#!/usr/bin/ruby

begin
	require 'zlib'
	def ckcrc(str, crc)
		Zlib.crc32(str) == crc
	end
rescue LoadError
	def ckcrc(str, crc)
		true
	end
end

class Ydec
	def initialize(fd = nil)
		@ybeginline = true
		@outfile = nil
		@outlen = nil
		@linelen = nil

		@ypartline = false
		@partoffset = nil
		@partsize = nil
		@partcrc = nil

		@curbuf = nil
		@specialchar = false

		mass_process fd if fd
	end

	def mass_process(io)
		l = nil
		io.each_line { |l|
			parse_line l
		}
	end

	# returns true if you should pass the next line
	def parse_line(l)
		l = l.chomp
		if @ybeginline
			parse_ybegin $1 if l =~ /^=ybegin\s+(.*?)\s*$/
			!@ybeginline
		elsif @ypartline
			parse_ypart  $1 if l =~ /^=ypart\s+(.*?)\s*$/
			!@ypartline
		elsif @curbuf
			if l =~ /^=yend\s+(.*?)\s*$/
				parse_yend $1
			else
				ydecode l
			end
			!!@curbuf
		end
	end

	def parse_ybegin(l)
		raise "invalid ybegin #{l.inspect}" unless l =~ /(.*) name=(.*)/
		l = $1
		@outfile = $2
		@ypartline = (l =~ /\bpart\b/)
		puts "ydec: decoding #{@outfile.inspect}#{' (part)' if @ypartline}"
		@outfile.gsub!(/[^a-zA-Z0-9_.+\-\[\]\(\)#'" ]/, '_')
		l.scan(/(\w+)=(\w+)/).each { |k, v|
			case k
			when 'line': @linelen = v.to_i
			when 'size': @outlen = v.to_i
			when 'part'
			else puts "unknown ybegin field #{k.inspect} = #{v.inspect}"
			end
		}
		@curbuf = ''
		@ybeginline = false
		true
	end
	
	def parse_ypart(l)
		l.scan(/(\w+)=(\w+)/).each { |k, v|
			case k
			when 'begin': @partoffset = v.to_i - 1
			when 'end':   @partsize = v.to_i - @partoffset
			else puts "unknown ypart field #{k.inspect} = #{v.inspect}"
			end
		}
		puts "ydec: decoding part: #@partsize o at #@partoffset" if $VERBOSE
		@curbuf = ''
		@ypartline = false
		true
	end

	def parse_yend(l)
		sz = nil
		crc = nil
		pcrc = nil
		l.scan(/(\w+)=(\w+)/).each { |k, v|
			case k
			when 'size': sz = v.to_i
			when 'crc32': crc = v[0..7].hex
			when 'pcrc32': pcrc = v[0..7].hex
			when 'part'
			else puts "unknown yend field #{k.inspect} = #{v.inspect}"
			end
		}
		puts "ydec: finished" if $VERBOSE
		if @partsize
			if pcrc and not ckcrc(@curbuf, pcrc)
				puts "bad part crc"
			end
			if sz
				if sz != @partsize
					puts "sz #{sz} != ypart sz #@partsize"
				end
				if sz != @curbuf.size
					puts "sz #{sz} != curbuf.sz #{@curbuf.size}"
				end
			end
			if @partsize and @curbuf.size != @partsize
				puts "ypart sz #@partsize != curbuf.sz #{@curbuf.size}"
			end
			File.open(@outfile, 'w') {} unless File.exist? @outfile
			File.open(@outfile, 'r+') { |fd| fd.seek @partoffset ; fd.write @curbuf }
		else
			if crc and not ckcrc(@curbuf, crc)
				puts "bad crc"
			end
			if sz
				if sz != @outlen
					puts "sz #{sz} != outlen #@outlen"
				end
				if sz != @curbuf.size
					puts "sz #{sz} != curbuf.sz #{@curbuf.size}"
				end
			end
			if @outlen != @curbuf.size
				puts "outlen #@outlen != curbuf.sz #{@curbuf.size}"
			end
			File.open(@outfile, 'w') { |fd| fd.write @curbuf }
		end
		@curbuf = nil
		@ybeginline = true
	end

	begin
		raise :pute
		require 'dl'
		LIB_YDEC = DL.dlopen('./libydec.so')['dec_yline', 'IsI']
		def ydecode(l)
			len = LIB_YDEC.call(l, l.size)
			@curbuf << l[0..len]
		end
	rescue
	def ydecode(l)
		l.each_byte { |b|
			if @specialchar
				@specialchar = false
				@curbuf << ((b - 64 - 42) & 255)
			else
				case b
				when ?=
					@specialchar = true
				when ?\n, ?\r, ?\0
					puts "special char #{b.chr.inspect} in stream..."
				else
					@curbuf << ((b - 42) & 255)
				end
			end
		}
		if @specialchar
			puts "line ends with specialchar.."
			@specialchar = false
		end
	end
	end

end

if $0 == __FILE__
Ydec.new(ARGF)
end