class T::Private::Methods::Signature

def self.new_untyped(method:, mode: T::Private::Methods::Modes.untyped, parameters: method.parameters)
  # Using `NotTyped` ensures we'll get an error if we ever try validation on these.
  not_typed = T::Private::Types::NotTyped::INSTANCE
  raw_return_type = not_typed
  # Map missing parameter names to "argN" positionally
  parameters = parameters.each_with_index.map do |(param_kind, param_name), index|
    [param_kind, param_name || "arg#{index}"]
  end
  raw_arg_types = {}
  parameters.each do |_, param_name|
    raw_arg_types[param_name] = not_typed
  end
  self.new(
    method: method,
    method_name: method.name,
    raw_arg_types: raw_arg_types,
    raw_return_type: raw_return_type,
    bind: nil,
    mode: mode,
    check_level: :never,
    parameters: parameters,
    on_failure: nil,
  )
end

def arg_count
  @arg_types.length
end

def as_alias(alias_name)
  new_sig = clone
  new_sig.method_name = alias_name
  new_sig
end

def dsl_method
  "#{@mode}_method"
end

def each_args_value_type(args)
  # Manually split out args and kwargs based on ruby's behavior. Do not try to implement this by
  # getting ruby to determine the kwargs for you (e.g., by defining this method to take *args and
  # **kwargs). That won't work, because ruby's behavior for determining kwargs is dependent on the
  # the other parameters in the method definition, and our method definition here doesn't (and
  # can't) match the definition of the method we're validating. In addition, Ruby has a bug that
  # causes forwarding **kwargs to do the wrong thing: see https://bugs.ruby-lang.org/issues/10708
  # and https://bugs.ruby-lang.org/issues/11860.
  args_length = args.length
  if (args_length > @req_arg_count) && (!@kwarg_types.empty? || @has_keyrest) && args[-1].is_a?(Hash)
    kwargs = args[-1]
    args_length -= 1
  else
    kwargs = EMPTY_HASH
  end
  if !@has_rest && ((args_length < @req_arg_count) || (args_length > @arg_types.length))
    expected_str = @req_arg_count.to_s
    if @arg_types.length != @req_arg_count
      expected_str += "..#{@arg_types.length}"
    end
    raise ArgumentError.new("wrong number of arguments (given #{args_length}, expected #{expected_str})")
  end
  begin
    it = 0
    # Process given pre-rest args. When there are no rest args,
    # this is just the given number of args.
    while it < args_length && it < @arg_types.length
      yield @arg_types[it][0], args[it], @arg_types[it][1]
      it += 1
    end
    if @has_rest
      rest_count = args_length - @arg_types.length
      rest_count = 0 if rest_count.negative?
      rest_count.times do
        yield @rest_name, args[it], @rest_type
        it += 1
      end
    end
  end
  kwargs.each do |name, val|
    type = @kwarg_types[name]
    if !type && @has_keyrest
      type = @keyrest_type
    end
    yield name, val, type if type
  end
end

def initialize(method:, method_name:, raw_arg_types:, raw_return_type:, bind:, mode:, check_level:, on_failure:, parameters: method.parameters, override_allow_incompatible: false, defined_raw: false)
  @method = method
  @method_name = method_name
  @block_type = nil
  @block_name = nil
  @rest_type = nil
  @rest_name = nil
  @keyrest_type = nil
  @keyrest_name = nil
  @return_type = T::Utils.coerce(raw_return_type)
  @bind = bind ? T::Utils.coerce(bind) : bind
  @mode = mode
  @check_level = check_level
  @has_rest = false
  @has_keyrest = false
  @parameters = parameters
  @on_failure = on_failure
  @override_allow_incompatible = override_allow_incompatible
  @defined_raw = defined_raw
  # Use T.untyped in lieu of T.nilable to try to avoid unnecessary allocations.
  arg_types = T.let(nil, T.untyped)
  kwarg_types = T.let(nil, T.untyped)
  req_arg_count = 0
  req_kwarg_names = T.let(nil, T.untyped)
  # If sig params are declared but there is a single parameter with a missing name
  # **and** the method ends with a "=", assume it is a writer method generated
  # by attr_writer or attr_accessor
  writer_method = !(raw_arg_types.size == 1 && raw_arg_types.key?(nil)) && parameters == UNNAMED_REQUIRED_PARAMETERS && method_name[-1] == "="
  # For writer methods, map the single parameter to the method name without the "=" at the end
  parameters = [[:req, method_name[0...-1].to_sym]] if writer_method
  is_name_missing = parameters.any? {|_, name| !raw_arg_types.key?(name)}
  if is_name_missing
    param_names = parameters.map {|_, name| name}
    missing_names = param_names - raw_arg_types.keys
    raise "The declaration for `#{method.name}` is missing parameter(s): #{missing_names.join(', ')}"
  elsif parameters.length == raw_arg_types.size
  else
    param_names = parameters.map {|_, name| name}
    has_extra_names = parameters.count {|_, name| raw_arg_types.key?(name)} < raw_arg_types.size
    if has_extra_names
      extra_names = raw_arg_types.keys - param_names
      raise "The declaration for `#{method.name}` has extra parameter(s): #{extra_names.join(', ')}"
    end
  end
  if parameters.size != raw_arg_types.size
    raise "The declaration for `#{method.name}` has arguments with duplicate names"
  end
  i = 0
  raw_arg_types.each do |type_name, raw_type|
    param_kind, param_name = parameters[i]
    if type_name != param_name
      hint = ""
      # Ruby reorders params so that required keyword arguments
      # always precede optional keyword arguments. We can't tell
      # whether the culprit is the Ruby reordering or user error, so
      # we error but include a note
      if param_kind == :keyreq && parameters.any? {|k, _| k == :key}
        hint = "\n\nNote: Any required keyword arguments must precede any optional keyword " \
               "arguments. If your method declaration matches your `def`, try reordering any " \
               "optional keyword parameters to the end of the method list."
      end
      raise "Parameter `#{type_name}` is declared out of order (declared as arg number " \
            "#{i + 1}, defined in the method as arg number " \
            "#{parameters.index {|_, name| name == type_name} + 1}).#{hint}\nMethod: #{method_desc}"
    end
    type = T::Utils.coerce(raw_type)
    case param_kind
    when :req
      if (arg_types ? arg_types.length : 0) > req_arg_count
        # Note that this is actually is supported by Ruby, but it would add complexity to
        # support it here, and I'm happy to discourage its use anyway.
        #
        # If you are seeing this error and surprised by it, it's possible that you have
        # overridden the method described in the error message. For example, Rails defines
        # def self.update!(id = :all, attributes)
        # on AR models. If you have also defined `self.update!` on an AR model you might
        # see this error. The simplest resolution is to rename your method.
        raise "Required params after optional params are not supported in method declarations. Method: #{method_desc}"
      end
      (arg_types ||= []) << [param_name, type]
      req_arg_count += 1
    when :opt
      (arg_types ||= []) << [param_name, type]
    when :key, :keyreq
      (kwarg_types ||= {})[param_name] = type
      if param_kind == :keyreq
        (req_kwarg_names ||= []) << param_name
      end
    when :block
      @block_name = param_name
      @block_type = type
    when :rest
      @has_rest = true
      @rest_name = param_name
      @rest_type = type
    when :keyrest
      @has_keyrest = true
      @keyrest_name = param_name
      @keyrest_type = type
    else
      raise "Unexpected param_kind: `#{param_kind}`. Method: #{method_desc}"
    end
    i += 1
  end
  @arg_types = arg_types || EMPTY_LIST
  @kwarg_types = kwarg_types || EMPTY_HASH
  @req_arg_count = req_arg_count
  @req_kwarg_names = req_kwarg_names || EMPTY_LIST
end

def kwarg_names
  @kwarg_types.keys
end

def method_desc
  loc = if @method.source_location
    @method.source_location.join(':')
  else
    "<unknown location>"
  end
  "#{@method} at #{loc}"
end

def owner
  @method.owner
end