Gmail の検索条件を ruby の DSL で扱えるようにした

gmail_search.rb

class Gmail
  def initialize(&block)
    @block = block
    @items = []
  end
  def run    
    self.instance_eval(&@block)
    @items.join(" ")
  end
  def cond(condition, &block)
    eval_context(block) do |text|
      case condition
      when :and
        "(#{text})"
      when :or
        "{#{text}}"
      when :not
        "-#{text}"
      else
        fail
      end
    end
  end
  def eval_context(block)
    text = self.class.new(&block).run
    compiled_text = yield text
    @items.push(compiled_text)
    compiled_text
  end
  def t(text)
    @items << text
  end
  def inbox(&block)
    eval_context(block) {|text| "in:(#{text})"}
  end
  [:subject, :to, :from].each do |method_name|
    define_method(method_name) do |&block|
      eval_context(block) {|text| "#{method_name}:(#{text})"}
    end
  end
end
def gmail(&block)
  Gmail.new(&block).run
end

puts gmail {
  cond(:or) {
    cond(:and) {
      inbox { t 'anywhere' }
      to { t '[email protected]' }
      subject {
        t '＜連絡＞'
        cond(:or) {
          t 'Aさん'
          t 'Bさん'
          t 'Cさん'
          t 'D様'
          t 'E様'
          t '上様'
          t '田中太郎様'
        }
      }
    }
    cond(:and) {
      from { t '[email protected]' }
      cond(:not) {
        to { t 'example.org' }
      }
    }
  }
}