import sys
from uuid import UUID
from gluster import *

# Negative-lookup-caching example.  If a file wasn't there the last time we
# looked, it's probably still not there.  This translator keeps track of
# those failed lookups for us, and returns ENOENT without needing to pass the
# call any further for repeated requests.

# If we were doing this for real, we'd need separate caches for each xlator
# instance.  The easiest way to do this would be to have xlator.__init__
# "register" each instance in a module-global dict, with the key as the C
# translator address and the value as the xlator object itself.  For testing
# and teaching, it's sufficient just to have one cache.  The keys are parent
# GFIDs, and the entries are lists of names within that parent that we know
# don't exist.
cache = {}

# TBD: we need a better way of handling per-request data (frame->local in C).
dl.get_id.restype = c_long
dl.get_id.argtypes = [ POINTER(call_frame_t) ]

def uuid2str (gfid):
    return str(UUID(''.join(map("{0:02x}".format, gfid))))

class xlator (Translator):

    def __init__ (self, c_this):
        self.requests = {}
        Translator.__init__(self,c_this)

    def lookup_fop (self, frame, this, loc, xdata):
        pargfid = uuid2str(loc.contents.pargfid)
        print "lookup FOP: %s:%s" % (pargfid, loc.contents.name)
        # Check the cache.
        if cache.has_key(pargfid):
            if loc.contents.name in cache[pargfid]:
                print "short-circuiting for %s:%s" % (pargfid,
                    loc.contents.name)
                dl.unwind_lookup(frame,0,this,-1,2,None,None,None,None)
                return 0
        key = dl.get_id(frame)
        self.requests[key] = (pargfid, loc.contents.name[:])
        # TBD: get real child xl from init, pass it here
        dl.wind_lookup(frame,POINTER(xlator_t)(),loc,xdata)
        return 0

    def lookup_cbk (self, frame, cookie, this, op_ret, op_errno, inode, buf,
                    xdata, postparent):
        print "lookup CBK: %d (%d)" % (op_ret, op_errno)
        key = dl.get_id(frame)
        pargfid, name = self.requests[key]
        # Update the cache.
        if op_ret == 0:
            print "found %s, removing from cache" % name
            if cache.has_key(pargfid):
                cache[pargfid].discard(name)
        elif op_errno == 2:    # ENOENT
            print "failed to find %s, adding to cache" % name
            if cache.has_key(pargfid):
                cache[pargfid].add(name)
            else:
                cache[pargfid] = set([name])
        del self.requests[key]
        dl.unwind_lookup(frame,cookie,this,op_ret,op_errno,
                         inode,buf,xdata,postparent)
        return 0

    def create_fop (self, frame, this, loc, flags, mode, umask, fd, xdata):
        pargfid = uuid2str(loc.contents.pargfid)
        print "create FOP: %s:%s" % (pargfid, loc.contents.name)
        key = dl.get_id(frame)
        self.requests[key] = (pargfid, loc.contents.name[:])
        # TBD: get real child xl from init, pass it here
        dl.wind_create(frame,POINTER(xlator_t)(),loc,flags,mode,umask,fd,xdata)
        return 0

    def create_cbk (self, frame, cookie, this, op_ret, op_errno, fd, inode,
                    buf, preparent, postparent, xdata):
        print "create CBK: %d (%d)" % (op_ret, op_errno)
        key = dl.get_id(frame)
        pargfid, name = self.requests[key]
        # Update the cache.
        if op_ret == 0:
            print "created %s, removing from cache" % name
            if cache.has_key(pargfid):
                cache[pargfid].discard(name)
        del self.requests[key]
        dl.unwind_create(frame,cookie,this,op_ret,op_errno,fd,inode,buf,
                         preparent,postparent,xdata)
        return 0