#!/usr/bin/ruby1.8
#
#  yunta83@gmail.com
#  BSD license
#


require 'rubygems'
require 'rfuse_ng'
require 'narray'

class Stat
	attr_accessor :uid,:gid,:mode,:size,:atime,:mtime,:ctime,:dev,:ino,:nlink,:rdev,:blksize,:blocks
	def initialize(mode=0,size=0)
		@mode,@size,@uid,@gid,@atime,@mtime,@ctime,@dev,@ino,@nlink,@rdev,@blksize,@blocks = [mode,size]+[0]*11
	end
end


class E2fsFsFs < RFuse::Fuse

	def initialize(mnt,kernelopt,libopt,dev)
		dump = `dumpe2fs '#{dev}' 2>/dev/null`
		dump =~ /^Block size:\s+([0-9]+)/m
		@blockSize = $1.to_i
		dump =~ /^Free blocks: (.*)/
		freeBlocks = $1.to_i
		ranges = []
		dump.scan(/^  Free blocks: (.*)/) { 
			ranges += $1.split(",").collect { |range|
				range = range.split("-").collect{ |x| x.to_i }
				range << range[0] if range.size == 1
				range
			}
		}
		@size = ranges.collect { |a,b| b-a }.inject(0) { |a,b| a+b } * @blockSize
		@map = NArray.int(freeBlocks)
		@sizes = NArray.int(freeBlocks)
		first = last = 0
		ranges.sort.reverse.each { |a,b|
			last = first + b - a + 1
			@map[first..last-1] = NArray[a..b]
			@sizes[first..last-1] = NArray[(b-a+1)..1]
			first = last
		}
		@device = File.new(dev,"r+")
		super(mnt,kernelopt,libopt)
	end

	def readdir(ctx,path,filler,offset,ffi)
		return if offset > 0
		filler.push("data",Stat.new(0100777),0)
	end

	def getattr(ctx,path)
		raise Errno::ENOTDIR.new(path) if path != "/" and path != "/data"
		Stat.new((path == "/" and 040777 or 0100777),(path == "/" and 0 or @size))
	end


	def open(ctx,path,ffi)
	end

	def read(ctx,path,size,offset,fi)
#		STDERR.write("READ: size %i offset %i\n"%[size,offset])
		out = []
		transfer(size,offset) { |physicalAddress,toRead|
#			STDERR.write("reading %i from %i\n"%[toRead,physicalAddress])
			@device.seek(physicalAddress)
			out << @device.read(toRead)
		}
		out.join("")
	end

	def write(ctx,path,buf,offset,fi)
		last = 0
		transfer(buf.size,offset) { |physicalAddress,toWrite|
#			STDERR.write("writing %i to %i\n"%[toWrite,physicalAddress])
			@device.seek(physicalAddress)
			@device.write(buf[last..(last+toWrite-1)])
			last += toWrite
		}
		return buf.length
	end

private

	def transfer(size,offset)

		logicalBlock = offset / @blockSize
		initialOffset = offset % @blockSize
		physicalAddress = @map[logicalBlock]*@blockSize+initialOffset
		transferSize = [size,@sizes[logicalBlock]*@blockSize-initialOffset].min
		
		while true
#			STDERR.write("logicalBlock %i available blocks: %i physicalBlock: %i transferBlocks: %i+%i "%[logicalBlock,@sizes[logicalBlock],@map[logicalBlock],transferSize/@blockSize,transferSize%@blockSize])
			yield physicalAddress,transferSize
			size -= transferSize
			break if size <= 0
			logicalBlock += transferSize / @blockSize
			physicalAddress = @map[logicalBlock]*@blockSize
			transferSize = [size,@sizes[logicalBlock]*@blockSize].min
		end

		raise :WTF if size < 0
	end

end

if ARGV.size != 2
	puts "2 parameters needed:"
	puts "\truby e2fsfsfs.rb DEVICE MOUNTPOINT"
	exit
end


fo = E2fsFsFs.new(ARGV[1],["default_permissions"],[],ARGV[0]);

#kernel:  default_permissions,allow_other,kernel_cache,large_read,direct_io
#         max_read=N,fsname=NAME
#library: debug,hard_remove

Signal.trap("TERM") do
	fo.exit
	fo.unmount
end

begin
	fo.loop
rescue
	print "Error:" + $!
end