redis_ranking.rb

#!/usr/bin/env ruby
require 'redis'

class UserNotFoundException < Exception; end
class UserRanking 
  KEY="ranking"

  def initialize(user_id)
    @redis= Redis.new

    @user_id= user_id
    @myscore= (@redis.zscore KEY, user_id).to_i
    if @myscore > 0
      @myindex= @redis.zrevrank KEY, user_id
      @myrank= get_rank(@myscore)      
      puts <<"EOS"
UserID: #{@user_id}
Score : #{@myscore}
Rank  : #{@myrank}  
EOS
    else
      raise UserNotFoundException, "User not found"
    end    
  end
  
  def get_rank(score)
    score= score.to_i
    (@redis.zcount KEY, score+1, Float::INFINITY) + 1
  end

  def display(ranking, scores={})
    if ranking
      ranking.each_slice(2).with_index do |(uid, score), i|
        rank= scores[score] || 0
        if rank < 1
          rank= get_rank(score)
          scores[score]= rank
        end
        str= "%7d %11s: %3d" % [rank, uid, score]
        str << " <--- " if uid == @user_id
        puts str
      end
    end
  end

  def top10()
    puts "[Top10]"
    ranking= @redis.zrevrange( KEY, 0, 9,  {withscores: true})
    display ranking, {ranking[1] => 1}
  end

  def near10() 
    puts "[Near10]"
    scores= {@myscore => @myrank}
    range= 5
    first= (@myindex - range > 0) ? @myindex-range : 0
    ranking= @redis.zrevrange(KEY, first, @myindex + range, {withscores: true})
    display ranking, scores 
  end
end

if $0 == __FILE__
  # write this
  user_id= ARGV[0] || "User0234567"
  ranking = UserRanking.new(user_id)
  ranking.top10()
  ranking.near10()
end