class ViewModel::ActiveRecord::Visitor

def changes(_view)
  ViewModel::Changes.new
end

def ignore_association!(name)
  @ignored_associations.add(name.to_s)
end

def initialize(visit_referenced: true, visit_shared: true, for_edit: false)
  @visit_referenced = visit_referenced
  @visit_shared     = visit_shared
  @for_edit         = for_edit
end

def post_visit(_view, context: nil); end

def pre_visit(_view, context: nil)
  true
end

def reset_state!
  @ignored_associations = Set.new
end

def run_callback(hook, view, context:, **args)
  context.run_callback(hook, view, **args) if context
end

def visit(view, context: nil)
  reset_state!
  return unless pre_visit(view, context: context)
  run_callback(ViewModel::Callbacks::Hook::BeforeVisit, view, context: context)
  run_callback(ViewModel::Callbacks::Hook::BeforeDeserialize, view, context: context) if for_edit
  class_name = view.class.name.underscore.gsub('/', '__')
  visit      = :"visit_#{class_name}"
  end_visit  = :"end_visit_#{class_name}"
  visit_children =
    if respond_to?(visit, true)
      self.send(visit, view, context: context)
    else
      true
    end
  if visit_children
    # visit the underlying viewmodel for each association, ignoring any
    # customization
    ignored_associations = @ignored_associations
    view.class._members.each do |name, member_data|
      next unless member_data.association?
      next if ignored_associations.include?(name)
      next if member_data.referenced? && !visit_referenced
      next if !member_data.owned? && !visit_shared
      children = Array.wrap(view._read_association(name))
      children.each do |child|
        if context
          child_context = view.context_for_child(name, context: context)
        end
        self.visit(child, context: child_context)
      end
    end
  end
  self.send(end_visit, view, context: context) if respond_to?(end_visit, true)
  if for_edit
    view_changes = changes(view)
    run_callback(ViewModel::Callbacks::Hook::OnChange, view, context: context, changes: view_changes) if view_changes.changed?
    run_callback(ViewModel::Callbacks::Hook::AfterDeserialize, view, context: context, changes: view_changes)
  end
  run_callback(ViewModel::Callbacks::Hook::AfterVisit, view, context: context)
  post_visit(view, context: context)
end