Object> m_home_object;                     // [[HomeObject]]
    struct ClassData {
        Vector<ClassFieldDefinition> fields;    // [[Fields]]
        Vector<PrivateElement> private_methods; // [[PrivateMethods]]
    };
    ClassData& ensure_class_data() const;
    mutable OwnPtr<ClassData> m_class_data;

    mutable bool m_may_need_lazy_prototype_instantiation { false };
    bool m_is_method { false };
};

template<>
inline bool Object::fast_is<ECMAScriptFunctionObject>() const { return is_ecmascript_function_object(); }

}
