module Fluent::Plugin::FileOutput::SymlinkBufferMixin

def generate_chunk(metadata)
  chunk = super
  # "symlink" feature is to link from symlink_path to the latest file chunk. Records with latest
  # timekey will be appended into that file chunk. On the other side, resumed file chunks might NOT
  # have timekey, especially in the cases that resumed file chunks are generated by Fluentd v0.12.
  # These chunks will be enqueued immediately, and will be flushed soon.
  latest_metadata = metadata_list.select{|m| m.timekey }.sort_by(&:timekey).last
  if chunk.metadata == latest_metadata
    sym_path = @_output_plugin_for_symlink.extract_placeholders(@_symlink_path, chunk)
    FileUtils.mkdir_p(File.dirname(sym_path), mode: @_output_plugin_for_symlink.dir_perm)
    FileUtils.ln_sf(chunk.path, sym_path)
  end
  chunk
end

def output_plugin_for_symlink=(output_plugin)
  @_output_plugin_for_symlink = output_plugin
end

def symlink_path=(path)
  @_symlink_path = path
end