# = Events
#
# A simple events mechanism.
#
# === Design:
#
# As always we try to keep the design simple:
# Events = strings (hiearchical notation)
# Handlers = named Procs
# The handlers are named so that we can remove them
# by name. Also usefull for documentation purposes.
#
# === TODO:
#
# Add a class of events to allow filtering of certain
# events. Perhaps name can be used for this!
#
# code: tml
#
# (c) 2002-2003 Navel, all rights reserved.
# $Id: events.rb 71 2004-10-18 10:50:22Z gmosx $

module N;

# = EventManager
#
# === Example:
#
# $ev.event("id/user/login", user)
# $ev.add_handler("id/user/login", "login-score", proc { |user|
#	user["score"] += 1
# })
#
class EventManager
	attr :events
	attr_accessor :logger

	def initialize(logger = nil)
		@events = Hash.new
		@logger = logger
	end

	# Register an event handler.
	#
	# === Input:
	# event = the event
	# name = the name of the handler
	# proc = the proc of the hadler
	#
	def add_handler(event, name, proc)
		unless event_handlers = @events[event]
			@events[event] = event_handlers = Hash.new
		end
		event_handlers[name] = proc
	end

	# Remove the named handler from the event.
	#
	def remove_handler(event, name)
		if event_handlers = @events[event]
			event_handlers.delete(name)
		else
			$log.debug "ev: cannot remove, handler #{name} not found for event #{event}" if $DBG
		end
	end

	# Remove all handlers for the event.
	#
	# === Input:
	# event = the event
	# name = the name of the handler
	#
	def remove_all_handlers(event)
		@events[event] = Hash.new
	end

	# Fire an event
	#
	# === Input:
	# event = the event to fire
	# param = parameters for the handler, use an array
	# 		  for multiple parameters.
	#
	def event(event, params)
		if event_handlers = @events[event]
			# call all event handler procs
			for handler in event_handlers.values
				# call the handler with the params.
				handler.call(params)
			end
		end
		if @logger
			if params.is_a?(Array)
				pstr = params.collect{|i| i.to_s()}.join(", ")
			else
				pstr = params.to_s()
			end
			@logger.info("#{event}: #{pstr}")
		end
	end
	alias_method :fire, :event
end

#
#
#
class Event
	@@manager = EventManager.new()
	
	def self.add_handler(event, name, proc)
	end
	
	def self.fire(event, params)
		@@manager.fire(event, params)
	end
end

end # module