# frozen_string_literal: true
# typed: true

class T::Private::Methods::Signature
  attr_reader :method, :method_name, :arg_types, :kwarg_types, :block_type, :block_name,
              :rest_type, :rest_name, :keyrest_type, :keyrest_name, :bind,
              :return_type, :mode, :req_arg_count, :req_kwarg_names, :has_rest, :has_keyrest,
              :check_level, :parameters, :on_failure, :override_allow_incompatible

  def self.new_untyped(method:, mode: T::Private::Methods::Modes.untyped, parameters: method.parameters)
    # Using `Untyped` ensures we'll get an error if we ever try validation on these.
    not_typed = T::Private::Types::NotTyped.new
    raw_return_type = not_typed
    raw_arg_types = parameters.map do |_param_kind, param_name|
      [param_name, not_typed]
    end.to_h

    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 initialize(method:, method_name:, raw_arg_types:, raw_return_type:, bind:, mode:, check_level:, parameters: method.parameters, on_failure:, override_allow_incompatible: false)
    @method = method
    @method_name = method_name
    @arg_types = []
    @kwarg_types = {}
    @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
    @req_arg_count = 0
    @req_kwarg_names = []
    @has_rest = false
    @has_keyrest = false
    @parameters = parameters
    @on_failure = on_failure
    @override_allow_incompatible = override_allow_incompatible

    declared_param_names = raw_arg_types.keys
    # 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 = declared_param_names != [nil] && parameters == [[:req]] && 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
    param_names = parameters.map {|_, name| name}
    missing_names = param_names - declared_param_names
    extra_names = declared_param_names - param_names
    if !missing_names.empty?
      raise "The declaration for `#{method.name}` is missing parameter(s): #{missing_names.join(', ')}"
    end
    if !extra_names.empty?
      raise "The declaration for `#{method.name}` has extra parameter(s): #{extra_names.join(', ')}"
    end
    
    if parameters.size != raw_arg_types.size
      raise "The declaration for `#{method.name}` has arguments with duplicate names"
    end

    parameters.zip(raw_arg_types) do |(param_kind, param_name), (type_name, raw_type)|
      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 " \
              "#{declared_param_names.index(type_name) + 1}, defined in the method as arg number " \
              "#{param_names.index(type_name) + 1}).#{hint}\nMethod: #{method_desc}"
      end

      type = T::Utils.coerce(raw_type)

      case param_kind
      when :req
        if @arg_types.length > @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.
          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
    end
  end

  attr_writer :method_name
  protected :method_name=

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

  def arg_count
    @arg_types.length
  end

  def kwarg_names
    @kwarg_types.keys
  end

  def owner
    @method.owner
  end

  def dsl_method
    "#{@mode}_method"
  end

  # @return [Hash] a mapping like {arg_name: [val, type], ...}, for only those args actually present.
  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

    arg_types = @arg_types

    if @has_rest
      arg_types += [[@rest_name, @rest_type]] * (args_length - @arg_types.length)

    elsif (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
      while it < args_length
        yield arg_types[it][0], args[it], arg_types[it][1]
        it += 1
      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 method_desc
    if @method.source_location
      loc = @method.source_location.join(':')
    else
      loc = "<unknown location>"
    end
    "#{@method} at #{loc}"
  end

  EMPTY_HASH = {}.freeze
end