class Embulk::Filter::ExampleFilterPlugin

def self.transaction(config, in_schema, &control)
  task = {
    'key' => config.param('key', :string, default: "filter_key"),
    'value' => config.param('value', :string, default: "filter_value")
  }
  idx = in_schema.size
  out_columns = in_schema + [Column.new(idx, task['key'], :string)]
  puts "Example filter started."
  yield(task, out_columns)
  puts "Example filter finished."
end

def add(page)
  page.each do |record|
    @page_builder.add(record + [@value])
  end
end

def close
end

def finish
  @page_builder.finish
end

def initialize(task, in_schema, out_schema, page_builder)
  super
  @value = task['value']
end