Commit the pile of initial work. Largely taken from company internal

repos, allowed to be newly released.  Portions already in production,
coverage still needs to be boosted.  Enjoy.

FossilOrigin-Name: 0f17fa483f55467bdf9e8f99dace58e6a90f5a8a7e595bdd79dfda5c92d16b7f

lib/symphony/metronome/scheduledevent.rb

@@ -0,0 +1,174 @@
+#!/usr/bin/env ruby
+# vim: set nosta noet ts=4 sw=4:
+
+require 'set'
+require 'sequel'
+require 'sqlite3'
+require 'yajl'
+require 'symphony/metronome'
+
+Sequel.extension :migration
+
+
+### A class the represents the relationship between an interval and
+### an event.
+###
+class Symphony::Metronome::ScheduledEvent
+	extend Loggability, Configurability
+	include Comparable
+
+	log_to :symphony
+	config_key :metronome
+
+
+	# Configure defaults.
+	#
+	CONFIG_DEFAULTS = {
+		db: 'sqlite:///tmp/metronome.db',
+		splay: 0
+	}
+
+	class << self
+		# A Sequel-style DB connection URI.
+		attr_reader :db
+
+		# Adjust recurring intervals by a random window.
+		attr_reader :splay
+	end
+
+
+	######################################################################
+	# C L A S S  M E T H O D S
+	######################################################################
+
+	### Configurability API.
+	###
+	def self::configure( config=nil )
+		config = self.defaults.merge( config || {} )
+		@db    = Sequel.connect( config.delete(:db) )
+		@splay = config.delete( :splay )
+
+		# Ensure the database is current.
+		#
+		migrations_dir = Symphony::Metronome::DATADIR + 'migrations'
+		unless Sequel::Migrator.is_current?( self.db, migrations_dir.to_s )
+			Sequel::Migrator.apply( self.db, migrations_dir.to_s )
+		end
+	end
+
+
+	### Return a set of all known events, sorted by date of execution.
+	### Delete any rows that are invalid expressions.
+	###
+	def self::load
+		now    = Time.now
+		events = SortedSet.new
+
+		# Force reset the DB handle.
+		self.db.disconnect
+
+		self.log.debug "Parsing/loading all actions."
+		self.db[ :metronome ].each do |event|
+			begin
+				event = new( event )
+				events << event
+			rescue ArgumentError, Symphony::Metronome::TimeParseError => err
+				self.log.error "%p while parsing \"%s\": %s" % [
+					err.class,
+					event[:expression],
+					err.message
+				]
+				self.log.debug "  " + err.backtrace.join( "\n  " )
+				self.db[ :metronome ].filter( :id => event[:id] ).delete
+			end
+		end
+
+		return events
+	end
+
+
+	######################################################################
+	# I N S T A N C E  M E T H O D S
+	######################################################################
+
+	### Create a new ScheduledEvent object.
+	###
+	def initialize( row )
+		@event    = Symphony::Metronome::IntervalExpression.parse( row[:expression], row[:created] )
+		@options  = row.delete( :options )
+		@id       = row.delete( :id )
+		self.reset_runtime
+
+		unless self.class.splay.zero?
+			splay = Range.new( - self.class.splay, self.class.splay )
+			@runtime = self.runtime + rand( splay )
+		end
+	end
+
+	# The parsed interval expression.
+	attr_reader :event
+
+	# The unique ID number of the scheduled event.
+	attr_reader :id
+
+	# The options hash attached to this event.
+	attr_reader :options
+
+	# The exact time that this event will run.
+	attr_reader :runtime
+
+
+	### Set the datetime that this event should fire next.
+	###
+	def reset_runtime
+		now = Time.now
+
+		# Start time is in the future, so it's sufficent to be considered the run time.
+		#
+		if self.event.starting >= now
+			@runtime = self.event.starting
+			return
+		end
+
+		# Otherwise, the event should already be running (start time has already
+		# elapsed), so schedule it forward on it's next interval iteration.
+		#
+		@runtime = now + self.event.interval
+	end
+
+
+	### Perform the action attached to the event.  Yields the
+	### deserialized options, the action ID to the supplied block if
+	### this event is okay to execute.
+	###
+	### Automatically remove the event if it has expired.
+	###
+	def fire
+		rv = self.event.fire?
+
+		if rv
+			opts = Yajl.load( self.options )
+			yield opts, self.id
+		end
+
+		self.delete if rv.nil?
+		return rv
+	end
+
+
+	### Permanently remove this event from the database.
+	###
+	def delete
+		self.log.debug "Removing action %p" % [ self.id ]
+		self.class.db[ :metronome ].filter( :id => self.id ).delete
+	end
+
+
+	### Comparable interface, order by next run time, soonest first.
+	###
+	def <=>( other )
+		return self.runtime <=> other.runtime
+	end
+
+end # Symphony::Metronome::ScheduledEvent
+