require 'madeleine'
require 'madeleine/automatic'
require 'madeleine/zmarshal'
require 'singleton'
require 'yaml'

class MadeleineService
  include Madeleine::Automatic::Interceptor

  @@storage_path = self.name.downcase + "_storage"
  automatic_read_only :snapshot_interval_hours, :take_snapshot, :clean_old_snapshots,
                      :restart, :request_stop

  class << self
    def storage_path
      @@storage_path
    end
  
    def storage_path=(storage_path)
      @@storage_path = storage_path
    end

    def instance
      if @system.nil?
        @madeleine_server = MadeleineServer.new(self) 
        @system = @madeleine_server.system
      end
      @system
    end
    
    def restart
      MadeleineServer.delete_storage(self)
      @system = nil
      instance
    end

    def clean_old_snapshots
      instance
      @madeleine_server.clean_storage(self)
    end
    
    def take_snapshot
      instance
      @madeleine_server.force_snapshot
    end
    
    def snapshot_interval_hours
      instance
      @madeleine_server.snapshot_interval.div MadeleineServer::ONE_HOUR rescue 1
    end
    
    def snapshot_interval_hours= hours
      instance
      @madeleine_server.snapshot_interval = hours.to_i * MadeleineServer::ONE_HOUR rescue MadeleineServer::ONE_HOUR
    end

    def request_stop
      instance
      @madeleine_server.request_stop
    end
    
  end
end

require 'fileutils'
class MadeleineServer

  attr_reader :storage_path
  attr_accessor :snapshot_interval

  # Clears all the command_log and snapshot files located in the storage directory, so the
  # database is essentially dropped and recreated as blank. Used in tests.
  def self.delete_storage(service)
    if (File.directory?(service.storage_path))
      FileUtils.rm_rf(Dir[service.storage_path + '/*.command_log'])
      FileUtils.rm_rf(Dir[service.storage_path + '/*.snapshot'])
    else
      FileUtils.mkdir_p(service.storage_path)
    end
  end
  
  def clean_storage(service)
    force_snapshot
    command_logs = Dir[service.storage_path + '/*.command_log']
    raise 'Error: existing command_logs after snapshot' unless command_logs.empty?

    snapshots = Dir[service.storage_path + '/*.snapshot']
    FileUtils.rm_rf(snapshots.sort[0..-2])
  end
  

  def initialize(service)
    @storage_path = service.storage_path
    @snapshot_interval = ONE_HOUR
    marshaller = Madeleine::ZMarshal.new()
    @server = Madeleine::Automatic::AutomaticSnapshotMadeleine.new(service.storage_path, 
        marshaller) { service.new }
    start_snapshot_thread
  end

  def system
    @server.system
  end

  def command_log_present?
    not Dir[storage_path + '/*.command_log'].empty?
  end

  def force_snapshot
    begin
      hours_since_last_snapshot = 0
      @server.take_snapshot
    rescue => e
      sleep(ONE_MINUTE)
      retry
    end
  end
  
  
  ONE_MINUTE = 60
  ONE_HOUR   = ONE_MINUTE * 60
  MAX_INTERVAL_HOURS = 24 * 2

  def start_snapshot_thread
    @snapshot_thread = Thread.new(@server) {
      hours_since_last_snapshot = 0
      while not @request_stop
        sleep(snapshot_interval)
        hours_since_last_snapshot += snapshot_interval.div ONE_HOUR
        begin
          # Take a snapshot if there is a command log
          if command_log_present? or hours_since_last_snapshot > MAX_INTERVAL_HOURS
            #  'Taking a Madeleine snapshot'
            @server.take_snapshot
            hours_since_last_snapshot = 0
            puts "[#{DateTime.now.strftime '%F %T'}] INFO Taking snapshot"
          else
            puts "[#{DateTime.now.strftime '%F %T'}] INFO Skipping snapshot (no command logs)"
          end
        rescue => e
          # wait for a minute (not to spoof the log with the same error)
          # and go back into the loop, to keep trying
          sleep(ONE_MINUTE)
          retry
        end
      end
    }
  end
  
  def request_stop
    begin
      @request_stop = true
      if @snapshot_thread and @snapshot_thread.alive?
        @snapshot_thread.wakeup
        @snapshot_thread.join
      end
      @server.take_snapshot if command_log_present?
    rescue => detail
      puts detail
    end
  end

end