# vim: set nosta noet ts=4 sw=4:

require 'strscan'

require 'stringio'

#

# Chunker: A convenience library for parsing __END__ tokens consistently.

#

# == Version

#

#	$Id$

#

# == Author

#

# * Mahlon E. Smith <mahlon@martini.nu>

#

# :include: LICENSE

#

### Namespace for the datablock parser.

###

module Chunker

	# VCS Revision

	VCSRev = %q$Rev$

	# VCS Id

	VCSId = %q$Id$

	# Package version

	VERSION = '1.0.0'

	### Parser class for __END__ data blocks.

	### Find each __TOKEN__ within the __END__, and put each into a

	### DATA_TOKEN constant within the namespace that included us.

	###

	class DataParser

		# The mark for a DATA block.

		END_TOKEN = /^__END__\r?\n/

		# The mark for a 'sub' block.

		CHUNK_TOKEN = /^__([A-Z\_0-9]+)__\r?\n/

		### Constructor: Given a +klass+ and an +io+ to the class file,

		### extract the data blocks and install constants.

		###

		def initialize( klass, io )

			io.open if io.closed?

			end_string = io.read.split( END_TOKEN, 2 ).last

			@klass   = klass

			@scanner = StringScanner.new( end_string )

			io.close

			# put each chunk into its own constant

			#

			if @scanner.check_until( CHUNK_TOKEN )

				self.extract_blocks

			# no sub blocks, put the whole mess into DATA_END

			#

			else

				@klass.const_set( :DATA_END, StringIO.new( end_string ) )

			end

		end

		#########

		protected

		#########

		### Parse the current +io+ for data blocks, set contents to

		### IO constants in the including class.

		###

		def extract_blocks

			label = nil

			while @scanner.scan_until( CHUNK_TOKEN ) and ! @scanner.eos?

				data = ''

				# First pass, __END__ contents (until next token, instead

				# of entire data block.)

				#

				if label.nil?

					label = 'END'

					data  = @scanner.pre_match

					@scanner.pos = self.next_position

				else

					label = @scanner[1]

					# Pull the next token text out of the data, set up the next pass

					#

					if data = @scanner.scan_until( CHUNK_TOKEN )

						data = data[ 0, data.length - @scanner[0].length ]

						@scanner.pos = self.next_position

					# No additional blocks

					#

					else

						data = @scanner.rest

					end

				end

				# Add the IO constant to the class that included me.

				@klass.const_set( "DATA_#{label}".to_sym, StringIO.new( data ) )

			end

		end

		### Return the next scanner position for searching.

		###

		def next_position

			return @scanner.pos - @scanner[0].length

		end

	end

	### Hook included: Find the file path for how we arrived here, and open

	### it as an IO object.  Parse the IO for data block tokens.

	###

    def self.included( klass )

		# klass.instance_eval{ __FILE__ }   awww, nope.

		# __FILE__ won't work here, so we find the filename via caller().

		io = File.open( caller(1).last.sub(/:.*?$/, ''), 'r' )

		DataParser.new( klass, io )

    end

end