module MetricFu
  CHURN_DIR = File.join(MetricFu::BASE_DIRECTORY, 'churn')
  
  def self.generate_churn_report
    MetricFu::Churn.generate_report(CHURN_DIR, MetricFu.churn_options )
    system("open #{CHURN_DIR}/index.html") if open_in_browser?
  end
  
  class Churn < Base::Generator

    def initialize(base_dir, options={})
      @base_dir = base_dir
      if File.exist?(".git")
        @source_control = Git.new(options[:start_date])
      elsif File.exist?(".svn")
        @source_control = Svn.new(options[:start_date])
      else
        raise "Churning requires a subversion or git repo"
      end

      @minimum_churn_count = options[:minimum_churn_count] || 5
    end

    def analyze
      @changes = parse_log_for_changes.reject! {|file, change_count| change_count < @minimum_churn_count}
    end

    private

    def parse_log_for_changes
      changes = {}

      logs = @source_control.get_logs
      logs.each do |line|
        changes[line] ? changes[line] += 1 : changes[line] = 1
      end
      changes
    end


    class SourceControl
      def initialize(start_date=nil)
        @start_date = start_date
      end

      private
      def require_rails_env
        # not sure if the following works because active_support might only be in vendor/rails
        # require 'activesupport'
        require RAILS_ROOT + '/config/environment'
      end
    end

    class Git < SourceControl
      def get_logs
        `git log #{date_range} --name-only --pretty=format:`.split(/\n/).reject{|line| line == ""}
      end

      private
      def date_range
        if @start_date
          require_rails_env
          "--after=#{@start_date.call.strftime('%Y-%m-%d')}"
        end
      end

    end

    class Svn < SourceControl
      def get_logs
        `svn log #{date_range} --verbose`.split(/\n/).map { |line| clean_up_svn_line(line) }.compact
      end

      private
      def date_range
        if @start_date
          require_rails_env
          "--revision {#{@start_date.call.strftime('%Y-%m-%d')}}:{#{Time.now.strftime('%Y-%m-%d')}}"
        end
      end

      def clean_up_svn_line(line)
        m = line.match(/\W*[A,M]\W+(\/.*)\b/)
        m ? m[1] : nil
      end
    end

  end
end