module FFI
  class Struct[out P < AbstractMemory, unchecked out E]
    type layout = Library::ffi_lib_type | singleton(StructLayout::Field) | [layout, Integer]

    type ptr = Type::Mapped[
      StructByReference[Struct[AbstractMemory, untyped], AbstractMemory],
      AbstractMemory, Struct[AbstractMemory, untyped], untyped
    ]
    def self.ptr: (?untyped flags) -> ptr # https://github.com/ffi/ffi/issues/1073
    alias self.by_ref self.ptr
    def self.in: () -> ptr
    def self.out: () -> ptr
    def self.val: () -> StructByValue[singleton(Struct)]
    alias self.by_value self.val

    alias self.alloc_inout self.new
    alias self.alloc_in self.new
    alias self.alloc_out self.new
    alias self.new_inout self.new
    alias self.new_in self.new
    alias self.new_out self.new

    def self.auto_ptr: () -> Type::Mapped[
        ManagedStructConverter[ManagedStruct[AutoPointer, untyped], AutoPointer],
        Pointer, ManagedStruct[AutoPointer, untyped], untyped
      ]
    def self.layout: (*layout | Integer) -> StructLayout
              | (Hash[Symbol, layout]) -> StructLayout
    def self.size=: (Integer size) -> Integer

    def self?.alignment: () -> Integer
    def self?.members: () -> Array[Symbol]
    def self?.offset_of: (Symbol name) -> Integer
    def self?.offsets: () -> Array[[Symbol, Integer]]
    def self?.size: -> Integer

    def initialize: (?P pointer, *layout args) -> void
    def []: (Symbol field_name) -> E
    def []=: (Symbol field_name, E value) -> E
    alias align alignment
    def clear: () -> self
    def layout: () -> StructLayout
    def null?: () -> bool
    def order: (AbstractMemory::order_in order) -> Struct[P, E]
              | () -> AbstractMemory::order_out
    def pointer: () -> P
    alias to_ptr pointer
    def values: () -> Array[E]

    class InlineArray[out P < AbstractMemory, unchecked out E]
      include Enumerable[E]
      include AbstractMemory::_Size

      def initialize: (P memory, StructLayout::Field field) -> self
      def []: (Integer index) -> E
      def []=: (Integer index, E value) -> E
      def each: () { (E) -> void } -> self
      def to_a: () -> Array[E]
      def to_ptr: () -> P
    end

    class ManagedStructConverter[S < ManagedStruct[P, untyped], P < AutoPointer] < StructByReference[S, P]
      def initialize: ...
      def from_native: (Pointer ptr, untyped ctx) -> S
    end
  end

  class ManagedStruct[out P < AutoPointer, unchecked out E] < Struct[P, E]
    def self.release: (AbstractMemory ptr) -> void
    def initialize: (Pointer pointer) -> self
  end

  class Union[out P < AbstractMemory, unchecked out E] < Struct[P, E]
    def self.builder: () -> StructLayoutBuilder
  end
end