# Copyright (C) 2007 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

from bzrformats.knit import KnitCorrupt


def _load_data_py(kndx, fp):
    """Read in a knit index."""
    cache = kndx._cache
    history = kndx._history

    kndx.check_header(fp)
    # readlines reads the whole file at once:
    # bad for transports like http, good for local disk
    # we save 60 ms doing this one change (
    # from calling readline each time to calling
    # readlines once.
    # probably what we want for nice behaviour on
    # http is a incremental readlines that yields, or
    # a check for local vs non local indexes,
    history_top = len(history) - 1
    for line in fp.readlines():
        rec = line.split()
        if len(rec) < 5 or rec[-1] != b":":
            # corrupt line.
            # FIXME: in the future we should determine if its a
            # short write - and ignore it
            # or a different failure, and raise. RBC 20060407
            continue

        try:
            parents = []
            for value in rec[4:-1]:
                if value[:1] == b".":
                    # uncompressed reference
                    parent_id = value[1:]
                else:
                    parent_id = history[int(value)]
                parents.append(parent_id)
        except (IndexError, ValueError) as e:
            # The parent could not be decoded to get its parent row. This
            # at a minimum will cause this row to have wrong parents, or
            # even to apply a delta to the wrong base and decode
            # incorrectly. its therefore not usable, and because we have
            # encountered a situation where a new knit index had this
            # corrupt we can't asssume that no other rows referring to the
            # index of this record actually mean the subsequent uncorrupt
            # one, so we error.
            raise KnitCorrupt(kndx._filename, f"line {rec!r}: {e}") from e

        version_id, options, pos, size = rec[:4]
        try:
            pos = int(pos)
        except ValueError as e:
            raise KnitCorrupt(
                kndx._filename, f"invalid position on line {rec!r}: {e}"
            ) from e
        try:
            size = int(size)
        except ValueError as e:
            raise KnitCorrupt(
                kndx._filename, f"invalid size on line {rec!r}: {e}"
            ) from e

        # See kndx._cache_version
        # only want the _history index to reference the 1st
        # index entry for version_id
        if version_id not in cache:
            history_top += 1
            index = history_top
            history.append(version_id)
        else:
            index = cache[version_id][5]
        cache[version_id] = (
            version_id,
            options.split(b","),
            pos,
            size,
            tuple(parents),
            index,
        )
        # end kndx._cache_version
