# peer.py - repository base classes for mercurial

#

# Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>

# Copyright 2006 Vadim Gelfer <vadim.gelfer@gmail.com>

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

from i18n import _

import error

import util

# abstract batching support

class future(object):

    '''placeholder for a value to be set later'''

    def set(self, value):

        if util.safehasattr(self, 'value'):

            raise error.RepoError("future is already set")

        self.value = value

class batcher(object):

    '''base class for batches of commands submittable in a single request

    All methods invoked on instances of this class are simply queued and

    return a a future for the result. Once you call submit(), all the queued

    calls are performed and the results set in their respective futures.

    '''

    def __init__(self):

        self.calls = []

    def __getattr__(self, name):

        def call(*args, **opts):

            resref = future()

            self.calls.append((name, args, opts, resref,))

            return resref

        return call

    def submit(self):

        pass

class localbatch(batcher):

    '''performs the queued calls directly'''

    def __init__(self, local):

        batcher.__init__(self)

        self.local = local

    def submit(self):

        for name, args, opts, resref in self.calls:

            resref.set(getattr(self.local, name)(*args, **opts))

def batchable(f):

    '''annotation for batchable methods

    Such methods must implement a coroutine as follows:

    @batchable

    def sample(self, one, two=None):

        # Handle locally computable results first:

        if not one:

            yield "a local result", None

        # Build list of encoded arguments suitable for your wire protocol:

        encargs = [('one', encode(one),), ('two', encode(two),)]

        # Create future for injection of encoded result:

        encresref = future()

        # Return encoded arguments and future:

        yield encargs, encresref

        # Assuming the future to be filled with the result from the batched

        # request now. Decode it:

        yield decode(encresref.value)

    The decorator returns a function which wraps this coroutine as a plain

    method, but adds the original method as an attribute called "batchable",

    which is used by remotebatch to split the call into separate encoding and

    decoding phases.

    '''

    def plain(*args, **opts):

        batchable = f(*args, **opts)

        encargsorres, encresref = batchable.next()

        if not encresref:

            return encargsorres # a local result in this case

        self = args[0]

        encresref.set(self._submitone(f.func_name, encargsorres))

        return batchable.next()

    setattr(plain, 'batchable', f)

    return plain

class peerrepository(object):

    def batch(self):

        return localbatch(self)

    def capable(self, name):

        '''tell whether repo supports named capability.

        return False if not supported.

        if boolean capability, return True.

        if string capability, return string.'''

        caps = self._capabilities()

        if name in caps:

            return True

        name_eq = name + '='

        for cap in caps:

            if cap.startswith(name_eq):

                return cap[len(name_eq):]

        return False

    def requirecap(self, name, purpose):

        '''raise an exception if the given capability is not present'''

        if not self.capable(name):

            raise error.CapabilityError(

                _('cannot %s; remote repository does not '

                  'support the %r capability') % (purpose, name))

    def local(self):

        '''return peer as a localrepo, or None'''

        return None

    def peer(self):

        return self

    def canpush(self):

        return True

    def close(self):

        pass