# upgrade.py - functions for in place upgrade of Mercurial repository

#

# Copyright (c) 2016-present, Gregory Szorc

#

# 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 stat

import tempfile

from .i18n import _

from . import (

    changelog,

    error,

    localrepo,

    manifest,

    revlog,

    scmutil,

    util,

    vfs as vfsmod,

)

def requiredsourcerequirements(repo):

    """Obtain requirements required to be present to upgrade a repo.

    An upgrade will not be allowed if the repository doesn't have the

    requirements returned by this function.

    """

    return {

        # Introduced in Mercurial 0.9.2.

        'revlogv1',

        # Introduced in Mercurial 0.9.2.

        'store',

    }

def blocksourcerequirements(repo):

    """Obtain requirements that will prevent an upgrade from occurring.

    An upgrade cannot be performed if the source repository contains a

    requirements in the returned set.

    """

    return {

        # The upgrade code does not yet support these experimental features.

        # This is an artificial limitation.

        'manifestv2',

        'treemanifest',

        # This was a precursor to generaldelta and was never enabled by default.

        # It should (hopefully) not exist in the wild.

        'parentdelta',

        # Upgrade should operate on the actual store, not the shared link.

        'shared',

    }

def supportremovedrequirements(repo):

    """Obtain requirements that can be removed during an upgrade.

    If an upgrade were to create a repository that dropped a requirement,

    the dropped requirement must appear in the returned set for the upgrade

    to be allowed.

    """

    return set()

def supporteddestrequirements(repo):

    """Obtain requirements that upgrade supports in the destination.

    If the result of the upgrade would create requirements not in this set,

    the upgrade is disallowed.

    Extensions should monkeypatch this to add their custom requirements.

    """

    return {

        'dotencode',

        'fncache',

        'generaldelta',

        'revlogv1',

        'store',

    }

def allowednewrequirements(repo):

    """Obtain requirements that can be added to a repository during upgrade.

    This is used to disallow proposed requirements from being added when

    they weren't present before.

    We use a list of allowed requirement additions instead of a list of known

    bad additions because the whitelist approach is safer and will prevent

    future, unknown requirements from accidentally being added.

    """

    return {

        'dotencode',

        'fncache',

        'generaldelta',

    }

deficiency = 'deficiency'

optimisation = 'optimization'

class improvement(object):

    """Represents an improvement that can be made as part of an upgrade.

    The following attributes are defined on each instance:

    name

       Machine-readable string uniquely identifying this improvement. It

       will be mapped to an action later in the upgrade process.

    type

       Either ``deficiency`` or ``optimisation``. A deficiency is an obvious

       problem. An optimization is an action (sometimes optional) that

       can be taken to further improve the state of the repository.

    description

       Message intended for humans explaining the improvement in more detail,

       including the implications of it. For ``deficiency`` types, should be

       worded in the present tense. For ``optimisation`` types, should be

       worded in the future tense.

    upgrademessage

       Message intended for humans explaining what an upgrade addressing this

       issue will do. Should be worded in the future tense.

    """

    def __init__(self, name, type, description, upgrademessage):

        self.name = name

        self.type = type

        self.description = description

        self.upgrademessage = upgrademessage

    def __eq__(self, other):

        if not isinstance(other, improvement):

            # This is what python tell use to do

            return NotImplemented

        return self.name == other.name

    def __ne__(self, other):

        return not self == other

    def __hash__(self):

        return hash(self.name)

allformatvariant = []

def registerformatvariant(cls):

    allformatvariant.append(cls)

    return cls

class formatvariant(improvement):

    """an improvement subclass dedicated to repository format"""

    type = deficiency

    ### The following attributes should be defined for each class:

    # machine-readable string uniquely identifying this improvement. it will be

    # mapped to an action later in the upgrade process.

    name = None

    # message intended for humans explaining the improvement in more detail,

    # including the implications of it ``deficiency`` types, should be worded

    # in the present tense.

    description = None

    # message intended for humans explaining what an upgrade addressing this

    # issue will do. should be worded in the future tense.

    upgrademessage = None

    # value of current Mercurial default for new repository

    default = None

    def __init__(self):

        raise NotImplementedError()

    @staticmethod

    def fromrepo(repo):

        """current value of the variant in the repository"""

        raise NotImplementedError()

    @staticmethod

    def fromconfig(repo):

        """current value of the variant in the configuration"""

        raise NotImplementedError()

class requirementformatvariant(formatvariant):

    """formatvariant based on a 'requirement' name.

    Many format variant are controlled by a 'requirement'. We define a small

    subclass to factor the code.

    """

    # the requirement that control this format variant

    _requirement = None

    @staticmethod

    def _newreporequirements(repo):

        return localrepo.newreporequirements(repo)

    @classmethod

    def fromrepo(cls, repo):

        assert cls._requirement is not None

        return cls._requirement in repo.requirements

    @classmethod

    def fromconfig(cls, repo):

        assert cls._requirement is not None

        return cls._requirement in cls._newreporequirements(repo)

@registerformatvariant

class fncache(requirementformatvariant):

    name = 'fncache'

    _requirement = 'fncache'

    default = True

    description = _('long and reserved filenames may not work correctly; '

                    'repository performance is sub-optimal')

    upgrademessage = _('repository will be more resilient to storing '

                       'certain paths and performance of certain '

                       'operations should be improved')

@registerformatvariant

class dotencode(requirementformatvariant):

    name = 'dotencode'

    _requirement = 'dotencode'

    default = True

    description = _('storage of filenames beginning with a period or '

                    'space may not work correctly')

    upgrademessage = _('repository will be better able to store files '

                       'beginning with a space or period')

@registerformatvariant

class generaldelta(requirementformatvariant):

    name = 'generaldelta'

    _requirement = 'generaldelta'

    default = True

    description = _('deltas within internal storage are unable to '

                    'choose optimal revisions; repository is larger and '

                    'slower than it could be; interaction with other '

                    'repositories may require extra network and CPU '

                    'resources, making "hg push" and "hg pull" slower')

    upgrademessage = _('repository storage will be able to create '

                       'optimal deltas; new repository data will be '

                       'smaller and read times should decrease; '

                       'interacting with other repositories using this '

                       'storage model should require less network and '

                       'CPU resources, making "hg push" and "hg pull" '

                       'faster')

@registerformatvariant

class removecldeltachain(formatvariant):

    name = 'removecldeltachain'

    default = True

    description = _('changelog storage is using deltas instead of '

                    'raw entries; changelog reading and any '

                    'operation relying on changelog data are slower '

                    'than they could be')

    upgrademessage = _('changelog storage will be reformated to '

                       'store raw entries; changelog reading will be '

                       'faster; changelog size may be reduced')

    @staticmethod

    def fromrepo(repo):

        # Mercurial 4.0 changed changelogs to not use delta chains. Search for

        # changelogs with deltas.

        cl = repo.changelog

        chainbase = cl.chainbase

        return all(rev == chainbase(rev) for rev in cl)

    @staticmethod

    def fromconfig(repo):

        return True

def finddeficiencies(repo):

    """returns a list of deficiencies that the repo suffer from"""

    deficiencies = []

    # We could detect lack of revlogv1 and store here, but they were added

    # in 0.9.2 and we don't support upgrading repos without these

    # requirements, so let's not bother.

    for fv in allformatvariant:

        if not fv.fromrepo(repo):

            deficiencies.append(fv)

    return deficiencies

def findoptimizations(repo):

    """Determine optimisation that could be used during upgrade"""

    # These are unconditionally added. There is logic later that figures out

    # which ones to apply.

    optimizations = []

    optimizations.append(improvement(

        name='redeltaparent',

        type=optimisation,

        description=_('deltas within internal storage will be recalculated to '

                      'choose an optimal base revision where this was not '

                      'already done; the size of the repository may shrink and '

                      'various operations may become faster; the first time '

                      'this optimization is performed could slow down upgrade '

                      'execution considerably; subsequent invocations should '

                      'not run noticeably slower'),

        upgrademessage=_('deltas within internal storage will choose a new '

                         'base revision if needed')))

    optimizations.append(improvement(

        name='redeltamultibase',

        type=optimisation,

        description=_('deltas within internal storage will be recalculated '

                      'against multiple base revision and the smallest '

                      'difference will be used; the size of the repository may '

                      'shrink significantly when there are many merges; this '

                      'optimization will slow down execution in proportion to '

                      'the number of merges in the repository and the amount '

                      'of files in the repository; this slow down should not '

                      'be significant unless there are tens of thousands of '

                      'files and thousands of merges'),

        upgrademessage=_('deltas within internal storage will choose an '

                         'optimal delta by computing deltas against multiple '

                         'parents; may slow down execution time '

                         'significantly')))

    optimizations.append(improvement(

        name='redeltaall',

        type=optimisation,

        description=_('deltas within internal storage will always be '

                      'recalculated without reusing prior deltas; this will '

                      'likely make execution run several times slower; this '

                      'optimization is typically not needed'),

        upgrademessage=_('deltas within internal storage will be fully '

                         'recomputed; this will likely drastically slow down '

                         'execution time')))

    return optimizations

def determineactions(repo, deficiencies, sourcereqs, destreqs):

    """Determine upgrade actions that will be performed.

    Given a list of improvements as returned by ``finddeficiencies`` and

    ``findoptimizations``, determine the list of upgrade actions that

    will be performed.

    The role of this function is to filter improvements if needed, apply

    recommended optimizations from the improvements list that make sense,

    etc.

    Returns a list of action names.

    """

    newactions = []

    knownreqs = supporteddestrequirements(repo)

    for d in deficiencies:

        name = d.name

        # If the action is a requirement that doesn't show up in the

        # destination requirements, prune the action.

        if name in knownreqs and name not in destreqs:

            continue

        newactions.append(d)

    # FUTURE consider adding some optimizations here for certain transitions.

    # e.g. adding generaldelta could schedule parent redeltas.