# frozen_string_literal: true

require "rbs"

module RbsActivesupport
  class MethodSearcher
    attr_reader :rbs_builder #: RBS::DefinitionBuilder

    # @rbs rbs_builder: RBS::DefinitionBuilder
    def initialize(rbs_builder) #: void
      @rbs_builder = rbs_builder
    end

    # @rbs delegate: Delegate
    def method_types_for(delegate) #: Array[String]
      delegate_to = lookup_method_types(delegate.namespace.to_type_name, delegate.to)
      return ["() -> untyped"] if delegate_to.any? { |t| t.type.return_type.is_a?(RBS::Types::Bases::Any) }

      return_types = delegate_to
                     .filter_map { |t| t.type.return_type.name } # steep:ignore NoMethod
                     .uniq
                     .flat_map { |t| lookup_method_types(t, delegate.method) }
                     .map(&:to_s)
      return_types << "() -> untyped" if return_types.empty?
      return_types
    end

    private

    # @rbs type_name: RBS::TypeName
    # @rbs method: Symbol
    def lookup_method_types(type_name, method) #: Array[RBS::MethodType]
      instance = rbs_builder.build_instance(type_name)
      method_def = instance.methods[method]
      return [] unless method_def

      method_def.defs.map(&:type)
    rescue StandardError
      []
    end
  end
end