# metadata.py -- code related to various metadata computation and access.

#

# Copyright 2019 Google, Inc <martinvonz@google.com>

# Copyright 2020 Pierre-Yves David <pierre-yves.david@octobus.net>

#

# 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, print_function

import multiprocessing

from . import (

    error,

    node,

    pycompat,

    util,

)

from .revlogutils import (

    flagutil as sidedataflag,

    sidedata as sidedatamod,

)

def computechangesetfilesadded(ctx):

    """return the list of files added in a changeset

    """

    added = []

    for f in ctx.files():

        if not any(f in p for p in ctx.parents()):

            added.append(f)

    return added

def get_removal_filter(ctx, x=None):

    """return a function to detect files "wrongly" detected as `removed`

    When a file is removed relative to p1 in a merge, this

    function determines whether the absence is due to a

    deletion from a parent, or whether the merge commit

    itself deletes the file. We decide this by doing a

    simplified three way merge of the manifest entry for

    the file. There are two ways we decide the merge

    itself didn't delete a file:

    - neither parent (nor the merge) contain the file

    - exactly one parent contains the file, and that

      parent has the same filelog entry as the merge

      ancestor (or all of them if there two). In other

      words, that parent left the file unchanged while the

      other one deleted it.

    One way to think about this is that deleting a file is

    similar to emptying it, so the list of changed files

    should be similar either way. The computation

    described above is not done directly in _filecommit

    when creating the list of changed files, however

    it does something very similar by comparing filelog

    nodes.

    """

    if x is not None:

        p1, p2, m1, m2 = x

    else:

        p1 = ctx.p1()

        p2 = ctx.p2()

        m1 = p1.manifest()

        m2 = p2.manifest()

    @util.cachefunc

    def mas():

        p1n = p1.node()

        p2n = p2.node()

        cahs = ctx.repo().changelog.commonancestorsheads(p1n, p2n)

        if not cahs:

            cahs = [node.nullrev]

        return [ctx.repo()[r].manifest() for r in cahs]

    def deletionfromparent(f):

        if f in m1:

            return f not in m2 and all(

                f in ma and ma.find(f) == m1.find(f) for ma in mas()

            )

        elif f in m2:

            return all(f in ma and ma.find(f) == m2.find(f) for ma in mas())

        else:

            return True

    return deletionfromparent

def computechangesetfilesremoved(ctx):

    """return the list of files removed in a changeset

    """

    removed = []

    for f in ctx.files():

        if f not in ctx:

            removed.append(f)

    if removed:

        rf = get_removal_filter(ctx)

        removed = [r for r in removed if not rf(r)]

    return removed

def computechangesetcopies(ctx):

    """return the copies data for a changeset

    The copies data are returned as a pair of dictionnary (p1copies, p2copies).

    Each dictionnary are in the form: `{newname: oldname}`

    """

    p1copies = {}

    p2copies = {}

    p1 = ctx.p1()

    p2 = ctx.p2()

    narrowmatch = ctx._repo.narrowmatch()

    for dst in ctx.files():

        if not narrowmatch(dst) or dst not in ctx:

            continue

        copied = ctx[dst].renamed()

        if not copied:

            continue

        src, srcnode = copied

        if src in p1 and p1[src].filenode() == srcnode:

            p1copies[dst] = src

        elif src in p2 and p2[src].filenode() == srcnode:

            p2copies[dst] = src

    return p1copies, p2copies

def encodecopies(files, copies):

    items = []

    for i, dst in enumerate(files):

        if dst in copies:

            items.append(b'%d\0%s' % (i, copies[dst]))

    if len(items) != len(copies):

        raise error.ProgrammingError(

            b'some copy targets missing from file list'

        )

    return b"\n".join(items)

def decodecopies(files, data):

    try:

        copies = {}

        if not data:

            return copies

        for l in data.split(b'\n'):

            strindex, src = l.split(b'\0')

            i = int(strindex)

            dst = files[i]

            copies[dst] = src

        return copies

    except (ValueError, IndexError):

        # Perhaps someone had chosen the same key name (e.g. "p1copies") and

        # used different syntax for the value.

        return None

def encodefileindices(files, subset):

    subset = set(subset)

    indices = []

    for i, f in enumerate(files):

        if f in subset:

            indices.append(b'%d' % i)

    return b'\n'.join(indices)

def decodefileindices(files, data):

    try:

        subset = []

        if not data:

            return subset

        for strindex in data.split(b'\n'):

            i = int(strindex)

            if i < 0 or i >= len(files):

                return None

            subset.append(files[i])

        return subset

    except (ValueError, IndexError):

        # Perhaps someone had chosen the same key name (e.g. "added") and

        # used different syntax for the value.

        return None

def _getsidedata(srcrepo, rev):

    ctx = srcrepo[rev]

    filescopies = computechangesetcopies(ctx)

    filesadded = computechangesetfilesadded(ctx)

    filesremoved = computechangesetfilesremoved(ctx)

    sidedata = {}

    if any([filescopies, filesadded, filesremoved]):

        sortedfiles = sorted(ctx.files())

        p1copies, p2copies = filescopies

        p1copies = encodecopies(sortedfiles, p1copies)

        p2copies = encodecopies(sortedfiles, p2copies)

        filesadded = encodefileindices(sortedfiles, filesadded)

        filesremoved = encodefileindices(sortedfiles, filesremoved)

        if p1copies:

            sidedata[sidedatamod.SD_P1COPIES] = p1copies

        if p2copies:

            sidedata[sidedatamod.SD_P2COPIES] = p2copies

        if filesadded:

            sidedata[sidedatamod.SD_FILESADDED] = filesadded

        if filesremoved:

            sidedata[sidedatamod.SD_FILESREMOVED] = filesremoved

    return sidedata

def getsidedataadder(srcrepo, destrepo):

    use_w = srcrepo.ui.configbool(b'experimental', b'worker.repository-upgrade')

    if pycompat.iswindows or not use_w:

        return _get_simple_sidedata_adder(srcrepo, destrepo)

    else:

        return _get_worker_sidedata_adder(srcrepo, destrepo)

def _sidedata_worker(srcrepo, revs_queue, sidedata_queue, tokens):

    """The function used by worker precomputing sidedata

    It read an input queue containing revision numbers

    It write in an output queue containing (rev, <sidedata-map>)

    The `None` input value is used as a stop signal.

    The `tokens` semaphore is user to avoid having too many unprocessed

    entries. The workers needs to acquire one token before fetching a task.

    They will be released by the consumer of the produced data.

    """

    tokens.acquire()

    rev = revs_queue.get()

    while rev is not None:

        data = _getsidedata(srcrepo, rev)

        sidedata_queue.put((rev, data))

        tokens.acquire()

        rev = revs_queue.get()

    # processing of `None` is completed, release the token.

    tokens.release()

BUFF_PER_WORKER = 50

def _get_worker_sidedata_adder(srcrepo, destrepo):

    """The parallel version of the sidedata computation

    This code spawn a pool of worker that precompute a buffer of sidedata

    before we actually need them"""

    # avoid circular import copies -> scmutil -> worker -> copies

    from . import worker

    nbworkers = worker._numworkers(srcrepo.ui)

    tokens = multiprocessing.BoundedSemaphore(nbworkers * BUFF_PER_WORKER)

    revsq = multiprocessing.Queue()

    sidedataq = multiprocessing.Queue()

    assert srcrepo.filtername is None

    # queue all tasks beforehand, revision numbers are small and it make

    # synchronisation simpler

    #

    # Since the computation for each node can be quite expensive, the overhead

    # of using a single queue is not revelant. In practice, most computation

    # are fast but some are very expensive and dominate all the other smaller

    # cost.

    for r in srcrepo.changelog.revs():

        revsq.put(r)

    # queue the "no more tasks" markers

    for i in range(nbworkers):

        revsq.put(None)

    allworkers = []

    for i in range(nbworkers):

        args = (srcrepo, revsq, sidedataq, tokens)

        w = multiprocessing.Process(target=_sidedata_worker, args=args)

        allworkers.append(w)

        w.start()

    # dictionnary to store results for revision higher than we one we are

    # looking for. For example, if we need the sidedatamap for 42, and 43 is

    # received, when shelve 43 for later use.

    staging = {}

    def sidedata_companion(revlog, rev):

        sidedata = {}

        if util.safehasattr(revlog, b'filteredrevs'):  # this is a changelog

            # Is the data previously shelved ?

            sidedata = staging.pop(rev, None)

            if sidedata is None:

                # look at the queued result until we find the one we are lookig

                # for (shelve the other ones)

                r, sidedata = sidedataq.get()

                while r != rev:

                    staging[r] = sidedata

                    r, sidedata = sidedataq.get()

            tokens.release()

        return False, (), sidedata

    return sidedata_companion

def _get_simple_sidedata_adder(srcrepo, destrepo):

    """The simple version of the sidedata computation

    It just compute it in the same thread on request"""

    def sidedatacompanion(revlog, rev):

        sidedata = {}

        if util.safehasattr(revlog, 'filteredrevs'):  # this is a changelog

            sidedata = _getsidedata(srcrepo, rev)

        return False, (), sidedata

    return sidedatacompanion

def getsidedataremover(srcrepo, destrepo):

    def sidedatacompanion(revlog, rev):

        f = ()

        if util.safehasattr(revlog, 'filteredrevs'):  # this is a changelog

            if revlog.flags(rev) & sidedataflag.REVIDX_SIDEDATA:

                f = (

                    sidedatamod.SD_P1COPIES,

                    sidedatamod.SD_P2COPIES,

                    sidedatamod.SD_FILESADDED,

                    sidedatamod.SD_FILESREMOVED,

                )

        return False, f, {}

    return sidedatacompanion