module Clockwork
	class FailedToParse < StandardError; end;

	class Event
		attr_accessor :job, :last

		def initialize(period, job, block, options={})
			@period = period
			@job = job
			@at = parse_at(options[:at])
			@last = nil
			@block = block
		end

		def to_s
			@job
		end

		def time?(t)
			ellapsed_ready = (@last.nil? or (t - @last).to_i >= @period)
			time_ready = (@at.nil? or (t.hour == @at[0] and t.min == @at[1]))
			ellapsed_ready and time_ready
		end

		def run(t)
			@last = t
			@block.call(@job)
		rescue => e
			log_error(e)
		end

		def log_error(e)
			STDERR.puts exception_message(e)
		end

		def exception_message(e)
			msg = [ "Exception #{e.class} -> #{e.message}" ]

			base = File.expand_path(Dir.pwd) + '/'
			e.backtrace.each do |t|
				msg << "   #{File.expand_path(t).gsub(/#{base}/, '')}"
			end

			msg.join("\n")
		end

		def parse_at(at)
			return unless at
			m = at.match(/^(\d\d):(\d\d)$/)
			raise FailedToParse, at unless m
			hour, min = m[1].to_i, m[2].to_i
			raise FailedToParse, at if hour >= 24 or min >= 60
			[ hour, min ]
		end
	end

	extend self

	def handler(&block)
		@@handler = block
	end

	class NoHandlerDefined < RuntimeError; end

	def get_handler
		raise NoHandlerDefined unless (defined?(@@handler) and @@handler)
		@@handler
	end

	def every(period, job, options={}, &block)
		event = Event.new(period, job, block || get_handler, options)
		@@events ||= []
		@@events << event
		event
	end

	def run
		log "Starting clock for #{@@events.size} events: [ " + @@events.map { |e| e.to_s }.join(' ') + " ]"
		loop do
			tick
			sleep 1
		end
	end

	def log(msg)
		puts "[#{Time.now}] #{msg}"
	end

	def tick(t=Time.now)
		to_run = @@events.select do |event|
			event.time?(t)
		end

		to_run.each do |event|
			log "-> #{event}"
			event.run(t)
		end

		to_run
	end

	def clear!
		@@events = []
		@@handler = nil
	end
end

class Numeric
	def seconds; self; end
	alias :second :seconds

	def minutes; self * 60; end
	alias :minute :minutes

	def hours; self * 3600; end
	alias :hour :hours

	def days; self * 86400; end
	alias :day :days
end