deps.rb

require 'json'
require 'open-uri'

class DependencyChecker
  def initialize(*gems)
    @gems = gems.flatten
    @dep_cache = {}
  end
  
  def all_dependencies
    deps = @gems.flatten
    loop do
      size = deps.size
      deps.dup.each {|dep| deps |= dependencies_for(dep) }
      break if size == deps.size
    end
    deps.sort - @gems
  end
  
  private
  
  def dependencies_for(gem)
    return @dep_cache[gem] if @dep_cache[gem]
    #puts "Checking dependencies for #{gem}"
    json = JSON.parse(open("http://rubygems.org/api/v1/gems/#{gem}.json").read)
    @dep_cache[gem] = json['dependencies']['runtime'].map {|g| g['name'] }.uniq
  end
end

if ARGV.empty? 
  print "Enter gem names: "
  deps = gets.strip.split(/\s+|,/).map {|x| x.empty? ? nil : x }.compact
else
  deps = ARGV
end
puts "Recursive dependencies for #{deps.join(', ')}:"
puts DependencyChecker.new(*deps).all_dependencies