# Copyright 2007 Jay McGavren, jay@mcgavren.com.
# 
# This file is part of Zyps.
# 
# Zyps is free software; you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU Lesser General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

require 'zyps'


module Zyps


#Keeps all objects within a set of walls.
class Enclosure < EnvironmentalFactor
	
	#X coordinate of left boundary.
	attr_accessor :left
	#Y coordinate of top boundary.
	attr_accessor :top
	#X coordinate of right boundary.
	attr_accessor :right
	#Y coordinate of bottom boundary.
	attr_accessor :bottom
	
	def initialize(left = 0, top = 0, right = 0, bottom = 0)
		self.left, self.top, self.right, self.bottom = left, top, right, bottom
	end
	
	#If object is beyond a boundary, set its position equal to the boundary and reflect it.
	def act(object)
		if (object.location.x < @left) then
			object.location.x = @left
			object.vector.pitch = Utility.find_reflection_angle(90, object.vector.pitch)
		elsif (object.location.x > @right) then
			object.location.x = @right
			object.vector.pitch = Utility.find_reflection_angle(270, object.vector.pitch)
		end
		if (object.location.y > @top) then
			object.location.y = @top
			object.vector.pitch = Utility.find_reflection_angle(0, object.vector.pitch)
		elsif (object.location.y < @bottom) then
			object.location.y = @bottom
			object.vector.pitch = Utility.find_reflection_angle(180, object.vector.pitch)
		end
	end
	
end



#Keeps all objects at/under the assigned speed.
class SpeedLimit < EnvironmentalFactor
	
	#Maximum allowed speed in units.
	attr_accessor :maximum
	
	def initialize(units)
		self.maximum = units
	end
	
	#If object is over the speed, reduce its speed.
	def act(object)
		object.vector.speed = Utility.constrain_value(object.vector.speed, @maximum)
	end
	
end


#A force that pushes on all objects.
class Accelerator < EnvironmentalFactor
	
	#Vector to apply to objects.
	attr_accessor :vector
	
	def initialize(vector)
		self.vector = vector
		@clocks = {} #Don't use Hash.new <block>, as it can't transmit via DRb.
	end

	#Accelerate the target away from the actor, but limited by elapsed time.
	def act(object)
		#Track time since last action for each GameObject.
		@clocks[object] ||= Clock.new
		#Push on object.
		object.vector += Vector.new(@vector.speed * @clocks[object].elapsed_time, @vector.pitch)
	end

end

#Gravity pulls all objects downward.
class Gravity < Accelerator

	#Rate of acceleration.
	attr_accessor :force
	
	def initialize(force = 9.8)
		super(Vector.new(force, 90))
		self.force = force
	end
	
	def force= (force)
		@vector.speed = force
	end
	
end


#A force that slows all objects.
class Friction < EnvironmentalFactor
	
	#Rate of slowing.
	attr_accessor :force
	
	def initialize(force)
		self.force = force
		#Track time since last action for each GameObject.
		@clocks = {} #Don't use Hash.new <block>, as it can't transmit via DRb.
	end
	
	#Reduce the target's speed at the given rate.
	def act(object)
		#Track time since last action for each GameObject.
		@clocks[object] ||= Clock.new
		#Slow object.
		acceleration = @force * @clocks[object].elapsed_time
		speed = object.vector.speed
		if speed > 0
			speed -= acceleration 
			speed = 0 if speed < 0
		elsif speed < 0
			speed += acceleration
			speed = 0 if speed > 0
		end
		object.vector.speed = speed
	end
	
end


class PopulationLimit < EnvironmentalFactor
	
	#Environment to remove objects from.
	attr_accessor :environment
	#Maximum allowed population.
	attr_accessor :count
	
	def initialize(environment, count)
		self.environment = environment
		self.count = count
	end
	
	#Remove target if there are too many objects in environment.
	def act(object)
		if environment.objects.length > @count
			environment.objects.delete(object)
		end
	end
	
end


end #module Zyps