module Steep
  module Subtyping
    module Result
      type t = Skip | Expand | All | Any | Success | Failure

      class Base
        attr_reader relation: Relation[untyped]

        def initialize: (Relation[untyped] relation) -> void

        def failure?: () -> bool

        def success?: () -> bool

        def then: () { (self) -> void } -> self

        def else: () { (self) -> void } -> self

        def failure_path: (?Array[t] path) -> Array[t]?
      end

      class Skip < Base
        def success?: () -> false

        def failure?: () -> false

        def failure_path: (?untyped path) -> untyped
      end

      class Expand < Base
        attr_reader child: t

        def initialize: (Relation[untyped] relation) { (Relation[untyped]) -> t } -> void

        def success?: () -> bool

        def failure_path: (?Array[t] path) -> Array[t]?
      end

      class All < Base
        attr_reader branches: Array[t]

        def initialize: (Relation[untyped] relation) -> void

        @failure: bool

        # Returns `false` if no future `#add` changes the result.
        def add: [T < Object] (*Relation[T] relations) { (Relation[T]) -> t? } -> bool

        # Returns `false` if no future `#add` changes the result.
        def add_result: (t?) -> bool

        def success?: () -> bool

        def failure?: () -> bool

        def failure_path: (?Array[t] path) -> Array[t]?
      end

      class Any < Base
        attr_reader branches: Array[t]

        def initialize: (Relation[untyped] relation) -> void

        @success: bool

        # Returns `false` if no future `#add` changes the result.
        def add: [T < Object] (*Relation[T] relations) { (Relation[T]) -> t } -> bool

        def success?: () -> bool

        def failure_path: (?Array[t] path) -> Array[t]?
      end

      class Success < Base
        def success?: () -> true

        def failure_path: (?Array[t] path) -> Array[t]?
      end

      class Failure < Base
        type error = MethodMissingError | BlockMismatchError | ParameterMismatchError
                   | UnknownPairError | PolyMethodSubtyping | UnsatisfiedConstraints
                   | SelfBindingMismatch

        class MethodMissingError
          attr_reader name: untyped

          def initialize: (name: untyped) -> void

          def message: () -> ::String
        end

        class BlockMismatchError
          attr_reader name: untyped

          def initialize: (name: untyped) -> void

          def message: () -> ::String
        end

        class ParameterMismatchError
          attr_reader name: untyped

          def initialize: (name: untyped) -> void

          def message: () -> ::String
        end

        class UnknownPairError
          attr_reader relation: untyped

          def initialize: (relation: untyped) -> void

          def message: () -> ::String
        end

        class PolyMethodSubtyping
          attr_reader name: untyped

          def initialize: (name: untyped) -> void

          def message: () -> ::String
        end

        class UnsatisfiedConstraints
          attr_reader error: untyped

          def initialize: (untyped error) -> void

          def var: () -> untyped

          def sub_type: () -> untyped

          def super_type: () -> untyped

          def result: () -> untyped

          def message: () -> ::String
        end

        class SelfBindingMismatch
          def initialize: () -> void

          def message: () -> String
        end

        attr_reader error: error

        def initialize: (Relation[untyped] relation, error error) -> void

        def success?: () -> false

        def failure_path: (?Array[t] path) -> Array[t]?
      end

      module Helper
        def Skip: (Relation[untyped] relation) -> Skip

        def Expand: [T < Object] (Relation[T] relation) { (Relation[T]) -> t } -> Expand

        def All: (Relation[untyped] relation) { (All) -> void } -> All

        def Any: (Relation[untyped] relation) { (Any) -> void } -> Any

        def Success: (Relation[untyped] relation) -> Success

        alias success Success

        def Failure: (Relation[untyped] relation, Failure::error) -> Failure
                   | (Relation[untyped]) { () -> Failure::error } -> Failure
      end
    end
  end
end