# censor code related to censoring revision
# coding: utf8
#
# Copyright 2021 Pierre-Yves David <pierre-yves.david@octobus.net>
# Copyright 2015 Google, Inc <martinvonz@google.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

import binascii
import contextlib
import os

from ..node import (
    nullrev,
)
from .constants import (
    COMP_MODE_PLAIN,
    ENTRY_DATA_COMPRESSED_LENGTH,
    ENTRY_DATA_COMPRESSION_MODE,
    ENTRY_DATA_OFFSET,
    ENTRY_DATA_UNCOMPRESSED_LENGTH,
    ENTRY_DELTA_BASE,
    ENTRY_LINK_REV,
    ENTRY_NODE_ID,
    ENTRY_PARENT_1,
    ENTRY_PARENT_2,
    ENTRY_SIDEDATA_COMPRESSED_LENGTH,
    ENTRY_SIDEDATA_COMPRESSION_MODE,
    ENTRY_SIDEDATA_OFFSET,
    REVLOGV0,
    REVLOGV1,
)
from ..i18n import _

from .. import (
    error,
    pycompat,
    revlogutils,
    util,
)
from ..utils import (
    storageutil,
)
from . import (
    constants,
    deltas,
)


def v1_censor(rl, tr, censornode, tombstone=b''):
    """censors a revision in a "version 1" revlog"""
    assert rl._format_version == constants.REVLOGV1, rl._format_version

    # avoid cycle
    from .. import revlog

    censorrev = rl.rev(censornode)
    tombstone = storageutil.packmeta({b'censored': tombstone}, b'')

    # Rewriting the revlog in place is hard. Our strategy for censoring is
    # to create a new revlog, copy all revisions to it, then replace the
    # revlogs on transaction close.
    #
    # This is a bit dangerous. We could easily have a mismatch of state.
    newrl = revlog.revlog(
        rl.opener,
        target=rl.target,
        radix=rl.radix,
        postfix=b'tmpcensored',
        censorable=True,
    )
    newrl._format_version = rl._format_version
    newrl._format_flags = rl._format_flags
    newrl._generaldelta = rl._generaldelta
    newrl._parse_index = rl._parse_index

    for rev in rl.revs():
        node = rl.node(rev)
        p1, p2 = rl.parents(node)

        if rev == censorrev:
            newrl.addrawrevision(
                tombstone,
                tr,
                rl.linkrev(censorrev),
                p1,
                p2,
                censornode,
                constants.REVIDX_ISCENSORED,
            )

            if newrl.deltaparent(rev) != nullrev:
                m = _(b'censored revision stored as delta; cannot censor')
                h = _(
                    b'censoring of revlogs is not fully implemented;'
                    b' please report this bug'
                )
                raise error.Abort(m, hint=h)
            continue

        if rl.iscensored(rev):
            if rl.deltaparent(rev) != nullrev:
                m = _(
                    b'cannot censor due to censored '
                    b'revision having delta stored'
                )
                raise error.Abort(m)
            rawtext = rl._chunk(rev)
        else:
            rawtext = rl.rawdata(rev)

        newrl.addrawrevision(
            rawtext, tr, rl.linkrev(rev), p1, p2, node, rl.flags(rev)
        )

    tr.addbackup(rl._indexfile, location=b'store')
    if not rl._inline:
        tr.addbackup(rl._datafile, location=b'store')

    rl.opener.rename(newrl._indexfile, rl._indexfile)
    if not rl._inline:
        rl.opener.rename(newrl._datafile, rl._datafile)

    rl.clearcaches()
    rl._loadindex()


def v2_censor(revlog, tr, censornode, tombstone=b''):
    """censors a revision in a "version 2" revlog"""
    assert revlog._format_version != REVLOGV0, revlog._format_version
    assert revlog._format_version != REVLOGV1, revlog._format_version

    censor_revs = {revlog.rev(censornode)}
    _rewrite_v2(revlog, tr, censor_revs, tombstone)


def _rewrite_v2(revlog, tr, censor_revs, tombstone=b''):
    """rewrite a revlog to censor some of its content

    General principle

    We create new revlog files (index/data/sidedata) to copy the content of
    the existing data without the censored data.

    We need to recompute new delta for any revision that used the censored
    revision as delta base. As the cumulative size of the new delta may be
    large, we store them in a temporary file until they are stored in their
    final destination.

    All data before the censored data can be blindly copied. The rest needs
    to be copied as we go and the associated index entry needs adjustement.
    """
    assert revlog._format_version != REVLOGV0, revlog._format_version
    assert revlog._format_version != REVLOGV1, revlog._format_version

    old_index = revlog.index
    docket = revlog._docket

    tombstone = storageutil.packmeta({b'censored': tombstone}, b'')

    first_excl_rev = min(censor_revs)

    first_excl_entry = revlog.index[first_excl_rev]
    index_cutoff = revlog.index.entry_size * first_excl_rev
    data_cutoff = first_excl_entry[ENTRY_DATA_OFFSET] >> 16
    sidedata_cutoff = revlog.sidedata_cut_off(first_excl_rev)

    with pycompat.unnamedtempfile(mode=b"w+b") as tmp_storage:
        # rev → (new_base, data_start, data_end, compression_mode)
        rewritten_entries = _precompute_rewritten_delta(
            revlog,
            old_index,
            censor_revs,
            tmp_storage,
        )

        all_files = _setup_new_files(
            revlog,
            index_cutoff,
            data_cutoff,
            sidedata_cutoff,
        )

        # we dont need to open the old index file since its content already
        # exist in a usable form in `old_index`.
        with all_files() as open_files:
            (
                old_data_file,
                old_sidedata_file,
                new_index_file,
                new_data_file,
                new_sidedata_file,
            ) = open_files

            # writing the censored revision

            # Writing all subsequent revisions
            for rev in range(first_excl_rev, len(old_index)):
                if rev in censor_revs:
                    _rewrite_censor(
                        revlog,
                        old_index,
                        open_files,
                        rev,
                        tombstone,
                    )
                else:
                    _rewrite_simple(
                        revlog,
                        old_index,
                        open_files,
                        rev,
                        rewritten_entries,
                        tmp_storage,
                    )
    docket.write(transaction=None, stripping=True)


def _precompute_rewritten_delta(
    revlog,
    old_index,
    excluded_revs,
    tmp_storage,
):
    """Compute new delta for revisions whose delta is based on revision that
    will not survive as is.

    Return a mapping: {rev → (new_base, data_start, data_end, compression_mode)}
    """
    dc = deltas.deltacomputer(revlog)
    rewritten_entries = {}
    first_excl_rev = min(excluded_revs)
    with revlog._segmentfile._open_read() as dfh:
        for rev in range(first_excl_rev, len(old_index)):
            if rev in excluded_revs:
                # this revision will be preserved as is, so we don't need to
                # consider recomputing a delta.
                continue
            entry = old_index[rev]
            if entry[ENTRY_DELTA_BASE] not in excluded_revs:
                continue
            # This is a revision that use the censored revision as the base
            # for its delta. We need a need new deltas
            if entry[ENTRY_DATA_UNCOMPRESSED_LENGTH] == 0:
                # this revision is empty, we can delta against nullrev
                rewritten_entries[rev] = (nullrev, 0, 0, COMP_MODE_PLAIN)
            else:

                text = revlog.rawdata(rev, _df=dfh)
                info = revlogutils.revisioninfo(
                    node=entry[ENTRY_NODE_ID],
                    p1=revlog.node(entry[ENTRY_PARENT_1]),
                    p2=revlog.node(entry[ENTRY_PARENT_2]),
                    btext=[text],
                    textlen=len(text),
                    cachedelta=None,
                    flags=entry[ENTRY_DATA_OFFSET] & 0xFFFF,
                )
                d = dc.finddeltainfo(
                    info, dfh, excluded_bases=excluded_revs, target_rev=rev
                )
                default_comp = revlog._docket.default_compression_header
                comp_mode, d = deltas.delta_compression(default_comp, d)
                # using `tell` is a bit lazy, but we are not here for speed
                start = tmp_storage.tell()
                tmp_storage.write(d.data[1])
                end = tmp_storage.tell()
                rewritten_entries[rev] = (d.base, start, end, comp_mode)
    return rewritten_entries


def _setup_new_files(
    revlog,
    index_cutoff,
    data_cutoff,
    sidedata_cutoff,
):
    """

    return a context manager to open all the relevant files:
    - old_data_file,
    - old_sidedata_file,
    - new_index_file,
    - new_data_file,
    - new_sidedata_file,

    The old_index_file is not here because it is accessed through the
    `old_index` object if the caller function.
    """
    docket = revlog._docket
    old_index_filepath = revlog.opener.join(docket.index_filepath())
    old_data_filepath = revlog.opener.join(docket.data_filepath())
    old_sidedata_filepath = revlog.opener.join(docket.sidedata_filepath())

    new_index_filepath = revlog.opener.join(docket.new_index_file())
    new_data_filepath = revlog.opener.join(docket.new_data_file())
    new_sidedata_filepath = revlog.opener.join(docket.new_sidedata_file())

    util.copyfile(old_index_filepath, new_index_filepath, nb_bytes=index_cutoff)
    util.copyfile(old_data_filepath, new_data_filepath, nb_bytes=data_cutoff)
    util.copyfile(
        old_sidedata_filepath,
        new_sidedata_filepath,
        nb_bytes=sidedata_cutoff,
    )
    revlog.opener.register_file(docket.index_filepath())
    revlog.opener.register_file(docket.data_filepath())
    revlog.opener.register_file(docket.sidedata_filepath())

    docket.index_end = index_cutoff
    docket.data_end = data_cutoff
    docket.sidedata_end = sidedata_cutoff

    # reload the revlog internal information
    revlog.clearcaches()
    revlog._loadindex(docket=docket)

    @contextlib.contextmanager
    def all_files_opener():
        # hide opening in an helper function to please check-code, black
        # and various python version at the same time
        with open(old_data_filepath, 'rb') as old_data_file:
            with open(old_sidedata_filepath, 'rb') as old_sidedata_file:
                with open(new_index_filepath, 'r+b') as new_index_file:
                    with open(new_data_filepath, 'r+b') as new_data_file:
                        with open(
                            new_sidedata_filepath, 'r+b'
                        ) as new_sidedata_file:
                            new_index_file.seek(0, os.SEEK_END)
                            assert new_index_file.tell() == index_cutoff
                            new_data_file.seek(0, os.SEEK_END)
                            assert new_data_file.tell() == data_cutoff
                            new_sidedata_file.seek(0, os.SEEK_END)
                            assert new_sidedata_file.tell() == sidedata_cutoff
                            yield (
                                old_data_file,
                                old_sidedata_file,
                                new_index_file,
                                new_data_file,
                                new_sidedata_file,
                            )

    return all_files_opener


def _rewrite_simple(
    revlog,
    old_index,
    all_files,
    rev,
    rewritten_entries,
    tmp_storage,
):
    """append a normal revision to the index after the rewritten one(s)"""
    (
        old_data_file,
        old_sidedata_file,
        new_index_file,
        new_data_file,
        new_sidedata_file,
    ) = all_files
    entry = old_index[rev]
    flags = entry[ENTRY_DATA_OFFSET] & 0xFFFF
    old_data_offset = entry[ENTRY_DATA_OFFSET] >> 16

    if rev not in rewritten_entries:
        old_data_file.seek(old_data_offset)
        new_data_size = entry[ENTRY_DATA_COMPRESSED_LENGTH]
        new_data = old_data_file.read(new_data_size)
        data_delta_base = entry[ENTRY_DELTA_BASE]
        d_comp_mode = entry[ENTRY_DATA_COMPRESSION_MODE]
    else:
        (
            data_delta_base,
            start,
            end,
            d_comp_mode,
        ) = rewritten_entries[rev]
        new_data_size = end - start
        tmp_storage.seek(start)
        new_data = tmp_storage.read(new_data_size)

    # It might be faster to group continuous read/write operation,
    # however, this is censor, an operation that is not focussed
    # around stellar performance. So I have not written this
    # optimisation yet.
    new_data_offset = new_data_file.tell()
    new_data_file.write(new_data)

    sidedata_size = entry[ENTRY_SIDEDATA_COMPRESSED_LENGTH]
    new_sidedata_offset = new_sidedata_file.tell()
    if 0 < sidedata_size:
        old_sidedata_offset = entry[ENTRY_SIDEDATA_OFFSET]
        old_sidedata_file.seek(old_sidedata_offset)
        new_sidedata = old_sidedata_file.read(sidedata_size)
        new_sidedata_file.write(new_sidedata)

    data_uncompressed_length = entry[ENTRY_DATA_UNCOMPRESSED_LENGTH]
    sd_com_mode = entry[ENTRY_SIDEDATA_COMPRESSION_MODE]
    assert data_delta_base <= rev, (data_delta_base, rev)

    new_entry = revlogutils.entry(
        flags=flags,
        data_offset=new_data_offset,
        data_compressed_length=new_data_size,
        data_uncompressed_length=data_uncompressed_length,
        data_delta_base=data_delta_base,
        link_rev=entry[ENTRY_LINK_REV],
        parent_rev_1=entry[ENTRY_PARENT_1],
        parent_rev_2=entry[ENTRY_PARENT_2],
        node_id=entry[ENTRY_NODE_ID],
        sidedata_offset=new_sidedata_offset,
        sidedata_compressed_length=sidedata_size,
        data_compression_mode=d_comp_mode,
        sidedata_compression_mode=sd_com_mode,
    )
    revlog.index.append(new_entry)
    entry_bin = revlog.index.entry_binary(rev)
    new_index_file.write(entry_bin)

    revlog._docket.index_end = new_index_file.tell()
    revlog._docket.data_end = new_data_file.tell()
    revlog._docket.sidedata_end = new_sidedata_file.tell()


def _rewrite_censor(
    revlog,
    old_index,
    all_files,
    rev,
    tombstone,
):
    """rewrite and append a censored revision"""
    (
        old_data_file,
        old_sidedata_file,
        new_index_file,
        new_data_file,
        new_sidedata_file,
    ) = all_files
    entry = old_index[rev]

    # XXX consider trying the default compression too
    new_data_size = len(tombstone)
    new_data_offset = new_data_file.tell()
    new_data_file.write(tombstone)

    # we are not adding any sidedata as they might leak info about the censored version

    link_rev = entry[ENTRY_LINK_REV]

    p1 = entry[ENTRY_PARENT_1]
    p2 = entry[ENTRY_PARENT_2]

    new_entry = revlogutils.entry(
        flags=constants.REVIDX_ISCENSORED,
        data_offset=new_data_offset,
        data_compressed_length=new_data_size,
        data_uncompressed_length=new_data_size,
        data_delta_base=rev,
        link_rev=link_rev,
        parent_rev_1=p1,
        parent_rev_2=p2,
        node_id=entry[ENTRY_NODE_ID],
        sidedata_offset=0,
        sidedata_compressed_length=0,
        data_compression_mode=COMP_MODE_PLAIN,
        sidedata_compression_mode=COMP_MODE_PLAIN,
    )
    revlog.index.append(new_entry)
    entry_bin = revlog.index.entry_binary(rev)
    new_index_file.write(entry_bin)
    revlog._docket.index_end = new_index_file.tell()
    revlog._docket.data_end = new_data_file.tell()


def _get_filename_from_filelog_index(path):
    # Drop the extension and the `data/` prefix
    path_part = path.rsplit(b'.', 1)[0].split(b'/', 1)
    if len(path_part) < 2:
        msg = _(b"cannot recognize filelog from filename: '%s'")
        msg %= path
        raise error.Abort(msg)

    return path_part[1]


def _filelog_from_filename(repo, path):
    """Returns the filelog for the given `path`. Stolen from `engine.py`"""

    from .. import filelog  # avoid cycle

    fl = filelog.filelog(repo.svfs, path)
    return fl


def _write_swapped_parents(repo, rl, rev, offset, fp):
    """Swaps p1 and p2 and overwrites the revlog entry for `rev` in `fp`"""
    from ..pure import parsers  # avoid cycle

    if repo._currentlock(repo._lockref) is None:
        # Let's be paranoid about it
        msg = "repo needs to be locked to rewrite parents"
        raise error.ProgrammingError(msg)

    index_format = parsers.IndexObject.index_format
    entry = rl.index[rev]
    new_entry = list(entry)
    new_entry[5], new_entry[6] = entry[6], entry[5]
    packed = index_format.pack(*new_entry[:8])
    fp.seek(offset)
    fp.write(packed)


def _reorder_filelog_parents(repo, fl, to_fix):
    """
    Swaps p1 and p2 for all `to_fix` revisions of filelog `fl` and writes the
    new version to disk, overwriting the old one with a rename.
    """
    from ..pure import parsers  # avoid cycle

    ui = repo.ui
    assert len(to_fix) > 0
    rl = fl._revlog
    if rl._format_version != constants.REVLOGV1:
        msg = "expected version 1 revlog, got version '%d'" % rl._format_version
        raise error.ProgrammingError(msg)

    index_file = rl._indexfile
    new_file_path = index_file + b'.tmp-parents-fix'
    repaired_msg = _(b"repaired revision %d of 'filelog %s'\n")

    with ui.uninterruptible():
        try:
            util.copyfile(
                rl.opener.join(index_file),
                rl.opener.join(new_file_path),
                checkambig=rl._checkambig,
            )

            with rl.opener(new_file_path, mode=b"r+") as fp:
                if rl._inline:
                    index = parsers.InlinedIndexObject(fp.read())
                    for rev in fl.revs():
                        if rev in to_fix:
                            offset = index._calculate_index(rev)
                            _write_swapped_parents(repo, rl, rev, offset, fp)
                            ui.write(repaired_msg % (rev, index_file))
                else:
                    index_format = parsers.IndexObject.index_format
                    for rev in to_fix:
                        offset = rev * index_format.size
                        _write_swapped_parents(repo, rl, rev, offset, fp)
                        ui.write(repaired_msg % (rev, index_file))

            rl.opener.rename(new_file_path, index_file)
            rl.clearcaches()
            rl._loadindex()
        finally:
            util.tryunlink(new_file_path)


def _is_revision_affected(ui, fl, filerev, path):
    """Mercurial currently (5.9rc0) uses `p1 == nullrev and p2 != nullrev` as a
    special meaning compared to the reverse in the context of filelog-based
    copytracing. issue6528 exists because new code assumed that parent ordering
    didn't matter, so this detects if the revision contains metadata (since
    it's only used for filelog-based copytracing) and its parents are in the
    "wrong" order."""
    try:
        raw_text = fl.rawdata(filerev)
    except error.CensoredNodeError:
        # We don't care about censored nodes as they never carry metadata
        return False
    has_meta = raw_text.startswith(b'\x01\n')
    if has_meta:
        (p1, p2) = fl.parentrevs(filerev)
        if p1 != nullrev and p2 == nullrev:
            return True
    return False


def _from_report(ui, repo, context, from_report, dry_run):
    """
    Fix the revisions given in the `from_report` file, but still checks if the
    revisions are indeed affected to prevent an unfortunate cyclic situation
    where we'd swap well-ordered parents again.

    See the doc for `debug_fix_issue6528` for the format documentation.
    """
    ui.write(_(b"loading report file '%s'\n") % from_report)

    with context(), open(from_report, mode='rb') as f:
        for line in f.read().split(b'\n'):
            if not line:
                continue
            filenodes, filename = line.split(b' ', 1)
            fl = _filelog_from_filename(repo, filename)
            to_fix = set(
                fl.rev(binascii.unhexlify(n)) for n in filenodes.split(b',')
            )
            excluded = set()

            for filerev in to_fix:
                if _is_revision_affected(ui, fl, filerev, filename):
                    msg = b"found affected revision %d for filelog '%s'\n"
                    ui.warn(msg % (filerev, filename))
                else:
                    msg = _(b"revision %s of file '%s' is not affected\n")
                    msg %= (binascii.hexlify(fl.node(filerev)), filename)
                    ui.warn(msg)
                    excluded.add(filerev)

            to_fix = to_fix - excluded
            if not to_fix:
                msg = _(b"no affected revisions were found for '%s'\n")
                ui.write(msg % filename)
                continue
            if not dry_run:
                _reorder_filelog_parents(repo, fl, sorted(to_fix))


def repair_issue6528(ui, repo, dry_run=False, to_report=None, from_report=None):
    from .. import store  # avoid cycle

    @contextlib.contextmanager
    def context():
        if dry_run or to_report:  # No need for locking
            yield
        else:
            with repo.wlock(), repo.lock():
                yield

    if from_report:
        return _from_report(ui, repo, context, from_report, dry_run)

    report_entries = []

    with context():
        files = list(
            (file_type, path)
            for (file_type, path, _e, _s) in repo.store.datafiles()
            if path.endswith(b'.i') and file_type & store.FILEFLAGS_FILELOG
        )

        progress = ui.makeprogress(
            _(b"looking for affected revisions"),
            unit=_(b"filelogs"),
            total=len(files),
        )
        found_nothing = True

        for file_type, path in files:
            if (
                not path.endswith(b'.i')
                or not file_type & store.FILEFLAGS_FILELOG
            ):
                continue
            progress.increment()
            filename = _get_filename_from_filelog_index(path)
            fl = _filelog_from_filename(repo, filename)

            # Set of filerevs (or hex filenodes if `to_report`) that need fixing
            to_fix = set()
            for filerev in fl.revs():
                # TODO speed up by looking at the start of the delta
                # If it hasn't changed, it's not worth looking at the other revs
                # in the same chain
                affected = _is_revision_affected(ui, fl, filerev, path)
                if affected:
                    msg = b"found affected revision %d for filelog '%s'\n"
                    ui.warn(msg % (filerev, path))
                    found_nothing = False
                    if not dry_run:
                        if to_report:
                            to_fix.add(binascii.hexlify(fl.node(filerev)))
                        else:
                            to_fix.add(filerev)

            if to_fix:
                to_fix = sorted(to_fix)
                if to_report:
                    report_entries.append((filename, to_fix))
                else:
                    _reorder_filelog_parents(repo, fl, to_fix)

        if found_nothing:
            ui.write(_(b"no affected revisions were found\n"))

        if to_report and report_entries:
            with open(to_report, mode="wb") as f:
                for path, to_fix in report_entries:
                    f.write(b"%s %s\n" % (b",".join(to_fix), path))

        progress.complete()