class EngineYardCloudInstance
  INSTANCE_DESCRIPTIONS_CACHE_PATH = defined?(RAILS_ROOT) ? "#{RAILS_ROOT}/config/engine_yard_instance_descriptions.yml" : '/etc/engine_yard_instance_descriptions.yml'
  
  attr_accessor :instance_id
  def initialize(instance_id)
    @instance_id = instance_id.to_sym
  end
  
  def refresh
    self.class.refresh
  end
  
  def method_missing(name, *args, &block)
    name = name.to_sym
    if me = self.class.data[instance_id] and me.has_key?(name)
      me[name]
    else
      super
    end
  end
  
  class << self
    def app
      find_all_by_instance_roles :app, :app_master
    end
    
    def db
      find_all_by_instance_roles :db
    end
    
    def utility
      find_all_by_instance_roles :utility
    end
    
    def all
      data.map { |k, _| new k }
    end
    
    def first
      new data.to_a.first.first
    end
    
    def find_by_instance_id(instance_id)
      new instance_id.to_sym
    end
    
    def find_all_by_instance_roles(*args)
      data.select { |_, v| Array.wrap(args).include? v[:instance_role] }.map { |k, _| new k }
    end
    
    def refresh
      @_data = nil
      @_dna = nil
      refresh_instance_descriptions true
    end
    
    def data
      return @_data if @_data
      hash = Hash.new
      cached_instance_descriptions.each do |instance_description|
        key = instance_description[:aws_instance_id].dup
        hash[key] ||= Hash.new
        current = hash[key]
        # using current as a pointer
        if dna[:db_host] == instance_description[:dns_name] or dna[:db_host] == instance_description[:private_dns_name]
          current[:instance_role] = :db
        elsif Array.wrap(dna[:utility_instances]).include? instance_description[:private_dns_name]
          current[:instance_role] = :utility
        elsif dna[:master_app_server][:private_dns_name] == instance_description[:private_dns_name]
          current[:instance_role] = :app_master
        else
          current[:instance_role] = :app
        end
        current[:private_dns_name] = instance_description[:private_dns_name]
        current[:dns_name] = instance_description[:dns_name]
        current[:aws_instance_id] = instance_description[:aws_instance_id]
        current[:aws_state] = instance_description[:aws_state]
      end
      @_data = hash.recursive_symbolize_keys!
    end
    
    private
    
    def dna
      @_dna ||= EngineYardCloudChef.dna
    end
    
    def cached_instance_descriptions(refresh = false)
      refresh_instance_descriptions refresh
      @_cached_instance_descriptions ||= YAML.load(IO.read(INSTANCE_DESCRIPTIONS_CACHE_PATH))
    end
    
    def refresh_instance_descriptions(refresh)
      if refresh or !File.readable?(INSTANCE_DESCRIPTIONS_CACHE_PATH)
        ec2 = RightAws::Ec2.new dna[:aws_secret_id], dna[:aws_secret_key]
        @_cached_instance_descriptions = ec2.describe_instances.map(&:recursive_symbolize_keys!)
        begin
          File.open(INSTANCE_DESCRIPTIONS_CACHE_PATH, 'w') { |f| f.write @_cached_instance_descriptions.to_yaml }
        rescue Errno::EACCES
          $stderr.puts "[EY CLOUD AWARENESS GEM] Not caching instance data because #{INSTANCE_DESCRIPTIONS_CACHE_PATH} can't be written to"
        end
      end
    end
  end
end