# merge.py - directory-level update/merge handling for Mercurial

#

# Copyright 2006, 2007 Matt Mackall <mpm@selenic.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 errno

import os

import shutil

import struct

from .i18n import _

from .node import (

    bin,

    hex,

    nullhex,

    nullid,

    nullrev,

)

from . import (

    copies,

    destutil,

    error,

    filemerge,

    obsolete,

    subrepo,

    util,

    worker,

)

_pack = struct.pack

_unpack = struct.unpack

def _droponode(data):

    # used for compatibility for v1

    bits = data.split('\0')

    bits = bits[:-2] + bits[-1:]

    return '\0'.join(bits)

class mergestate(object):

    '''track 3-way merge state of individual files

    The merge state is stored on disk when needed. Two files are used: one with

    an old format (version 1), and one with a new format (version 2). Version 2

    stores a superset of the data in version 1, including new kinds of records

    in the future. For more about the new format, see the documentation for

    `_readrecordsv2`.

    Each record can contain arbitrary content, and has an associated type. This

    `type` should be a letter. If `type` is uppercase, the record is mandatory:

    versions of Mercurial that don't support it should abort. If `type` is

    lowercase, the record can be safely ignored.

    Currently known records:

    L: the node of the "local" part of the merge (hexified version)

    O: the node of the "other" part of the merge (hexified version)

    F: a file to be merged entry

    C: a change/delete or delete/change conflict

    D: a file that the external merge driver will merge internally

       (experimental)

    m: the external merge driver defined for this merge plus its run state

       (experimental)

    X: unsupported mandatory record type (used in tests)

    x: unsupported advisory record type (used in tests)

    Merge driver run states (experimental):

    u: driver-resolved files unmarked -- needs to be run next time we're about

       to resolve or commit

    m: driver-resolved files marked -- only needs to be run before commit

    s: success/skipped -- does not need to be run any more

    '''

    statepathv1 = 'merge/state'

    statepathv2 = 'merge/state2'

    @staticmethod

    def clean(repo, node=None, other=None):

        """Initialize a brand new merge state, removing any existing state on

        disk."""

        ms = mergestate(repo)

        ms.reset(node, other)

        return ms

    @staticmethod

    def read(repo):

        """Initialize the merge state, reading it from disk."""

        ms = mergestate(repo)

        ms._read()

        return ms

    def __init__(self, repo):

        """Initialize the merge state.

        Do not use this directly! Instead call read() or clean()."""

        self._repo = repo

        self._dirty = False

    def reset(self, node=None, other=None):

        self._state = {}

        self._local = None

        self._other = None

        for var in ('localctx', 'otherctx'):

            if var in vars(self):

                delattr(self, var)

        if node:

            self._local = node

            self._other = other

        self._readmergedriver = None

        if self.mergedriver:

            self._mdstate = 's'

        else:

            self._mdstate = 'u'

        shutil.rmtree(self._repo.join('merge'), True)

        self._results = {}

        self._dirty = False

    def _read(self):

        """Analyse each record content to restore a serialized state from disk

        This function process "record" entry produced by the de-serialization

        of on disk file.

        """

        self._state = {}

        self._local = None

        self._other = None

        for var in ('localctx', 'otherctx'):

            if var in vars(self):

                delattr(self, var)

        self._readmergedriver = None

        self._mdstate = 's'

        unsupported = set()

        records = self._readrecords()

        for rtype, record in records:

            if rtype == 'L':

                self._local = bin(record)

            elif rtype == 'O':

                self._other = bin(record)

            elif rtype == 'm':

                bits = record.split('\0', 1)

                mdstate = bits[1]

                if len(mdstate) != 1 or mdstate not in 'ums':

                    # the merge driver should be idempotent, so just rerun it

                    mdstate = 'u'

                self._readmergedriver = bits[0]

                self._mdstate = mdstate

            elif rtype in 'FDC':

                bits = record.split('\0')

                self._state[bits[0]] = bits[1:]

            elif not rtype.islower():

                unsupported.add(rtype)

        self._results = {}

        self._dirty = False

        if unsupported:

            raise error.UnsupportedMergeRecords(unsupported)

    def _readrecords(self):

        """Read merge state from disk and return a list of record (TYPE, data)

        We read data from both v1 and v2 files and decide which one to use.

        V1 has been used by version prior to 2.9.1 and contains less data than

        v2. We read both versions and check if no data in v2 contradicts

        v1. If there is not contradiction we can safely assume that both v1

        and v2 were written at the same time and use the extract data in v2. If

        there is contradiction we ignore v2 content as we assume an old version

        of Mercurial has overwritten the mergestate file and left an old v2

        file around.

        returns list of record [(TYPE, data), ...]"""

        v1records = self._readrecordsv1()

        v2records = self._readrecordsv2()

        if self._v1v2match(v1records, v2records):

            return v2records

        else:

            # v1 file is newer than v2 file, use it

            # we have to infer the "other" changeset of the merge

            # we cannot do better than that with v1 of the format

            mctx = self._repo[None].parents()[-1]

            v1records.append(('O', mctx.hex()))

            # add place holder "other" file node information

            # nobody is using it yet so we do no need to fetch the data

            # if mctx was wrong `mctx[bits[-2]]` may fails.

            for idx, r in enumerate(v1records):

                if r[0] == 'F':

                    bits = r[1].split('\0')

                    bits.insert(-2, '')

                    v1records[idx] = (r[0], '\0'.join(bits))

            return v1records

    def _v1v2match(self, v1records, v2records):

        oldv2 = set() # old format version of v2 record

        for rec in v2records:

            if rec[0] == 'L':

                oldv2.add(rec)

            elif rec[0] == 'F':

                # drop the onode data (not contained in v1)

                oldv2.add(('F', _droponode(rec[1])))

        for rec in v1records:

            if rec not in oldv2:

                return False

        else:

            return True

    def _readrecordsv1(self):

        """read on disk merge state for version 1 file

        returns list of record [(TYPE, data), ...]

        Note: the "F" data from this file are one entry short

              (no "other file node" entry)

        """

        records = []

        try:

            f = self._repo.vfs(self.statepathv1)

            for i, l in enumerate(f):

                if i == 0:

                    records.append(('L', l[:-1]))

                else:

                    records.append(('F', l[:-1]))

            f.close()

        except IOError as err:

            if err.errno != errno.ENOENT:

                raise

        return records

    def _readrecordsv2(self):

        """read on disk merge state for version 2 file

        This format is a list of arbitrary records of the form:

          [type][length][content]

        `type` is a single character, `length` is a 4 byte integer, and

        `content` is an arbitrary byte sequence of length `length`.

        Mercurial versions prior to 3.7 have a bug where if there are

        unsupported mandatory merge records, attempting to clear out the merge

        state with hg update --clean or similar aborts. The 't' record type

        works around that by writing out what those versions treat as an

        advisory record, but later versions interpret as special: the first

        character is the 'real' record type and everything onwards is the data.

        Returns list of records [(TYPE, data), ...]."""

        records = []

        try:

            f = self._repo.vfs(self.statepathv2)

            data = f.read()

            off = 0

            end = len(data)

            while off < end:

                rtype = data[off]

                off += 1

                length = _unpack('>I', data[off:(off + 4)])[0]

                off += 4

                record = data[off:(off + length)]

                off += length

                if rtype == 't':

                    rtype, record = record[0], record[1:]

                records.append((rtype, record))

            f.close()

        except IOError as err:

            if err.errno != errno.ENOENT:

                raise

        return records

    @util.propertycache

    def mergedriver(self):

        # protect against the following:

        # - A configures a malicious merge driver in their hgrc, then

        #   pauses the merge

        # - A edits their hgrc to remove references to the merge driver

        # - A gives a copy of their entire repo, including .hg, to B

        # - B inspects .hgrc and finds it to be clean

        # - B then continues the merge and the malicious merge driver

        #  gets invoked

        configmergedriver = self._repo.ui.config('experimental', 'mergedriver')

        if (self._readmergedriver is not None

            and self._readmergedriver != configmergedriver):

            raise error.ConfigError(

                _("merge driver changed since merge started"),

                hint=_("revert merge driver change or abort merge"))

        return configmergedriver

    @util.propertycache

    def localctx(self):

        if self._local is None:

            raise RuntimeError("localctx accessed but self._local isn't set")

        return self._repo[self._local]

    @util.propertycache

    def otherctx(self):

        if self._other is None:

            raise RuntimeError("localctx accessed but self._local isn't set")

        return self._repo[self._other]

    def active(self):

        """Whether mergestate is active.

        Returns True if there appears to be mergestate. This is a rough proxy

        for "is a merge in progress."

        """

        # Check local variables before looking at filesystem for performance

        # reasons.

        return bool(self._local) or bool(self._state) or \

               self._repo.vfs.exists(self.statepathv1) or \

               self._repo.vfs.exists(self.statepathv2)

    def commit(self):

        """Write current state on disk (if necessary)"""

        if self._dirty:

            records = self._makerecords()

            self._writerecords(records)

            self._dirty = False

    def _makerecords(self):

        records = []

        records.append(('L', hex(self._local)))

        records.append(('O', hex(self._other)))

        if self.mergedriver:

            records.append(('m', '\0'.join([

                self.mergedriver, self._mdstate])))

        for d, v in self._state.iteritems():

            if v[0] == 'd':

                records.append(('D', '\0'.join([d] + v)))

            # v[1] == local ('cd'), v[6] == other ('dc') -- not supported by

            # older versions of Mercurial

            elif v[1] == nullhex or v[6] == nullhex:

                records.append(('C', '\0'.join([d] + v)))

            else:

                records.append(('F', '\0'.join([d] + v)))

        return records

    def _writerecords(self, records):

        """Write current state on disk (both v1 and v2)"""

        self._writerecordsv1(records)

        self._writerecordsv2(records)

    def _writerecordsv1(self, records):

        """Write current state on disk in a version 1 file"""

        f = self._repo.vfs(self.statepathv1, 'w')

        irecords = iter(records)

        lrecords = irecords.next()

        assert lrecords[0] == 'L'

        f.write(hex(self._local) + '\n')

        for rtype, data in irecords:

            if rtype == 'F':

                f.write('%s\n' % _droponode(data))

        f.close()

    def _writerecordsv2(self, records):

        """Write current state on disk in a version 2 file

        See the docstring for _readrecordsv2 for why we use 't'."""

        # these are the records that all version 2 clients can read

        whitelist = 'LOF'

        f = self._repo.vfs(self.statepathv2, 'w')

        for key, data in records:

            assert len(key) == 1

            if key not in whitelist:

                key, data = 't', '%s%s' % (key, data)

            format = '>sI%is' % len(data)

            f.write(_pack(format, key, len(data), data))

        f.close()

    def add(self, fcl, fco, fca, fd):

        """add a new (potentially?) conflicting file the merge state

        fcl: file context for local,

        fco: file context for remote,

        fca: file context for ancestors,

        fd:  file path of the resulting merge.

        note: also write the local version to the `.hg/merge` directory.

        """

        if fcl.isabsent():

            hash = nullhex

        else:

            hash = util.sha1(fcl.path()).hexdigest()

            self._repo.vfs.write('merge/' + hash, fcl.data())

        self._state[fd] = ['u', hash, fcl.path(),