Source code for timelinelib.db.utils

# Copyright (C) 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018  Rickard Lindberg, Roger Lindberg
#
# This file is part of Timeline.
#
# Timeline 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 3 of the License, or
# (at your option) any later version.
#
# Timeline 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 Timeline.  If not, see <http://www.gnu.org/licenses/>.


import codecs
import os.path

from timelinelib.canvas.data.exceptions import TimelineIOError
from timelinelib.wxgui.utils import register_unlock_function
from timelinelib.wxgui.dialogs.getfilepath.view import open_get_file_path_dialog, FUNC_NEW
from timelinelib.wxgui.dialogs.getdirpath.view import open_get_dir_path_dialog


def safe_write(path, encoding, write_fn):
    """
    Write to path in such a way that the contents of path is only modified
    correctly or not modified at all.

    In some extremely rare cases the contents of path might be incorrect, but
    in those cases the correct content is always present in another dbfile.
    """
    def raise_error(specific_msg, cause_exception):
        err_general = _("Unable to save timeline data to '%s'. File left unmodified.") % path
        err_template = "%s\n\n%%s\n\n%%s" % err_general
        raise TimelineIOError(err_template % (specific_msg, cause_exception))
    tmp_path = create_non_exising_path(path, "tmp")
    backup_path = create_non_exising_path(path, "bak")
    # Write data to tmp dbfile
    try:
        if encoding is None:
            dbfile = open(tmp_path, "w")
        else:
            dbfile = codecs.open(tmp_path, "w", encoding)
        try:
            try:
                write_fn(dbfile)
            except Exception as e:
                raise_error(_("Unable to write timeline data."), e)
        finally:
            dbfile.close()
    except IOError as e:
        raise_error(_("Unable to write to temporary dbfile '%s'.") % tmp_path, e)
    # Copy original to backup (if original exists)
    if os.path.exists(path):
        try:
            os.rename(path, backup_path)
        except Exception as e:  # Can this only be a OSError?
            raise_error(_("Unable to take backup to '%s'.") % backup_path, e)
    # Copy tmp to original
    try:
        os.rename(tmp_path, path)
    except Exception as e:  # Can this only be a OSError?
        raise_error(_("Unable to rename temporary dbfile '%s' to original.") % tmp_path, e)
    # Delete backup (if backup was created)
    if os.path.exists(backup_path):
        try:
            os.remove(backup_path)
        except Exception as e:  # Can this only be a OSError?
            raise_error(_("Unable to delete backup dbfile '%s'.") % backup_path, e)


def create_non_exising_path(base, suffix):
    i = 1
    while True:
        new_path = "%s.%s%i" % (base, suffix, i)
        if os.path.exists(new_path):
            i += 1
        else:
            return new_path


def safe_locking(controller, edit_function, exception_handler=None):
    if controller.ok_to_edit():
        try:
            register_unlock_function(controller.edit_ends)
            edit_function()
        except Exception as e:
            if exception_handler is not None:
                controller.edit_ends()
                exception_handler(e)
            else:
                raise
        finally:
            controller.edit_ends()


def get_modification_date(path):
    try:
        return os.path.getmtime(path)
    except:
        return 0


def get_new_path_from_user(timetype, path):
    if timetype == "dir":
        return open_get_dir_path_dialog()
    else:
        return open_get_file_path_dialog(FUNC_NEW, path)