word_filter.rb

class WordFilter
  attr_reader :words
  attr_accessor :censor_message

  def initialize(*words)
    @words = words
    @censor_message = "censored"
  end

  def detect(message)
    message =~ create_regexpression
  end

  def censor(message)
    user_part, message = split_from_message(message)
    user_part + message.gsub(create_regexpression, "<#{censor_message}>")
  end

  def add_words(*words)
    @words += words
    @words.uniq!
  end

  def delete_words(*words)
    words.each do |w|
      @words.delete(w)
    end
  end

  private
  def create_regexpression
    /#{@words.sort.reverse.map{|w| Regexp.quote(w)}.join('|')}/
  end

  def split_from_message(message)
    if message =~ /(\S+:\s)(.+)/
      [$1,$2]
    else
      ["", message] 
    end
  end
end

word_filter_spec.rb

require 'rubygems'
require 'spec'
require 'word_filter'

describe WordFilter do
  it "NGWordをひとつ指定できること" do
    lambda do
      filter = WordFilter.new("NGWord")
    end.should_not raise_error
  end

  it "NGWordを指定しなくてもいいこと" do
    pending
  end

  it "NGWordを複数指定できること" do
    lambda do
      filter = WordFilter.new("NGWord1", "NGWord2")
    end.should_not raise_error
  end

  it "NGWordを追加できること" do
    filter = WordFilter.new("NGWord1")
    lambda do
      filter.add_words("NGWord2", "NGWord3")
    end.should_not raise_error
  end

  context "NGWordを追加したとき" do
    before do
      @filter = WordFilter.new("NGWord1")
      @filter.add_words("NGWord2", "NGWord3")
    end

    it "既存のNGWordを取得できること" do
      @filter.words.should be_include("NGWord1")
    end

    it "追加したNGWordを取得できること" do
      @filter.words.should be_include("NGWord2")
      @filter.words.should be_include("NGWord3")
    end

    it "追加したNGWordでdetectすること" do
      @filter.detect("NGWord2").should be_true
      @filter.detect("NGWord3").should be_true
    end

    it "追加したNGWordでcensorできること" do
      @filter.censor("NGWord2とNGWord3").should == "<censored>と<censored>"
    end
  end

  context "NGWordが文字列以外だったら" do
    it "文字列として扱う?" do
      pending
    end
  end

  context "特殊文字をNGWord指定したら" do
    it "\をdetectできること" do
      filter = WordFilter.new("\\")
      filter.detect("\\").should be_true
    end

    it "\をcensorできること" do
      filter = WordFilter.new("\\")
      filter.censor("\\").should == "<censored>"
    end
  end

  context "NGWordが別のNGWordを内包しているとき" do
    it "AAAAとAAAだったらAAAAでcensorする"do 
      filter = WordFilter.new("AAA", "AAAA")
      filter.censor("AAAA").should == "<censored>" 
    end

    it "1111と111だったら1111でcensorする"do 
      filter = WordFilter.new("111", "1111")
      filter.censor("1111").should == "<censored>" 
    end
  end
  
  context "NGWordが指定されている場合" do
    before do
      @filter = WordFilter.new("NGWord")
    end

    it "NGWordをdetectできること" do
      @filter.detect("NGWord").should be_true
    end

    it "NGWordじゃない場合detectしない" do
      @filter.detect("hoge").should be_false
    end

    it "NGWordをcensorできること" do
      @filter.censor("t_wada: あいうNGWord").should == "t_wada: あいう<censored>"
    end

    it "NGWordを含まなければそのまま返すこと" do
      @filter.censor("t_wada: あいうえお").should == "t_wada: あいうえお"
    end
  end

  context "NGWordが複数指定している場合" do
    before do
      @filter = WordFilter.new("NGWord1", "NGWord2")
    end

    it "NGWordをdetectできること" do
      @filter.detect("NGWord1").should be_true
      @filter.detect("NGWord2").should be_true
    end

    it "NGWordをcensorできること" do
      @filter.censor("t_wada: あいうNGWord1").should == "t_wada: あいう<censored>"
      @filter.censor("t_wada: あいうNGWord2").should == "t_wada: あいう<censored>"
      @filter.censor("t_wada: あいうえお").should == "t_wada: あいうえお"
    end

    it "NGWordを削除できること" do
      @filter.delete_words("NGWord1")
      @filter.words.should_not be_include("NGWord1")
    end

    it "NGWordを複数削除できること" do
      @filter.delete_words("NGWord1", "NGWord2")
      @filter.words.should_not be_include("NGWord1")
      @filter.words.should_not be_include("NGWord2")
    end
  end

  context "IDがNGWordだったら" do
    before do
      @filter = WordFilter.new('t_wada')
    end

    it "IDはcensorしない" do
      @filter.censor("t_wada: t_wada").should == "t_wada: <censored>"
    end
  end

  it "<censored>の文字列を変更できること" do
    filter = WordFilter.new("NGWord")
    filter.censor_message = "xxx"
    filter.censor("NGWord").should == "<xxx>"
  end
end