# 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,
    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 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)
    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