# repoview.py - Filtered view of a localrepo object

#

# Copyright 2012 Pierre-Yves David <pierre-yves.david@ens-lyon.org>

#                Logilab SA        <contact@logilab.fr>

#

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

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

import copy

import phases

import util

def computehidden(repo):

    """compute the set of hidden revision to filter

    During most operation hidden should be filtered."""

    assert not repo.changelog.filteredrevs

    if repo.obsstore:

        ### hide extinct changeset that are not accessible by any mean

        return frozenset(repo.revs(hiddenquery))

    return frozenset()

def computeunserved(repo):

    """compute the set of revision that should be filtered when used a server

    Secret and hidden changeset should not pretend to be here."""

    assert not repo.changelog.filteredrevs

    # fast path in simple case to avoid impact of non optimised code

    if phases.hassecret(repo) or repo.obsstore:

        return frozenset(repo.revs('hidden() + secret()'))

    return frozenset()

def computemutable(repo):

    """compute the set of revision that should be filtered when used a server

    Secret and hidden changeset should not pretend to be here."""

    assert not repo.changelog.filteredrevs

    # fast check to avoid revset call on huge repo

    if util.any(repo._phasecache.phaseroots[1:]):

        return frozenset(repo.revs('draft() + secret()'))

    return frozenset()

def computeimpactable(repo):

    """Everything impactable by mutable revision

    The mutable filter still have some chance to get invalidated. This will

    happen when:

    - you garbage collect hidden changeset,

    - public phase is moved backward,

    - something is changed in the filtering (this could be fixed)

    This filter out any mutable changeset and any public changeset that may be

    impacted by something happening to a mutable revision.

    This is achieved by filtered everything with a revision number egal or

    higher than the first mutable changeset is filtered."""

    assert not repo.changelog.filteredrevs

    cl = repo.changelog

    firstmutable = len(cl)

    for roots in repo._phasecache.phaseroots[1:]:

        if roots:

            firstmutable = min(firstmutable, min(cl.rev(r) for r in roots))

    return frozenset(xrange(firstmutable, len(cl)))

# function to compute filtered set

filtertable = {'hidden': computehidden,

               'unserved': computeunserved,

               'mutable':  computemutable,

               'impactable':  computeimpactable}

### Nearest subset relation

# Nearest subset of filter X is a filter Y so that:

# * Y is included in X,

# * X - Y is as small as possible.

# This create and ordering used for branchmap purpose.

# the ordering may be partial

subsettable = {None: 'hidden',

               'hidden': 'unserved',

               'unserved': 'mutable',

               'mutable': 'impactable'}

def filteredrevs(repo, filtername):

    """returns set of filtered revision for this filter name"""

    if filtername not in repo.filteredrevcache:

        func = filtertable[filtername]

        repo.filteredrevcache[filtername] = func(repo.unfiltered())

    return repo.filteredrevcache[filtername]

class repoview(object):

    """Provide a read/write view of a repo through a filtered changelog

    This object is used to access a filtered version of a repository without

    altering the original repository object itself. We can not alter the

    original object for two main reasons:

    - It prevents the use of a repo with multiple filters at the same time. In

      particular when multiple threads are involved.

    - It makes scope of the filtering harder to control.

    This object behaves very closely to the original repository. All attribute

    operations are done on the original repository:

    - An access to `repoview.someattr` actually returns `repo.someattr`,

    - A write to `repoview.someattr` actually sets value of `repo.someattr`,

    - A deletion of `repoview.someattr` actually drops `someattr`

      from `repo.__dict__`.

    The only exception is the `changelog` property. It is overridden to return

    a (surface) copy of `repo.changelog` with some revisions filtered. The

    `filtername` attribute of the view control the revisions that need to be

    filtered.  (the fact the changelog is copied is an implementation detail).

    Unlike attributes, this object intercepts all method calls. This means that

    all methods are run on the `repoview` object with the filtered `changelog`

    property. For this purpose the simple `repoview` class must be mixed with

    the actual class of the repository. This ensures that the resulting

    `repoview` object have the very same methods than the repo object. This

    leads to the property below.

        repoview.method() --> repo.__class__.method(repoview)

    The inheritance has to be done dynamically because `repo` can be of any

    subclasses of `localrepo`. Eg: `bundlerepo` or `httprepo`.

    """

    def __init__(self, repo, filtername):

        object.__setattr__(self, '_unfilteredrepo', repo)

        object.__setattr__(self, 'filtername', filtername)

    # not a cacheproperty on purpose we shall implement a proper cache later

    @property

    def changelog(self):

        """return a filtered version of the changeset

        this changelog must not be used for writing"""

        # some cache may be implemented later

        cl = copy.copy(self._unfilteredrepo.changelog)

        cl.filteredrevs = filteredrevs(self._unfilteredrepo, self.filtername)

        return cl

    def unfiltered(self):

        """Return an unfiltered version of a repo"""

        return self._unfilteredrepo

    def filtered(self, name):

        """Return a filtered version of a repository"""

        if name == self.filtername:

            return self

        return self.unfiltered().filtered(name)

    # everything access are forwarded to the proxied repo

    def __getattr__(self, attr):

        return getattr(self._unfilteredrepo, attr)

    def __setattr__(self, attr, value):

        return setattr(self._unfilteredrepo, attr, value)

    def __delattr__(self, attr):

        return delattr(self._unfilteredrepo, attr)

    # The `requirement` attribut is initialiazed during __init__. But

    # __getattr__ won't be called as it also exists on the class. We need

    # explicit forwarding to main repo here

    @property

    def requirements(self):

        return self._unfilteredrepo.requirements