# = Shader
#
# The equivalent of a 3d engine shader. Converts the page representation 
# to the html output. Actually converts it to a dynamic page ready for
# evaluation.
#
# === Design:
#
# We follow the xp methodology: the shader as simple as possible.
# In the future we may add mulitple xsls (xsl pipeline) but
# we done need them now, so we wont code them!
#
# - when compiling get the default shader and keep it in the
#   script structure.
#
#   noo better push them in a request stack!
#
# - when rendering:
#	if there is an override shader use it! (example: inject shader)
#	if there is a parent shader use it!
#	if there is a script shader use it!
#	if there is a user shader use it!
#	if there is an app shader use it!
#	no shading!
#
# === Think:
#
# - are inject override shaders possible ? (no they are
#   dynamic)
#
# === TODO:
#
# - add monitoring support for xsl's.
#
# code:
# George Moschovitis  <gm@navel.gr>
#
# (c) 2004 Navel, all rights reserved.
# $Id: shaders.rb 89 2004-10-20 12:55:58Z gmosx $

module N;

# = Shader
#
# One shader can utilize several xsls to render different pages.
# the shader selection may be time consuming but is performed once
# when transforming the script, so its essentially for free (and
# anyway the xsl transoformation is orders of magnitude slower)
#
# There is no need to keep post xsl. I can reuse the same xsl 
# by calling transform again. 
#
class Shader
	attr_accessor :name
	attr_accessor :xsl_filename
	# the xslt transoformer.
	attr_accessor :xslt
	attr_accessor :mtime
	
	def initialize(name, xsl_filename)
		# leave this require here. only inlcude the xslt 
		# library if the project needs it.
		require "xml/xslt"

		@name = name
		@xsl_filename = xsl_filename
		@xslt = XML::XSLT.new
		parse_xsl!
	end
	
	# transform the given document
	#
	def xsl_transform(document)
		@xslt.xml = document
		return @xslt.serve()
	end
	alias_method :transform, :xsl_transform
	
	def xsl
		parse_xsl! if $reload_xsl
		return @xsl
	end
	
	def to_s
		@name
	end
	
private 
	
	# Parse the xsl.
	#
	def parse_xsl!
		$log.debug "Parsing xsl '#{@xsl_filename}'" if $DBG
		@mtime = File.stat(@xsl_filename).mtime
		@xslt.xsl = File.read(@xsl_filename)
	end

end

# = NilShader
#
# A shader that does absolutely nothing.
#
# === WARNING: not tested.
#
class NilShader < Shader
	def initialize
		@name = "nil"
		@mtime = Time.at(0)
	end

	# No transform, just convert to a String.	
	def transform(document)
		return document.to_s
	end
end

# = ShaderManager
#
# Manages the shaders for the webapp.
#
# TODO: integrate with sitemap.
#
# === Design:
#
# - the shader selection may be time consuming but is performed once
#   when transforming the script, so its essentially for free (and
# 	anyway the xsl transoformation is orders of magnitude slower)
#
class ShaderManager
	# corresponding arrays
	attr_accessor :regex, :shaders 
	attr_accessor :default_shader

	def initialize
		@regex = []
		@shaders = []
	end

	def set_default(shader)
		@default_shader = shader
	end

	def add(regex, shader)
		@regex << regex
		@shaders << shader
	end

	def shader_for_path(path)
		@regex.each_with_index { |rx, idx|
			if path =~ rx
				return @shaders[idx]
			end
		}
		return @default_shader
	end

	def delete(regex)
		if idx = @regex.index(regex)
			@regex.delete_at(idx)
			@shaders.delete_at(idx)
		end
	end

end

end # module;