module BCDD::Result::Contract
  NONE: BCDD::Result::Contract::Evaluator

  def self.evaluate: (
    BCDD::Result::Data,
    BCDD::Result::Contract::Evaluator
  ) -> BCDD::Result::Contract::TypeChecker

  ToEnsure: ^(Hash[Symbol, untyped] | Array[Symbol], Hash[Symbol, Hash[Symbol, bool]])
    -> BCDD::Result::Contract::Interface

  def self.new: (
    success: Hash[Symbol, untyped] | Array[Symbol],
    failure: Hash[Symbol, untyped] | Array[Symbol],
    config: Hash[Symbol, Hash[Symbol, bool]]
  ) -> BCDD::Result::Contract::Evaluator
end

module BCDD::Result::Contract
  class TypeChecker
    attr_reader result_type: Symbol
    attr_reader expectations: BCDD::Result::Contract::Evaluator

    def initialize: (
      Symbol,
      expectations: BCDD::Result::Contract::Evaluator
    ) -> void

    def allow?: (Array[Symbol]) -> bool
    def allow_success?: (Array[Symbol]) -> bool
    def allow_failure?: (Array[Symbol]) -> bool

    private

    def validate: (
      Array[Symbol],
      expected: BCDD::Result::Contract::Interface,
      allow_empty: bool
    ) -> bool
  end
end

class BCDD::Result::Contract::Error < BCDD::Result::Error
  class UnexpectedType < BCDD::Result::Contract::Error
    def self.build: (type: Symbol, allowed_types: Set[Symbol])
        -> BCDD::Result::Contract::Error::UnexpectedType
  end

  class UnexpectedValue < BCDD::Result::Contract::Error
    def self.build: (type: Symbol, value: untyped, ?cause: Exception)
      -> BCDD::Result::Contract::Error::UnexpectedValue
  end
end

module BCDD::Result::Contract
  module Interface
    def ==: (BCDD::Result::Contract::Interface) -> bool

    def allowed_types: -> Set[Symbol]

    def type?: (Symbol) -> bool

    def type!: (Symbol) -> Symbol

    def type_and_value!: (BCDD::Result::Data) -> void

    def !=: (untyped) -> bool
  end
end

module BCDD::Result::Contract
  module Disabled
    extend Interface

    EMPTY_SET: Set[Symbol]
  end
end

module BCDD::Result::Contract
  class ForTypes
    include Interface

    def initialize: (Array[Symbol]) -> void
  end
end

module BCDD::Result::Contract
  class ForTypesAndValues
    include Interface

    def initialize: (
      Hash[Symbol, untyped],
      Hash[Symbol, Hash[Symbol, bool]]
    ) -> void

    private

    def nil_as_valid_value_checking?: -> bool
  end
end

module BCDD::Result::Contract
  class Evaluator
    include Interface

    attr_reader allowed_types: Set[Symbol]
    attr_reader success: BCDD::Result::Contract::Interface
    attr_reader failure: BCDD::Result::Contract::Interface

    def initialize: (
      BCDD::Result::Contract::Interface,
      BCDD::Result::Contract::Interface
    ) -> void

    private

    def for: (BCDD::Result::Data) -> BCDD::Result::Contract::Interface
  end
end