require 'rss/maker'

class StatusController < ApplicationController
  ######################################################################
  ### Check classes
  class Check
    def initialize (name = nil, &block)
      @name  = name  || self.class.to_s
      @check = block || Proc.new{ check }
    end
    attr_reader :name, :passed, :message, :checked_on

    def execute
      @passed     = true
      @checked_on = Time.now
      @check.call
    rescue Exception => err
      @passed     = false
      @message    = err.to_s
    end
  end

  class ConnectViaDBI < Check
    def check
      config  = ActiveRecord::Base.configurations[::RAILS_ENV]
      adapter = "dbi:%s:%s" % [config['adapter'], config['database']]
      require 'dbi'
      DBI::connect(adapter, config['username'], config['password']).disconnect
    end
  end

  class PeacefulDay < Check
    def check
      error_count = Syslog.count("DATEDIFF(NOW(),created_on) < 1 AND priority > 10")
      raise "%d errors occurred !!" % error_count if error_count > 0
    end
  end

protected

  def checks
    [
     Check.new("ライブラリ 'digest/md5'") { require 'digest/md5'},
     Check.new("ActiveRecord からの接続") {ActiveRecord::Base.connection.active?},
     ConnectViaDBI.new("DBI からの接続"),
     PeacefulDay.new("今日も平和"),
    ]
  end

public
  ######################################################################
  ### Actions
  def index
    render :inline=>"<%= auto_discovery_link_tag :rss, :action => 'rss' %>"
  end
  
  def rss
    rss = RSS::Maker.make("1.0") do |maker|
      error_count  = 0
  
      checks.each_with_index do |check, i|
        check.execute
        item  = maker.items.new_item
        item.link            = url_for(:id=>i)
        item.description     = check.passed ? "OK" : "NG"
        item.title           = "[%s] %s" % [item.description, check.name]
        item.content_encoded = check.message.to_s
        item.date            = check.checked_on
        error_count += 1 unless check.passed
      end

      maker.channel.about       = url_for
      maker.channel.link        = url_for
      maker.channel.title       = "[%s] %s" % [(error_count > 0) ? "NG":"OK", url_for(:controller=>'')]
      maker.channel.description = "%d checks, %d failures" % [checks.size, error_count]
    end

    @headers["Content-Type"] = 'application/xml; charset=UTF-8'
    render :text => rss, :layout => false
  end
end