#!/usr/bin/python

# A FUSE filesystem implementation to provide a file interface for
# vsys_publickeys VSYS script. To be used by OMF Resource Controller.

# Usage: ./keys_fs.py /keys
#        ls /keys
#        cat /keys/all

# NOTE:
# Sliver has to have following ccapabilities set.
# SECURE_MOUNT
# BINARY_MOUNT


import os
import sys
import stat
import errno
import fuse
import fcntl
import select
from fuse import Fuse

fuse.fuse_python_api = (0, 2)

keys_dir = "/keys"
keys_file = os.path.join(keys_dir, "all")

def read_keys():
    fin = os.open("/vsys/publickeys.in", os.O_NONBLOCK | os.O_WRONLY)
    fout = os.open("/vsys/publickeys.out", os.O_NONBLOCK | os.O_RDONLY)
    
    in_flags = fcntl.fcntl(fin, fcntl.F_GETFL)
    out_flags = fcntl.fcntl(fin, fcntl.F_GETFL)
    
    res = select.select([fout], [], [])
    
    fcntl.fcntl(fin, fcntl.F_SETFL, in_flags & ~os.O_NONBLOCK)
    fcntl.fcntl(fout, fcntl.F_SETFL, out_flags & ~os.O_NONBLOCK)
    
    f = os.fdopen(fout, "r")
    return f.read()

class MyStat(fuse.Stat):
    def __init__(self):
        self.st_mode = 0
        self.st_ino = 0
        self.st_dev = 0
        self.st_nlink = 0
        self.st_uid = 0
        self.st_gid = 0
        self.st_size = 0
        self.st_atime = 0
        self.st_mtime = 0
        self.st_ctime = 0

class KeyFS(Fuse):

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

    def getattr(self, path):
        st = MyStat()
        if path == '/':
            st.st_mode = stat.S_IFDIR | 0755
            st.st_nlink = 2
        else:
            st.st_mode = stat.S_IFREG | 0444
            st.st_nlink = 1
            st.st_size = len(read_keys())
        return st

    def readdir(self, path, offset):
        for r in  '.', '..', os.path.basename(keys_file):
            yield fuse.Direntry(r)

    def open(self, path, flags):
        accmode = os.O_RDONLY | os.O_WRONLY | os.O_RDWR
        if (flags & accmode) != os.O_RDONLY:
            return -errno.EACCES

    def read (self, path, size, offset):
        keys = read_keys()
        slen = len(keys)

        if offset < slen:
            if offset + size > slen:
                size = slen - offset
            buf = keys[offset:offset+size]
        else:
            buf = ''
        return buf



if __name__ == '__main__':
    fs = KeyFS()
    fs.multithreaded = 0
    fs.parse(values=fs, errex=1)
    try:
        if fs.fuse_args.mount_expected():
            os.chdir("/")
    except OSError:
        sys.stderr.write("can't enter root of underlying filesystem\n")
        sys.exit(1)

    fs.main()