module FFI
  module Type
    class Builtin
    end

    class Mapped
    end
  end

  class AbstractMemory
    def get_array_of_string: (::Integer, ::Integer) -> Array[String]
    def read_bytes: (::Integer) -> ::String
  end

  class Pointer < AbstractMemory
    NULL: Pointer

    def null?: () -> bool
  end

  class MemoryPointer < Pointer
    def self.from_string: (::String) -> MemoryPointer
  end

  class Enum
  end

  class Union
    def self.layout: (*(Symbol | Integer)) -> void
  end

  type union = top # TODO: handle user-defined unions

  class Struct
    # TODO: layout args are actually "Symbol | Union, Integer, *(Symbol | Union, Integer)"
    def self.layout: (*(Symbol | Integer | union)) -> void
    def self.by_ref: () -> Type::Mapped
    def self.size: () -> Integer

    def null?: () -> bool
    def initialize: (?Pointer) -> void
    def []: (Symbol) -> untyped
    def []=: (Symbol, untyped) -> untyped
    def pointer: () -> Pointer
  end

  class Function < Pointer
  end

  module Library
    # these can be worked around by typedef'ing to a Symbol
    type enum = top # TODO: handle user-defined enum constants
    type ref = top # TODO: handle by_ref references
    type typedef = top # TODO: handle non-builtin types

    def ffi_lib: (Array[String]) -> void
    def typedef: (ref | Symbol, Symbol) -> (Type::Builtin | Type::Mapped | typedef)
    def attach_function: (Symbol, Array[Symbol | Struct | enum], Symbol | Enum, ?blocking: bool) -> Function
    def callback: (Symbol, Array[Symbol | Enum | Struct], Symbol | Enum) -> Function
    def enum: (*untyped) -> Enum
  end
end