~bzr-pqm/bzr/bzr.dev

#! /usr/bin/python

# Copyright (C) 2005 Canonical Ltd

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

# Author: Martin Pool <mbp@canonical.com>

"""Weave - storage of related text file versions"""

# XXX: If we do weaves this way, will a merge still behave the same

# way if it's done in a different order?  That's a pretty desirable

# property.

# TODO: Nothing here so far assumes the lines are really \n newlines,

# rather than being split up in some other way.  We could accomodate

# binaries, perhaps by naively splitting on \n or perhaps using

# something like a rolling checksum.

# TODO: End marker for each version so we can stop reading?

# TODO: Check that no insertion occurs inside a deletion that was

# active in the version of the insertion.

# TODO: In addition to the SHA-1 check, perhaps have some code that

# checks structural constraints of the weave: ie that insertions are

# properly nested, that there is no text outside of an insertion, that

# insertions or deletions are not repeated, etc.

# TODO: Parallel-extract that passes back each line along with a

# description of which revisions include it.  Nice for checking all

# shas or calculating stats in parallel.

# TODO: Using a single _extract routine and then processing the output

# is probably inefficient.  It's simple enough that we can afford to

# have slight specializations for different ways its used: annotate,

# basis for add, get, etc.

# TODO: Perhaps the API should work only in names to hide the integer

# indexes from the user?

# TODO: Is there any potential performance win by having an add()

# variant that is passed a pre-cooked version of the single basis

# version?

# TODO: Have a way to go back and insert a revision V1 that is a parent 

# of an already-stored revision V2.  This means some lines previously 

# counted as new in V2 will be discovered to have actually come from V1.  

# It is probably necessary to insert V1, then compute a whole new diff 

# from the mashed ancestors to V2.  This must be repeated for every 

# direct child of V1.  The deltas from V2 to its descendents won't change,

# although their location within the weave may change.  It may be possible

# to just adjust the location of those instructions rather than 

# re-weaving the whole thing.  This is expected to be a fairly rare

# operation, only used when inserting data that was previously a ghost.

import sha

from difflib import SequenceMatcher

class WeaveError(Exception):

    """Exception in processing weave"""

class WeaveFormatError(WeaveError):

    """Weave invariant violated"""

class Weave(object):

    """weave - versioned text file storage.

    A Weave manages versions of line-based text files, keeping track

    of the originating version for each line.

    To clients the "lines" of the file are represented as a list of strings.

    These strings  will typically have terminal newline characters, but

    this is not required.  In particular files commonly do not have a newline

    at the end of the file.

    Texts can be identified in either of two ways:

    * a nonnegative index number.

    * a version-id string.

    Typically the index number will be valid only inside this weave and

    the version-id is used to reference it in the larger world.

    The weave is represented as a list mixing edit instructions and

    literal text.  Each entry in _weave can be either a string (or

    unicode), or a tuple.  If a string, it means that the given line

    should be output in the currently active revisions.

    If a tuple, it gives a processing instruction saying in which

    revisions the enclosed lines are active.  The tuple has the form

    (instruction, version).

    The instruction can be '{' or '}' for an insertion block, and '['

    and ']' for a deletion block respectively.  The version is the

    integer version index.  There is no replace operator, only deletes

    and inserts.  For '}', the end of an insertion, there is no

    version parameter because it always closes the most recently

    opened insertion.

    Constraints/notes:

    * A later version can delete lines that were introduced by any

      number of ancestor versions; this implies that deletion

      instructions can span insertion blocks without regard to the

      insertion block's nesting.

    * Similarly, deletions need not be properly nested with regard to

      each other, because they might have been generated by

      independent revisions.

    * Insertions are always made by inserting a new bracketed block

      into a single point in the previous weave.  This implies they

      can nest but not overlap, and the nesting must always have later

      insertions on the inside.

    * It doesn't seem very useful to have an active insertion

      inside an inactive insertion, but it might happen.

    * Therefore, all instructions are always"considered"; that

      is passed onto and off the stack.  An outer inactive block

      doesn't disable an inner block.

    * Lines are enabled if the most recent enclosing insertion is

      active and none of the enclosing deletions are active.

    * There is no point having a deletion directly inside its own

      insertion; you might as well just not write it.  And there

      should be no way to get an earlier version deleting a later

      version.

    _weave

        Text of the weave; list of control instruction tuples and strings.

    _parents

        List of parents, indexed by version number.

        It is only necessary to store the minimal set of parents for

        each version; the parent's parents are implied.

    _sha1s

        List of hex SHA-1 of each version.

    _names

        List of symbolic names for each version.  Each should be unique.

    _name_map

        For each name, the version number.

    _weave_name

        Descriptive name of this weave; typically the filename if known.

        Set by read_weave.

    """

    __slots__ = ['_weave', '_parents', '_sha1s', '_names', '_name_map',

                 '_weave_name']

    def __init__(self, weave_name=None):

        self._weave = []

        self._parents = []

        self._sha1s = []

        self._names = []

        self._name_map = {}

        self._weave_name = weave_name

    def copy(self):

        """Return a deep copy of self.

        The copy can be modified without affecting the original weave."""

        other = Weave()

        other._weave = self._weave[:]

        other._parents = self._parents[:]

        other._sha1s = self._sha1s[:]

        other._names = self._names[:]

        other._name_map = self._name_map.copy()

        other._weave_name = self._weave_name

        return other

    def __eq__(self, other):

        if not isinstance(other, Weave):

            return False

        return self._parents == other._parents \

               and self._weave == other._weave \

               and self._sha1s == other._sha1s 

    def __ne__(self, other):

        return not self.__eq__(other)

    def maybe_lookup(self, name_or_index):

        """Convert possible symbolic name to index, or pass through indexes."""

        if isinstance(name_or_index, (int, long)):

            return name_or_index

        else:

            return self.lookup(name_or_index)

    def lookup(self, name):

        """Convert symbolic version name to index."""

        try:

            return self._name_map[name]

        except KeyError:

            raise WeaveError("name %r not present in weave %r" %

                             (name, self._weave_name))

    def iter_names(self):

        """Yield a list of all names in this weave."""

        return iter(self._names)

    def idx_to_name(self, version):

        return self._names[version]

    def _check_repeated_add(self, name, parents, text, sha1):

        """Check that a duplicated add is OK.

        If it is, return the (old) index; otherwise raise an exception.

        """

        idx = self.lookup(name)

        if sorted(self._parents[idx]) != sorted(parents):

            raise WeaveError("name \"%s\" already present in weave "

                             "with different parents" % name)

        if sha1 != self._sha1s[idx]:

            raise WeaveError("name \"%s\" already present in weave "

                             "with different text" % name)            

        return idx

    def add(self, name, parents, text, sha1=None):

        """Add a single text on top of the weave.

        Returns the index number of the newly added version.

        name

            Symbolic name for this version.

            (Typically the revision-id of the revision that added it.)

        parents

            List or set of direct parent version numbers.

        text

            Sequence of lines to be added in the new version.

        sha -- SHA-1 of the file, if known.  This is trusted to be

            correct if supplied.

        """

        from bzrlib.osutils import sha_strings

        assert isinstance(name, basestring)

        if sha1 is None:

            sha1 = sha_strings(text)

        if name in self._name_map:

            return self._check_repeated_add(name, parents, text, sha1)

        parents = map(self.maybe_lookup, parents)

        self._check_versions(parents)

        ## self._check_lines(text)

        new_version = len(self._parents)

        # if we abort after here the (in-memory) weave will be corrupt because only

        # some fields are updated

        self._parents.append(parents[:])

        self._sha1s.append(sha1)

        self._names.append(name)

        self._name_map[name] = new_version

        if not parents:

            # special case; adding with no parents revision; can do

            # this more quickly by just appending unconditionally.

            # even more specially, if we're adding an empty text we

            # need do nothing at all.

            if text:

                self._weave.append(('{', new_version))

                self._weave.extend(text)

                self._weave.append(('}', None))

            return new_version

        if len(parents) == 1:

            pv = list(parents)[0]

            if sha1 == self._sha1s[pv]:

                # special case: same as the single parent

                return new_version

        ancestors = self.inclusions(parents)

        l = self._weave

        # basis a list of (origin, lineno, line)

        basis_lineno = []

        basis_lines = []

        for origin, lineno, line in self._extract(ancestors):

            basis_lineno.append(lineno)

            basis_lines.append(line)

        # another small special case: a merge, producing the same text

        # as auto-merge

        if text == basis_lines:

            return new_version            

        # add a sentinal, because we can also match against the final line

        basis_lineno.append(len(self._weave))

        # XXX: which line of the weave should we really consider

        # matches the end of the file?  the current code says it's the

        # last line of the weave?

        #print 'basis_lines:', basis_lines

        #print 'new_lines:  ', lines

        s = SequenceMatcher(None, basis_lines, text)

        # offset gives the number of lines that have been inserted

        # into the weave up to the current point; if the original edit instruction

        # says to change line A then we actually change (A+offset)

        offset = 0

        for tag, i1, i2, j1, j2 in s.get_opcodes():

            # i1,i2 are given in offsets within basis_lines; we need to map them

            # back to offsets within the entire weave

            #print 'raw match', tag, i1, i2, j1, j2

            if tag == 'equal':

                continue

            i1 = basis_lineno[i1]

            i2 = basis_lineno[i2]

            assert 0 <= j1 <= j2 <= len(text)

            #print tag, i1, i2, j1, j2

            # the deletion and insertion are handled separately.

            # first delete the region.

            if i1 != i2:

                self._weave.insert(i1+offset, ('[', new_version))

                self._weave.insert(i2+offset+1, (']', new_version))

                offset += 2

            if j1 != j2:

                # there may have been a deletion spanning up to

                # i2; we want to insert after this region to make sure

                # we don't destroy ourselves

                i = i2 + offset

                self._weave[i:i] = ([('{', new_version)] 

                                    + text[j1:j2] 

                                    + [('}', None)])

                offset += 2 + (j2 - j1)

        return new_version

    def add_identical(self, old_rev_id, new_rev_id, parents):

        """Add an identical text to old_rev_id as new_rev_id."""

        old_lines = self.get(self.lookup(old_rev_id))

        self.add(new_rev_id, parents, old_lines)

    def inclusions(self, versions):

        """Return set of all ancestors of given version(s)."""

        i = set(versions)

        for v in xrange(max(versions), 0, -1):

            if v in i:

                # include all its parents

                i.update(self._parents[v])

        return i

        ## except IndexError:

        ##     raise ValueError("version %d not present in weave" % v)

    def parents(self, version):

        return self._parents[version]

    def minimal_parents(self, version):

        """Find the minimal set of parents for the version."""

        included = self._parents[version]

        if not included:

            return []

        li = list(included)

        li.sort(reverse=True)

        mininc = []

        gotit = set()

        for pv in li:

            if pv not in gotit:

                mininc.append(pv)

                gotit.update(self.inclusions(pv))

        assert mininc[0] >= 0

        assert mininc[-1] < version

        return mininc

    def _check_lines(self, text):

        if not isinstance(text, list):

            raise ValueError("text should be a list, not %s" % type(text))

        for l in text:

            if not isinstance(l, basestring):

                raise ValueError("text line should be a string or unicode, not %s"

                                 % type(l))

    def _check_versions(self, indexes):

        """Check everything in the sequence of indexes is valid"""

        for i in indexes:

            try:

                self._parents[i]

            except IndexError:

                raise IndexError("invalid version number %r" % i)

    def annotate(self, name_or_index):

        return list(self.annotate_iter(name_or_index))

    def annotate_iter(self, name_or_index):

        """Yield list of (index-id, line) pairs for the specified version.

        The index indicates when the line originated in the weave."""

        incls = [self.maybe_lookup(name_or_index)]

        for origin, lineno, text in self._extract(incls):

            yield origin, text

    def _walk(self):

        """Walk the weave.

        Yields sequence of

        (lineno, insert, deletes, text)

        for each literal line.

        """

        istack = []

        dset = set()

        lineno = 0         # line of weave, 0-based

        for l in self._weave:

            if isinstance(l, tuple):

                c, v = l

                isactive = None

                if c == '{':

                    istack.append(v)

                elif c == '}':

                    istack.pop()

                elif c == '[':

                    assert v not in dset

                    dset.add(v)

                elif c == ']':

                    dset.remove(v)

                else:

                    raise WeaveFormatError('unexpected instruction %r'

                                           % v)

            else:

                assert isinstance(l, basestring)

                assert istack

                yield lineno, istack[-1], dset, l

            lineno += 1

    def _extract(self, versions):

        """Yield annotation of lines in included set.

        Yields a sequence of tuples (origin, lineno, text), where

        origin is the origin version, lineno the index in the weave,

        and text the text of the line.

        The set typically but not necessarily corresponds to a version.

        """

        for i in versions:

            if not isinstance(i, int):

                raise ValueError(i)

        included = self.inclusions(versions)

        istack = []

        dset = set()

        lineno = 0         # line of weave, 0-based

        isactive = None

        result = []

        WFE = WeaveFormatError

        for l in self._weave:

            if isinstance(l, tuple):

                c, v = l

                isactive = None

                if c == '{':

                    assert v not in istack

                    istack.append(v)

                elif c == '}':

                    istack.pop()

                elif c == '[':

                    if v in included:

                        assert v not in dset

                        dset.add(v)

                else:

                    assert c == ']'

                    if v in included:

                        assert v in dset

                        dset.remove(v)

            else:

                assert isinstance(l, basestring)

                if isactive is None:

                    isactive = (not dset) and istack and (istack[-1] in included)

                if isactive:

                    result.append((istack[-1], lineno, l))

            lineno += 1

        if istack:

            raise WFE("unclosed insertion blocks at end of weave",

                                   istack)

        if dset:

            raise WFE("unclosed deletion blocks at end of weave",

                                   dset)

        return result

    def get_iter(self, name_or_index):

        """Yield lines for the specified version."""

        incls = [self.maybe_lookup(name_or_index)]

        for origin, lineno, line in self._extract(incls):

            yield line

    def get_text(self, name_or_index):

        return ''.join(self.get_iter(name_or_index))

        assert isinstance(version, int)

    def get_lines(self, name_or_index):

        return list(self.get_iter(name_or_index))

    get = get_lines

    def mash_iter(self, included):

        """Return composed version of multiple included versions."""

        included = map(self.maybe_lookup, included)

        for origin, lineno, text in self._extract(included):

            yield text

    def dump(self, to_file):

        from pprint import pprint

        print >>to_file, "Weave._weave = ",

        pprint(self._weave, to_file)

        print >>to_file, "Weave._parents = ",

        pprint(self._parents, to_file)

    def numversions(self):

        l = len(self._parents)

        assert l == len(self._sha1s)

        return l

    def __len__(self):

        return self.numversions()

    def check(self, progress_bar=None):

        # check no circular inclusions

        for version in range(self.numversions()):

            inclusions = list(self._parents[version])

            if inclusions:

                inclusions.sort()

                if inclusions[-1] >= version:

                    raise WeaveFormatError("invalid included version %d for index %d"

                                           % (inclusions[-1], version))

        # try extracting all versions; this is a bit slow and parallel

        # extraction could be used

        nv = self.numversions()

        for version in range(nv):

            if progress_bar:

                progress_bar.update('checking text', version, nv)

            s = sha.new()

            for l in self.get_iter(version):

                s.update(l)

            hd = s.hexdigest()

            expected = self._sha1s[version]

            if hd != expected:

                raise WeaveError("mismatched sha1 for version %d; "

                                 "got %s, expected %s"

                                 % (version, hd, expected))

        # TODO: check insertions are properly nested, that there are

        # no lines outside of insertion blocks, that deletions are

        # properly paired, etc.

    def merge(self, merge_versions):

        """Automerge and mark conflicts between versions.

        This returns a sequence, each entry describing alternatives

        for a chunk of the file.  Each of the alternatives is given as

        a list of lines.

        If there is a chunk of the file where there's no diagreement,

        only one alternative is given.

        """

        # approach: find the included versions common to all the

        # merged versions

        raise NotImplementedError()

    def _delta(self, included, lines):

        """Return changes from basis to new revision.

        The old text for comparison is the union of included revisions.

        This is used in inserting a new text.

        Delta is returned as a sequence of

        (weave1, weave2, newlines).

        This indicates that weave1:weave2 of the old weave should be

        replaced by the sequence of lines in newlines.  Note that

        these line numbers are positions in the total weave and don't

        correspond to the lines in any extracted version, or even the

        extracted union of included versions.

        If line1=line2, this is a pure insert; if newlines=[] this is a

        pure delete.  (Similar to difflib.)

        """

        raise NotImplementedError()

    def plan_merge(self, ver_a, ver_b):

        """Return pseudo-annotation indicating how the two versions merge.

        This is computed between versions a and b and their common

        base.

        Weave lines present in none of them are skipped entirely.

        """

        inc_a = self.inclusions([ver_a])

        inc_b = self.inclusions([ver_b])

        inc_c = inc_a & inc_b

        for lineno, insert, deleteset, line in self._walk():

            if deleteset & inc_c:

                # killed in parent; can't be in either a or b

                # not relevant to our work

                yield 'killed-base', line

            elif insert in inc_c:

                # was inserted in base

                killed_a = bool(deleteset & inc_a)

                killed_b = bool(deleteset & inc_b)

                if killed_a and killed_b:

                    yield 'killed-both', line

                elif killed_a:

                    yield 'killed-a', line

                elif killed_b:

                    yield 'killed-b', line

                else:

                    yield 'unchanged', line

            elif insert in inc_a:

                if deleteset & inc_a:

                    yield 'ghost-a', line

                else:

                    # new in A; not in B

                    yield 'new-a', line

            elif insert in inc_b:

                if deleteset & inc_b:

                    yield 'ghost-b', line

                else:

                    yield 'new-b', line

            else:

                # not in either revision

                yield 'irrelevant', line

        yield 'unchanged', ''           # terminator

    def weave_merge(self, plan):

        lines_a = []

        lines_b = []

        ch_a = ch_b = False

        for state, line in plan:

            if state == 'unchanged' or state == 'killed-both':

                # resync and flush queued conflicts changes if any

                if not lines_a and not lines_b:

                    pass

                elif ch_a and not ch_b:

                    # one-sided change:                    

                    for l in lines_a: yield l

                elif ch_b and not ch_a:

                    for l in lines_b: yield l

                elif lines_a == lines_b:

                    for l in lines_a: yield l

                else:

                    yield '<<<<\n'

                    for l in lines_a: yield l