module Logging::Appenders

  # Accessor / Factory for the Growl appender.
  #
  def self.growl( *args )
    return ::Logging::Appenders::Growl if args.empty?
    ::Logging::Appenders::Growl.new(*args)
  end

  # This class provides an Appender that can send notifications to the Growl
  # notification system on Mac OS X.
  #
  # +growlnotify+ must be installed somewhere in the path in order for the
  # appender to function properly.
  #
  class Growl < ::Logging::Appender

    # :stopdoc:
    ColoredRegexp = %r/\e\[([34][0-7]|[0-9])m/
    # :startdoc:

    # call-seq:
    #    Growl.new( name, opts = {} )
    #
    # Create an appender that will log messages to the Growl framework on a
    # Mac OS X machine.
    #
    def initialize( name, opts = {} )
      super

      @growl = "growlnotify -w -n \"#{@name}\" -t \"%s\" -m \"%s\" -p %d &"

      @coalesce = opts.getopt(:coalesce, false)
      @title_sep = opts.getopt(:separator)

      # provides a mapping from the default Logging levels
      # to the Growl notification levels
      @map = [-2, -1, 0, 1, 2]

      map = opts.getopt(:map)
      self.map = map unless map.nil?
      setup_coalescing if @coalesce

      # make sure the growlnotify command can be called
      unless system('growlnotify -v >> /dev/null 2>&1')
        self.level = :off
        ::Logging.log_internal {'growl notifications have been disabled'}
      end
    end

    # call-seq:
    #    map = { logging_levels => growl_levels }
    #
    # Configure the mapping from the Logging levels to the Growl
    # notification levels. This is needed in order to log events at the
    # proper Growl level.
    #
    # Without any configuration, the following mapping will be used:
    #
    #    :debug  =>  -2
    #    :info   =>  -1
    #    :warn   =>  0
    #    :error  =>  1
    #    :fatal  =>  2
    #
    def map=( levels )
      map = []
      levels.keys.each do |lvl|
        num = ::Logging.level_num(lvl)
        map[num] = growl_level_num(levels[lvl])
      end
      @map = map
    end


  private

    # call-seq:
    #    write( event )
    #
    # Write the given _event_ to the growl notification facility. The log
    # event will be processed through the Layout associated with this
    # appender. The message will be logged at the level specified by the
    # event.
    #
    def write( event )
      title = ''
      priority = 0
      message = if event.instance_of?(::Logging::LogEvent)
          priority = @map[event.level]
          @layout.format(event)
        else
          event.to_s
        end
      return if message.empty?

      message = message.gsub(ColoredRegexp, '')
      if @title_sep
        title, message = message.split(@title_sep)
        title, message = '', title if message.nil?
      end

      growl(title.strip, message.strip, priority)
      self
    end

    # call-seq:
    #    growl_level_num( level )    => integer
    #
    # Takes the given _level_ as a string or integer and returns the
    # corresponding Growl notification level number.
    #
    def growl_level_num( level )
      level = Integer(level)
      if level < -2 or level > 2
        raise ArgumentError, "level '#{level}' is not in range -2..2"
      end
      level
    end

    # call-seq:
    #    growl( title, message, priority )
    #
    # Send the _message_ to the growl notifier using the given _title_ and
    # _priority_.
    #
    def growl( title, message, priority )
      message.tr!("`", "'")
      if @coalesce then coalesce(title, message, priority)
      else call_growl(title, message, priority) end
    end

    # call-seq:
    #    coalesce( title, message, priority )
    #
    # Attempt to coalesce the given _message_ with any that might be pending
    # in the queue to send to the growl notifier. Messages are coalesced
    # with any in the queue that have the same _title_ and _priority_.
    #
    # There can be only one message in the queue, so if the _title_ and/or
    # _priority_ don't match, the message in the queue is sent immediately
    # to the growl notifier, and the current _message_ is queued.
    #
    def coalesce( *msg )
      @c_mutex.synchronize do
        if @c_queue.empty?
          @c_queue << msg
          @c_thread.run

        else
          qmsg = @c_queue.last
          if qmsg.first != msg.first or qmsg.last != msg.last
            @c_queue << msg
          else
            qmsg[1] << "\n" << msg[1]
          end
        end
      end
    end

    # call-seq:
    #    setup_coalescing
    #
    # Setup the appender to handle coalescing of messages before sending
    # them to the growl notifier. This requires the creation of a thread and
    # mutex for passing messages from the appender thread to the growl
    # notifier thread.
    #
    def setup_coalescing
      @c_mutex = Mutex.new
      @c_queue = []

      @c_thread = Thread.new do
        loop do
          Thread.stop if @c_queue.empty?
          sleep 1
          @c_mutex.synchronize {
            call_growl(*@c_queue.shift) until @c_queue.empty?
          }
        end  # loop
      end  # Thread.new
    end

    # call-seq:
    #    call_growl( title, message, priority )
    #
    # Call the growlnotify application with the given parameters. If the
    # system call fails, the growl appender will be disabled.
    #
    def call_growl( *args )
      unless system(@growl % args)
        self.level = :off
        ::Logging.log_internal {'growl notifications have been disabled'}
      end
    end

  end  # Growl
end  # Logging::Appenders