class Listen::QueueOptimizer

def _calculate_add_remove_difference(actions, path, default_if_exists)
  added = actions.count { |x| x == :added }
  removed = actions.count { |x| x == :removed }
  diff = added - removed
  # TODO: avoid checking if path exists and instead assume the events are
  # in order (if last is :removed, it doesn't exist, etc.)
  if config.exist?(path)
    if diff > 0
      :added
    elsif diff.zero? && added > 0
      :modified
    else
      default_if_exists
    end
  else
    diff < 0 ? :removed : nil
  end
end

def _logical_action_for(path, actions)
  actions << :added if actions.delete(:moved_to)
  actions << :removed if actions.delete(:moved_from)
  modified = actions.find { |x| x == :modified }
  _calculate_add_remove_difference(actions, path, modified)
end

def _reinterpret_related_changes(cookies)
  table = { moved_to: :added, moved_from: :removed }
  cookies.flat_map do |_, changes|
    if (editor_modified = editor_modified?(changes))
      [[:modified, *editor_modified]]
    else
      not_silenced = changes.reject do |type, _, _, path, _|
        config.silenced?(Pathname(path), type)
      end
      not_silenced.map do |_, change, dir, path, _|
        [table.fetch(change, change), dir, path]
      end
    end
  end
end

def _squash_changes(changes)
  # We combine here for backward compatibility
  # Newer clients should receive dir and path separately
  changes = changes.map { |change, dir, path| [change, dir + path] }
  actions = changes.group_by(&:last).map do |path, action_list|
    [_logical_action_for(path, action_list.map(&:first)), path.to_s]
  end
  config.debug("listen: raw changes: #{actions.inspect}")
  { modified: [], added: [], removed: [] }.tap do |squashed|
    actions.each do |type, path|
      squashed[type] << path unless type.nil?
    end
    config.debug("listen: final changes: #{squashed.inspect}")
  end
end

def editor_modified?(changes)
  return unless changes.size == 2
  from_type = from = nil
  to_type = to_dir = to = nil
  changes.each do |data|
    case data[1]
    when :moved_from
      from_type, _from_change, _, from, = data
    when :moved_to
      to_type, _to_change, to_dir, to, = data
    end
  end
  # Expect an ignored moved_from and non-ignored moved_to
  # to qualify as an "editor modify"
  if from && to && config.silenced?(Pathname(from), from_type) && !config.silenced?(Pathname(to), to_type)
    [to_dir, to]
  end
end

def initialize(config)
  @config = config
end

def smoosh_changes(changes)
  # TODO: adapter could be nil at this point (shutdown)
  cookies = changes.group_by do |_, _, _, _, options|
    (options || {})[:cookie]
  end
  _squash_changes(_reinterpret_related_changes(cookies))
end