#!/usr/bin/env python

#    Copyright (C) 2001  Jeff Epler  <jepler@unpythonic.dhs.org>
#    Copyright (C) 2006  Csaba Henk  <csaba.henk@creo.hu>
#    Copyright (C) 2009  Steve Slaven  <bpk@hoopajoo.net>
#
#    This program can be distributed under the terms of the GNU LGPL.
#    See the file COPYING.
#

import os, sys, shutil, fcntl, fuse, re
import tempfile, sha, pickle, gzip
from errno import *
from stat import *
from fuse import Fuse

import pdb

if not hasattr(fuse, '__version__'):
    raise RuntimeError, \
        "your fuse-py doesn't know of fuse.__version__, probably it's too old."

fuse.fuse_python_api = (0, 2)

fuse.feature_assert('stateful_files', 'has_init')

magic_blocksize = 1024 * 32
magic_depth = 5
debug_level = 4

def dmsg(level,message):
    if level <= debug_level:
        print str(level) + ": " + message

def flag2mode(flags):
    md = {os.O_RDONLY: 'r', os.O_WRONLY: 'w', os.O_RDWR: 'w+'}
    m = md[flags & (os.O_RDONLY | os.O_WRONLY | os.O_RDWR)]

    if flags | os.O_APPEND:
        m = m.replace('w', 'a', 1)

    return m

# This will write out a data block, it will return a key that can get this
# data back later
def save_chunk( chunk ):
    dmsg( 2, "Begin save_chunk" )
    # Save this hash string, similar to the backuppc algo
    digest = sha.new( str(len(chunk)) + chunk ).digest()

    # Write out our chunk
    chars = list( digest )
    dmsg( 4, chars )

    # We make the hexdigest here, yeah we could just call hexdigest()
    # but we need to essentially do this same thing to reassemble the
    # file anyway
    hexdigest = ''.join( [ "%02x" % ord( x ) for x in chars ] )

    # Subparts just needs the first N chars
    subparts = [ "%02x" % ord( x ) for x in chars[ :magic_depth ] ]

    dmsg( 4, subparts )
    subpath = '/'.join( subparts )
    dmsg( 3, "Subpath: " + subpath )

    # Make sure this sub path exists
    nextpart = "./storage"
    for part in subparts:
        nextpart += "/" + part
        if not os.path.exists( nextpart ):
            dmsg( 3, "Creating subdir: " + nextpart )
            os.mkdir( nextpart )

    # Find a chunk slot
    sub = 0
    while True:
        checkpath = "./storage/" + subpath + "/" + hexdigest + "_" + str( sub )
        dmsg( 3, "Checking: " + checkpath )
        if os.path.exists( checkpath ):
            # Check if this is our data
            verify = gzip.open( checkpath, "r" )
            verify_contents = verify.read()
            verify.close()

            if verify_contents == chunk:
                dmsg( 3, "Found existing block" )
                break
            else:
                dmsg( 3, "Block exists but is not the same" )
                sub += 1
        else:
            # We found a spot, dump our data here
            dmsg( 3, "No block here, creating new block" )
            savechunk = gzip.open( checkpath, "w" )
            savechunk.write( chunk )
            savechunk.close
            break

    dmsg( 3, "Got chunk slot: " + str( sub ) )
    return( [ digest, sub ] )

# This will return a data block by key that was saved previously
def load_chunk( key ):
    ( hash, seq ) = key
    dmsg( 2, "Begin load_chunk" )

    chars = list( hash )
    dmsg( 4, chars )

    # Todo: make a digest -> path function to share with deflate
    hexdigest = ''.join( [ "%02x" % ord( x ) for x in chars ] )
    dmsg( 3, "Hash is: " + hash + " sub " + seq )
    subparts = [ "%02x" % ord( x ) for x in chars[ :magic_depth ] ]
    subpath = '/'.join( subparts )
    dmsg( 3, "Subpath: " + subpath )

    subpath += "/" + hexdigest + "_" + str( seq )

    dmsg( 3, "Chunk path: " + subpath )

    if os.path.exists( "./storage/" + subpath ):
        dmsg( 3, "Exporting chunk" )
        readchunk = gzip.open( "./storage/" + subpath )
        chunk = readchunk.read()
        readchunk.close()
    else:
        raise IOError

    return chunk

# Inflate a file, src is a packed file, dest is where the unpacked file
# should go
# we assume our chunks are in storage/
def inflate( src, dest ):
    dmsg( 1, "inflate!" )

    out = open( dest, "w" )

    dmsg( 3, "Unpickling: " + src )
    # TODO: return an IO error if inflating fails
    inp = gzip.open( src, "r" )
    magic = pickle.load( inp )
    inp.close()
    dmsg( 3, "Got data: " + str( magic ) )

    #pdb.set_trace()

    # Now unserialize the chunks back in to a file
    for key in magic[ 'data' ]:
        out.write( load_chunk( key ) )

    dmsg( 2, "File inflated" )
    out.close()

# TODO: deflate only if the file has been modified

# Deflate a file, src is the unpacked file, dest is where we want to pack
# to, and we assume storage/ is where chunks are stored
def deflate( src, dest ):
    dmsg( 2, "deflate!" )
    inp = open( src, "r" )

    hashs = []
    # This is retarded:
    # http://groups.google.com/group/comp.lang.python/browse_thread/thread/ed25388487b3ac7b
    #
    # Why can't I just do:
    # while( chunk = inp.read( magic_blocksize ) ):
    # I though python was supposed to be easier! :(

    while True:
        chunk = inp.read( magic_blocksize )
        if len( chunk ) == 0:
            break

        key = save_chunk( chunk )
        hashs.append( key )

    inp.close()

    out = gzip.open( dest, "w" )
    pickle.dump( {
        'stat': os.stat( src ),
        'data': hashs
    }, out )
    out.close()

class FuseArchiveStat(fuse.Stat):
    def __init__(self, stat):
        self.st_mode = stat.st_mode
        self.st_ino = stat.st_ino
        self.st_dev = stat.st_dev
        self.st_rdev = stat.st_rdev
        self.st_nlink = stat.st_nlink
        self.st_uid = stat.st_uid
        self.st_gid = stat.st_gid
        self.st_size = stat.st_size
        self.st_atime = stat.st_atime
        self.st_mtime = stat.st_mtime
        self.st_ctime = stat.st_mtime
        self.st_blocks = stat.st_blocks
        self.st_blksize = stat.st_blksize

    def overstat( self, size ):
        self.st_size = size
        # Yeah we shouldn't always just add 1
        self.st_blocks = int( self.st_size / 512 ) + 1

class FuseArchive(Fuse):

    def __init__(self, *args, **kw):

        Fuse.__init__(self, *args, **kw)
        self.root = None

    # Fix getattr and fgetattr to?
    def getattr(self, path):
        treefile = "./tree" + path
        stats = os.lstat( treefile )

        if os.path.isfile( treefile ):
            dmsg( 3, "Reading file to get size: " + path )

            #pdb.set_trace()

            # Override size
            inp = gzip.open( treefile )
            magic = pickle.load( inp )
            inp.close()

            dmsg( 3, "Overridding getattr" )
            stats = FuseArchiveStat( stats )
            stats.overstat( magic[ 'size' ] )

        return stats

    def readlink(self, path):
        return os.readlink("./tree" + path)

    def readdir(self, path, offset):
        for e in os.listdir("./tree" + path):
            yield fuse.Direntry(e)

    def unlink(self, path):
        os.unlink("./tree" + path)

    def rmdir(self, path):
        os.rmdir("./tree" + path)

    def symlink(self, path, path1):
        os.symlink(path, "./tree" + path1)

    def rename(self, path, path1):
        os.rename("./tree" + path, "./tree" + path1)

    def link(self, path, path1):
        os.link("./tree" + path, "./tree" + path1)

    def chmod(self, path, mode):
        os.chmod("./tree" + path, mode)

    def chown(self, path, user, group):
        os.chown("./tree" + path, user, group)

    def truncate(self, path, len):
        # Truncate using the ftruncate on the file
        dmsg( 2, "Using FuseArchiveFile to truncate " + path + " to " + str(len) )
        f = self.FuseArchiveFile( path, os.O_APPEND, 0 )
        f.ftruncate(len)
        f.release( 0 )

    def mknod(self, path, mode, dev):
        os.mknod("./tree" + path, mode, dev)

    def mkdir(self, path, mode):
        os.mkdir("./tree" + path, mode)

    def utime(self, path, times):
        os.utime("./tree" + path, times)

#    The following utimens method would do the same as the above utime method.
#    We can't make it better though as the Python stdlib doesn't know of
#    subsecond preciseness in acces/modify times.
#  
#    def utimens(self, path, ts_acc, ts_mod):
#      os.utime("." + path, (ts_acc.tv_sec, ts_mod.tv_sec))

    def access(self, path, mode):
        if not os.access("./tree" + path, mode):
            return -EACCES

#    This is how we could add stub extended attribute handlers...
#    (We can't have ones which aptly delegate requests to the underlying fs
#    because Python lacks a standard xattr interface.)
#
#    def getxattr(self, path, name, size):
#        val = name.swapcase() + '@' + path
#        if size == 0:
#            # We are asked for size of the value.
#            return len(val)
#        return val
#
#    def listxattr(self, path, size):
#        # We use the "user" namespace to please XFS utils
#        aa = ["user." + a for a in ("foo", "bar")]
#        if size == 0:
#            # We are asked for size of the attr list, ie. joint size of attrs
#            # plus null separators.
#            return len("".join(aa)) + len(aa)
#        return aa

    def statfs(self):
        """
        Should return an object with statvfs attributes (f_bsize, f_frsize...).
        Eg., the return value of os.statvfs() is such a thing (since py 2.2).
        If you are not reusing an existing statvfs object, start with
        fuse.StatVFS(), and define the attributes.

        To provide usable information (ie., you want sensible df(1)
        output, you are suggested to specify the following attributes:

            - f_bsize - preferred size of file blocks, in bytes
            - f_frsize - fundamental size of file blcoks, in bytes
                [if you have no idea, use the same as blocksize]
            - f_blocks - total number of blocks in the filesystem
            - f_bfree - number of free blocks
            - f_files - total number of file inodes
            - f_ffree - nunber of free file inodes
        """

        return os.statvfs(".")

    def fsinit(self):
        os.chdir(self.root)

    class FuseArchiveFile(object):

        def __init__(self, path, flags, *mode):
            # Inflate the file
            dmsg( 1, "Init file: " + path )
            self.orig_path = path

            # init rw and offset
            self.offset = 0
            self.rd = False
            self.wr = False
            self.size = 0

            # This is the current in-memory chunk and offset in to data[]
            self.chunk = None
            self.chunk_index = 0
            self.chunk_modified = False
            self.chunk_size = magic_blocksize

            # The chunk table
            self.chunks = []

            # TODO: Better flag handling here?
            if flags | os.O_RDONLY:
                self.rd = True

            if flags | os.O_RDWR:
                self.rd = True
                self.wr = True

            if flags | os.O_WRONLY:
                self.wr = True

            if flags | os.O_APPEND:
                self.wr = True
                # TODO: handle offset -1
                self.offset = -1

            if os.path.exists( "./tree" + self.orig_path ):
                # Read in file info table
                src = "./tree" + self.orig_path
                dmsg( 3, "Unpickling: " + src )
                # TODO: return an IO error if inflating fails
                inp = gzip.open( src, "r" )
                magic = pickle.load( inp )
                inp.close()
                dmsg( 3, "Got data: " + str( magic ) )
                self.size = magic[ 'size' ]
                self.chunks = magic[ 'chunks' ]
                self.chunk_size = magic[ 'chunk_size' ]
            else:
                if self.wr:
                    dmsg( 2, "File doesn't exist and we're going to write, creating temp empty file" )
                    self.flush()

            self.direct_io = False
            self.keep_cache = False

            #pdb.set_trace()
            dmsg( 3, str(self) + " init complete" )

        def _load_chunk( self, index ):
            # Save this chunk if modified
            if self.chunk_modified:
                self._save_chunk()

            dmsg( 3, "Loading chunk " + str(index) )
            key = None

            try:
                key = self.chunks[ index ]
            except IndexError:
                dmsg( 3, "Index doesn't exist" )

            if key:
                dmsg( 3, "Index: " + str( key ) )
                self.chunk = load_chunk( key )
            else:
                dmsg( 3, "No chunk at this index, loading nothing" )
                self.chunk = None

            self.chunk_index = index
            self.chunk_modified = False

        def _save_chunk():
            dmsg( 3, "Saving chunk " + self.chunk_index )
            key = save_chunk( self.chunk )
            self.chunks[ index ] = key
            dmsg( 3, "Key was " + str( key ) )

        def read(self, length, offset):
            dmsg( 3, "Reading from " + self.orig_path + " offset: " + str( offset )
                + " length: " + str( length ) )

            data_read = 0
            data = None
            index = int( offset / self.chunk_size )
            rest = offset % self.chunk_size

            # Keep reading chunks until we have at least this much data
            while data_read < length:
                dmsg( 3, "Pulling chunk data" )
                self._load_chunk( index )
                chunk_remaining = self.chunk_size - rest
                data += substr( self.chunk[ rest:chunk_remaining ] )
                data_read = len( data )
                index += 1
                rest = 0

            return data[ :length ]

        def write(self, buf, offset):
            dmsg( 3, "Writing to " + self.orig_path + " offset: " + str( offset ) )

            index = int( offset / self.chunk_size )
            rest = offset % self.chunk_size

            buf_offset = 0
            buf_len = len(buf)

            dmsg( 3, "Length: " + str( buf_len ) )
            while( buf_offset < buf_len ):
                dmsg( 3, "Pulling in chunk for writing" )
                self._load_chunk( index )
                buf_remain = buf_len - buf_offset
                if rest < buf_remain:
                    dmsg( 3, "Writing " + str( rest ) + " bytes, buffer boundry" )
                else:
                    dmsg( 3, "Writing final " + str( buf_remain ) + " bytes" )

            self.chunk_modified = True
            return len(buf)

        # BUG: If you cp -a a file then quickly ls -l sometimes it doesn't show
        # up right?  like wrong size and stuff?
        # Maybe because release doesn't return a fuse message and is async?
        def release(self, flags):
            # Deflate the file
            dmsg( 2, "Release: " + self.orig_path )
            self.flush()

        def _fflush(self):
            if self.wr:
                dmsg( 3, "_fflush!" )
                # Save our main data
                out = gzip.open( "./tree" + self.orig_path, "w" )
                pickle.dump( {
                    'size': self.size,
                    'chunks': self.chunks,
                    'chunk_size': self.chunk_size
                }, out )
                out.close()

            return 1


        # Currently we treat fsync as flush since we don't keep any data
        # hanging around anyway in fh stuff
        def fsync(self, isfsyncfile):
            dmsg( 2, "fsync " + self.orig_path )
            self._fflush()
            #if isfsyncfile and hasattr(os, 'fdatasync'):
            #    os.fdatasync(self.fd)
            #else:
            #    os.fsync(self.fd)

        def flush(self):
            dmsg( 2, "flush " + self.orig_path )
            self._fflush()

        def fgetattr(self):
            print "WARNING: fgetattr is broken!!!!"
            return os.lstat( "./tree" + self.orig_path )

        def ftruncate(self, len):
            if len > 0:
                print "WARNING: ftruncate is broken!!!"

            self.chunks = []
            self._load_chunk( 0 )
            self._fflush()

        def lock(self, cmd, owner, **kw):
            dmsg( 3, "WARNING: locking unsupported" )
            return 1

            # The code here is much rather just a demonstration of the locking
            # API than something which actually was seen to be useful.

            # Advisory file locking is pretty messy in Unix, and the Python
            # interface to this doesn't make it better.
            # We can't do fcntl(2)/F_GETLK from Python in a platfrom independent
            # way. The following implementation *might* work under Linux. 
            #
            # if cmd == fcntl.F_GETLK:
            #     import struct
            # 
            #     lockdata = struct.pack('hhQQi', kw['l_type'], os.SEEK_SET,
            #                            kw['l_start'], kw['l_len'], kw['l_pid'])
            #     ld2 = fcntl.fcntl(self.fd, fcntl.F_GETLK, lockdata)
            #     flockfields = ('l_type', 'l_whence', 'l_start', 'l_len', 'l_pid')
            #     uld2 = struct.unpack('hhQQi', ld2)
            #     res = {}
            #     for i in xrange(len(uld2)):
            #          res[flockfields[i]] = uld2[i]
            #  
            #     return fuse.Flock(**res)

            # Convert fcntl-ish lock parameters to Python's weird
            # lockf(3)/flock(2) medley locking API...
            op = { fcntl.F_UNLCK : fcntl.LOCK_UN,
                   fcntl.F_RDLCK : fcntl.LOCK_SH,
                   fcntl.F_WRLCK : fcntl.LOCK_EX }[kw['l_type']]
            if cmd == fcntl.F_GETLK:
                return -EOPNOTSUPP
            elif cmd == fcntl.F_SETLK:
                if op != fcntl.LOCK_UN:
                    op |= fcntl.LOCK_NB
            elif cmd == fcntl.F_SETLKW:
                pass
            else:
                return -EINVAL

            fcntl.lockf(self.fd, op, kw['l_start'], kw['l_len'])


    def main(self, *a, **kw):

        self.file_class = self.FuseArchiveFile

        # This is where fragments go
        if not os.path.exists( 'storage' ):
            os.mkdir( 'storage' )

        # This is where the real files exist
        if not os.path.exists( 'tree' ):
            os.mkdir( 'tree' )

        return Fuse.main(self, *a, **kw)


def main():

    usage = """
Userspace nullfs-alike: mirror the filesystem tree from some point on.

""" + Fuse.fusage

    server = FuseArchive(version="%prog " + fuse.__version__,
                 usage=usage,
                 dash_s_do='setsingle')

    server.multithreaded = False

    server.parse(values=server, errex=1)

    if len(server.parser.largs) != 2:
        print "Usage: " + sys.argv[0] + " storageDirectory mountDirectory"
        sys.exit(1)

    server.root = server.parser.largs[0]

    try:
        if server.fuse_args.mount_expected():
            os.chdir(server.root)
    except OSError:
        print >> sys.stderr, "can't enter root of underlying filesystem"
        sys.exit(1)

    server.main()


if __name__ == '__main__':
    main()