# typed: strict
# frozen_string_literal: true

# On Ruby 3.2 or newer, Class defines an attached_object method that returns the
# attached class of a singleton class without iterating ObjectSpace. On older
# versions of Ruby, we fall back to iterating ObjectSpace.
if Class.method_defined?(:attached_object)
  require "tapioca/runtime/attached_class_of_32"
else
  require "tapioca/runtime/attached_class_of_legacy"
end

module Tapioca
  module Runtime
    module Reflection
      include AttachedClassOf

      extend T::Sig
      extend self

      CLASS_METHOD = T.let(Kernel.instance_method(:class), UnboundMethod)
      CONSTANTS_METHOD = T.let(Module.instance_method(:constants), UnboundMethod)
      NAME_METHOD = T.let(Module.instance_method(:name), UnboundMethod)
      SINGLETON_CLASS_METHOD = T.let(Object.instance_method(:singleton_class), UnboundMethod)
      ANCESTORS_METHOD = T.let(Module.instance_method(:ancestors), UnboundMethod)
      SUPERCLASS_METHOD = T.let(Class.instance_method(:superclass), UnboundMethod)
      OBJECT_ID_METHOD = T.let(BasicObject.instance_method(:__id__), UnboundMethod)
      EQUAL_METHOD = T.let(BasicObject.instance_method(:equal?), UnboundMethod)
      PUBLIC_INSTANCE_METHODS_METHOD = T.let(Module.instance_method(:public_instance_methods), UnboundMethod)
      PROTECTED_INSTANCE_METHODS_METHOD = T.let(Module.instance_method(:protected_instance_methods), UnboundMethod)
      PRIVATE_INSTANCE_METHODS_METHOD = T.let(Module.instance_method(:private_instance_methods), UnboundMethod)
      METHOD_METHOD = T.let(Kernel.instance_method(:method), UnboundMethod)
      UNDEFINED_CONSTANT = T.let(Module.new.freeze, Module)

      REQUIRED_FROM_LABELS = T.let(["<top (required)>", "<main>"].freeze, T::Array[String])

      T::Sig::WithoutRuntime.sig { params(constant: BasicObject).returns(T::Boolean) }
      def constant_defined?(constant)
        !UNDEFINED_CONSTANT.eql?(constant)
      end

      sig do
        params(
          symbol: String,
          inherit: T::Boolean,
          namespace: Module,
        ).returns(BasicObject).checked(:never)
      end
      def constantize(symbol, inherit: false, namespace: Object)
        namespace.const_get(symbol, inherit)
      rescue NameError, LoadError, RuntimeError, ArgumentError, TypeError
        UNDEFINED_CONSTANT
      end

      sig { params(object: BasicObject).returns(T::Class[T.anything]).checked(:never) }
      def class_of(object)
        CLASS_METHOD.bind_call(object)
      end

      sig { params(constant: Module).returns(T::Array[Symbol]) }
      def constants_of(constant)
        CONSTANTS_METHOD.bind_call(constant, false)
      end

      sig { params(constant: Module).returns(T.nilable(String)) }
      def name_of(constant)
        name = NAME_METHOD.bind_call(constant)
        name&.start_with?("#<") ? nil : name
      end

      sig { params(constant: Module).returns(T::Class[T.anything]) }
      def singleton_class_of(constant)
        SINGLETON_CLASS_METHOD.bind_call(constant)
      end

      sig { params(constant: Module).returns(T::Array[Module]) }
      def ancestors_of(constant)
        ANCESTORS_METHOD.bind_call(constant)
      end

      sig { params(constant: T::Class[T.anything]).returns(T.nilable(T::Class[T.anything])) }
      def superclass_of(constant)
        SUPERCLASS_METHOD.bind_call(constant)
      end

      sig { params(object: BasicObject).returns(Integer).checked(:never) }
      def object_id_of(object)
        OBJECT_ID_METHOD.bind_call(object)
      end

      sig { params(object: BasicObject, other: BasicObject).returns(T::Boolean).checked(:never) }
      def are_equal?(object, other)
        EQUAL_METHOD.bind_call(object, other)
      end

      sig { params(constant: Module).returns(T::Array[Symbol]) }
      def public_instance_methods_of(constant)
        PUBLIC_INSTANCE_METHODS_METHOD.bind_call(constant)
      end

      sig { params(constant: Module).returns(T::Array[Symbol]) }
      def protected_instance_methods_of(constant)
        PROTECTED_INSTANCE_METHODS_METHOD.bind_call(constant)
      end

      sig { params(constant: Module).returns(T::Array[Symbol]) }
      def private_instance_methods_of(constant)
        PRIVATE_INSTANCE_METHODS_METHOD.bind_call(constant)
      end

      sig { params(constant: Module).returns(T::Array[Module]) }
      def inherited_ancestors_of(constant)
        if Class === constant
          ancestors_of(superclass_of(constant) || Object)
        else
          Module.new.ancestors
        end
      end

      sig { params(constant: Module).returns(T.nilable(String)) }
      def qualified_name_of(constant)
        name = name_of(constant)
        return if name.nil?

        if name.start_with?("::")
          name
        else
          "::#{name}"
        end
      end

      sig { params(method: T.any(UnboundMethod, Method)).returns(T.untyped) }
      def signature_of(method)
        T::Utils.signature_for_method(method)
      rescue LoadError, StandardError
        nil
      end

      sig { params(type: T::Types::Base).returns(String) }
      def name_of_type(type)
        type.to_s.gsub(/\bAttachedClass\b/, "T.attached_class")
      end

      sig { params(constant: Module, method: Symbol).returns(Method) }
      def method_of(constant, method)
        METHOD_METHOD.bind_call(constant, method)
      end

      # Returns an array with all classes that are < than the supplied class.
      #
      #   class C; end
      #   descendants_of(C) # => []
      #
      #   class B < C; end
      #   descendants_of(C) # => [B]
      #
      #   class A < B; end
      #   descendants_of(C) # => [B, A]
      #
      #   class D < C; end
      #   descendants_of(C) # => [B, A, D]
      sig do
        type_parameters(:U)
          .params(klass: T.all(T::Class[T.anything], T.type_parameter(:U)))
          .returns(T::Array[T.type_parameter(:U)])
      end
      def descendants_of(klass)
        result = ObjectSpace.each_object(klass.singleton_class).reject do |k|
          T.cast(k, Module).singleton_class? || T.unsafe(k) == klass
        end

        T.unsafe(result)
      end

      # Examines the call stack to identify the closest location where a "require" is performed
      # by searching for the label "<top (required)>". If none is found, it returns the location
      # labeled "<main>", which is the original call site.
      sig { params(locations: T.nilable(T::Array[Thread::Backtrace::Location])).returns(String) }
      def resolve_loc(locations)
        return "" unless locations

        resolved_loc = locations.find { |loc| REQUIRED_FROM_LABELS.include?(loc.label) }
        return "" unless resolved_loc

        resolved_loc.absolute_path || ""
      end

      sig { params(constant: Module).returns(T::Set[String]) }
      def file_candidates_for(constant)
        relevant_methods_for(constant).filter_map do |method|
          method.source_location&.first
        end.to_set
      end

      sig { params(constant: Module).returns(T.untyped) }
      def abstract_type_of(constant)
        T::Private::Abstract::Data.get(constant, :abstract_type) ||
          T::Private::Abstract::Data.get(singleton_class_of(constant), :abstract_type)
      end

      sig { params(constant: Module).returns(T::Boolean) }
      def final_module?(constant)
        T::Private::Final.final_module?(constant)
      end

      sig { params(constant: Module).returns(T::Boolean) }
      def sealed_module?(constant)
        T::Private::Sealed.sealed_module?(constant)
      end

      private

      sig { params(constant: Module).returns(T::Array[UnboundMethod]) }
      def relevant_methods_for(constant)
        methods = methods_for(constant).select(&:source_location)
          .reject { |x| method_defined_by_forwardable_module?(x) }

        return methods unless methods.empty?

        constants_of(constant).flat_map do |const_name|
          if (mod = child_module_for_parent_with_name(constant, const_name.to_s))
            relevant_methods_for(mod)
          else
            []
          end
        end
      end

      sig { params(constant: Module).returns(T::Array[UnboundMethod]) }
      def methods_for(constant)
        modules = [constant, singleton_class_of(constant)]
        method_list_methods = [
          PUBLIC_INSTANCE_METHODS_METHOD,
          PROTECTED_INSTANCE_METHODS_METHOD,
          PRIVATE_INSTANCE_METHODS_METHOD,
        ]

        modules.product(method_list_methods).flat_map do |mod, method_list_method|
          method_list_method.bind_call(mod, false).map { |name| mod.instance_method(name) }
        end
      end

      sig { params(parent: Module, name: String).returns(T.nilable(Module)) }
      def child_module_for_parent_with_name(parent, name)
        return if parent.autoload?(name)

        child = constantize(name, inherit: true, namespace: parent)
        return unless Module === child
        return unless name_of(child) == "#{name_of(parent)}::#{name}"

        child
      end

      sig { params(method: UnboundMethod).returns(T::Boolean) }
      def method_defined_by_forwardable_module?(method)
        method.source_location&.first == Object.const_source_location(:Forwardable)&.first
      end

      sig { params(name: String).returns(T::Boolean) }
      def has_aliased_namespace?(name)
        name_parts = name.split("::")
        name_parts.pop # drop the constant name, leaving just the namespace

        name_parts.each_with_object([]) do |name_part, namespaces|
          namespaces << "#{namespaces.last}::#{name_part}".delete_prefix("::")
        end.any? do |namespace|
          constant = constantize(namespace)
          next unless Module === constant

          # If the constant name doesn't match the namespace,
          # the namespace must contain an alias
          name_of(constant) != namespace
        end
      end
    end
  end
end