# Copyright 2005, John H. Aughey (jha@aughey.com)

# Permission to use, copy, modify, and distribute this software for 
# any purpose and without fee is hereby granted, provided that the above
# copyright notice appear in all copies.

# THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR
# IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
#-----------------------------------------------------------------------------

require 'sketchup.rb'

class Cleanup
	#-----------------------------------------------------------------------------
	# First check to see if we have already loaded this file so that we only 
	# add the item to the menu once
	if( not file_loaded?("cleanup_model.rb") )
	
	    # This will add a separator to the menu, but only once
	    add_separator_to_menu("Edit")
	    
	    # To add an item to a menu, you identify the menu, and then
	    # provide a title to display and a block to execute.  In this case,
	    # the block just calls the create_box function
	    UI.menu("Edit").add_item("Remove Unused Edges") { Cleanup.cleanup_model }
	end
	
	
	# This script cleans up unneeded edges from a model.
	# An unneeded edge is either an edge that doesn't form a face, or
	# and edge that can be removed and not effect any existing face.
	def self.cleanup_model
	    model = Sketchup.active_model
	    model.start_operation "Cleanup Operation"
	    
	    entities = model.active_entities
	
		# Store all of the edges to delete in a separate container to be deleted
		# after we have found all unneeded edges.
		todelete = []
		entities.each do |entity|
			todelete.push entity if entity.kind_of?(Sketchup::Edge) and edge_can_be_removed?(entity)
		end

		# Erase everything in our todelete list
		entities.erase_entities todelete
		 
	    # Now we are done and we can end the operation
	    model.commit_operation
	end
	
	
	private
	def self.edge_can_be_removed?(edge)
		faces = edge.faces

		# Delete the edge if it doesn't contribute to a face
		return true if faces.length == 0;
		# If it contributes to more than one face, it can not be removed
		return false if faces.length != 2;
	
		# It must contribute to only 2 faces to be a canidate.
		# If someone can think of a situation where an edge could
		# contribute to more than 2 faces and still be a canidate
		# for removal, please let me know.
		normal0 = faces[0].normal
		normal1 = faces[1].normal
	
		dot = normal0.dot normal1
			
		# What should the tolerance be on the dot product
		# for two faces to be co-planar?

		# Check for two faces pointing in the same direction
		if dot > 0.99999
			# Check that the materials are the same
			return true if same_side_material?(faces[0],faces[1])
		end
		# Check for co-planar faces, but reversed normals
		if dot < -0.99999
			# Check that the material are the same
			return true if opposite_side_material?(faces[0],faces[1])
		end
	end
	
	def self.same_side_material?(face1,face2)
		face1.material == face2.material and face1.back_material == face2.back_material
	end
	def self.opposite_side_material?(face1,face2)
		face1.material == face2.back_material and face1.back_material == face2.material
	end

end

#-----------------------------------------------------------------------------
file_loaded("cleanup_model.rb")