# repository.py - Interfaces and base classes for repositories and peers.

#

# Copyright 2017 Gregory Szorc <gregory.szorc@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 __future__ import absolute_import

import abc

from .i18n import _

from . import (

    error,

)

class _basepeer(object):

    """Represents a "connection" to a repository.

    This is the base interface for representing a connection to a repository.

    It holds basic properties and methods applicable to all peer types.

    This is not a complete interface definition and should not be used

    outside of this module.

    """

    __metaclass__ = abc.ABCMeta

    @abc.abstractproperty

    def ui(self):

        """ui.ui instance."""

    @abc.abstractmethod

    def url(self):

        """Returns a URL string representing this peer.

        Currently, implementations expose the raw URL used to construct the

        instance. It may contain credentials as part of the URL. The

        expectations of the value aren't well-defined and this could lead to

        data leakage.

        TODO audit/clean consumers and more clearly define the contents of this

        value.

        """

    @abc.abstractmethod

    def local(self):

        """Returns a local repository instance.

        If the peer represents a local repository, returns an object that

        can be used to interface with it. Otherwise returns ``None``.

        """

    @abc.abstractmethod

    def peer(self):

        """Returns an object conforming to this interface.

        Most implementations will ``return self``.

        """

    @abc.abstractmethod

    def canpush(self):

        """Returns a boolean indicating if this peer can be pushed to."""

    @abc.abstractmethod

    def close(self):

        """Close the connection to this peer.

        This is called when the peer will no longer be used. Resources

        associated with the peer should be cleaned up.

        """

class _basewirecommands(object):

    """Client-side interface for communicating over the wire protocol.

    This interface is used as a gateway to the Mercurial wire protocol.

    methods commonly call wire protocol commands of the same name.

    """

    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod

    def branchmap(self):

        """Obtain heads in named branches.

        Returns a dict mapping branch name to an iterable of nodes that are

        heads on that branch.

        """

    @abc.abstractmethod

    def capabilities(self):

        """Obtain capabilities of the peer.

        Returns a set of string capabilities.

        """

    @abc.abstractmethod

    def debugwireargs(self, one, two, three=None, four=None, five=None):

        """Used to facilitate debugging of arguments passed over the wire."""

    @abc.abstractmethod

    def getbundle(self, source, **kwargs):

        """Obtain remote repository data as a bundle.

        This command is how the bulk of repository data is transferred from

        the peer to the local repository

        Returns a generator of bundle data.

        """

    @abc.abstractmethod

    def heads(self):

        """Determine all known head revisions in the peer.

        Returns an iterable of binary nodes.

        """

    @abc.abstractmethod

    def known(self, nodes):

        """Determine whether multiple nodes are known.

        Accepts an iterable of nodes whose presence to check for.

        Returns an iterable of booleans indicating of the corresponding node

        at that index is known to the peer.

        """

    @abc.abstractmethod

    def listkeys(self, namespace):

        """Obtain all keys in a pushkey namespace.

        Returns an iterable of key names.

        """

    @abc.abstractmethod

    def lookup(self, key):

        """Resolve a value to a known revision.

        Returns a binary node of the resolved revision on success.

        """

    @abc.abstractmethod

    def pushkey(self, namespace, key, old, new):

        """Set a value using the ``pushkey`` protocol.

        Arguments correspond to the pushkey namespace and key to operate on and

        the old and new values for that key.

        Returns a string with the peer result. The value inside varies by the

        namespace.

        """

    @abc.abstractmethod

    def stream_out(self):

        """Obtain streaming clone data.

        Successful result should be a generator of data chunks.

        """

    @abc.abstractmethod

    def unbundle(self, bundle, heads, url):

        """Transfer repository data to the peer.

        This is how the bulk of data during a push is transferred.

        Returns the integer number of heads added to the peer.

        """

class _baselegacywirecommands(object):

    """Interface for implementing support for legacy wire protocol commands.

    Wire protocol commands transition to legacy status when they are no longer

    used by modern clients. To facilitate identifying which commands are

    legacy, the interfaces are split.

    """

    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod

    def between(self, pairs):

        """Obtain nodes between pairs of nodes.

        ``pairs`` is an iterable of node pairs.

        Returns an iterable of iterables of nodes corresponding to each

        requested pair.

        """

    @abc.abstractmethod

    def branches(self, nodes):

        """Obtain ancestor changesets of specific nodes back to a branch point.

        For each requested node, the peer finds the first ancestor node that is

        a DAG root or is a merge.

        Returns an iterable of iterables with the resolved values for each node.

        """

    @abc.abstractmethod

    def changegroup(self, nodes, kind):

        """Obtain a changegroup with data for descendants of specified nodes."""

    @abc.abstractmethod

    def changegroupsubset(self, bases, heads, kind):

        pass

class peer(_basepeer, _basewirecommands):

    """Unified interface and base class for peer repositories.

    All peer instances must inherit from this class and conform to its

    interface.

    """

    @abc.abstractmethod

    def iterbatch(self):

        """Obtain an object to be used for multiple method calls.

        Various operations call several methods on peer instances. If each

        method call were performed immediately and serially, this would

        require round trips to remote peers and/or would slow down execution.

        Some peers have the ability to "batch" method calls to avoid costly

        round trips or to facilitate concurrent execution.

        This method returns an object that can be used to indicate intent to

        perform batched method calls.

        The returned object is a proxy of this peer. It intercepts calls to

        batchable methods and queues them instead of performing them

        immediately. This proxy object has a ``submit`` method that will

        perform all queued batchable method calls. A ``results()`` method

        exposes the results of queued/batched method calls. It is a generator

        of results in the order they were called.

        Not all peers or wire protocol implementations may actually batch method

        calls. However, they must all support this API.

        """

    def capable(self, name):

        """Determine support for a named capability.

        Returns ``False`` if capability not supported.

        Returns ``True`` if boolean capability is supported. Returns a string

        if capability support is non-boolean.

        """

        caps = self.capabilities()

        if name in caps:

            return True

        name = '%s=' % name

        for cap in caps:

            if cap.startswith(name):

                return cap[len(name):]

        return False

    def requirecap(self, name, purpose):

        """Require a capability to be present.

        Raises a ``CapabilityError`` if the capability isn't present.

        """

        if self.capable(name):

            return

        raise error.CapabilityError(

            _('cannot %s; remote repository does not support the %r '

              'capability') % (purpose, name))

class legacypeer(peer, _baselegacywirecommands):

    """peer but with support for legacy wire protocol commands."""